Patent Application
20230347096
This application claims priority from South African Patent Application No. 2020/04960, filed Aug. 12, 2020.
The present disclosure relates to a positive pressure breathing circuit and a method for ventilating a patient. The breathing circuit can be used in any type of pressurized breathing therapy including, for example, continuous positive air(way) pressure (CPAP) therapy and bilevel positive air pressure therapy where the inspiratory and expiratory pressures differ.
Breathing circuits can help a patient to breath by opening up their airways and/or supplying specific breathing gases for a particular medicinal purpose. Breathing circuits may supply breathing gases at a flow rate that is higher than an average inspiratory flow rate to ensure there is no shortage of breathing gases. Specifically, in the case of constant positive airway pressure therapy, known as CPAP therapy, the flow supplied to the patient is usually higher than the peak inspiratory flow, rather than the average inspiratory flow.
This means that any breathing gases supplied during exhalation, or during a pause in breathing, may be wasted by being vented. There is therefore a need for a breathing circuit and a method that can reduce this wastage, or at least provide an alternative to existing breathing circuits.
An embodiment relates to a positive pressure breathing circuit for ventilating a patient, the breathing circuit including:
The first gas may be pressurized air. The first gas may be pressurized air enriched with oxygen.
In one example, the second gas may be pressurized oxygen gas.
In another example, the second gas may be a pressurized gas including one or any combination of: oxygen gas, heliox, or an anaesthetic gas. The anaesthetic gas could be nitrous oxide or a 50:50 mixture of nitrous oxide and oxygen gas.
Pressurized oxygen gas may be supplied from a liquified oxygen source, a bottled oxygen source or from an oxygen concentrator source.
During inhalation, the breathing gas the patient initially receives includes the pressurized second gas that is stored in the inspiratory member and the pressurized second gas entering the inspiratory member. When all of the stored oxygen gas has been inhaled or entered the patient interface, the breathing gas received by the patient includes the second gas entering the inspiratory member and the first gas in the inspiratory member. During exhalation the first non-return valve closes and the second gas entering the inspiratory member partially “backfills” the inspiratory member so as to replenish the stored (pressurized) second gas therein. The second gas is supplied to the inspiratory member at a higher pressure than the pressurized air supplied to the inspiratory member.
The inspiratory member may be sized to store a volume of the second gas that is supplied to the inspiratory member at a constant flow rate. An advantage of this feature is that there is no need to coordinate when the second gas is supplied to the patient, for instance, fluctuating the supply of the second gas during patient inhalation or exhalation.
The volume of the second gas, such as oxygen, that enters the inspiratory member during exhalation is equal to, or less than, a tidal volume of the patient, thereby minimising wastage of the second gas by venting pressurized air from the inspiratory member.
The gas passageway of the inspiratory member receives both the first and second gases during patient inhalation and exhalation.
The gas passageway of the inspiratory member has a constant internal volume. Although the gas passageway of the inspirator may be made of flexible material, the material is non-stretchable. That is to say, the internal volume of the passageway is relatively fixed in the sense that the gas passageway does not expand and does not inflate. For example, the passageway does not inflate during patient exhalation.
The inspiratory member can be an inspiratory tube, suitably an elongate inspiratory tube with an elongate gas passageway.
The inspiratory tube may have a length ranging from about 0.5 m to 2.5 m, or about a length ranging from 0.75 to 2.0 m, or a length ranging from about 1.5 to 1.8 m. The gas passageway may include a main passage of constant diameter, in which the diameter may range from about 18 to 25 mm, or the diameter is about 22 mm.
The inspiratory member may have an internal volume ranging from about 100 ml to 760 ml, for storing the second gas and some of the first gas. For example, the internal volume of the inspiratory member may be about 315, 350 or 500 ml.
In further examples, the internal volume may range from about 315 ml to 760 ml for adult patients, or range from about 400 to 600 ml. For pediatric patients, the internal volume may range from about 100 ml to 450 ml, or range from about 200 to 400 ml. For neonatal patients, the internal volume may range from about 50 to 200 ml, or range from about 100 to 150 ml.
The inspiratory member ideally has an internal volume that allows the pressurized oxygen gas that is stored in the inspiratory member to be inhaled by the patient in a single inhalation so that venting of the pressurized oxygen gas from the inspiratory member during exhalation can be avoided, thereby minimizing wastage of the pressurized oxygen gas.
The volume of the pressurized oxygen gas that may enter the inspiratory member during patient exhalation may range from about 50 to 90 percent by vol % of a tidal volume of a patient, or range from about 60 to 70 percent by vol % of a tidal volume of a patient.
The volume of the pressurized oxygen gas that may enter the inspiratory member during patient exhalation can equal an estimation of an alveoli volume of the patient.
The pressure of exhaled gases in the expiratory member may be greater than the pressure of the breathing gas in inspiratory member.
The expiratory member may include an expiratory tube having an elongate gas passageway.
The expiratory member has a second non-return device that can regulate the pressure at which gases are vented from the expiratory member.
The second non-return device inhibits gases exhaled from re-entering the patient interface via the expiratory member.
In one example, the second non-return device is a positive end expiratory pressure valve (PEEP valve). The positive end expiratory pressure valve of the expiratory member provides back pressure of the expired gases to the patient interface at a level that is operable to prevent oxygen gas leakage through the non-return valve of the inspiratory tube during exhalation.
In another example, the second non-return device is a bubbling bath in which the exhaled gases are required to exit the expiratory tube at a depth of liquid which determines the pressure at which gases are exhaled.
In one example, the pressure regulation device may include a first pressure relief valve configured to control the pressure of the first gas to the inspiratory member.
In another example, the pressure regulation device may include a second pressure relief valve configured to vent the first gas from the breathing circuit.
The pressure regulation device may include a further positive end expiratory pressure valve (further PEEP valve) on the distal portion of the inspiratory member.
The second pressure relief valve may be the further positive end expiratory pressure valve for the inspiratory member.
The pressure regulation device may include the inspiratory member including a further positive end expiratory pressure valve (further PEEP valve) on the distal portion of the inspiratory member.
The further positive end expiratory pressure valve may be configured to vent the pressurized first gas from the inspiratory tube during patient exhalation. In one example, the pressure in the inspiratory member is regulated by venting the pressurized first gas therefrom. In another example, the pressure in the inspiratory member may be regulated by adjusting the output of a gas flow generator, such as adjusting the speed of a fan of a gas flow generator. In yet another example, the pressure in the inspiratory member may be regulated by adjusting a gas flow control valve that supplies the first gas into the respiratory member.
The further positive end expiratory valve may vent pressurized air from the inspiratory member, in which more of the pressurized first gas is vented during patient expiration than during patient inhalation.
The positive end expiratory pressure valve of the expiratory member may have a pressure setting ranging from about 2.5 to 20.0 cmH2O, or ranging from about 8.0 to 12.0 cmH2O, or about 10.0 cmH2O.
The further positive end expiratory pressure valve of the inspiratory member may have a pressure setting ranging from 0.5 to 1.0 cmH2O less than the pressure setting of the positive end expiratory valve of the expiratory member. This reduces the likelihood of the breathing gas from being spontaneously discharged from the breathing circuit. More particularly, this arrangement inhibits the second gas from being vented from the breathing circuit by the positive end expiratory pressure valve of the expiratory member whilst the second gas is backfilling the inspiratory member.
The distal portion of the inspiratory member may have a first gas inlet adjacent to the further positive end expiratory pressure valve of the inspiratory tube, in which the first gas inlet is connectable to a source of the pressurized first gas.
The inspiratory member may be sufficiently long so that the stored second gas is inhibited from being discharged from the inspiratory member with the first gas via the further positive end expiratory pressure valve.
The positive end expiratory valve of the expiratory member may be operable to vent exhaled gases at a higher pressure than the pressure at which the first gas is vented from the inspiratory member.
The positive end expiratory valve and the further positive end expiratory valve may be operable to vent exhaled gases at a higher pressure from the expiratory member than the pressurized first gas from the inspiratory member respectively.
The positive end expiratory valve of the expiratory member may be a passive valve. For example, the positive end expiratory valve may have a fixed operating pressure or an operating pressure that can be manually adjusted. That is to say, the valve does not require active control measures or an actuator to continually monitor and adjust the operating pressure of the valve.
Similarly, the further positive end expiratory valve of the inspiratory member may be a passive valve. For example, the further positive end expiratory valve may have a fixed operating pressure or an operating pressure that can be manually adjusted. That is to say, the valve does not require active control measures or an actuator to continually monitor and adjust the operating pressure of the valve.
The positive end expiratory pressure valve of the expiratory member may have a higher pressure setting than a pressure setting of the further positive end expiratory pressure valve of the inspiratory member. In other words, there is a differential in the pressure settings that inhibits flow of the breathing gas from the inspiratory member to the expiratory member other than that caused by the patient.
The first non-return valve may be located on the proximal portion of the inspiratory member.
The first non-return valve may be located on the proximal portion of the inspiratory member, and be arranged proximal to where the second gas enters the inspiratory member. That is, the first non-return valve may be between the patient interface and where the second gas enters the inspiratory member.
The first non-return valve is located adjacent to the patient interface.
The proximal portion of the inspiratory member may have a second gas inlet upstream of the first non-return valve, at which the second gas inlet is connectable to the source of the pressurized second gas.
The breathing circuit may include a patient interface. The patient interface may be a sealed patient interface. For example, the patient interface includes either one or any combination of a full-face mask (also known as an oro-nasal mask), a sealed nasal cannula, a sealed oral mask, a sealed nasal mask, a nasal pillows interface, or a tracheostomy tube. The first non-return valve may be arranged on the patient interface.
The patient interface may have an inlet connection that connects to the inspiratory member, and an outlet connection that connects to the expiratory member.
The patient interface may have a coupling to which a Y-piece, is or can be connected, in which one leg of the Y-piece is an inlet connection that connects to the inspiratory member, and another leg is an outlet connection that connects to the expiratory member.
The positive end expiratory pressure valve of the expiratory member may be fitted directly to the outlet connection of the Y-piece.
The inspiratory member may be directly connected to the patient interface either with or without a Y-piece. That is to say, there are no intervening operations such as humidifiers, heat exchanges or other items that have the potential increase dead space in the breathing circuit between the inspiratory member and the patient interface.
The first gas may be continuously supplied to the inspiratory member.
The first gas may be supplied at a rate that is greater than or equal to the peak inspiratory flow rate of a patient. The peak inspiratory flow rate will be particular to individual patients.
The second gas may be supplied to the inspiratory member at a constant flow rate.
Another embodiment relates to a method of ventilating a patient, the method including steps of:
The step of supplying the pressurized first gas may be carried out continuously to the distal portion of the inspiratory member.
The step of supplying the pressurized first gas may be carried out at a rate that is greater than or equal to peak inspiratory flow rate of a patient.
The expiratory member may have a positive end expiratory pressure valve that is configured to vent the expired gases and inhibit the exhaled gases from re-entering the patient interface.
In one example, the pressure regulation device may include a first pressure relief valve configured to control the pressure of the first gas supplied to the inspiratory member, and the method include operating the first pressure relief valve.
In another example, the pressure regulation device may include a second pressure relief valve configured to vent the first gas from the breathing circuit, and the method may include operating the second pressure relief valve.
The pressure regulation device may include the inspiratory member including a further positive end expiratory pressure valve, and the method may include a step of setting the pressure at which the further positive end expiratory pressure valve vents excess first gas from the inspiratory member.
The method may include selecting a pressure setting of at least one of the positive end expiratory pressure valve of the expiratory member and the further positive end expiratory pressure valve of the inspiratory member, so that the pressure setting of the positive end expiratory pressure valve of the inspiratory member is lower than that of the expiratory member. The second pressure relief valve may be the further positive end expiratory pressure valve for the inspiratory member.
The method may include selecting a pressure setting of the positive end expiratory pressure valve of the expiratory member within a range from about 2.5 to 20.0 cmH2O, or a range from about 8.0 to 12.0 cmH2O, or about 10.0 cmH2O.
The method may include selecting a pressure setting of the positive end expiratory pressure valve of the inspiratory member that ranges from about 0.5 to 1.0 cmH2O less that the pressure setting of the positive end expiratory valve of the expiratory member.
The step of supplying the second gas may include controlling the flow rate of the second gas to the inspiratory member at a rate depending on the requirements of the patient. For instance, when the second gas is oxygen gas the flow rate will depend on the oxygen saturation concentration of the patient's blood.
The flow rate of the second gas may be controlled independently of any one or any combination of:
In other words, the flow rate of the second gas supplied to the inspiratory member can be determined so that the volume of the second gas stored in the inspiratory member tube during exhalation and supplied to the inspiratory member during inhalation will occupy the alveoli volume of the patient, meaning that enriched second gas need not be vented from the breathing circuit or drawn into dead space of the patient or of the breathing circuit. As a result, there will be less wastage of the second gas by reducing venting of the second gas from the breathing circuit without being inhaled, and by having a higher portion of the second gas in alveoli volume of a patient's lungs than in the dead space.
In the situation where the second gas includes enriched oxygen gas, controlling the flow rate of the oxygen gas supplied to the inspiratory member may be based on a level of oxygen saturation in the patient's blood.
During patient exhalation, the second gas entering the inspiratory member can flow backwards along the inspiratory member which acts as a constant pressure storage volume by displacing air out of the inspiratory member via the further positive end expiratory pressure valve of the inspiratory tube.
During patient inhalation, the breathing gas from the inspiratory member will initially be the second gas that had been stored in the inspiratory member and then the first gas. That is to say, during patient inhalation, the breathing gas the patient initially receives includes the second gas that was stored in the inspiratory member before the first gas.
When the first gas is air, supplying the air may be carried out in the range from about 2 to 120 l/min.
For example, in the case of an adult patient, the air may be supplied to the inspiratory member at a range from about 40 to 120 l/min, or range from about 50 to 70 l/min. In the case of pediatric patients, the air may be supplied to the inspiratory member at a range from about 3 to 50 l/min, or a range from about 4 to 40 l/min. In the case of neonatal patients, air may be supplied to the inspiratory member at a range from about 2 to 10 l/min, or at a range from about 3 to 6 l/min.
The inspiratory tube may have a length ranging from about 0.5 m to 2.5 m, or a length ranging from about 0.75 to 2.0 m, or a length ranging from about 1.5 to 1.8 m. The gas passageway may include a main passage of constant diameter, in which the diameter may range from about 18 to 25 mm, or a diameter about 22 mm.
The inspiratory member may have an internal volume ranging from about 100 ml to 760 ml, for storing the second gas and some of the first gas. For example, the internal volume of the inspiratory member may be about 315, 350 or 500 ml.
In further examples, the internal volume may range from about 315 ml to 760 ml for adult patients, or range from about 400 to 600 ml. For pediatric patients, the internal volume may range from about 100 ml to 450 ml, or range from about 200 to 400 ml. For neonatal patients, the internal volume may range from about 50 to 200 ml, or range from about 100 to 150 ml.
Another embodiment relates to a continuous positive air pressure breathing circuit for a patient, the breathing circuit including:
The inspirator may be an inspiratory tube.
The expirator may be an expired gas tube.
The first non-return device of the inspirator may be a non-return valve located adjacent to the patient delivery device.
The first non-return device of the inspirator may be located close to an inlet connection on the patient delivery device so that no expired gases can be discharged into the inspirator.
The first non-return device of the inspirator may be a non-return valve located between the patient delivery device and where the second gas enters the inspirator.
The second non-return device may be a positive end expiratory pressure valve that can be fitted to the expirator.
The positive end expiratory pressure valve may provide back pressure of expired gases and may be set to be sufficient to inhibit oxygen leakage through the first non-return means during exhalation.
In one example, the pressure regulation device may include a first pressure relief valve configured to control the pressure at which the first gas is supplied to the inspirator.
In another example, the pressure regulation device may include a second pressure relief valve configured to vent the first gas from the inspirator.
The pressure regulation device may include a further positive end expiratory pressure valve for venting the first gas from the breathing circuit. The second pressure relief valve may be the further positive end expiratory pressure valve for the inspirator.
The pressure regulation device may include a further positive end expiratory pressure valve for venting the first gas from the breathing circuit.
The further positive end expiratory pressure valve may vent the first gas from the breathing circuit without venting the second gas.
The inspirator may be connectable to the further positive end expiratory pressure valve that discharges excess pressurized air supplied to the inspirator upstream of the patient.
The positive end expiratory pressure valve of the expirator and the further positive end expiratory pressure valve of the inspirator each have a pressure setting and there is a differential in the pressure settings so as to prevent flow from the inspirator to the expirator other than that caused by the patient. For instance, the positive end expiratory pressure valve of the expirator has a higher pressure setting than the further positive end expiratory pressure valve of the inspirator.
The first gas may be supplied continuously to the inspirator. For example, at a constant flow rate.
The first gas may be supplied at a rate that is greater than or equal to peak inspiratory flow rate of a patient.
The first gas and the second gas are supplied concurrently to the inspiratory member.
An embodiment also relates to a method of operating the breath circuit described herein, wherein the method includes operating the breathing circuit at a positive pressure by maintaining an oversupply of the first gas into the inspirator.
The method may include supplying the first gas continuously to the inspirator.
The method may include supplying the first gas at a rate that is greater than or equal to peak inspiratory flow rate of a patient.
The method may include setting the pressure at a pressure which the further positive end expiratory pressure valve vents the first gas that is in excess from the inspirator.
When the expirator may have a positive end expiratory pressure valve for venting expired gas, and the inspirator has a further positive end expiratory pressure valve, the method may include selecting pressure settings of the positive end expiratory pressure valve of the expirator and the further positive end expiratory pressure valve of the inspirator so that there is differential between the pressure settings that will prevent net flow from the inspirator into the expirator other than that caused by the breathing of the patient.
The method may include controlling the flow of second gas to the inspirator at a fixed rate depending on the requirement of the patient.
The pressure regulation device may include a first pressure relief valve and the method include operating the pressure relief valve to control the pressure of the first gas supplied to the inspirator.
The pressure regulation device includes a second pressure relief valve configured to vent the first gas from the inspiratory member, and the method includes operating the second pressure relief valve to control the pressure of the inspiratory member
Another embodiment relates to a continuous positive air pressure ventilator comprising:
The first gas may be air. The second gas may be compressed oxygen. One or both of the first and second gases may pass through a humidifier before being delivered to the inspirator.
The non-return means on the inspirator means may be a non-return valve.
The non-return means on the expirator may be a positive end expiratory pressure valve.
The inspirator may further include a positive end expiratory pressure valve.
These and other features, aspects, and advantages of the present disclosure are described with reference to the drawings of certain embodiments, which are intended to schematically illustrate certain embodiments and not to limit the disclosure.
An embodiment will now be described in the following text which includes reference numerals that correspond to features illustrated in the accompanying drawings. To maintain clarity of the drawings, however, not all reference numerals are included in each figure of the drawings. Although certain examples are described herein, those of skill in the art will appreciate that the disclosure extends beyond the specifically disclosed examples and/or uses and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the disclosure herein disclosed should not be limited by any particular examples described herein.
The breathing circuit 10 includes an inspiratory member 12 having a gas passageway, which in one example is also referred to as an inspiration tube.
The breathing circuit 12 also includes an expiratory member 13 that vents exhaled gases from the patient interface 14. In one example, the expiratory member 13 may be connected directly onto the patient interface 14. In another example, and depicted in
The non-return valve 15 of the inspiratory member 12 inhibits the exhaled gases from entering the inspiratory member 12 and may be any suitable valve. Examples of suitable valves include a one-way flap valve, a biased valve that is biased into a closed position, or a diaphragm valve. The non-return valve 15 closes when the gas pressure downstream of the non-return valve 15 in the patient interface 14 is greater than the pressure in the gas passageway. The non-return valve 15 opens, suitably automatically, when the patient spontaneously inhales. The inspiratory member 12 and the expiratory member 13 including T-pieces or Y-pieces that supply the first and second gases 11, 20 to the gas passageway may be made of any suitable medical grade material.
The breathing circuit also includes a pressure regulating device 23 that regulates the pressure in the inspiratory member 12. For instance, the pressure regulation device may include a pressure relief valve 22 (see
In the example shown in
As illustrated in
The further PEEP valve 17 of the inspiratory member may have a pressure setting ranging from 0.5 to 1.0 cmH2O less than the pressure setting of the PEEP valve 16 of the expiratory member. This inhibits the breathing gas from being spontaneously discharged from the breathing circuit 10. If this was not the case, the beathing gas could bypass the patient without being inhaled and the second gas could not accumulate in the breathing circuit during patient exhalation.
The further PEEP valve 17 may be disconnectable from the inspiratory member 12 and the first PEEP valve 16 may be disconnectable from the expiratory member 13 or the patient interface 14. The first PEEP valve 16 and the further PEEP valve 17 may be disconnected and reconnected as required using suitable couplings including 10 mm, 15 mm, 18 mm or 22 mm conduit couplings.
Depending on the operational requirements, either one or a combination of the first PEEP valve 16 or the further PEEP valve 17 can be any suitable valve, including a fixed value PEEP valve or an adjustable PEEP valve. The fixed value PEEP valve operates by a bias to remain closed until the upstream side of the PEEP valve is exposed to pressure that causes the valve to open until the pressure on the upstream side of the valve falls to or below the opening pressure. An adjustable PEEP valve has a bias that can be adjusted such that the pressure value at which the PEEP valve opens a can be adjusted as desired.
During patient inhalation and exhalation, the second gas 20 enters the proximal portion via the second gas inlet 19 at a constant rate, and the first gas 11 enters the distal portion via the first gas 11 inlet 18 at a constant rate. At the start of patient exhalation, or during a pause between inhalation ending and exhalation starting, the non-return valve 15 closes and the second gas 20 back fills the gas passageway of the inspiratory member 12. During patient exhalation, the second gas and the first gas 11 forms a gas/gas interface that moves along the gas passageway away from the second gas inlet 19 toward the distal portion, thereby storing a volume of the second gas 20 in the inspiratory member 12 during patient exhalation. The volume of the second gas 20, such as oxygen, that enters the inspiratory member 12 during exhalation is equal to, or less than, a tidal volume of the patient, thereby minimizing wastage of the second gas 20 by venting the first gas 11 from the inspiratory member 12 instead of the second gas 20. Ideally, the volume of the gas passageway of inspiratory member 12 is selected such that all of the second gas 20 that is stored in the inspiratory member 12 and the second gas 20 supplied into the inspiratory member 12 from the second gas inlet 19 during patient inhalation is equal to, or less than the alveolar volume of the patient.
Set out below in Table 1 is a list of exemplary internal volumes of an inspiratory member 12 having a 22 mm internal diameter. For useability and to ensure adequate internal volume is provided, the inspiratory member 12 has an internal diameter of 22 mm and a length in the ranging from 1.5 m to 1.8 m for adult patients.
In the case of
The first gas 11 and the second gas 20 can be any suitable breathable gases. For example, the first gas 11 may be any breathable gas such as air, air enriched with oxygen, or any suitable anaesthetic gas. In the situation where the first gas 11 is air, air may be supplied to the inspiratory member 12 in the range of the 2 to 120 l/min depending on the patient. In the case of an adult patient, air may be supplied to the inspiratory member 12 in the range of the 40 to 120 l/min, or in the range of 50 to 70 l/min. In the case of pediatric patients, air may be supplied to the inspiratory member 12 in the range of the 3 to 50 l/min, or in the range of 4 to 40 l/min. In the case of neonatal patients, air may be supplied to the inspiratory member 12 in the range of the 2 to 10 l/min, or in the range of 3 to 6 l/min.
Similarly, the second gas 20 may be any breathable gas including any one or any combination of air enriched with oxygen, oxygen, helium, heliox, or any anaesthetic gas. The anaesthetic gas may be nitrous oxide or a 50:50 mixture of nitrous oxide and oxygen gas.
One of the benefits is that the first gas 11 is vented from the breathing circuit 10 with little venting, or no venting of the second gas 20. This enables better usage of the second gas 20, such as oxygen in the treatment of patients suffering from respiratory diseases during an outbreak, such as COVID-19. In other words, whilst oxygen efficiency can yield cost savings in treating patients in situations where the supply of oxygen is constrained an oxygen efficient system will allow more patients to be treated or to allow higher levels of oxygen enrichment to be provided to the same number of patients.
In one example, the sources 11, 20 of the first and second gases 11, 20 can be any suitable source, including pressure cylinders containing the required gases, or inwall hospital supply. In another example, flow generators including blowers can be arranged to draw the gas from a storage facility or from ambient air. For instance, the source 11 of the first gas 11 may be filtered air, ambient air, or ambient air that has been filtered. The source 11 of the air may be pressurized by a flow generator, and the source 20 of the second gas 20 may be compressed oxygen gas, such as a liquified oxygen source, a bottled oxygen source, or an oxygen concentrator source. In addition, the first and second gases 20 may optionally, be humidified prior to delivery to the patient.
In the situation where the breathing circuit 10 is used to provide supplemental oxygen gas as the second gas 20, the flow of oxygen gas can be adjusted based on patient response, for example the level of oxygen saturation in the patient's blood.
The non-return device of the expiratory member such as the first PEEP valve 16, and the non-return means of the inspiratory member such as the further PEEP value 17 can be used to regulate pressure of the inspiratory member 12 and indeed the breathing circuit 10. Thereby enabling a constant flow rate of the second gas 20 to be used, which is decoupled from regulating the pressure of the breathing circuit 10.
The following is a non-exhaustive list of some features of the breathing circuit illustrated in
Based on the assessment of the therapy requirements of the patient, flow rates of the first gas 11 and the second gas 20 to the inspiratory member 12 may be determined and controlled 33, 34 as shown in
The second gas 20, for example oxygen, may be supplied at a flow rate based on the assessment of the oxygen saturation level of the patient's blood. For example, where the oxygen flow required is between 30 and 50% of the tidal volume, the oxygen flow may be controlled to range from 0.6 to 3.3 l/min.
Similarly, the user may select an inspiratory member 12 having the required internal volume to store the required amount of at least the second gas 20. For adult patients, where the respiratory member 12 has an internal diameter of 22 mm the respiratory member may, for example, have a length in the range of 1.5 to 1.8 m. The air flow rates, oxygen gas flow rates and length and internal diameter of the inspiratory member 12 can be selected by the user. Set up below in Table 2 are examples of flow rates and inspiratory member volumes for adult patients, pediatric patients and neonatal patients. As can be seen the flow rates and inspiratory member 12 volumes vary for each category of patient.
The method may include selecting 35 a pressure setting of at least one of the first PEEP valve 16 and the further PEEP valve 17 of the inspiratory member 12, so that the pressure setting of the further PEEP valve 17 of the inspiratory member 12 is lower than that of the first PEEP valve 16 of expiratory member 13. The pressure setting of the further PEEP valve 17 of the inspiratory member 12 ranges from 0.5 to 1.0 cmH2O less than the pressure setting of the first PEEP valve 16 of the expiratory member 13.
The method may also include selecting 35 a pressure setting of the first PEEP valve 16 of the expiratory member 13 within a range from 2.5 to 20.0 cmH2O, or ranging from 8.0 to 12.0 cmH2O, or 10.0 cmH2O.
As described above the pressure settings of the PEEP valves 16, 17 may be fixed or adjustable. In the case of fixed PEEP valves, each valve can be swapped out as required with a PEEP valve of the required pressure rating/setting.
Supplying the oxygen gas into the proximal portion of the inspiratory member 12, includes the oxygen gas entering the inspiratory member 12 on a distal side of the non-return valve 15. Furthermore the method may include supplying the pressurized air into the distal portion of the inspiratory member 12 during patient exhalation while a volume of the pressurized oxygen gas enters and is stored in the inspiratory member 12. As this occurs, the pressure in the inspiratory member is regulated via the further PEEP valve 17 of the inspiratory member 12 which vents 36 excess air from the inspiratory member 12. The oxygen gas may be supplied at a pressure greater than the pressure of the air so that the oxygen can backfill the inspiratory member 12. In other words, the second gas 20 is supplied at a pressure greater to the inspiratory member 12 than the first gas 11 so that the second gas 20 can backfill the inspiratory member 12. The first PEEP valve 16 of the expiratory member 13 vents exhaled gas 37.
One of the benefits of the breathing circuit 10 allows direct adjusting of the flow of the second gas 20, such as supplemental oxygen to the patient on the basis of the patient's response in terms of the level of oxygen saturation in the patient's blood. Conventionally measured with a pulse oximeter. This can be thought of as being equivalent to titrating the patient with oxygen to achieve the required response. An advantage provided by this method is that it avoids the excessive wastage of oxygen, or any second gas 20, in comparison to other high flow nasal cannular oxygen. The flow of the second gas 20 to the patient can be controlled irrespective of pressure and the total flow of the pressure therapy provided to the patient. The flow can be controlled independently of any one or any combination of:
The flow rate of the second gas 20 supplied to the inspiratory member 12 can be determined so that the volume of the second gas 20 stored in the inspiratory member 12 during exhalation and supplied to the inspiratory member 12 during inhalation will occupy the alveoli volume of the patient, meaning that enriched second gas 20 need not be vented from the breathing circuit 10 or drawn into dead space of the patient or dead space of the breathing circuit 10, if there is any. That is to say another operation benefit of the breathing circuit 10 is based on an understanding of alveolar “oxygen efficiency” which results from the design of the breathing circuit 10. This understanding can help avoid the oversupply of oxygen to a patient which provides no added benefit, avoiding oxygen wastage when the patient is experiencing close to 100% oxygen in the patient's lungs. Particularly if patient shows minimal response to increased oxygen concentration.
The breathing circuit 10 can achieve a high level of oxygen efficiency whilst reducing rebreathing of expired gasses. Some of the features of the breathing circuit 10 that contribute to these and other benefits are as follows.
We have simulated the expected performance of the breathing circuit 10 described herein and illustrated in
The simulation also included the assumption that the first and second gases 11, 20 obey ideal gases laws within the inspiration tube, that is the oxygen flowing into and out of the inspiration tube 12 exhibits “plug flow” behaviour and that there is no mixing between the oxygen and the air supplied into the inspiration tube. In the case of the embodiment shown in
During the initial portion of patient inhalation, the tidal flow is supplied by a combination of the supplemental oxygen flow entering the inspiration tube and stored oxygen drawn from the inspiration tube. Once the stored oxygen gas has been depleted, at approximately 0.7 seconds, the tidal flow was supplied by a combination of the supplemental oxygen flow and air drawn from the inspiration tube. The air being drawn from the inspiration tube is shown by the dotted line, and the supplemental oxygen flow is shown by the solid line.
As can be seen in
At the end of patient inhalation, the average oxygen concentration drops to the value that can be calculated directly from the patient's minute ventilation and the supplemental oxygen flow rate. Specifically, for the simulated conditions,
Based on an oxygen concentration in air of 21% by volume, the average concentration of inhaled gas is 60.5% according to Equation 1:
(Air flow/Minute ventilation)*oxygen concentration of air+(Supplemental oxygen/Minute ventilation)*oxygen concentration of supplemental oxygen EQ 1.
2.5/5.0*21+2.5/5.0*100=60.5% EQ 1.
The vertical dashed line in
One of the outcomes of the simulation is that no supplemental oxygen will be wasted to atmosphere without being inspired by the patient. Moreover, we believe that substantial deviation from plug flow in the inspiratory tube can occur without causing any wastage of oxygen to atmosphere. More particularly, as the supplemental oxygen flow is increased towards the minute ventilation flow, this will raise the FiO2, the degree of deviation from plug flow (mixing between stored oxygen and air) will have an impact on the amount of oxygen gas that could be vented to the atmosphere. The extent of the impact will need to be determined in practice for the specific breathing circuit and its operating conditions.
The CPAP flow rate was set at 40 l/min, being greater than the maximum respiration rate, and five times the minute ventilation rate of 8 l/min. The supplemental oxygen flow rate set a constant 2.5 l/min. As described above, tidal volume during patient inhalation comprised the stored oxygen and air until approximately 0.7 seconds, and from 0.7 second to 1.14 seconds fresh oxygen and air from the inspiratory tube was inhaled. From the start of patient inhalation until 1.14 seconds, the inhaled gases entered the alveolar volume at a FiO2 of approximately 69.6%. From 1.14 seconds to 2.0 seconds patient inhalation included the supplemental oxygen and air from the inspiration tube which entered the inspiration dead space. From 2.0 second to 6.0 seconds, patient exhalation occurred, during which, air was vented from the inspiration tube at a rate of CPAP flow rate plus the 2.5 l/min being rate at which the supplemental oxygen back filled the inspiration tube.
The simulation targeted a FiO2 of 60%. At this FiO2, no supplemental oxygen is wasted in the exhaled gases in the sense that all the stored oxygen that was inhaled preferentially entering the alveoli volume. Furthermore, there is now no rebreathing of CO2 and so the exhalation profile and its duration have no impact on the rebreathing of CO2.
In terms of the mechanisms that assisted in achieving this oxygen efficiency, there are three main aspects:
One of the operational features of the breathing circuit disclosed herein is that the gas from the dead space was vented with the exhaled gases, as opposed to some breathing circuits which focus on recovering and reusing the expired “dead space” gas. In this way the current proposal is substantially different.
Conditional language used herein, such as, among others, “can,” “might,” “may,” “for example,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list. Further, the term “each,” as used herein, in addition to having its ordinary meaning, can mean any subset of a set of elements to which the term “each” is applied.
Disjunctive language such as the phrase “at least one of X, Y and Z,” unless specifically stated otherwise, is to be understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z, or a combination thereof. Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y and at least one of Z to each be present.
Unless otherwise explicitly stated, articles such as “a” or “an” should generally be interpreted to include one or more described items. Accordingly, phrases such as “a device configured to” are intended to include one or more recited devices. Such one or more recited devices can also be collectively configured to carry out the stated recitations. For example, “a processor configured to carry out recitations A, B and C” can include a first processor configured to carry out recitation A working in conjunction with a second processor configured to carry out recitations B and C.
While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the devices or methods illustrated can be made without departing from the spirit of the disclosure. As will be recognized, certain embodiments described herein can be embodied within a form that does not provide all of the features and benefits set forth herein, as some features can be used or practiced separately from others.
In this specification, the following terms have the following meanings:
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020/04960 | Dec 2020 | ZA | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/NZ2021/050176 | 10/12/2021 | WO |
