Patent Application
20250135135
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 bi-level positive air pressure therapy where the inspiratory and expiratory pressures differ.
Breathing circuits can help a patient to breathe by delivering gas to open up their airways and/or supplying specific breathing gases for a particular medicinal purpose. The breathing gases may be supplied at a flow rate that is higher than an average inspiratory flow rate to ensure there is no shortage of breathing gases. In the case of CPAP therapy, the flow supplied to the patient is usually higher than the peak inspiratory flow, rather than the average inspiratory flow.
Some traditional breathing circuits for ventilating a patient use a mixed breathing gas including a blend of air and oxygen gas that is supplied to a patient via an inspiratory tube. The required oxygen saturation levels in the patient's blood can be achieved by adjusting the ratio of the oxygen in the oxygen/air blend. However, a problem with this breathing circuit is the positive pressure experienced by the patient is the result of a continuous supply of the mixed breathing gas during both inhalation and exhalation, which results in a significant wastage of the oxygen gas. An improved breathing circuit allows increased amounts of oxygen gas to be delivered to the patient during inhalation to minimize its wastage during exhalation. However, the improved breathing circuits often required multiple pressure regulation devices to be carefully operated to allow exhaled gases to be vented from the circuit and to allow excess air supplied to also be vented simultaneously.
There is therefore a need for an alternative breathing circuit and a method.
An embodiment relates to a positive pressure breathing circuit for ventilating a patient, the breathing circuit comprising:
A distal portion of the inspiratory tube may be connectable to the source of the pressurized first gas.
A proximal portion of the inspiratory tube may be connectable to the source of the pressurized second gas.
The proximal portion of the inspiratory tube may be connectable to the patient interface.
The inspiratory tube may include a first non-return valve.
The first non-return valve may be arranged between the patient interface and the second gas entering the inspiratory tube.
The first non-return valve may be configured to inhibit the exhaled gas from entering the inspiratory tube. Throughout this specification, the first non-return valve inhibits the exhaled gas from passing upstream of the first non-return valve, but this does not necessarily mean that the first non-return valve completely blocks the flow.
The expiratory tube may include a second non-return valve.
The second non-return valve may be configured to inhibit the first gas from entering the patient interface from the expiratory tube. That is to say, to inhibit the excess supply of the first gas conveyed from the inspiratory tube from entering the patient interface from the expiratory tube. Throughout this specification, the second non-return valve inhibits the flow of the excess supply of the first gas passing upstream of the second non-return valve, which does not necessarily mean that the second non-return valve completely blocks the flow.
The expiratory tube may be configured so that the exhaled gas received by the expiratory tube downstream of the second non-return valve is vented from the breathing circuit.
The expiratory tube and the inspiratory tube may be connectable downstream of the second non-return valve.
The distal portion of the inspiratory tube may be connectable to the distal portion of the expiratory tube for conveying the excess supply of the first gas.
The proximal portions of the inspiratory and the expiratory tubes are connectable directly or indirectly with the patient interface to form a loop configuration.
The expiratory tube may be configured so that all of the excess supply of the first gas conveyed to the expiratory tube and all the exhaled gas in the expiratory tube are vented from the breathing circuit.
The expiratory tube may be configured so that all of the excess supply of the first gas conveyed to the expiratory tube downstream of the second non-return valve and all the exhaled gas in the expiratory tube downstream of the second non-return valve are vented from the breathing circuit.
The second non-return valve also inhibits the exhaled gas from being rebreathed.
The expiratory tube may have a substantially constant volume. That is to say in one example, the expiratory tube may not have a volume changing structure such as a bellows, collapsible chamber, or flexible walled passage or alike. The volume of the expiratory tube may fluctuate by a small amount due to pressure changes, but the macro structure of the expiratory tube is not configured to change with changes in pressure.
The expiratory tube may have a substantially constant volume upstream of the second non-return valve.
The expiratory tube may have a substantially constant volume downstream of the second non-return valve.
The inspiratory tube may have a substantially constant volume. The volume of the inspiratory tube may fluctuate by a small amount due to pressure changes, but the macro structure of the inspiratory tube is not configured to change with changes in pressure.
The inspiratory tube is configured so that a volume of the second gas can enter and be loaded in the inspiratory tube whilst the first gas can be supplied to the inspiratory tube, and the first gas supplied in excess can be conveyed to the expiratory tube and vented from the expiratory tube. This can occur during patient exhalation.
The inspiratory tube is configured so that the second gas can enter the inspiratory tube whilst the first gas can be supplied to the inspiratory tube, and the first gas supplied in excess can be conveyed to the expiratory tube and vented from the expiratory tube. This can occur during patient inhalation and exhalation.
In one example, the breathing circuit comprises a bypass tube interconnecting the inspiratory tube and the expiratory tube that conveys the first gas from the inspiratory tube to the expiratory tube.
In another example, the inspiratory tube and the expiratory tube are directly interconnected. In this instance, the breathing circuit may include a first gas connector that interconnects the inspiratory tube and the expiratory tube. The first gas connector may, for example, include a multi limb joiner such as a Y-shaped joiner, a T-shaped joiner and so forth, and a manifold having one or two inlets, and one or more outlets.
The inspiratory tube may have a first gas inlet for the first gas, the first gas inlet may be configured so that the first gas enters laterally to the inspiratory tube and parallel or coaxial to the bypass tube.
The first gas inlet may include a first tube connector having multiple limbs, including a first limb that is connectable to a first gas source, a second limb that is connectable to the inspiratory tube, and a third limb that is connectable directly or indirectly to the expiratory tube. Indirect connection may be provided by the bypass tube interconnecting the inspiratory tube and the expiratory tube.
The second limb of the first tube connector may be arranged laterally to the first limb, and the third limb may be arranged linearly with the first limb. The first tube connector provides flow resistance to the first gas entering the inspiratory tube.
The inspiratory tube may have a second gas inlet for the second gas, the second gas inlet may be configured so that the second gas enters the inspiratory tube lateral to a longitudinal axis of the inspiratory tube. The second gas inlet may be arranged upstream of the first non-return valve.
The second gas inlet may include a second tube connector having multiple limbs, including a first limb that is connectable to a second gas source, a second limb that is connectable to the inspiratory tube extending toward the first non-return valve, and a third limb that is connectable to the inspiratory tube that extends upstream of the second gas inlet.
The inspiratory tube and the expiratory tube may have a continuous open line so the first gas can be conveyed from the inspiratory tube to the expiratory tube in one direction.
In the situation where the bypass tube interconnects the inspiratory tube and the expiratory tube, the bypass tube may be connected to the expiratory tube by a third tube connector having multiple limbs, including a first limb that is connectable to the bypass tube, a second limb that is connectable to a distal portion of the expiratory tube downstream of the second non-return valve, and the third limb is connected to the remainder of the distal portion of the expiratory tube extending away from the second non-return valve. The third limb is arranged parallel to, or co-axially with, the first limb, and the second limb is arranged laterally to the first limb. That is to say, the first and third tube connectors are configured to allow the first gas to be conveyed therethrough to provide less flow resistance to the first gas flowing from the first gas source to the expiratory tube compared to the flow resistance to the first gas entering and flowing along the inspiratory tube.
The first gas received by the expiratory tube is vented from the breathing circuit without being accumulated or stored, and the expiratory tube is configured so that the exhaled gas passes through the second non-return valve and is vented from the breathing tube without being accumulated or stored.
The expiratory tube may be configured so that the first gas and the exhaled gas downstream of the second non-return valve are vented from the breathing circuit without re-entering the inspiratory tube.
The breathing circuit may be configured so that there is greater flow resistance for the first gas from the inspiratory tube to the expiratory tube via the patient interface than the flow resistance for the excess of the first gas from the inspiratory tube to the expiratory tube.
The breathing circuit also reduces inefficient use of the second gas by preventing it from continuously passing through the patient interface. This is achieved primarily by the first non-return valve being closed during exhalation. In addition, the breathing circuit has flow resistance that inhibits the flow of the second gas from the inspiratory tube to the expiratory tube by the pressure drop across the first and second non-return valves, and the pressure drop over the lengths of the inspiratory tube and the expiratory tube.
The inspiratory tube may be configured so that the first gas and the second gas entering the inspiratory tube inhibits the exhaled gas from entering the inspiratory tube. For example, the inspiratory tube may have an open passageway.
The breathing circuit may comprise a pressure regulation device configured to regulate pressure in the expiratory tube.
The pressure regulation device may include a pressure relief valve configured to vent the first gas and the exhaled gas from the expiratory tube. The pressure relief valve of the expiratory tube may be a passive valve. For example, the pressure relief valve may be a positive end expiratory pressure valve having 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 pressure regulation device may include a positive end expiratory pressure valve (PEEP valve) on the distal portion of the expiratory tube.
The positive end expiratory pressure valve of the expiratory tube 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 first non-return valve may be arranged downstream of where the second gas enters the inspiratory tube. That is, the first non-return valve may be between the patient interface and where the second gas enters the inspiratory tube.
The first non-return valve may be located adjacent to the patient interface.
The first non-return valve may be located proximal to where the second gas enters the inspiratory tube.
The breathing circuit may also include a gas flow generator that supplies the pressurized first gas; and a sensor that senses when the patient breathes, the sensor having an output signal that is used to operate the gas flow generator
The sensor may include a gas meter in the expiratory tube. That is to say, the gas meter measures a property of the gas in the expiratory tube and the output of the gas meter is used to operate the flow generator. The property of the gas meter may be any suitable property including gas flow rate, gas pressure, gas temperature, gas humidity or gas concentration, such as oxygen or carbon dioxide concentration.
The sensor may include a flow sensor located upstream of the second non-return valve and a pressure sensor located downstream of the second non-return valve. That is to say, the flow sensor measures the flow of the exhaled gas in the expiratory tube and the pressure sensor measures the pressure of the exhaled gas and the first gas being vented from the expiratory tube.
The breathing circuit may include a controller that receives the outputs of the flow and pressure sensors, and the controller has a processor that calculates a control output that is used to operate the flow generator and adjust the gas flow generator to target a desired pressure.
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 inspiratory tube may include a gas passageway of constant diameter, in which the diameter may range from about 18 to 25 mm, or the diameter is about 22 mm.
The inspiratory tube 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 tube 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 tube ideally has an internal volume that allows the pressurized oxygen gas that is stored in the inspiratory tube to be inhaled by the patient in a single inhalation so that venting of the pressurized oxygen gas from the inspiratory tube 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 tube 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 tube during patient exhalation can equal an estimation of an alveoli volume of the patient.
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.
The breathing circuit may include a patient interface. The patient interface may be a sealed patient interface. 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 tube, and an outlet connection that connects to the expiratory tube.
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 tube, and another leg is an outlet connection that connects to the expiratory tube.
The inspiratory tube 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 and moisture exchangers, or other items that have the potential to increase dead space in the breathing circuit between the inspiratory tube and the patient interface.
An embodiment relates to a positive pressure breathing circuit for ventilating a patient, the breathing circuit comprising:
A distal portion of the inspiratory tube may be connectable to the source of the pressurized first gas.
A proximal portion of the inspiratory tube may be connectable to the source of the pressurized second gas.
The proximal portion of the inspiratory tube may be connectable to the patient interface.
The breathing circuit may include a first non-return valve arranged in the inspiratory tube downstream of where the second gas source connects to the inspiratory tube.
The breathing circuit may include a second non-return valve arranged in the expiratory tube.
The loop configuration may include the first tube connector having three limbs. In one example, the first limb is connectable to the first gas source, a second limb is connectable to a distal portion of the inspiratory tube, and a third limb is connectable to the expiratory tube.
In another example, the loop configuration may have a bypass tube interconnecting the inspiratory limb and the expiratory limb. The bypass tube may be connected to the inspiratory tube using any suitable three limb connector.
In situations where the loop configuration has the bypass tube, the second connection limb may connect the bypass tube to the expiratory tube.
An embodiment relates to a device that can be arranged between a gas non-return valve and a gas tube, the device includes a body having a bay portion that connects to the non-return valve, and a flow director extending from the bay portion that receives gas from the gas tube, wherein the flow director has a flow constriction that is configured to increase speed of the gas passing therethrough and faces toward the non-return valve so that the gas that exits the flow director assists in biasing the non-return valve into an operating position.
The bay portion may be fixedly connected to an outlet of the non-return valve.
The bay portion may be removably connected to an outlet of the non-return valve.
The non-return valve may be the second non-return valve described herein.
The bay portion may be fixedly connected to the gas tube. In one example, the gas tube may be the bypass tube described herein.
The bay portion may be removably connected to the gas tube.
The operating position of the non-return valve may be a closed position.
The flow constriction may have a nozzle that faces toward the non-return valve.
The flow constriction may have a passageway that narrows in a direction of flow of the first gas.
The flow constriction may have converging walls in the direction of flow of the first gas.
The flow constriction has a discharge portion having an outlet for discharging the gas passing through the flow director, in which the discharge portion has a constant diameter.
The flow constriction may include a converging portion that narrows in a direction of flow of the first gas.
The flow constriction may have an outlet orifice that faces toward the second non-return valve. The outlet orifice may have cross-sectional area ranging from about 10 to 80% less than a cross-section area of the inspiratory tube, and suitably ranging from about 20 to 70% less, and suitably ranging from about 30 to 60% less, and suitably ranging from about 40 to 50% less than a cross-section area of the inspiratory tube.
The non-return valve and the flow director may be oppositely disposed on the bay portion.
The body may have an outer wall that defines the bay portion.
The body may have an outer wall having opposite ends that connect to the non-return valve and the gas tube, the outer wall also defining the bay portion as a cavity between the opposite ends.
The device may have a tubular formation extending from the outer wall in which the flow director is located.
The body of the device may have a discharge outlet for discharging the gas passing through the flow director and the non-return valve. That is to say, the non-return valve has an outlet that opens into the bay portion. The discharge outlet may extend from the outer wall.
The discharge outlet may be integrally formed with the expiratory tube described herein.
The device may be included in the breathing circuit described herein. For example, the first gas in the bypass tube, may pass through the flow director to help bias the non-return valve, suitably the second non-return valve in a closed position during patient inhalation.
An embodiment relates to a positive pressure breathing circuit for ventilating a patient, the breathing circuit including:
A distal portion of the inspiratory tube may be connectable to the source of the pressurized first gas.
A proximal portion of the inspiratory tube may be connectable to the source of the pressurized second gas.
The proximal portion of the inspiratory tube may be connectable to the patient interface.
The expiratory tube may include a second non-return valve.
The inspiratory tube may include a first non-return valve that is arranged between the patient interface and the second gas entering the inspiratory tube.
Flow of the first gas through the flow director may fluctuate, for example, cycle from a higher flow when the patient exhales, meaning the patient exhaling will need to overcome any bias of the second non-return valve in the closed position.
The flow director may be a constriction in the expiratory tube that opens toward the second non-return valve.
The flow director may be a nozzle.
The flow director may have a passageway that narrows in a direction of flow of the first gas, in which the passageway has an opening that faces toward the second non-return valve. The purpose of the flow director is to direct the first gas exiting the flow director at an increased speed to impact on the second non-return valve, thereby providing additional biasing to close the second non-return valve. In other words, the excess first gas can provide a velocity head for closing the second non-return valve.
An embodiment relates to a positive pressure breathing circuit for ventilating a patient, the breathing circuit comprising:
A distal portion of the inspiratory tube may be connectable to the source of the pressurized first gas.
A proximal portion of the inspiratory tube may be connectable to the source of the pressurized second gas.
The proximal portion of the inspiratory tube may be connectable to the patient interface.
The breathing circuit may include a gas flow generator that supplies the first gas.
The inspiratory tube may include a first non-return valve that is arranged downstream of the second gas entering the inspiratory tube.
The first non-return valve may be configured to inhibit the exhaled gas from entering the inspiratory tube.
The expiratory tube may include a second non-return valve.
The second non-return valve may inhibit the first gas from entering the patient interface from the expiratory tube.
The gas flow generator may be a variable flow generator that is operable at a higher pressure and a lower pressure. Typically the gas flow generator operates at the higher pressure when the sensor detects inhalation, and at the lower pressure when the sensor detects exhalation. The flow generator may cycle between the higher pressure and the lower pressure during continuous patient breathing. That is to say, the positive pressure breathing circuit may be a bi-level breathing circuit for bi-level positive air pressure therapy, also known as BiPAP. However, it will be appreciated by those skilled in the art that the pressure levels are nominal and that the breathing circuit will be operated over a pressure range.
The sensor may include a flow sensor located upstream of the second non-return valve and a pressure sensor located downstream of the second non-return valve. That is to say, the flow sensor measures the flow of the exhaled gas in the expiratory tube and the pressure sensor measures the pressure of the exhaled gas and the first gas being vented from the expiratory tube.
The breathing circuit may include a controller that receives the outputs from the flow sensor and the pressure sensors, and the controller has a processor that calculates a control output that is used to operate the flow generator and adjust the flow generator to target a desired pressure.
Another embodiment relates to a method of ventilating a patient, the method including steps of:
The step of supplying the first gas to the inspiratory tube includes supplying in an excess amount and conveying excess supply of the first gas from the inspiratory tube to the expiratory tube, and venting the excess supply of the first gas and the exhaled gas from the expiratory tube.
The inspiratory tube may include a first non-return valve.
The first non-return valve may inhibit the exhaled gas from entering the inspiratory tube.
The expiratory tube may include a second non-return valve.
The second non-return valve may inhibit the first gas from entering the patient interface from the expiratory tube.
Supplying the pressurized second gas into the proximal portion of the inspiratory tube may include the second gas entering the inspiratory tube upstream from the first non-return valve.
The method may further include the step of venting the first gas and the exhaled gas received by the expiratory tube from the breathing circuit.
The first gas and the exhaled gas may be vented from the breathing circuit downstream of the second non-return valve.
The step of supplying the pressurized first gas may be carried out continuously to the distal portion of the inspiratory tube.
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 step of providing the breathing circuit includes the breathing circuit having a pressure regulating device, and the method includes regulating the pressure in the breathing circuit.
The pressure regulating device may be a positive end expiratory valve (PEEP valve) in the expiratory tube downstream of the second non-return valve, and the method may include operating the PEEP valve to vent the exhaled gas and the first gas from the breathing circuit at a desired pressure.
The method may include selecting a pressure setting of the PEEP valve of the expiratory tube 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 step of supplying the second gas may include controlling the flow rate of the second gas to the inspiratory tube 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. In one example, the controlling the flow rate of the second gas may include supplying the second gas at a constant rate.
In another example, controlling the flow rate of the first gas may include cycling output pressure of the flow generator between high pressure during patient inhalation and low pressure during patient exhalation. For example, controlling the flow rate of the first gas may include cycling output pressure of the flow generator between high pressure flow and low pressure flow based on inhalation of the patient and exhalation, respectively.
The breathing circuit provided may include a gas flow sensor in the expiratory tube upstream of the second non-return valve and a pressure sensor located downstream of the second non-return valve, and the method may include detecting when the patient is exhaling based on an output of the flow sensor and detecting the pressure of first gas being supplied to the breathing circuit based on an output of the pressure sensor.
The breathing circuit may include a controller that receives the outputs of the gas flow and pressure sensors, and the controller has a processor that calculates a control output that is used to operate the flow generator and adjust the flow generator to target a desired pressure.
The controller may detect a trigger gas flow rate shortly after the start of the patient exhaling and toward the end of the patient exhaling. The trigger gas flow rate may be in the range from about 3 to 15% of the maximum exhaling flow rate, and suitably about 5 to 10% of the maximum exhaling flow rate.
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 tube can be determined so that the volume of the second gas stored in the inspiratory tube during exhalation and supplied to the inspiratory tube 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 the 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 tube may be based on a level of oxygen saturation in the patient's blood.
During patient exhalation, the second gas entering the inspiratory tube can flow backwards along the inspiratory tube which acts as a constant pressure storage volume by displacing air out of the inspiratory tube via the further positive end expiratory pressure valve of the inspiratory tube.
During patient inhalation, the breathing gas from the inspiratory tube will initially be the second gas that had been stored in the inspiratory tube 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 tube 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 tube 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 tube 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 tube 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 inspiratory tube may include a gas passage of constant diameter, in which the diameter may range from about 18 to 25 mm, or a diameter about 22 mm.
The inspiratory tube 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 tube 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 breathing circuit provided by the method described herein may include any one or a combination of the features described herein. Similarly, the method described herein may include any one or a combination of the features of the breathing circuit.
The embodiments described in the paragraphs [0005], [0066], [0075], [0095], [0105] and [0118] may include any one or a combination of the features described herein.
Throughout this specification the term “excess supply of the first gas”, or variations thereof, refers to an amount of the first gas supplied by the flow generator that is not delivered to the patient interface.
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 Figures. To maintain clarity of the Figures, however, not all reference numerals are included in each Figure. 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 tube 11 having a gas passageway that conveys gas toward a sealed patient interface 21 and an expiratory tube 12 also having a gas passageway that conveys gas away from the patient interface 21. As can be seen in
The inspiratory tube 11 has a proximal portion 27 close to the patient that is connectable to the sealed patient interface 21 for supplying a breathing gas, and a distal portion 26 more remote from the patient that has a first gas inlet 15 that is connectable to the first gas source 13. The proximal portion 27 of the inspiratory tube 11 also includes a second gas inlet 17 that is connectable to a second gas source 14 of a pressurized second gas 18 and includes a first non-return valve 19 that is located upstream of the patient interface 21 and downstream of the second gas inlet 17 where the second gas 18 enters the inspiratory tube 11. The first non-return valve 19 inhibits exhaled gas 32 from entering the inspiratory tube 11 and is located in the proximal portion 27 of the inspiratory tube 11 and is located proximal to the second gas inlet 17. In addition, the first non-return valve 19 inhibits the second gas passing to the patient interface 21 during patient exhalation. In another example, not illustrated, the first non-return valve 19 may be located on the patient interface 21.
The expiratory tube 12 includes a second non-return valve 20 that inhibits exhaled gas 32 from re-entering the patient interface 21 after having been exhaled and inhibits the first gas 16 from entering the patient interface 21 from the expiratory tube 12. As can be seen in
The first and second non-return valves 19, 20 may be any suitable valves, include a one-way flap valve, a biased valve that is biased into a closed position, or a diaphragm valve. The first non-return valve 19 closes when the gas pressure downstream of the first non-return valve 19, for instance in the patient interface 21, is greater than the pressure in the inspiratory tube 11. The first non-return valve 19 opens, suitably automatically, when the patient spontaneously inhales. More particularly during patient inhalation, the first non-return valve 19 is in an opened position and the second non-return valve 20 is in a closed position. Similarly, the second non-return valve 20 opens when the patient spontaneously exhales, so that during patient exhalation, the first non-return valve 19 is in a closed position and the second non-return valve 20 is in the opened position. The first and second non-return valves 19 and 20 provide flow resistance when in the closed position and to a degree when in the opened position. In practice this means that first non-return valve 19 has flow resistance even when in the opened position, and similarly, the second non-return valve 20 has flow resistance even when in the opened position. The flow resistance provided by the first and second non-return valves 19 and 20 reduces the risk of the first gas 16 supplied in excess passing through the inspiratory tube 11 and out through the expiratory tube 12 via the patient interface 21, which if this occurred would reduce the efficiency in use of the second gas 18.
In addition, when the patient exhales, the pressure at which the patient spontaneously exhales, which does not need to be higher than the pressure of the second gas source 14 can cause the first non-return valve 19 to change to the closed position. This further reduces the risk of the first gas 16 supplied in excess passing through the inspiratory tube 11 and out through the expiratory tube 12 which if occurred, would reduce the efficiency of the second gas used by the breathing circuit.
In
The second gas inlet 17 is a second T-shaped tube connector having three limbs. Specifically, a first limb is connected to a second gas source via a second supply line 55, a second limb is connected to a proximal portion 27 of the inspiratory tube 11 that includes the first non-return valve 19, the second limb being lateral to the first limb, and a third limb is connected to the inspiratory tube 11 that extends upstream of the second gas inlet 17. The third limb is arranged parallel to, or co-axially with, the second limb.
In
In
In the case of
An enlarged cross-sectional view of the device 56 is shown in
The breathing circuit 10 also includes a pressure regulation device 22 for regulating the pressure in the breathing circuit 10. The pressure regulation device 22 includes, in part, the inherent pressure of the first gas source 13 and/or a control valve (not illustrated) that may throttle pressure of the first gas 16 delivered to the inspiratory tube 11 by the first gas source 13 and, optionally, the flow generator 33 connected to the first gas source 13 for supplying the first gas 16 (see
The pressure relief valve 61 may be any suitable device, such as a fixed value positive end expiratory valve (PEEP valve) 62 (see
During patient inhalation and exhalation, the second gas 18 from a second gas source 14 enters the proximal portion 27 of the inspiratory tube 11 via the second gas inlet 17 at a constant rate, and the first gas 16 from a first gas source 13 enters the distal portion 26 via the first gas inlet 15 at a constant rate. At the start of patient exhalation, or during a pause between inhalation ending and exhalation starting, the first non-return valve 19 closes and the second gas 18 back fills the gas passageway of the inspiratory tube 11 in a direction from the second gas inlet 17 toward the distal portion 26. During patient exhalation, the second gas 18 and the first gas 16 form a gas/gas interface that moves along the gas passageway away from the second gas inlet toward the distal portion, thereby storing a volume of the second gas 18 in the inspiratory tube 11 during patient exhalation. The volume of the second gas 18, such as oxygen, that enters the inspiratory tube 11 during exhalation is equal to, or less than, a tidal volume of the patient, thereby minimizing wastage of the second gas 18 by avoiding venting the first gas 16 during exhalation. Ideally, the internal volume of the inspiratory tube 11 is selected such that all of the second gas 18 that is stored in the inspiratory tube 11 and the second gas 18 supplied into the inspiratory tube 11 from the second gas source 14 during patient inhalation is equal to, or less than the tidal volume of the patient. Ideally, the inspiratory tube 11 has a known storage volume of at least two thirds of the patient's tidal volume for storing the second gas.
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.
Set out below in Table 1 is a list of exemplary internal volumes of an inspiratory tube having a 22 mm internal diameter. For usability and to ensure adequate internal volume is provided, the inspiratory tube has an internal diameter of 22 mm and a length in the ranging from 1.5 m to 1.8 m for adult patients.
The first gas 16 and the second gas 18 can be any suitable breathable gases. For example, the first gas 16 may be any breathable gas such as air, air enriched with oxygen, or any suitable anaesthetic gas. In the situation where the first gas 16 is air, air may be supplied to the inspiratory tube 11 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 tube 11 in the range of 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 tube 11 in the range of 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 tube 11 in the range of the 2 to 10 L/min, or in the range of 3 to 6 L/min.
Similarly, the second gas 18 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 exhaled gas 32 and the first gas 16 are vented from the breathing circuit 10 with little venting, or no venting of the second gas 18. This enables better usage of the second gas 18, 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 for a given amount of oxygen gas or to allow higher levels of oxygen enrichment to be provided to the same number of patients.
The first and second gases 16, 18 can be supplied by any suitable sources, including pressure cylinders containing the required gases or in-wall hospital supply. In addition, as shown in
In the situation where the breathing circuit 10 is used to provide supplemental oxygen gas as the second gas, supplying the second gas/oxygen gas can be adjusted based on patient response, for example the level of oxygen saturation in the patient's blood. Oxygen gas may be supplied at a constant 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.
Based on the assessment of the therapy requirements of the patient, the first gas 16 and the second gas 18 can be supplied to the inspiratory tube 11 at a flow rate that may be determined and controlled.
Controlling 43 the flow rate of the first gas 16 is based on the peak respiratory flow requirement of the patient, and controlling 44 the flow rate of the second gas 18 is based on the fraction of inhaled oxygen gas (FiO2) for the therapy requirement of the patient.
In this situation, the first gas 16 for example air, may be supplied at a constant rate or at a constant pressure. Examples of suitable flow rates range from about 40 to 120 L/min for adult patients, or about 60 L/min. Set out below in Table 2 are examples of flow rates and inspiratory tube 11 volumes for adult patients, pediatric patients and neonatal patients. As can be seen the flow rates and inspiratory tube 11 volumes vary for each category of patient.
In the case of
Depending on the breathing requirements of the patient, including whether the patient is inhaling or exhaling, the controller 38 may, in one example, determine a new desired outlet pressure and adjusts the flow rate or speed of the flow generator 33 to achieve a desired pressure. In another example, the controller may determine a new outlet flow rate or speed of the flow generator 33. The controller 38 outputs a control signal 39 that is calculated from one or more of the sensor outputs 35 and 37 to operate the flow generator 33. The control signal 37 is represented in
The first gas 16 may be filtered air, ambient air, or ambient air that has been filtered. In the case of
The second gas 18, 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 tube 11 having a known internal volume to store the required amount of at least the second gas. For adult patients, where the inspiratory tube 11 has an internal diameter of 22 mm the inspiratory tube 11 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 tube 11 can be selected by the user. Table 2 above has further examples of flow rates and inspiratory tube 11 volumes for adult patients, pediatric patients and neonatal patients
Supplying 42 the second gas 18, such as oxygen gas to the proximal portion 27 of the inspiratory tube 11, includes the oxygen gas entering the inspiratory tube 11 upstream of the first non-return valve 19. Furthermore the method may include supplying the pressurized air into the distal portion 26 of the inspiratory tube 11 during patient exhalation while a volume of the pressurized oxygen gas enters and is stored in the inspiratory tube 11. As this occurs, excess air supplied to the inspiratory tube 11 is conveyed to the expiratory tube 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 tube. In other words, the second gas 18 is supplied at a pressure greater to the inspiratory tube 11 than the first gas 16 so that the second gas 18 can backfill the inspiratory tube 11.
The method may include venting 46, 47 the first gas 16 from the expiratory tube 12 at any stage during the breathing cycle. During exhalation, exhaled gas 32 will also pass the second non-return valve 20 and enter the distal portion of the expiratory tube. The exhaled gas 32 downstream of the second non-return valve 20 is prevented from being re-inhaled and is vented from the circuit 10. In addition, the first gas 16 conveyed to the expiratory tube 12 will be vented from the circuit 10 on account of the second gas 18 entering the inspiratory tube 11 downstream of the first gas 16 entering the inspiratory tube 11.
The first gas 16 can be supplied by a variable flow generator 33 when, for example, the breathing circuit is used to supply bi-level positive air pressure therapy in which the first gas is supplied to the inspiratory tube at an inspiratory pressure that is greater than an expiratory pressure. With reference to
Although not shown in the Figures, the breathing circuit may also include: i) anti-asphyxiation valves, ii) flow rate flags to indicate that the appropriate excess flow necessary to maintain the required positive pressure, iii) purifiers such as anti-viral and bacterial filters for protecting healthcare staff, and iv) humidifiers for humidifying one or more of the first and second gases prior to delivery to the patient to increase patient comfort and reduce dehydration. The humidifiers may be arranged in the inspiratory and the expiratory tubes.
The components of the breathing circuit described herein, including the inspiratory tube and the expiratory tube may be made of any suitable medical grade materials, including flexible plastic tubing that is substantially non-stretchable. Moreover, suitably the inspiratory and the expiratory tubes meet the ISO-5367 standard for compliance.
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 of the inventions 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.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/NZ2022/050018 | 2/11/2022 | WO |
