Patent Application
20240115829
The present disclosure generally relates to respiratory gas therapy. More particularly, the present disclosure relates to respiratory gas therapy systems, apparatuses, kits and methods for treating patients undergoing anaesthetic or anaesthesia related procedures.
Intubation is often practiced on patients who are unable to spontaneously breathe. The inability to breathe may be the result of one or several factors, including severe illness, injury, or deep sedation through the use of a general anaesthetic agent. A challenge for anaesthesiologists, including emergency, intensive care and surgical physicians, is to secure a tracheal tube (i.e., intubate) rapidly without causing hypoxia. In the best case intubation may take 45-60 seconds; however, in other cases, particularly if the patient's airway is difficult to traverse (for example, due to cancer, obesity, or severe injury), intubation can take much longer. Patients who are breathing room air will desaturate within this time between sedative/paralytic administration and achieving a secured airway. A patient desaturates when the oxygen concentration in their blood reduces.
To prevent hypoxemia during intubation, a medical professional performing the intubation will often pre-oxygenate the patient to be intubated by applying a face mask and delivering oxygen for a period of time until the patient's blood oxygen saturation level (measured using, for example, near infrared spectroscopy, pulse oximetry, or any other suitable process and equipment) reaches approximately 100%. Pre-oxygenation can provide a buffer against undesirable declines in oxygen saturation, but for long intubation procedures, it is often necessary to interrupt the intubation process and reapply the face mask to again increase the patient's oxygen saturation level to adequate levels. The interruption of the intubation process, which can happen several times for a difficult intubation process, can be frustrating to the medical professional. Additionally, the patient can experience rises in blood carbon dioxide due to the poor management of physiological dead space. Similar difficulties can be encountered with sedated spontaneously breathing patients undergoing, for example, upper endoscopies. Pre-oxygenation with 100% oxygen or almost 100%, (for example 90% or higher) has been shown to markedly increase the duration of safe apnea—defined as the time until a patient reaches a blood oxygen saturation level of 88-90%. Saturations below this level can rapidly deteriorate to critical levels (<70%) on the oxyhemoglobin dissociation curve posing significant risk to the patient. Ideally patients should continue to receive pre-oxygenation until they achieve greater than 90% end-tidal oxygen levels, showing the lungs have been denitrogenised and an oxygen reservoir established in the functional residual capacity of the lungs. Denitrogenation of the lungs creates an alveolar oxygen reservoir that serves to maintain oxygen saturation levels for a small post-ventilatory window.
Patients may lose respiratory function during anaesthesia, or sedation, or more generally during certain medical procedures. Prior to a medical procedure a patient may be pre-oxygenated by a medical professional to provide a reservoir of oxygen saturation, and this pre-oxygenation is generally carried out with a bag and a face mask. Once under general anaesthesia, patients must be intubated to ventilate the patient. In some cases, intubation is completed in 30 to 60 seconds, but in other cases, particularly if the patient's airway is difficult to traverse (for example, due to cancer, severe injury, obesity or spasm of the neck muscles), intubation will take significantly longer. While pre-oxygenation provides a buffer against declines in oxygen saturation, for long intubation procedures, it is necessary to interrupt the intubation process and reapply the face mask to increase the patient's oxygen saturation to adequate levels. The interruption of the intubation process may happen several times for difficult intubation processes, which is time consuming and puts the patient at severe health risk. After approximately three attempts at intubation the medical procedure will be abandoned.
Patients require oxygenation and/or CO2 removal during medical procedures such as anaesthesia. It is difficult to provide the right level of oxygenation and/or CO2 removal. The time to pre-oxygenate and the highest achievable end-tidal oxygen level vary considerably between patients, application method and who is applying it.
In accordance with a first aspect of the disclosure, there is provided a system for oxygenating a patient in relation to anaesthesia using high flow gas delivery comprising: a flow source, and a controller for determining oxygenation requirements of the patient before or during anaesthesia.
The controller may be adapted to control the flow and/or oxygen concentration of the high flow gas to assist oxygenation of the patient according to the oxygenation requirements.
The controller may be adapted to maintain the flow and/or oxygen concentration of the high flow gas.
The controller may be adapted to increase flow and/or oxygen concentration of the high flow gas to assist oxygenation of the patient if sufficient oxygenation has not occurred.
The controller may include a timer adapted to indicate the period of time over which gases have been delivered.
The controller may be adapted to determine if sufficient oxygenation has not occurred by monitoring one or more respiratory gases and/or monitoring the patient's blood oxygen saturation level.
The one or more respiratory gases may comprise oxygen and the system may comprise an oxygen gas analyser.
The controller may be adapted receive input indicating a first quantity of oxygen inhaled by the patient Oi and a second quantity of oxygen exhaled by the patient Oo, and the controller is configured to: control the flow source to deliver a first flow therapy, receive the input indicating Oi and Oo over at least one respiratory cycle, and control the flow source to continue delivering the first flow therapy or to deliver a second flow therapy on the basis of a function of the Oi and Oo.
The one or more respiratory gases may comprise nitrogen and the system may comprise a nitrogen gas analyser.
The controller may be adapted to receive input indicating a first quantity of nitrogen inhaled by the patient Ni and a second quantity of nitrogen exhaled by the patient No, and the controller is configured to: control the flow source to deliver a first flow therapy, receive input indicating Ni and No over at least one respiratory cycle, and control the flow source to continue delivering the first flow therapy or to deliver a second flow therapy on the basis of a function of the Ni and No.
In accordance with a second aspect of the disclosure, there is provided a method of oxygenating a patient in relation to anaesthesia using high flow gas delivery comprising determining oxygenation requirements of the patient before or during anaesthesia.
The method may further comprise controlling the flow and/or oxygen concentration of the high flow gas to assist oxygenation of the patient according to the oxygenation requirements.
The method may further comprise maintaining the flow and/or oxygen concentration of the high flow gas.
The method may further comprise increasing the flow and/or oxygen concentration of the high flow gas to assist oxygenation of the patient if sufficient oxygenation has not occurred.
Determining if sufficient oxygenation has not occurred may comprise monitoring one or more respiratory gases and/or monitoring the patient's blood oxygen saturation level.
The method may further comprise timing the period of time over which gases have been delivered.
The method may further comprise monitoring the one or more respiratory gases comprises monitoring oxygen.
The method may further comprise monitoring oxygen comprises receiving input indicating a first quantity of oxygen inhaled by the patient Oi and a second quantity of oxygen exhaled by the patient Oo, and: controlling the flow source to deliver a first flow therapy, receiving the input indicating Oi and Oo over at least one respiratory cycle, and controlling the flow source to continue delivering the first flow therapy or to deliver a second flow therapy on the basis of a function of the Oi and Oo.
The one or more respiratory gases may comprise nitrogen and the method may comprise monitoring nitrogen.
Monitoring nitrogen may comprise receiving input indicating a first quantity of nitrogen inhaled by the patient Ni and a second quantity of nitrogen exhaled by the patient No, and: controlling the flow source to deliver a first flow therapy, receiving the input indicating Ni and No over at least one respiratory cycle, and controlling the flow source to continue delivering the first flow therapy or to deliver a second flow therapy on the basis of a function of the Ni and No.
In accordance with a third aspect of the disclosure, there is provided a system for oxygenating a patient in relation to anaesthesia using high flow gas delivery comprising: a flow source, and a controller for determining oxygenation requirements of the patient before anaesthesia when the patient is breathing.
The controller may be adapted to control the flow source to provide a high flow gas flow.
The controller may be adapted to control the flow source to provide an initial gas flow rate based on at least the BMI or any other patient parameters in combination with BMI.
The initial gas flow rate may be above 30 L/min.
Upon monitoring the transcutaneous O2 level, the controller may be adapted to increase oxygen concentration in the gas flow if the oxygen saturation level is lower than 99%, the transcutaneous O2 level is lower than 380 mmHg, and the transcutaneous O2 level minus a predetermined value is lower than a previous value.
Upon monitoring the transcutaneous CO2 level, the controller may be adapted to increase oxygen concentration of the gas flow if the transcutaneous CO2 level is greater than 30 mmHg and if the new transcutaneous CO2 level is greater than a previous saturation level plus a predetermined value.
Upon monitoring blood oxygen saturation level, the controller may be adapted to produce a warning if the blood oxygen saturation level has fallen.
Upon monitoring blood oxygen saturation and transcutaneous CO2, the controller may be adapted to indicate the end of the pre-oxygenation phase if the oxygen saturation is greater than 99% and the transcutaneous CO2 is equal to or less than 30 mmHg.
In accordance with a fourth aspect of the disclosure, there is provided a system for oxygenating a patient in relation to anaesthesia using high flow gas delivery comprising: a flow source, and a controller for determining oxygenation requirements of the patient during anaesthesia when the patient is apnoeic.
The controller may be adapted to control the flow source to provide a high flow gas flow.
The controller may be adapted to control the flow source to provide an initial gas flow rate based on at least the BMI or any other patient parameters in combination with BMI such that flow rate is proportional to BMI.
The initial gas flow rate may be above 70 L/min.
Upon monitoring blood oxygen saturation level, the controller may be adapted to produce a warning if the blood oxygen saturation level is less than 92%.
Upon monitoring the blood oxygen saturation, the controller may be adapted to increase the flow of the gas flow if the average rate of change of blood oxygen saturation is negative, and if the rate of change of blood oxygen saturation is not increasing, and if the flow or 100 L/minute or greater.
Upon monitoring the blood oxygen saturation, the controller may be adapted to increase the flow of the gas flow if the average rate of change of blood oxygen saturation is negative, if the flow is less than 100 L/minute and if the rate of change of blood oxygen saturation is not increasing.
Upon monitoring the blood oxygen saturation, the controller may be adapted to warn the clinician if the average rate of change of blood oxygen saturation is negative, if the flow is 100 L/minute or greater and if the oxygen concentration is 99% or greater.
Upon monitoring the blood oxygen saturation, the controller may be adapted to increase the flow and/or oxygen concentration of the gas flow if the average rate of change of blood oxygen saturation is negative and if the rate of change of blood oxygen saturation is increasing.
Upon monitoring the blood oxygen saturation, the controller may be adapted to decrease oxygen concentration of the gas flow if the average rate of change of blood oxygen saturation is zero or positive and if the average level of blood oxygen saturation is 99% or greater.
There is provided a method of oxygenating a patient in relation to anaesthesia using high flow gas delivery comprising determining oxygenation requirements of the patient before anaesthesia when the patient is breathing.
The method may further comprise controlling the flow source to provide a high flow gas flow.
The method may further comprise controlling the flow source to provide an initial gas flow rate based on at least the BMI or any other patient parameters in combination with BMI.
The initial gas flow rate may be above 30 L/min.
The method may further comprise controlling the oxygen concentration in the gas flow if the oxygen saturation level is lower than 99%, the transcutaneous O2 level is lower than 380 mmHg, and the transcutaneous O2 level minus a predetermined value is lower than a previous value.
The method may further comprise increasing oxygen concentration of the gas flow if the transcutaneous CO2 level is greater than 30 mmHg and if the new transcutaneous CO2 level is greater than a previous saturation level plus a predetermined value.
The method may further comprise, upon monitoring blood oxygen saturation level, producing a warning if the blood oxygen saturation level has fallen.
The method may further comprise, upon monitoring blood oxygen saturation and transcutaneous CO2, indicating the end of the pre-oxygenation phase if the oxygen saturation is greater than 99% and the transcutaneous CO2 is equal to or less than 30 mmHg.
There is provided a method of oxygenating a patient in relation to anaesthesia using high flow gas delivery comprising determining oxygenation requirements of the patient during anaesthesia when the patient is apnoeic.
The method may further comprise controlling the flow source to provide a high flow gas flow.
The method may further comprise, controlling the flow source to provide an initial gas flow rate based on at least the BMI or any other patient parameters in combination with BMI such that flow rate is proportional to BMI.
The initial gas flow rate may be above 70 L/min.
The method may further comprise, upon monitoring blood oxygen saturation level, the controller may be adapted to produce a warning if the blood oxygen saturation level is less than 92%.
The method may further comprise, upon monitoring the blood oxygen saturation, increasing the flow of the gas flow if the average rate of change of blood oxygen saturation is negative, and if the rate of change of blood oxygen saturation is not increasing, and if the flow or 100 L/minute or greater.
The method may further comprise, upon monitoring the blood oxygen saturation, increasing the flow of the gas flow if the average rate of change of blood oxygen saturation is negative, if the flow is less than 100 L/minute and if the rate of change of blood oxygen saturation is not increasing.
The method may further comprise, upon monitoring the blood oxygen saturation, warning the clinician if the average rate of change of blood oxygen saturation is negative, if the flow is 100 L/minute or greater and if the oxygen concentration is 99% or greater.
The method may further comprise, upon monitoring the blood oxygen saturation, increasing the flow and/or oxygen concentration of the gas flow if the average rate of change of blood oxygen saturation is negative and if the rate of change of blood oxygen saturation is increasing.
The method may further comprise, upon monitoring the blood oxygen saturation, decreasing oxygen concentration of the gas flow if the average rate of change of blood oxygen saturation is zero or positive and if the average level of blood oxygen saturation is 99% or greater.
Certain features, aspects and advantages of at least one of the configurations disclosed herein include the realization that a nasal cannula or other nasal interface can be used to deliver gases to a patient undergoing intubation or endoscopy. The delivery of gas therapy (e.g. high flow gas therapy) together with supplemental oxygen can substantially reduce or prevent the rise of blood carbon dioxide while maintaining blood oxygenation saturation levels within an acceptable range. The gas composition delivered using the gas therapy can be a function of, for example, the patient's blood oxygen saturation or nitrogen respiration ratio (e.g. ratio of expired nitrogen to inspiration nitrogen). If the flow is heated and humidified, the health of the patient's respiratory airway can preserved. Additionally, several systems, kits and/or arrangements are disclosed that may be useful for optimizing gas therapy for patients undergoing intubation or endoscopy.
Thus, in accordance with certain features, aspects and advantages of at least one of the embodiments disclosed herein, a respiratory therapy system is disclosed. The respiratory therapy system may comprise a flow source or generator adapted to provide a gas flow to a patient. The respiratory therapy system may comprise a sensor. In some configurations, the sensor may be adapted to measure a characteristic of the patient, such as but not limited to the patient's blood oxygen saturation. In some configurations, the sensor may be adapted to measure a characteristic of a respiratory gas. The sensor may be adapted to measure a first quantity of nitrogen inhaled by the patient Ni and a second quantity of nitrogen exhaled by the patient No. The respiratory therapy system may comprise a hardware controller. The hardware controller may be configured to control the flow generator to deliver a first flow therapy, receive the measured Ni and No and/or the measured blood oxygen saturation and/or other patient characteristics over at least one respiratory cycle, and control the flow generator to continue delivering the first flow therapy or to deliver a second flow therapy on the basis of a function of the measured Ni and No and/or measured blood oxygen saturation.
In some configurations, if the No is less than or equal to the Ni¬, plus a threshold nitrogen variance Np, the flow generator may be controlled to deliver the second flow therapy.
In some configurations, if the ratio of No:Ni is less than or equal to a predetermined nitrogen ratio Np_r, the flow generator may be controlled to deliver the second flow therapy.
In some configurations, different concentrations of gases may be delivered in the second flow therapy than in the first flow therapy.
In some configurations, during preoxygenation the first flow therapy may comprise delivery of a first gas composition comprising a first concentration of ambient gas Ga1 and a first concentration of oxygen Go1, and the second flow therapy may comprise delivery of a second concentration of ambient gas G¬a2 and a second concentration of oxygen Go2. In some such configurations, Go1¬may be greater than Go2. In some such configurations, the ratio of Go1 to (Ga1+Go1) may be greater than the ratio of Go2 to (Ga2+Go2).
Additionally, in accordance with certain features, aspects and advantages of at least one of the embodiments disclosed herein, a respiratory therapy kit is disclosed. The respiratory therapy kit may comprise a patient interface, a humidifier comprising an inlet adapted to be connected to a flow generator, and a conduit adapted to fluidly communicate or allow for fluid communication between the humidifier and the patient interface. The patient interface, the conduit and/or at least a part of the humidifier may be integrally moulded or in the form of a single part.
In some configurations, the humidifier may further comprise a fluid reservoir. In some such configurations, the respiratory therapy kit may further comprise a heating device. The heating device may comprise a chemical heater adapted to heat fluid in the fluid reservoir. The heating device may comprise a manually actuatable switch configured to activate the chemical heater.
In some configurations, the patient interface may comprise a port configured to accept a drug delivery device. In some such configurations, the respiratory therapy kit may comprise a drug delivery device adapted to be located in the port. The drug delivery device may comprise a manually actuatable metering mechanism configured to allow for the release of medication.
Additionally, in accordance with certain features, aspects and advantages of at least one of the embodiments disclosed herein, a respiratory therapy system is disclosed. The respiratory therapy system may comprise a respiratory therapy apparatus. The respiratory therapy apparatus may comprise a flow generator, a humidifier, and/or an integrated flow generator/humidifier apparatus. The respiratory therapy system may also comprise a patient interface configured to be removably attachable to a conduit, and a conduit adapted to extend between the respiratory therapy apparatus and the patient interface. The respiratory therapy apparatus and the conduit may be integrally moulded or be in the form of a single part.
In some configurations, the respiratory therapy system may further comprise a disinfection arrangement adapted to disinfect at least a section of the conduit. In some such configurations, the respiratory therapy system may further comprise a hardware controller configured to control the disinfection arrangement, wherein the hardware controller controls the disinfection arrangement dependent on whether or not the patient interface is attached to the conduit. In some such configurations, the respiratory therapy system may further comprise a hardware controller configured to control the disinfection arrangement, wherein the hardware controller is configured to activate the disinfection arrangement after removal of the patient interface from the conduit. In the above configurations or as demonstrated or implied elsewhere in this disclosure, the respiratory therapy system may further comprise a flow or pressure sensor. The hardware controller may be configured to, in use, utilize signals from the flow or pressure sensor or values derived therefrom (e.g. from the signals of the flow sensor or of the pressure sensor) to determine if the patient interface is or is not attached to the conduit. The signals may be used to, for example, help control the on/off state and/or the intensity of disinfection of the disinfection arrangement.
In some configurations, the respiratory therapy system may further comprise a one-way valve adapted to prevent the flow of exhaled gases into the conduit. The one-way valve may be positioned within the conduit.
The present disclosure relates to methods, apparatus and systems for estimating pre-oxygenation parameters for these patients. In particular, the present methods, apparatus and systems may be used to determine a sufficient level of pre-oxygenation, and/or predict the time required for the patient to be sufficiently pre-oxygenated and/or monitor the level of pre-oxygenation of the patient.
In accordance with certain features, aspects and advantages of at least one of the embodiments disclosed herein, a method is disclosed for estimating and/or determining one or more pre-oxygenation parameters for a patient undergoing pre-oxygenation therapy. The method disclosed comprises one or more of the following steps:
In some configurations, the pre-oxygenation parameters comprise:
In some configurations, the respiratory gas is one or more of oxygen, nitrogen, and carbon dioxide.
In some configurations, the step of measuring and/or tracking the concentration of one or more respiratory gases in the patient's expired gas is performed using a mass spectrometer.
In some configurations, the step of measuring and/or tracking the concentration of one or more respiratory gases in the patient's expired gas is performed using a gas analyser.
In some configurations, the gas analyser is one or more of an oxygen gas analyser, a nitrogen gas analyser, and a carbon dioxide analyser.
In some configurations, the step of measuring and/or tracking the concentration of one or more respiratory gases in the patient's blood is performed via pulse oximetry.
In some configurations, the tracer is introduced to the patient's respiratory tract via inhalation prior to delivery of the pre-oxygenation therapy.
In some configurations, the tracer is introduced to the patient's respiratory tract via inhalation during an initial warm-up phase of the pre-oxygenation therapy.
In some configurations, the tracer is one or more of nitrogen, helium, argon and sulfur-hexafluoride.
In some configurations, the concentration of the tracer is measured and/or tracked using one or more of:
In some configurations, the step of measuring and/or tracking the one or more physical properties of the patient's expired gas is used to estimate the fractional concentrations of one or more respiratory gases in the expired gas.
In some configurations, said one or more physical properties comprises:
In some configurations, said one or more measuring and/or tracking steps is performed continuously.
In some configurations, said continuous measurement and/or tracking is performed until the patient is sufficiently pre-oxygenated.
In some configurations, sufficient pre-oxygenation is indicated by a sustained end-tidal oxygen concentration and/or blood oxygen saturation level greater than 70%, preferably 87%.
In some configurations, sufficient pre-oxygenation is indicated by a sustained end-tidal oxygen concentration and/or blood oxygen saturation level greater than 95%.
In some configurations, sufficient pre-oxygenation is indicated by substantially steady-state concentration(s) and/or blood saturation level(s) of one or more respiratory gases and/or tracer.
In some configurations, the method further comprises the steps of:
In some configurations, the non-linear model is an exponential curve.
In some configurations, the treatment factor is four.
In some configurations, said time until sufficient pre-oxygenation is further multiplied by a safety factor.
In some configurations, the time constant is the time taken for the concentration of nitrogen in the expired gas to drop to substantially 37% of the concentration of nitrogen in the first measurement of expired gas.
In some configurations, the time constant is the time taken for the concentration of tracer in the expired gas to drop to substantially 37% of the concentration of tracer in the first measurement of expired gas.
In some configurations, the time constant is the time taken for the concentration of oxygen in the expired gas to increase by substantially 63% of the difference between the desired level (EtO2=87%) and the concentration of oxygen in the first measurement of expired gas. If the first EtO2 measurement was 50%, for example, then the time constant would be the time taken for the oxygen concentration to increase by (87-50)*0.63 percent.
In some configurations, the time constant is the time taken for the blood saturation of oxygen to increase by substantially 63% of the difference between the desired level (95% or greater, preferably 100%) and the patient's blood saturation of oxygen prior to or at the start of the pre-oxygenation procedure. For example, if there is a target final saturation level of 100% and the initial saturation level was 90%, then the time constant would be the time taken for the percentage saturation to increase from 90% to (90+(100−90)*0.63)=96.3%
In some configurations, the time constant is the quotient of dividing the patient's functional residual capacity by the patient's alveolar ventilation.
In some configurations, pre-oxygenation is delivered via high flow therapy.
In some configurations, pre-oxygenation is delivered via a sealed or unsealed nasal interface, preferably a nasal cannula.
In some configurations, apparatus is disclosed configured for estimating and/or determining one or more pre-oxygenation parameters, comprising one or more sensors configured to:
In some configurations, the pre-oxygenation parameters comprise:
In some configurations, the apparatus further comprises a processor configured to:
In some configurations, the apparatus further comprises a timer configured to indicate the estimated time remaining until the patient is sufficiently pre-oxygenated.
In some configurations, the apparatus further comprises a control interface or a connection to a control interface of a pre-oxygenation therapy apparatus or system providing pre-oxygenation therapy to said patient.
As relatively high gas delivery flow rates may be used with the embodiments or configurations described herein, the gases being supplied or delivered to the user or patient may be delivered to different parts of the user's or a patient's airway.
Delivering oxygen through high flow therapy e.g. flow rates above 10 L/min achieves pre-oxygenation to higher levels faster than traditional methods using a facemask with an oxygen reservoir, non-rebreather masks, self-inflating bag-valve-masks with or without 1-way valves. Other high flow rates are contemplated.
For example, according to those various embodiments and configurations described herein, a flowrate of gases supplied, such as a high flow rate, provided to an interface or via a system, such as through a flowpath, may comprise a gas flow rate of greater than 15 L/min (Liters per minute), greater than or equal to about 20 L/min, greater than or equal to about 30 L/min, greater than or equal to about 40 L/min, greater than or equal to about 50 L/min, greater than or equal to about 60 L/min, greater than or equal to about 70 L/min, greater than or equal to about 80 L/min, greater than or equal to about 90 L/min, greater than greater than or equal to about 100 L/min, greater than about or equal to 110 L/min, greater than about or equal to 120 L/min, greater than about or equal to 130 L/min, greater than about or equal to 140 L/min or up to about 150 L/min. In certain embodiments, useful ranges of a high gas flow can be selected between any of the aforementioned flow rates including but not limited to from about 40 L/min to about 80 L/min, from about 50 L/min to about 80 L/min, from about 70 L/min to about 100 L/min, about 70 L/min to about 80 L/min, about 100 L/min to about 150 L/min and about greater than 15 L/min to about 150 L/min and about 30 L/min to about 150 L/min. These flow rates can be provided using a patient interface and in certain embodiments through a nasal interface.
Such relatively high flowrates of gases may assist in providing the supplied gases into a user's airway, or to different parts of a user's airway, for example such flowrates may allow for a delivery of such gases to the upper or lower airway regions. Upper airway region typically includes the nasal cavity, pharynx and larynx, while the lower airway region typically includes the trachea, primary bronchi and lungs.
It should be understood that alternative embodiments may comprise any or all combinations of two or more of the parts, elements or features illustrated, described or referred to in this specification.
In accordance with at least one embodiment disclosed herein is a method of oxygenating a patient in relation to anaesthesia using high flow gas delivery comprising determining oxygenation requirements of the patient before or during anaesthesia.
In some configurations determining oxygenation requirements comprises one or more of:
Determining oxygenation requirements comprises determining oxygen concentration and/or oxygen flow rate.
In some configurations the stages of anaesthesia comprise one or more of:
In some configurations detecting the stage of anaesthesia by detecting breathing pressure to determine if the patient is: a) breathing and in the pre-oxygenation state, or b) not breathing and in the apnoeic stage.
In some configurations the method further comprises detecting the stage of anaesthesia by detecting the expired CO2 to determine if the patient is: a) breathing and in the pre-oxygenation state, or b) not breathing and in the apnoeic stage.
In some configurations monitoring O2 supply and/or CO2 removal comprises monitoring one or more of:
In some configurations the method further comprises controlling one or parameters of the high flow gas to assist oxygenation of the patient according to the oxygenation requirements.
In some configuration controlling one or more parameters of the high flow gas comprises controlling one or more of:
In some configurations the method further comprises, upon monitoring O2 supply and/or CO2 removal, increasing flow and/or oxygen concentration if:
In some configurations upon determining a short duration of one or more stages of anaesthesia, increasing the flow and/or oxygen concentration.
In some configurations the high flow gas is delivered and the oxygenation requirements are determined using a high flow therapy apparatus.
In accordance with at least one embodiment disclosed herein is a system for oxygenating a patient in relation to anaesthesia using high flow gas delivery comprising: a flow source, and a controller for determining oxygenation requirements of the patient before or during anaesthesia.
In some configurations determining oxygenation requirements comprises one or more of:
In some configurations the stages of anaesthesia comprise one or more of:
In some configurations the controller further detects the stage of anaesthesia by detecting breathing pressure to determine if the patient is: a) breathing and in the pre-oxygenation state, or b) not breathing and in the apnoeic stage.
In some configurations the controller further detects the stage of anaesthesia by detecting the expired CO2 to determine if the patient is: a) breathing and in the pre-oxygenation state, or b) not breathing and in the apnoeic stage.
In some configurations monitoring O2 supply and/or CO2 removal comprises monitoring one or more of:
In some configurations the controller further controls one or parameters of the high flow gas to assist oxygenation of the patient according to the oxygenation requirements.
In some configurations controlling one or more parameters of the high flow gas comprises controlling one or more of:
In some configurations the method further comprises the controller, upon monitoring O2 supply and/or CO2 removal, increasing flow and/or oxygen concentration if:
In some configurations upon determining a short duration of one or more stages of anaesthesia, the controller increases the flow and/or oxygen concentration.
In accordance with at least one embodiment disclosed herein is a system for oxygenating a patient in relation to anaesthesia using high flow gas delivery comprising: a flow source, one or more sensors to monitor parameters in order to establish: 1) oxygenation requirements, 2) stage of anaesthesia treatment 3), and/or O2 and CO2 changes, and a controller connected to the sensors for determining oxygenation requirements, stage of anaesthesia and/or O2, CO2 changes of the patient before or during anaesthesia.
In accordance with at least one embodiment disclosed herein is a system for oxygenating a patient in relation to anaesthesia using high flow gas delivery comprising: a flow source, one or more sensors to monitor parameters in order to establish: 1) oxygenation requirements, 2) stage of anaesthesia treatment 3), and/or O2 and CO2 changes, and a controller connected to the sensors and configured to determine changes in the parameters and modify one or more of the settings of the flow source and/or or control other parts of the system in order to compensate for the changes and allow for change in therapy dose.
In some configurations the information related to the patient can be accessed remotely from a database. Further the system can automatically provide therapy settings based on stored patient information. Also a clinician can remotely operate the system.
The term “comprising” as used in this specification means “consisting at least in part of”. When interpreting each statement in this specification that includes the term “comprising”, features other than that or those prefaced by the term may also be present. Related terms such as “comprise” and “comprises” are to be interpreted in the same manner.
The invention consists in the foregoing and also envisages constructions of which the following gives examples only.
Specific embodiments and modifications thereof will become apparent to those skilled in the art from the detailed description herein having reference to the figures that follow, of which:
6 shows a flow chart illustrating a respiratory therapy method.
The present disclosure relates to respiratory gas therapy systems, apparatus, kits and methods for treating patients undergoing intubation or endoscopy. The present disclosure also relates to apparatus, systems, and methods for estimating pre-oxygenation parameters for a patient undergoing pre-oxygenation respiratory gas therapy. The present disclosure also particularly relates to determining oxygenation requirements for a patient in relation to anaesthesia, and providing gas flow with parameters meeting the oxygenation requirements.
It is an object of certain embodiments disclosed herein to provide a method or apparatus which will go at least some way towards addressing the foregoing problems or which will at least provide the industry with a useful choice. It is also an object of one or more of the disclosed embodiments to determine and/or provide oxygenation requirements of a patient in relation to anaesthesia and/or to at least provide the public with a useful choice.
For the sake of convenience, certain features present or annotated with reference numerals in some figures of the present disclosure are not shown or annotated with reference numerals in other figures of the present disclosure. For example,
The present disclosure relates to methods, systems and/or apparatus to assist medical professionals with pre-oxygenation procedures, to reduce the risk of the patient becoming hypoxic or hypoxemic in the subsequent intubation procedure. The disclosure herein may provide for particular usefulness in medical procedures where a patient is sedated or for patients where respiratory drive is compromised or where a patient's respiratory drive has been purposely reduced.
The present methods, systems and/or apparatus are particularly useful for medical procedures where a patient is sedated, as they often stop spontaneous breathing. Additionally, the present methods, systems and/or apparatus may be useful for patients whose respiratory drive has been compromised or purposely reduced.
A continuous supply of oxygen is essential to sustain healthy respiratory function during anaesthesia. When this supply is compromised, hypoxia can occur. During anaesthesia, the patient is monitored to ensure this does not happen. If oxygen supply is compromised the clinician stops the medical procedure and facilitates oxygen supply. This can be achieved for example by manually ventilating the patient through bag mask systems.
In an improvement, (high) flow gas (e.g. oxygen or a mix of oxygen and one or more other gases) can be delivered to a patient to reduce the risk of hypoxia. This high flow gas can be provided prior to anaesthesia (pre-oxygenation) while the patient is still breathing, or during anaesthesia or anaesthesia procedures, including when the patient might be apnoeic. This gas flow might be provided at a constant flow rate to deliver the “dose” oxygen required (patient oxygen requirement) to avoid hypoxia. This dose can also be referred to as the required “therapy” or “support”. The dose relates to the one or more parameters of the high flow gas being delivered, and an optimal or required dose relates to the high flow gas parameters that provide a patient with their oxygen requirements. For example, the parameters might be (although are not limited to) one or more of:
In general terms, the dose/oxygen requirements are determined before anaesthesia and/or during (e.g. thorough continuous or periodic monitoring) anaesthesia; and then the parameters of the high gas flow are altered accordingly (manually or automatically) to provide the required oxygenation to the patient. It should be noted that reference to “anaesthesia” and its stages throughout this specification can refer to actual anaesthesia, and the period prior to anaesthesia (such as the pre-oxygenation stage).
With reference to the non-limiting exemplary embodiment shown in
The flow source 102 is configured to draw in ambient air or air outside of the system 100 and pass the air to the humidifier 104. In some configurations, the flow source 102 may comprise some other gas generation means. For example, in some configurations, the flow source 102 may comprise a container of compressed air or another gas and a valve arrangement adapted to control the rate at which gases leave the container. As another example, in some configurations, the flow source 102 may comprise an oxygen concentrator. In some configurations, the flow source 102 may be adapted to deliver a high flow therapy.
“High flow therapy”, “High gas flow” or “high gas flows” as used herein is defined as the volumetric movement of a portion/parcel of gas or mixtures of gases into the patient's airways at rates exceeding the fraction of inspired oxygen requirements at peak inspiratory flow demand. In particular, in one embodiment, high gas flow (or high gas flows) refers to gas flow rate of greater than 15 L/min (Liters per minute), greater than or equal to about 20 L/min, greater than or equal to about 30 L/min, greater than or equal to about 40 L/min, greater than or equal to about 50 L/min, greater than or equal to about 60 L/min, greater than or equal to about 70 L/min, greater than or equal to about 80 L/min, greater than or equal to about 90 L/min, greater than greater than or equal to about 100 L/min, greater than about or equal to 110 L/min, greater than about or equal to 120 L/min, greater than about or equal to 130 L/min, greater than about or equal to 140 L/min or up to about 150 L/min. In certain embodiments, useful ranges of a high gas flow can be selected between any of the aforementioned flow rates including but not limited to from about 40 L/min to about 80 L/min, from about 50 L/min to about 80 L/min, from about 70 L/min to about 100 L/min, about 70 L/min to about 80 L/min, about 100 L/min to about 150 L/min and about greater than 15 L/min to about 150 L/min and about 30 L/min to about 150 L/min. These flow rates can be provided using a patient interface and in certain embodiments through a nasal interface.
In any of the embodiments described herein, the high gas flow can be humidified. In some configurations the gas flow may be humidified to contain greater than 10 mg/L of water, or greater than 20 mg/L, or greater than 30 mg/L, or up to 44 mg/L. In some configurations the gas flow may be heated to 21° C. to 42° C., or 25° C. to 40° C., or 31° C. to 37° C., or about 31° C., or about 37° C.
The system 100 also comprises a housing 106 that at least partially houses both the flow source 102 and the humidifier 104 (e.g. the system 100 may comprise an integrated flow source/humidifier apparatus), although in some configurations the flow source 102 and humidifier 104 may have separate housings. A controller 108 is shown to be in electronic communication with the flow source 102 and the humidifier 104, although in some configurations the controller 108 might only communicate with the flow source 102 or the humidifier 104. The controller 108 may comprise a microcontroller or some other architecture configured to direct the operation of controllable components of the system 100, including but not limited to the flow source 102 and/or the humidifier 104. An input/output module 110 (such as a display and/or input device) is shown to be in electronic communication with the controller 108. The input device is for receiving information from a user (e.g. clinician or patient) that can be used for determining oxygenation requirements. The input/output module 110 may be configured to allow a user to interface with the controller 108 to facilitate the control of controllable components of the system 100, including but not limited to the flow source 102 and/or the humidifier 104. In some configurations the gas flow may be humidified to contain greater than 10 mg/L of water, or greater than 20 mg/L, or greater than 30 mg/L, or up to 44 mg/L. In some configurations the gas flow may be heated to 21° C. to 42° C., or 25° C. to 40° C., or 31° C. to 37° C., or about 31° C., or about 37° C. The input/output module 110 might comprise, for example, one or more buttons, knobs, dials, switches, levers, touch screens, speakers, displays and/or other input or output peripherals that a user might use to view data and/or input commands to control components of the system 100
As further shown in
As shown in
As shown the nasal cannula 116 also comprises a sensing module 120 adapted to measure a characteristic of gases passing through the nasal cannula 116, although the sensing module 120 could be positioned and adapted to measure the characteristics of gases at or near other parts of the system 100. For example, in some configurations, the sensing module 120 could be positioned in the nasal cannula 116 or upstream of the nasal cannula 116 (in some configurations proximal to the flow source 102). The sensing module 120 may comprise one or more sensors adapted to measure various characteristics of gases, including but not limited to pressure, flow rate, temperature, absolute humidity, relative humidity, enthalpy, gas composition, oxygen concentration, carbon dioxide concentration, and/or nitrogen concentration. For example, the sensing module may comprises one or more gas analyzers. Gas properties determined by the sensing module 120 may be utilized in a number of ways, including but not limited to closed loop control of parameters of the gases. For example, in some configurations flow rate data taken by a sensing module 120 may be used to determine the respiratory cycle of the patient to facilitate the delivery of flow in synchronicity with portions of the respiratory cycle. The sensing module 120 communicates with the controller 108 over a first data line 122. The first data line 122 may comprise a wired data communication connection such as but not limited to a data cable, or a wireless data communication connection such as but not limited to WiFi, Bluetooth, or NFC. Optionally, in some configurations, both power and data may be communicated over the same first data line 122. For example, the sensing module 120 may comprise a modulator that may allow a data signal to be ‘overlaid’ on top of a power signal. Optionally, the data signal may be superimposed over the power signal and the combined signal may be demodulated before use by the controller 108.
Additionally as shown, a physiological sensor module 121 may be present. The physiological sensor module 121 may be configured to detect various characteristics of the patient or of the health of the patient, including but not limited to heart rate, EEG signal, EKG/ECG signal, blood oxygen concentration, blood oxygen saturation (via, for example, a pulse oximeter), blood CO2 concentration, transcutaneous CO2 (TcCO2) and/or blood glucose. The physiological sensor module 121 may comprises a gas analyser. Similarly, the physiological sensor module 121 may communicate with the controller 108 over a second data line 123. The second data line 123 may comprise wired or wireless data communication connections similarly to the first data line 122, and both power and data may be communicated similarly. The physiological sensor module 121 may be used, for example, to determine the oxygenation of the patient such that a physician may know when to begin the process of intubating the patient or performing an endoscopic procedure on the patient. In some such configurations, a pulse oximeter may be used to determine the blood oxygen saturation of the patient. If the blood oxygen saturation increased to meet or exceed a threshold blood oxygen saturation level Tb, the system 100 may output an indication or alarm to a physician (via, for example, an output module of a user interface) indicating that the physician should begin the process of intubation or endoscopy.
With reference to the non-limiting exemplary embodiment shown in
In some cases, delivering a high flow gas therapy at a relatively high temperature, for example between about 21° C. and about 43° C., or between about 24° C. and about 43° C., or between about 27° C. and about 43° C., or between about 30° C. and about 43° C., or between about 33° C. and about 43° C., or between about 37° C. and about 43° C., and/or delivering a high flow gas therapy at a relatively high humidity, for example between about 24 mg/L and about 44 mg/L, or between about 29 mg/L and about 44 mg/L, or between about 34 mg/L and about 44 mg/L, or between about 39 mg/L and about 44 mg/L, or about 44 mg/L, can be beneficial for keeping a patient's airways relatively moist and healthy during an intubation process or an upper endoscopy, particularly if the process or endoscopy is prolonged due to, for example, a difficult airway. The high flow therapy may be continuously or discontinuously be delivered (at, for example, the flow rates and oxygen concentrations described above or elsewhere in this disclosure) during processes of intubation or endoscopy to prolong the apneic window during such processes.
When handling a patient that is to undergo intubation, particularly if the patient is or will be incapable of spontaneous respiration (for example, when sedated with a general anesthetic agent) and will be ventilated using gas therapy (e.g. high flow therapy through, for example, a nasal cannula) it is important to properly oxygenate the patient and maintain an acceptable blood oxygen saturation level. This may be particularly important for morbidly obese patients, who are more likely to quickly desaturate. In some cases it can also be useful to prevent a patient from being excessively oxygenated. A second consideration may be given to maintaining acceptable levels of carbon dioxide in the patient's blood and/or respiratory system. A third consideration may be given to reducing the gas flow rate used to deliver therapy if it can be shown that the gas flow rate used may be greater than the minimum necessary to maintain proper levels of oxygen saturation and carbon dioxide. A further consideration is to reduce the risk of barotrauma and/or gastric distension.
Accordingly, with reference to the non-limiting exemplary embodiment shown in
Step 204 comprises a check to ascertain if the patient is sufficiently oxygenated. This step may be practiced in a variety of ways, including but not limited to methods A and/or B as shown in
With further reference to step 204, in method B, the quantity of nitrogen gas inhaled by the patient (Ni) and the quantity of nitrogen gas exhaled by the patient (No) may be measured (for example, using the sensing module 120 described elsewhere with reference to
In some configurations, methods A and B of
In an alternative configuration, the system 100 and method may determine a ratio of inhaled oxygen to exhaled oxygen to determine if there is a sufficient amount of oxygenation of the patient. In this alternative, the controller 108 is adapted to measure a first quantity of oxygen inhaled by the patient Oi and a second quantity of oxygen exhaled by the patient Oo. The controller 108 is configured to control the flow source 102 to deliver a first flow therapy, receive the measured Oi and Oo over at least one respiratory cycle, and control the flow source 102 to continue delivering the first flow therapy or to deliver a second flow therapy on the basis of a function of the measured Oi and Oo.
The concentration/amount of inhaled oxygen Oi will be known because it is set by the controller 108. For example, the system will deliver a maximum of 99% oxygen as inhaled oxygen. The expired oxygen Oo can be measured by a sensor in the physiological sensing module 121. The expired oxygen will increase and approach about 90% at which point the patient has been oxygenated to an acceptable level. A lower acceptable level may be about 80%. At the acceptable level, the expired oxygen may reach a plateau. At that stage, the ratio of inhaled oxygen Oi to exhaled oxygen Oo will approach 0.90. The patient will also expired some water and some CO2. A lower acceptable level may be about 0.80. It will be understood that this process is limited to situations where the patient is breathing spontaneously.
With further reference to
In other configurations, the physician may be alarmed or informed that the intubation or endoscopy should be started based on some other sensed data (for example, data of various sensors described elsewhere in this disclosure) (for example, when data parameters meet or exceed predetermined or derived or calculated threshold values). In some configurations, and particularly if the patient is being deeply sedated with anaesthetic agents, the patient may not be spontaneously breathing. The second gas therapy T2 may be a gas therapy primarily configured to maintain adequate ventilation of the patient and manage dead space, including but not limited to anatomical dead space. The second gas composition C2 may comprise, for example, 80% air and 20% oxygen, although in other configurations other air/oxygen mixtures or just air (e.g. 100% air) or 100% oxygen may be used. In some configurations, the second gas composition C2 may comprise less oxygen than the first gas composition C1 (e.g. the first gas composition C1 may comprise a first level of oxygen Go1 which is greater than a second level of oxygen Go2 of the second gas composition C2). In some configurations, the second gas composition C2 may comprise more oxygen than the first gas composition C1 (e.g. the first gas composition C1 may comprise a first level of oxygen Go1 which is less than a second level of oxygen Go2 of the second gas composition C2). In some configurations, the second gas composition C2 may comprise more air than the first gas composition C1 (e.g the first gas composition C1 may comprise a first level of ambient gas Ga1 which is less than a second level of ambient gas Ga2 of the second gas composition C2). In some configurations, the ratio Go1:(Ga1+Go1) may be greater than the ratio Go2:(Ga2+Go2).
In step 210, a check may be made to see if the patient is adequately oxygenated. The blood oxygen saturation Osat may be determined (for example, using the physiological sensor module 121 described elsewhere with reference to
In step 212, a check may be made to see if the second gas therapy T2 has been effective at managing the patient's blood carbon dioxide, ventilation, and/or dead space. Many tests or determinations for these variables may be utilized. In some cases it may take time before the effect of the second gas therapy T2 on the above can be determined. In some configurations, a first Boolean value E1 may be generated in response to determining if the patient's blood carbon dioxide CO2_m (which may be found, for example, using the physiological sensor module 121 described elsewhere with reference to
If (E1=false) and (E2=false), it may be that the second gas therapy T2 has not been delivered for long enough to achieve an acceptable CO2_m, and step 208 may be practiced again. If (E1=true) and (E2=false), the second gas therapy T2 may have been delivered for long enough and/or at a high enough flow rate to achieve an acceptable CO2_m, but it may be useful to allow for additional time for the measured or determined CO2_m to normalize or be verified after a number of measurements, and so step 208 may be practiced again, although in some configurations, the method 200 may practice step 214 instead. If (E1=false) and (E2=true), it may be that the flow rate F2 delivered is too low or otherwise is not sufficiently effective. A new flow rate F2 may be calculated in step 218. The new flow rate F2 may be higher than the previously used flow rate F2, and in some configurations the first threshold time to may be altered. The composition of the gas may have more oxygen than the previously used gas. The method 200 may then loop back to step 206. If (E1=true) and (E2=true) it may be determined that the delivered flow rate F2 is sufficient and that enough time t has passed, and so step 214 may be practiced. Oxygen saturation can be used as a proxy measurement for blood CO2 since it is easier to measure O2 saturation.
In step 214, it may be found that the flow rate F2 is higher than it needs to be. If a second threshold time 42 has been met or passed since the time count variable t was initialized in step 206 (e.g. if t≥tt2), a new flow rate F2 may be calculated in step 216. The new flow rate F2 may be less than the previously used flow rate F2, and may be a percentage of the previously used flow rate or may be some other new flow rate F2. If (t<tt2), it may be determined that not enough time has passed to determine if the flow rate F2 is higher than necessary, and step 208 may be practiced again.
As an alternative to steps 206 onwards, the flow may be set to a predetermined level eg: 30 lpm, and maintained at that level until the patient is oxygenated (according to step 204) and then user is notified that the patient is oxygenated. In this alternative, there is no change in the flow rate, no change in the composition of the gas, and no time monitoring.
The flow rate may be increased if sufficient oxygenation is not occurring within the expected time frame, for example 3 or 5 minutes. In this case the monitoring after apnea would not proceed (ie: steps 206 onwards).
Flow may be increased by user once the patient is asleep or at the onset of apnea, for example to 70 lpm. Or the clinician may notify the system that patient is asleep or an increase in flow is required and the system automatically increases the flow to 70 lpm, for example.
In addition, other systems and/or kits may be useful for delivering flow therapy (e.g. high flow therapy) to patients undergoing, for example, intubations or upper endoscopies.
The patient-facing outlet 140 of the conduit 112 may connect to the gas inlet 142 of the nasal cannula 116 through a variety of attachment mechanisms known to those skilled in the art, including but not limited to latch/catch arrangements or bayonet fittings.
The system 100 comprises a disinfection arrangement 135 adapted to disinfect at least a section of the conduit 112, although in some configurations the disinfection arrangement 135 may not be present. The disinfection arrangement 135 may be, for example, attached to the conduit 112. The disinfection arrangement 135 may comprise, for example, one or more electromagnetic radiation emitters (positioned inside the conduit 112, for example). The one or more emitters may comprise an ultraviolet light source (e.g. UV LED), a microwave emitter, and/or some other radiation emitter configured to sterilize at least a portion of the gas flow path inside the conduit 112. In some configurations, the system 100 can be controlled to channel high temperature gases through the conduit 112 to assist in disinfection. The high temperature gases may be configured to carry enough moisture to increase the total enthalpy of the gases, further promoting disinfection of the conduit 112. In some configurations, the system 100 can be controlled such that a conduit heater of the conduit 112 is activated to assist in disinfection. Means for sterilizing the gas flow path can reduce concerns of patient infection through the introduction of undesired pathogens.
As further shown in
A one-way valve 138 is shown in
In some cases, then, the systems, apparatus, kits and methods shown or implied in the disclosure with reference to
In other cases, it may be that a medical professional treating the patient may wish to use a partially or fully disposable kit to oxygenate and/or treat the patient with flow therapy (e.g. high flow therapy). In
The respiratory therapy kit 300 may comprise a heating device 314. The heating device 314 may be adapted to heat water in the reservoir 308. The heating device 314 may be non-permanently attachable to the reservoir 308, may be permanently attached to the reservoir 308 or may be integrally moulded with at least a portion of a wall of the reservoir 308. The reservoir 308 may comprise, for example, a latch 316 that may be joined with a catch 318 attached to the heating device 314, or vice versa. The heating device 314 may comprise a chemical heater. The chemical heater may comprise, for example, a reservoir 322 configured to contain a quantity of a reactive reagent liquid such as but not limited to water and a bubble or payload 324 comprising a quantity of a reactive reagent solid such as but not limited to magnesium metal encased by a layer or membrane adapted to isolate the reactive reagent solid from the reactive reagent liquid. The heating device 314 may comprise a manually actuatable switch 320 adapted to allow for a user to activate the heating device 314. For example, the manually actuatable switch 320 may comprise a rod 326 comprising a sharp end 328 adapted to pierce the membrane of the payload 324 and a button 330. Pressing on the button 330 may force the sharp end 328 to thrust towards the payload 324 and pierce the membrane, exposing the reactive reagent solid to the reactive reagent liquid and causing an exothermic chemical reaction that may heat water in the reservoir 322. The button 330 may be biased with a spring or other biasing mechanism to prevent accidental and/or premature piercing of the membrane of the payload 324. The use of a relatively small volume of water in the reservoir 308 promotes a relatively quick heat up and dispersal of moisture into gases passing through the humidifier 302.
With further reference to
With reference to
The method described in relation to
After saturation, also maintain blood CO2 levels as low as possible, and warn the clinician if the levels rise above a threshold level.
The physiological parameters of the patient are monitored by the physiological sensor module 121. The specific signals used from the physiological sensor module 121 in this method are the partial pressure of oxygen and the partial pressure of CO2 in the patient (both are measured by the transcutaneous monitor), and the blood oxygen saturation.
It will be understood that the method described in relation to
The figures shown and referred to in relation to
The method starts at 401. In step 403, the patient's BMI is determined.
In step 405, the blood oxygen saturation level is measured by the physiological sensor module 121. In step 409, if the blood oxygen saturation level is below 92% on room air, the system provides a warning to the physician in step 411. This might be an audible warning, or a warning displayed on the display screen of the controller input/output module 110.
In step 405, the transcutaneous CO2 reading is also measured by the physiological sensor module 121. If this is greater than 45 mmHg (step 413), the module provides a warning to the physician in step 415. This might be an audible warning, or a warning displayed on the display screen of the controllerinput/output module 110.
The transcutaneous O2 reading is measured by the physiological sensor module 121.
In step 407, the values are displayed.
For patients of BMI<27, an initial humidified flow of 60% oxygen, 40% nitrogen is supplied through the cannula at 30 l/min (step 417). This corresponds to a mix of 50% oxygen, 50% air.
For patients of BMI between 27 and 35 (step 419), an initial humidified flow 60% oxygen, 40% nitrogen is supplied through the cannula at 451/min(step 421). This corresponds to a mix of 50% oxygen, 50% air.
In step 423, for patients of BMI above 35, an initial humidified flow of 60% oxygen, 40% nitrogen is supplied through the cannula at 55 l/min (step 425). This corresponds to a mix of 50% oxygen, 50% air.
In step 427, automatic titration for phase 1 is started and the preoxygenation timer is started to monitor the preoxygenation time (step 429). The time is displayed by the controller input/output module 110 at 1 sec intervals.
The At step 429, the blood oxygen saturation, transcutaneous O2, and Transcutaneous CO2 of the patient are measured and displayed at 30 second intervals by the physiological sensor module (step 429).
At each 30 second interval (step 431) measurements of blood oxygen saturation level, transcutaneous O2, and Transcutaneous CO2 are made by the physiological sensor module 121 at step 433, displayed at step 435, and stored in the controller 108.
In step 437, if the oxygen saturation level is lower than 99%(437),% and if the transcutaneous O2 level is lower than 380 mmHg (in step 439) then the measured transcutaneous O2 level is compared with the measurement made 30 sec earlier in step 441. If the new transcutaneous O2 level is less than the old transcutaneous O2 level plus 15 mmHg, the oxygen content in the gas composition is increased at step 443. For example, if the initial transcutaneous O2 reading was 155 mmHg and the new reading after 30 seconds was less than 160 mmHg, the oxygen content in the gas supplied to the cannula might be increased by 5% to 65% and the nitrogen content would then be consequently decreased to 35%—this corresponds to a gas mix of 43.75% air and 56.25% oxygen.
In step 445, if transcutaneous O2 is equal or greater than 380 mmHg, the oxygen concentration in the flow to the cannula is not adjusted.
In step 437, if the oxygen saturation is equal to or greater than 99%, the oxygen concentration in the flow to the cannula is not adjusted.
In step 445, if the transcutaneous CO2 level is greater than 30 mmHg, then, the measured transcutaneous CO2 level is compared with the measurement made 30 sec earlier (in step 447). If the new transcutaneous CO2 level is greater than the old saturation level minus 2 mmHg, the oxygen content in the gas composition is increased (in step 449). For example, if the initial transcutaneous CO2 reading was 40 mmHg and the new reading after 30 seconds was greater than 38 mmHg, the oxygen content in the gas supplied to the cannula might be increased by 5% to 65% and the nitrogen content would then be consequently decreased to 35%—this corresponds to a gas mix of 43.75% air and 56.25% oxygen.
In step 445, if the transcutaneous O2 level is less than or equal to 30 mmHg, the oxygen concentration in the flow to the cannula is not adjusted.
In step 451, the measured blood oxygen saturation level is compared with the blood oxygen saturation level measured 30 sec earlier.
If the blood oxygen saturation level has fallen, then a warning is given (in step 453). This might be an audible warning or a warning displayed on the screen of the physiological sensor module 121. If the blood oxygen saturation level has not fallen, then a warning is not given (step 453).
If the blood oxygen saturation is greater than or equal to 99% AND the transcutaneous CO2 reading is less than or equal to 30 mmHg (at step 455), then, at step 457 a message to indicate the end of the pre-oxygenation phase is displayed on the display of the physiological sensor module (457).
If those conditions are not met, a new set of measurements is taken by the physiological sensor module 121 after a 30 sec interval (in step 431), and the automatic titration method for preoxygenation continues (in step 433).
At any point during the Phase 1 method, the clinician may disengage automatic control of the oxygen concentration and flow rate applied to the cannula and then manually adjust the concentration of oxygen in the flow to the cannula and the flow rate while observing the physiological measurements. During this time, the rate of measurement and display of physiological parameters increases to once every 10 seconds. When this adjustment has been made, the clinician has the option of re-engaging automatic control of these quantities. The method then restarts from the beginning of section j.
When the display of the controller input/output module 110 indicates that preoxygenation is complete, the clinician may move on to anaesthetise and paralyse the patient.
Phase 2 (Patient is Apnoeic)
When the patient has lost consciousness and paralysis has taken effect, the clinician indicates this to the controller (108 in step 469), for example, by pressing a button or other means (in step 471). The controller 108 now stops executing the part of the method for Phase 1 of the procedure and enters the method for Phase 2. It sets initial conditions for Phase 2 (step 473).
For patients of BMI<27 (step 475), an initial humidified flow of 95% oxygen, 5% nitrogen is supplied through the cannula at 70l/min.
For patients of BMI between 27 and 35 (step 479), an initial humidified flow 95% oxygen, 5% nitrogen the supplied through the cannula at 80l/min.
For patients of BMI above 35 (step 479), an initial humidified flow of 95% oxygen, 5% nitrogen is supplied through the cannula at 90l/min.
The physiological sensor makes initial measurements (for Phase 2) of the oxygen saturation level of the blood, the transcutaneous O2, and the transcutaneous CO2 and these values are stored in the controller (in step 483).
Throughout Phase 2 of the procedure, the physiological sensor module 121 makes measurements of the oxygen saturation level of the blood, the transcutaneous O2, and the transcutaneous CO2 (other parameters may also be measured) at 10 second intervals (step 489). The values are displayed and stored in the controller 108.
When each new set of measurements is made, the controller 108 calculates the average rate of change of the measured parameters over the past three readings (step 491), and the rate of change of the parameters since the last reading (step 493). These values are used together to determine if the rate of change of each parameter is increasing or decreasing with time.
At each 10 second interval (step 485) if the blood oxygen saturation level is less than 92% (in step 495), then a warning is given to the clinician (in 497). This may an audible warning, or indicated on the controller, the display of the input/output module 110, or both.
If the blood oxygen saturation level is not less than 92% (in step 495), then a warning is not given to the clinician.
If the average rate of change of blood oxygen saturation is negative (in step 499), and if the rate of change of blood oxygen saturation is increasing (in step 501), then the flow is increased to 100 l/min and the concentration of oxygen in the flow is increased to 99%, with the remaining 1% of gas supplied being nitrogen (in step 503).
If the rate of change of blood oxygen saturation level is not increasing, and if the flow is less than 100 l/min (in step 509), then, the flow is increased by 5 l/min (in step 511).
If the flow is 100 l/min, and if the oxygen concentration in the flow is less than 99% (step 513), then the oxygen concentration is increased by 1% (in step 517) with a consequent decrease in the nitrogen concentration.
If the oxygen concentration is 99% (in step 513), a warning is given to the clinician that the patient it not responding to increases in oxygen concentration and flow (in step 515). This warning may be audible, or it may be displayed on the display of the controller, or it may be both.
If the average rate of change of blood oxygen saturation is zero or positive (in step 499) and if the average level of blood oxygen saturation is 99% or greater (in step 505), then the concentration of oxygen in the flow is reduced by 1% (in step 507) with a consequent increase in the concentration of nitrogen. If the average level of blood oxygen saturation is less than 99% (in step 505), then no change is made to the concentration of oxygen in the flow.
At any time during the method from step 485 onwards, the clinician may disengage automatic control of the gas composition and flow supplied to the cannula and make manual adjustments (steps 519 and 521). Under these circumstances, the rate of measurement and display of physiological parameters (in step 523) increases to once per second (in step 525). The clinician is then able to re-engage automatic control of the gas composition and flow to the cannula (in step 527). The Phase 2 method then restarts at step 485.
With reference to
Additionally or alternatively, the present methods, systems, and/or apparatus may be used to determine the likelihood of the pre-oxygenation procedure achieving a target end-tidal oxygen level for the patient. Additionally or alternatively, the present methods, systems and/or apparatus may be used to determine and/or monitor the end-tidal oxygen level of a patient undergoing the pre-oxygenation procedure. Additionally or alternatively, the present methods, systems and/or apparatus may be used to determine if a patient has been sufficiently pre-oxygenated during the pre-oxygenation procedure. Additionally or alternatively, the present methods, systems and/or apparatus may be used to determine and/or monitor changes in the pre-oxygenation level of a patient undergoing the pre-oxygenation procedure.
The present method may involve measuring and/or tracking the concentration of one or more respiratory gases in the patient's expired gas. Pre-oxygenation can also be thought of as de-nitrogenation, as it is the nitrogen within the lungs that is being displaced by a high inspired oxygen concentration. End-tidal oxygen and/or nitrogen can therefore be measured to give an indication on the progression of pre-oxygenation.
The gas analysers may be used to measure the concentration of the respiratory gas(es) to be monitored. Specific gas analyser, for example, an oxygen gas analyser or a nitrogen gas analyser may be used to track the end-tidal concentration of the relevant gas.
Mass spectrometry may be used to measure the fractional concentrations of the different gases in the patient's expired gas (which is collected for analysis). One or more of these time-varying concentrations may be monitored.
Measurement and/or tracking of the concentration of the one or more respiratory gas may be performed substantially in real time.
Continuous gas measurements could also be used. For example, oxygen and nitrogen could be continuously measured during breathing throughout the pre-oxygenation procedure.
Additionally or alternatively, the present method involves measuring and/or tracking the concentration of one or more respiratory gases in the patient's blood (i.e., the blood saturation of the one or more gas). For example, the oxygen saturation of the patient's blood may be measured via pulse oximetry. Other methods of measuring the concentration of oxygen or other gases in the patient's blood may be utilised.
Sufficient pre-oxygenation is indicated by and/or corresponds to a stable or sustained (i.e., steady-state, plateau phase) end-tidal oxygen level and/or blood oxygen saturation level greater than 70%. In some configurations, sufficient pre-oxygenation is indicated by and/or corresponds to a sustained end-tidal oxygen level and/or blood oxygen saturation level greater than 90%. An example is shown in
Sufficient pre-oxygenation is indicated by and/or corresponds to a stable or sustained (i.e., steady-state, plateau phase) end-tidal nitrogen level that is minimal or close to zero, as nitrogen is replaced with oxygen. An example is shown in
Additionally or alternatively, the present method involves measuring and/or tracking the concentration of a tracer introduced to the patient's respiratory tract.
A tracer may be introduced into the lungs and the time to wash it out could be determined to monitor the pre-oxygenation level. Measuring and/or monitoring the concentration of the tracer in the patient's expired gas could be used to indicate when pre-oxygenation is complete. This will generally be at the point where there is substantially no tracer left.
Accordingly, in some configurations, sufficient pre-oxygenation is indicated by and/or corresponds to a stable or sustained (i.e., steady-state, plateau phase) end-tidal tracer level that is minimal or close to zero.
Tracers need to be highly insoluble in water (so they are not taken into the bloodstream) and readily diffusible (so they can be mixed with the air in the lungs). Examples of tracers which may be used include nitrogene, helium, argon and sulfur-hexafluoride, or any suitable combination thereof.
The tracer may be inhaled by the patient before the pre-oxygenation procedure is initiated.
The tracer may be inhaled by the patient during an initial warm-up phase of the pre-oxygenation therapy.
The concentration of the tracer in the patient's expired gas may be measured and/or monitored using, for example, an emission spectrometer, an ultrasonic gas analyser, or a respiratory mass spectrometer.
Additionally or alternatively, the present method involves measuring and/or tracking one or more physical properties of the patient's expired gas. Since pre-oxygenation results in changes to the gas mixture (e.g., decrease in nitrogen, increase in oxygen), the composition of the expired gas mixture may be correlated with the level of pre-oxygenation.
Physical properties of the gas mixture (e.g. density, viscosity, acoustic response etc.) could be measured to determine when the gas mixture has changed to the desired composition (e.g., from mainly nitrogen to mainly oxygen). Accordingly, such measurements may be used to estimate and/or monitor the fractional concentrations of the different respiratory gases in the patient's expired gas.
The concentration measurement(s) obtained via the methods described above over time may be displayed to the user, thus allowing the user to make an informed decision on the patient's pre-oxygenation state.
The concentration measurement(s) over time may be monitored, and when the measurement(s) has/have been in plateau for a certain amount of time (i.e., the measurement(s) reaches steady-state), this may indicate successful pre-oxygenation.
Further, if inspired oxygen is measured and is lower than what is being delivered from the source (due to air entrainment), the difference could be used as an indication of what the likely end-tidal oxygen value will be.
Further, instead of, or in addition to continuously monitoring the concentration measurement(s), measurement(s) obtained at or around the initial phase of the pre-oxygenation procedure may be used to predict the time remaining until sufficient pre-oxygenation.
Accordingly, in some configurations, the measurement(s) of the expired concentration and/or blood saturation of the one or more respiratory gases and/or tracer obtained at the initial phase of the pre-oxygenation procedure may be used to estimate the rate of change of these parameters. The rate of change may be fitted to a non-linear mathematical model. The time constant for the model may be calculated and multiplied with a treatment factor to estimate the time until sufficient pre-oxygenation may be achieved.
In one example, the change in oxygen concentration can be described by an exponential wash-in curve as it displaces nitrogen in the lungs. Conversely the change in nitrogen concentration can be described by an exponential wash-out curve as nitrogen is displaced from the lungs. These can be seen in
Once a suitable model is determined, the prediction methodology may be implemented in different ways, two of which will be described in more detail below.
In a first exemplary method, the interface supplying the pre-oxygenation flow to the patient is applied and pre-oxygenation therapy is initiated. The relevant expired gas level (i.e., one or more of oxygen, nitrogen, tracer, etc., as described above) is measured from the patient's first breath, and used as the baseline value for subsequent calculations. The method may be modified to incorporate one or more suitable methods for determining the patient's breath phase.
Using the first expired gas measurement as the baseline value, the time constant can be obtained. In the case of a wash-out curve (e.g., nitrogen, tracer, etc.), the time constant is the time taken for the measurement to drop to approximately 37% of its baseline value. For the oxygen wash-in curve, the time constant is the time taken for the measurement to increase by approximately 63% of the difference between the desired level and the level of the first expired gas measurement. It should be understood that these constants (and any other constants listed as examples in this specification) are approximations and may be varied according to the accuracy required. For example, a value between the range of 33% to 41% may be used for wash-out and a value of 59% to 67% may be used for wash-in.
The time constant may be multiplied by a treatment factor to obtain an estimate of when the wash-out or wash-in process is approximately 98% complete. In the example where an exponential curve is used to model the change in the expired gas level, a suitable treatment factor is four. Accordingly, this calculation could be used as the prediction for the remaining time left to pre-oxygenate the patient (i.e., an indication of the time until sufficient pre-oxygenation may be achieved).
There may be an optional step to multiply the 98% complete time with a safety factor. The safety factor may, for example, be an additional 20% to 50% of the estimated time.
The measurement(s) may be stopped once the level has dropped to approximately 37% of its baseline value (for wash-out models) or increased by approximately 63% of its baseline value (for wash-in models), since the model may be sufficient for predicting subsequent changes to the relevant gas levels.
Alternatively, the relevant expired gas concentration may be monitored throughout the pre-oxygenation process and the predicted time may be adjusted as the process continues. At the 98% complete time, the monitored value(s) may be assessed to see if the value(s) has/have stabilised and is pre-oxygenation is complete.
In a second exemplary method, the time constant may be estimated by dividing the patient's functional residual capacity by the patient's alveolar ventilation.
The patient's functional residual capacity may be estimated using several methods, including nitrogen washout tests, helium dilution, body plethysmography, and/or using a look up table (which may, for example, estimate that the functional residual capacity of a healthy patient is approximately 30 mL/kg and the functional residual capacity of an obese patient is approximately 15 mL/kg).
In one embodiment, the estimated value may be calculated by or input into a control interface of the pre-oxygenation therapy system or apparatus. Further, if the patient's weight is required to estimate the functional residual capacity, his/her weight may be input into the control interface or otherwise obtained (e.g., via weighing scales built into the hospital bed).
The patient's alveolar ventilation may be estimated using the following formula:
Alveolar Ventilation=(Tidal Volume×Respiratory Rate)−(Dead Space Volume×Respiratory Rate)
The patient's tidal volume may be measured and/or monitored using any suitable method, e.g. spirometry, etc.
The patient's respiratory rate may be measured and/or monitored using any suitable method, e.g. pheumography, using a stethoscope, etc.
The patient's dead space volume may be estimated using several methods including nitrogen washout tests, measuring expired CO2, estimating using the Bohr equation, or using a look up table (which may, for example, estimate that the dead space volume of a healthy patient is approximately 2 mL/kg).
The time constant is estimated as the quotient of the patient's functional residual capacity divided by the patient's alveolar ventilation. As with the first exemplary prediction method, the time constant may be multiplied by a treatment factor (e.g., four for an exponential model) to obtain an estimate of when the wash-out or wash-in process is 98% complete. Accordingly, this calculation could be used as the prediction for the remaining time left to pre-oxygenate the patient (i.e., an indication of the time until sufficient pre-oxygenation may be achieved).
Similarly, there is an optional step to multiply the 98% complete time with a safety factor.
Additionally, there is also an optional step to monitor one or more expired gas concentration throughout the process and adjust the pre-oxygenation time as the process continues. At the 98% complete time, the monitored value(s) may be assessed to see if the value(s) has/have stabilised and is pre-oxygenation is complete.
It should be noted, although the wash-in and wash-out process may generally be modelled as exponential processes, this is only one example. Under different respiratory support methods (CPAP, high flow, etc.) the process may be more accurately modelled using a different nonlinear function. Subsequently, the estimation of the time constant, and treatment of the time constant could be different depending on the treatment method.
The present disclosure also relates to suitable apparatus and systems for implementing the methods described. Specifically, the apparatus/system may comprises at least one or more sensors to measure and/or track one or more of the following: the concentration of one or more respiratory gases in the patient's expired gas, the concentration of one or more respiratory gases in the patient's blood (i.e., blood saturation), the concentration of a tracer introduced to the patient's respiratory tract, or one or more physical properties of the patient's expired gas.
The apparatus/system may further comprise a processor configured to fit the rate of change of the patient's expired concentration and/or blood saturation of said one or more respiratory gases and/or tracer to a non-linear model, determine a time constant for said model, multiply the time constant with a treatment factor to estimate the time until sufficient pre-oxygenation may be achieved, and indicate when the patient has been sufficiently pre-oxygenated.
The processor may be integral with or connected to the control interface of the pre-oxygenation therapy system, to obtain input from the control interface and/or to control the control interface.
The processor may further comprise a countdown timer configured to indicate to the medical professional the estimated time remaining until the patient is sufficiently pre-oxygenated. The timer may have a suitable user interface, for example in the form of coloured lights (e.g., red indicates that the patient should continue to be pre-oxygenated, orange indicates nearing adequate pre-oxygenation and green indicates that pre-oxygenation is complete). There could also be an audial (e.g., audio) or other visual indication when pre-oxygenation is complete. Haptic feedback may also be provided, optionally in combination with other types of indicators.
Pre-oxygenation may be delivered via high flow therapy. Further, pre-oxygenation (whether high flow or not) may be delivered to the patient via a nasal cannula. Delivering high flows of oxygen gas (for example, flows as high as 60 L/min) via a nasal cannula, may be more effective at rapidly pre-oxygenating the patient and can be used to effectively manage the volume of anatomical deadspace (e.g. the volume of gases in the airway of the patient that can potentially be re-breathed) such that rises in blood carbon dioxide concentration can be minimized.
Alternatively, pre-oxygenation may be delivered using other methods, including a facemask with an oxygen reservoir, non re-breather masks, self-inflating bag-valve-masks with or without one-way valves.
Delivering oxygen through high flow therapy e.g. flow rates above 10 L/min can achieve pre-oxygenation to higher levels faster than traditional methods using a facemask with an oxygen reservoir, non re-breather masks, self-inflating bag-valve-masks with or without 1-way valves. Other high flow rates are contemplated, such high flow rates being those as described herein.
Flows delivered can be humidified to minimize potential tissue damage that might occur from the delivery of high flows of dry gas for a prolonged period of time. Referring to
The system/apparatus of
In the embodiment of
Referring to the flow diagram in
The controller 108 is configured to carry out the determination of oxygen requirements and to control the parameters of high gas flow in accordance with that determination. First, during a pre-anaesthesia stage, the controller 108 determines oxygenation requirements of the patient, step 171. These can be oxygenation requirements that are based on the prediction of what might be required before and/or during anaesthesia based on historical/empirical data. The controller 108 receives input from the sensors 158a-158d and/or the user via the input interface 110. From that input and/or stored data (such as look up tables, historical data, parameters, relationships, the graphs or the like) the controller 108 determines the oxygenation requirement, step 171. The determination could take place through any processing, look up table, relationship (empirical or mathematical) or the like. Non-exhaustive examples of such input and determination processing are as follows. One or more alone or in combination could be used to make the oxygen requirement determination.
The user (such as anaesthetist or other clinician, or the patient) provides, input via the interface 110, a pre-operative assessment to estimate the level of risk for every patient. This level of risk relates to the risk of the patient entering hypoxia during anaesthesia. The controller 108 then determines oxygenation requirements, step 171, based on the level of risk and/or the user (e.g. anaesthetist or clinician) provides input indicative of the actual oxygenation requirement and/or dose/therapy settings and/or the actual parameter settings for the high flow gas delivery. Any of the input could be provided as a setting or range of settings or as one or more input values. The system could alert the user of the recommended settings or control the system to provide the settings, as to be described later.
Alternatively or additionally, and more generally, the user enters information from which oxygenation requirements can be determined, such information not necessarily directly indicating risk levels, or not being indicative of risk levels at all.
Sensor input could be used alternatively or additionally.
Next, once oxygenation requirements are determined, the controller 108 operates the flow source 102, humidifier 104 and/or other aspects of the system 100 to control the parameters of the high flow gas 153 delivered to the patient, step 172, so that the gas flow 153 meets the oxygenation requirements during a pre-anaesthesia (pre-oxygenation) stage. This can comprise altering one or more of:
Examples of user input for determining oxygenation requirements and the resultant parameter settings are as follows.
The user enters the value on a scale. For example the user could choose a number from 1 (minimal risk) to 10 (high risk). The system could then choose the optimal settings for that scale number.
The user enters information such as age, weight, BMI, lung volumes, metabolic rate, body fat measure (e.g. percentage) and/or other patient factors that could be used individually or any combination to choose the optimal therapy settings (oxygen requirements). For example, a sum score method could be used with two or more of the factors listed. This can be used to predict the level of support (oxygenation) that will be required
The user enters pre-existing patient conditions. For example, if a patient is at risk of barotrauma the flow could be minimised to meet peak inspiratory demand but not deliver excess flow.
Existing limits on hardware could be used to choose the optimal therapy settings. For example, if the surgical environment is experiencing a shortage in oxygen the settings could be altered. 100% oxygen could be delivered only during inspiration and the flow could be set to meet the patient's peak inspiratory demand to ensure minimal wastage
Different levels of support could be optimal in different stages of undergoing anaesthesia. The high flow system 100 can optionally detect when a change in stage has occurred and alert the user or automatically determine new oxygenation requirements and/or change the gas flow parameters to me those new requirements. For example, after the pre-oxygenation stage, the patient is administered the anaesthesia and enters and anaesthesia stage. Breathing function can diminish and the patient can become apnoeic. Different oxygenation requirements exist to those pre-anaesthesia.
Therefore, the controller 108 is further configured to detect the anaesthesia stage (or change in anaesthesia stage), step 173. Possible methods for detecting a change in state are as follows.
The controller 108 uses the pressure waveform (from a pressure sensor) to detect when the patient is breathing or not (e.g. transition from pre-oxygenation to apnoea).
The controller 108 uses the expired CO2 waveform (form a sensor) to detect when the patient is breathing or not (e.g. transition from pre-oxygenation to apnoea)
While the controller 108 is monitoring the state, step 162, the high flow gas 153 is delivered as per the parameters previously determined and set. After a change in stage is determined (such as transitioning from the pre-oxygenation stage to the anaesthesia stage) the controller/system 108/100 can continue delivering gas flow 153 with the same parameter settings. However, the system 100 can also go into a monitoring phase, step 174, wherein by the oxygenation requirements are re-determined, optionally in a continuously or periodic manner, step 174. Again previous or fresh input from a user via the input interface 110 can be used to determine the oxygenation requirements, in addition or alternatively to using sensor input 158a-158d. The oxygenation requirement can be determined in the same manner as described above for the pre-oxygenation stage, with the possible difference being that it is re-determined continuously or periodically based on updated input from the sensors and/or user.
The gas flow 153 parameters are then adjusted by the controller 108 to meet new oxygen requirements, these parameters being the same as described above, step 175. Even if updated input is not received, the oxygenation requirement might be re-determined on the basis that the stage of anaesthesia has changed, or alternatively the oxygenation requirement is not specifically re-determined, but a different oxygenation requirement is presumed and the high flow gas parameters are set accordingly for the new stage.
A particular non-limiting example of the function due to change in anaesthesia state is shown in
A continuous supply of oxygen and removal of carbon dioxide is essential to sustain healthy respiratory function. In addition to the method described above, the system can also be configured to monitor supply of oxygen and removal of carbon dioxide, step 174. Possible non-limiting methods of monitoring these comprise:
SpO2 may be monitored using any suitable sensor like a gas analyser or pulse oximeter.
In step 174, the trends/values of these parameters could be used to detect when the therapy settings (gas flow parameters) could be changed. The system is configured to then alert the user or automatically control the therapy dose (that is, gas flow parameters).
For example, if the SpO2 starts to decrease past 90%, or other levels determined by the clinician as desirable from their assessment of the patient, for example, 91%, 92%, 93%, 94%, or 95%, the flow and or oxygen concentration (if not already at 100%) could increase to provide a higher level of support, step 175. If the end-tidal CO2 value or trend shows an increase, the therapy support could increase as a higher level of support is needed, step 175. This should not be limited to oxygen and carbon dioxide. Other measured parameters (e.g. heart rate, blood pressure) could also be used to change the therapy dose settings.
During the preoxygenation stage, any suitable preoxygenation titration method may be used, such as the method of
In further embodiments, when the predicted or monitored pre-oxygenation or apnoeic time is small, the gas parameters can be changed accordingly. For example, if the estimated time of the anaesthesia stages (pre-oxygenation or during anaesthesia/apnea) is too short, the gas parameters can be adjusted to provide a higher level of support for more time—for example the oxygen concentration, flow rate, oxygen volume, pressure and/or gas composition can be changed, for example. Various methods of predicting the duration of the stages could be used.
As relatively high gas delivery flow rates may be used with the embodiments or configurations described herein, the gases being supplied or delivered to the user or patient can may be delivered to different parts of the user's or a patient's airway.
Such relatively high flow rates of gases may assist in providing the supplied gases into a user's airway, or to different parts of a user's airway, for example such flow rates may allow for a delivery of such gases to the upper or lower airway regions as shown in
The embodiments described can utilise the knowledge of the respiratory flow wave and/or the transition between inspiration and expiration. Possible methods and apparatus for respiratory flow wave, meeting (e.g. peak) inspiratory demand and estimating (e.g. peak) inspiratory demand can be used. It should also be noted that the following can utilise switching modes of operation between inspiration and expiration. The exact moment of switching should not be limited to the exact transition point.
In some configurations the information related to the patient can be accessed remotely from a database. Further the system can automatically provide therapy settings based on stored patient information. Also a clinician can remotely operate the system.
The foregoing description of the invention includes preferred forms thereof. Modifications may be made thereto without departing from the scope of the invention.
Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of “including, but not limited to.”
Where, in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers or components are herein incorporated as if individually set forth.
The disclosed methods, apparatus and systems may also be said broadly to comprise the parts, elements and features referred to or indicated in the disclosure, individually or collectively, in any or all combinations of two or more of said parts, elements or features.
Recitation of ranges herein is merely intended to serve as a shorthand method of referring individually to each separate sub-range or value falling within the range, unless otherwise indicated herein, and each separate sub-range or value is incorporated into the specification as if it were individually recited herein.
Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world.
Certain features, aspects and advantages of some configurations of the present disclosure have been described with reference to use of the gas humidification system with a respiratory therapy system. However, certain features, aspects and advantages of the use of the gas humidification system as described may be advantageously be used with other therapeutic or non-therapeutic systems requiring the humidification of gases. Certain features, aspects and advantages of the methods and apparatus of the present disclosure may be equally applied to usage with other systems.
Although the present disclosure has been described in terms of certain embodiments, other embodiments apparent to those of ordinary skill in the art also are within the scope of this disclosure. Thus, various changes and modifications may be made without departing from the spirit and scope of the disclosure. For instance, various components may be repositioned as desired. Moreover, not all of the features, aspects and advantages are necessarily required to practice the present disclosure. Accordingly, the scope of the present disclosure is intended to be defined only by the claims that follow.
Items
A1. A respiratory therapy system comprising:
A2. The respiratory therapy system of item A1, wherein if the No is less than or equal to the Ni plus a predetermined nitrogen variance value Np, the flow source or flow generator is controlled to deliver the second flow therapy.
A3. The respiratory therapy system of item A1, wherein if the ratio of No:Ni is less than or equal to a predetermined nitrogen ratio Np_r, the flow source or flow generator is controlled to deliver the second flow therapy.
A4. The respiratory therapy system of item A1, wherein different concentrations of gases are delivered in the second flow therapy than in the first flow therapy.
A5. The respiratory therapy system of item A1, wherein the first flow therapy comprises delivery of a first gas composition comprising a first level of ambient gas Ga1 and a first level of oxygen Go1, and wherein the second flow therapy comprises delivery of a second level of ambient gas Ga2 and a second level of oxygen Go2.
A6. The respiratory therapy system of item A6, wherein Go1>Go2.
A7. The respiratory therapy system of item A6, wherein Go1:(Ga1+Go1)>Go2:(Ga2+Go2).
A8. A respiratory therapy kit comprising:
A9. The respiratory therapy kit of item A8, wherein the humidifier further comprises a fluid reservoir.
A10. The respiratory therapy kit of item A9, further comprising a heating device comprising a chemical heater adapted to heat fluid in the fluid reservoir.
A11. The respiratory therapy kit of item A10, wherein the heating device comprises a manually actuatable switch configured to activate the chemical heater.
A12. The respiratory therapy kit of item A8, wherein the patient interface comprises a port configured to accept a drug delivery device.
A13. The respiratory therapy kit of item A12, further comprising a drug delivery device adapted to be located in the port, wherein the drug delivery device comprises a manually actuatable metering mechanism configured to allow for the release of medication.
A14. A respiratory therapy system, comprising:
A15. The respiratory therapy system of item A15, further comprising a disinfection arrangement adapted to disinfect at least a section of the conduit.
A16. The respiratory therapy system of item A16, further comprising a hardware controller configured to control the disinfection arrangement, wherein the hardware controller controls the disinfection arrangement dependent on whether or not the patient interface is attached to the conduit.
A17. The respiratory therapy system of item A16, further comprising a hardware controller configured to control the disinfection arrangement, wherein the hardware controller is configured to activate the disinfection arrangement after removal of the patient interface from the conduit.
A18. The respiratory therapy system of items A17 or A18, further comprising a flow sensor or pressure sensor, wherein the hardware controller is configured to, in use, utilize signals from the flow sensor or pressure sensor or values derived therefrom to determine if the patient interface is or is not attached to the conduit.
A19. The respiratory therapy system of item A15, further comprising a one-way valve adapted to prevent the flow of exhaled gases into the conduit.
A20. The respiratory therapy system of item A15, wherein the respiratory therapy apparatus comprises a flow source or flow generator, a humidifier, or an integrated flow source or flow generator/humidifier apparatus.
B1. A method for estimating and/or determining one or more pre-oxygenation parameters for a patient undergoing pre-oxygenation therapy, comprising one or more of:
B2. The method of item B1, wherein the one or more pre-oxygenation parameters comprise(s):
B3. The method of item B1 or B2, wherein said respiratory gas is one or more of oxygen and nitrogen.
B4. The method of any one of the preceding B items, wherein the step of measuring and/or tracking the concentration of one or more respiratory gases in the patient's expired gas is performed using a mass spectrometer.
B5. The method of any one of the preceding B items, wherein the step of measuring and/or tracking the concentration of one or more respiratory gases in the patient's expired gas is performed using a gas analyser.
B6. The method of item B4, wherein said gas analyser is one or more of an oxygen gas analyser and a nitrogen gas analyser.
B7. The method of any one of the preceding B items, wherein the step of measuring and/or tracking the concentration of one or more respiratory gases in the patient's blood is performed via pulse oximetry.
B8. The method of any one of the preceding B items, wherein the tracer is one or more of nitrogen, helium, argon and sulfur-hexafluoride.
B9. The method of any one of the preceding B items, wherein the concentration of the tracer is measured and/or tracked using one or more of:
B10. The method of any one of the preceding B items, wherein the tracer is introduced to the patient's respiratory tract via inhalation prior to delivery of the pre-oxygenation therapy.
B11. The method of any one of items B1 to B10, wherein the tracer is introduced to the patient's respiratory tract via inhalation during an initial warm-up phase of the pre-oxygenation therapy.
B12. The method of any one of the preceding B items, wherein the step of measuring and/or tracking the one or more physical properties of the patient's expired gas is used to estimate the fractional concentrations of one or more respiratory gases in the expired gas.
B13. The method of any one of the preceding B items, wherein said one or more physical properties comprises:
B14. The method of any one of the preceding B items, wherein said one or more measuring and/or tracking steps is performed continuously.
B15. The method of item B14, wherein said continuous measurement and/or tracking is performed until the patient is sufficiently pre-oxygenated.
B16. The method of any one of the preceding B items, wherein sufficient pre-oxygenation is indicated by a sustained end-tidal oxygen concentration and/or blood oxygen saturation level greater than 90%.
B17. The method of any one of the preceding B items, wherein sufficient pre-oxygenation is indicated by substantially steady-state concentration(s) and/or blood saturation level(s) of said one or more respiratory gases and/or said tracer.
B18. The method of any one of the preceding B items, further comprising the steps of:
B19. The method of item B18, wherein the non-linear model is an exponential curve.
B20. The method of item B19, wherein the treatment factor is four.
B21. The method of any one of items B18 to B20, wherein said time until sufficient pre-oxygenation is further multiplied by a safety factor.
B22. The method of any one of items B18 to B21, wherein the time constant is the time taken for the concentration of nitrogen in the expired gas to drop to substantially 37% of the concentration of nitrogen in the first measurement of expired gas.
B23. The method of any one of items B18 to B21, wherein the time constant is the time taken for the concentration of tracer in the expired gas to drop to substantially 37% of the concentration of tracer in the first measurement of expired gas.
B24. The method of any one of items B18 to B21, wherein the time constant is the time taken for the concentration of oxygen in the expired gas to increase by substantially 63% of the concentration of oxygen in the first measurement of expired gas.
B25. The method of any one of items B18 to B21, wherein the time constant is the time taken for the blood saturation of oxygen to increase by substantially 63% of the patient's blood saturation of oxygen prior to or at the start of the pre-oxygenation procedure.
B26. The method of any one of items B18 to B21, wherein the time constant is the quotient of dividing the patient's functional residual capacity by the patient's alveolar ventilation.
B27. The method of any one of the preceding B items, wherein pre-oxygenation is delivered via high flow therapy.
B28. The method of any one of the preceding B items, wherein pre-oxygenation is delivered via a nasal cannula.
B29. Apparatus configured for estimating and/or determining one or more pre-oxygenation parameters for a patient undergoing pre-oxygenation therapy comprising one or more sensors configured to:
B30. The apparatus of item B29, wherein said one or more pre-oxygenation parameters comprise(s):
B31. The apparatus of item B29 or B30, further comprising a processor configured to:
B32. The apparatus of item B31, further comprising a timer configured to indicate the estimated time remaining until the patient is sufficiently pre-oxygenated.
B33. The apparatus of any one of items B29 to B32 further comprising a control interface or a connection to a control interface of a pre-oxygenation therapy apparatus or system providing pre-oxygenation therapy to said patient.
B34. A system for estimating and/or determining one or more pre-oxygenation parameters for a patient undergoing pre-oxygenation therapy, the system configured to implement the method of any one of items B1 to B28.
B35. A system for estimating and/or determining one or more pre-oxygenation parameters for a patient undergoing pre-oxygenation therapy, the system comprising a patient interface and the apparatus of any one of items B29 to B33.
10402
C 1. A method of oxygenating a patient in relation to anaesthesia using high flow gas delivery comprising determining oxygenation requirements of the patient before or during anaesthesia.
C 2. A method according to item C1 wherein determining oxygenation requirements comprises one or more of:
C 3. A method according to item C2 wherein the stages of anaesthesia comprise one or more of:
C 4. A method according to item C2 or C3 further comprising detecting the stage of anaesthesia by detecting breathing pressure to determine if the patient is: a) breathing and in the pre-oxygenation state, or b) not breathing and in the apnoeic stage.
C 5. A method according to item C2, C3 or C4 further comprising detecting the stage of anaesthesia by detecting the expired CO2 to determine if the patient is: a) breathing and in the pre-oxygenation state, or b) not breathing and in the apnoeic stage.
C 6. A method according any one of items C2 to C5 wherein monitoring O2 supply and/or CO2 removal comprises monitoring one or more of:
C 7. A method according to any one of the preceding C items further comprising controlling one or parameters of the high flow gas to assist oxygenation of the patient according to the oxygenation requirements.
C 8. A method according to item C7 wherein controlling one or more parameters of the high flow gas comprises controlling one or more of:
C 9. A method according to item C7 or C8 further comprising, upon monitoring O2 supply and/or CO2 removal, increasing flow and/or oxygen concentration if:
C 10. A method according to item C7, C8 or C9 wherein, upon determining a short duration of one or more stages of anaesthesia, increasing the flow and/or oxygen concentration.
C 11. A method according to any preceding item C, wherein the high flow gas is delivered and the oxygenation requirements are determined using a high flow therapy apparatus.
C 12. A system for oxygenating a patient in relation to anaesthesia using high flow gas delivery comprising:
C 13. A system according to item C12 wherein determining oxygenation requirements comprises one or more of:
C 14. A system according to item C13 wherein the stages of anaesthesia comprise one or more of:
C 15. A system according to item C13 or C14 wherein the controller further detects the stage of anaesthesia by detecting breathing pressure to determine if the patient is: a) breathing and in the pre-oxygenation state, or b) not breathing and in the apnoeic stage.
C 16. A system according to item C13, C14 or C15 wherein the controller further detects the stage of anaesthesia by detecting the expired CO2 to determine if the patient is: a) breathing and in the pre-oxygenation state, or b) not breathing and in the apnoeic stage.
C 17. A system according any one of items C13 to C16 wherein monitoring O2 supply and/or CO2 removal comprises monitoring one or more of:
C 18. A system according to any one of items C13 to C17 wherein the controller further controls one or parameters of the high flow gas to assist oxygenation of the patient according to the oxygenation requirements.
C 19. A system according to item C18 wherein controlling one or more parameters of the high flow gas comprises controlling one or more of:
C20. A system according to item C18 or C19 further comprising the controller, upon monitoring O2 supply and/or CO2 removal, increasing flow and/or oxygen concentration if:
C21. A system according to item C18, C19 or C20 wherein, upon determining a short duration of one or more stages of anaesthesia, the controller increases the flow and/or oxygen concentration.
| Number | Date | Country | |
|---|---|---|---|
| 62140592 | Mar 2015 | US | |
| 62140598 | Mar 2015 | US | |
| 62117817 | Feb 2015 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15549963 | Aug 2017 | US |
| Child | 18453941 | US |
