PRIORITY CLAIM

[001] This application claims priority to Australian Provisional Patent Application Australian Provisional Patent Application 2019902872 filed on 9 August 2019, the contents of which is hereby incorporated by reference.

FIELD

[002] The present disclosure relates, at least in part, to devices and components for mixing a gas with air for delivery to a patient, and to methods for mixing a gas with air for delivering to a patient.

BACKGROUND

[003] The provision of oxygen-air mixtures to anaesthetic circuits usually requires pressurised gas supplies (piped or in cylinders) and a gas blender. This equipment is bulky and expensive. Additionally, at some sites there is no piped medical air available in the anaesthetic rooms or in theatre recovery. As a result, there is often no other option than to provide 100% oxygen to patients in these areas.

[004] The use of pure oxygen has been shown to be detrimental to paediatric patients. In particular this applies to newborn and premature infants where pure oxygen damages both lungs (bronchopulmonary dysplasia) and eyes (retinopathy of prematurity). This damage is frequently irreversible leading to chronic lung disease and blindness. Even quite short periods of exposure may cause significant damage.

[005] In older children pure oxygen may also lead to basal lung collapse impairing oxygenation (absorption atelectasis). The consequences of this are not as serious but may mead to prolonged hospital stay following surgery. However in children with certain congenital heart conditions, exposure to 100% oxygen may significantly affect their systemic circulation (so called balanced circulation referring to a single ventricle physiology). [006] Neonatal intensive care units (NICU), paediatric intensive care units (PICU) and operating theatres (OT) typically have access to piped medical air which can then be blended with oxygen to achieve the desired and appropriate oxygen fraction (Fi02). However outside of these immediate areas the issue of reduced fraction of oxygen becomes more difficult. In many hospitals there is no piped air in the OT recovery areas or available for transport (unless a specialised blender is available). Therefore most postoperative patients are transported and recovered using 100% oxygen.

[007] Accordingly, there is a continuing need to be able to deliver oxygen mixed with air under conditions where access to piped medical air and oxygen is not available. The present disclosure relates to a device which can be used to mix air with oxygen, thereby reducing the Fi02, and enabling positive pressure ventilation (PPV) to be delivered to a patient.

SUMMARY

[008] The present disclosure relates, at least in part, to devices for mixing a gas with air for delivery to a patient, and to methods for mixing a gas with air for delivering to a patient.

[009] Certain embodiments of the present disclosure provide a device for mixing a gas with air for delivery to a patient, the device comprising: a gas inlet for delivering the gas under pressure to the device, the gas inlet comprising a venturi nozzle venting into a chamber for mixing the gas with air; a one way air inlet valve in gaseous communication with the chamber to allow entrained air to be drawn into the chamber and mixed with the gas, the entrained air being drawn into the chamber by the flow of the gas through the venturi nozzle into the chamber; and an outlet for delivering the gas mixed with air to the patient, the outlet being in gaseous communication with the chamber for mixing the gas with air.

[0010] Certain embodiments of the present disclosure provide use of a device as described herein to mix a gas with air for delivery under positive pressure to a patient. [0011] Certain embodiments of the present disclosure provide a method of providing a gas mixed with air to a patient, the method comprising use of a device as described herein to provide the gas mixed with air for delivery to the patient.

[0012] Certain embodiments of the present disclosure provide a positive pressure ventilation device for delivering a gas mixed with air to a patient, the device comprising: a gas inlet for delivering the gas under pressure to the device, the gas inlet comprising a venturi nozzle venting into a chamber for mixing the gas with air; a one way air inlet valve in gaseous communication with the chamber to allow entrained air to be drawn into the chamber and mixed with the gas, the entrained air being drawn into the chamber by the flow of the gas through the venturi nozzle into the chamber; and an outlet for delivering the gas mixed with air to the patient, the outlet being in gaseous communication with the chamber for mixing the gas with air.

[0013] Certain embodiments of the present disclosure provide use of a device as described herein to deliver gas under positive pressure to a patient.

[0014] Certain embodiments of the present disclosure provide a method of ventilating a patient, the method comprising use of a device as described herein to ventilate the patient.

[0015] Certain embodiments of the present disclosure provide a method of providing a gas mixed with air to a patient, the method comprising: delivering the gas under pressure via a gas inlet comprising a venturi nozzle venting into a chamber; introducing entrained air into the chamber via a one way air inlet valve to mix with the gas delivered under pressure, the entrained air being drawn into the chamber by the flow of the gas through the venturi nozzle into the chamber; and delivering the gas mixed with the entrained air to the patient, thereby providing the gas mixed with air to the patient. [0016] Certain embodiments of the present disclosure provide a device for providing gas mixed with air to a patient, the device using a method as described herein.

[0017] Certain embodiments of the present disclosure provide a method of adjusting the concentration of a gas to be provided to a patient, the method comprising: delivering the gas under pressure via a gas inlet comprising a venturi nozzle venting into a chamber; introducing entrained air into the chamber via a one way air inlet valve to mix with the gas delivered under pressure, the entrained air being drawn into the chamber by the flow of the gas through the venturi nozzle into the chamber; and adjusting the flow of the gas delivered to the chamber so as to adjust the concentration of the gas mixed with air to be delivered to the patient.

[0018] Certain embodiments of the present disclosure provide a one way inlet valve for providing gas under pressure to a breathing device, the inlet valve comprising: a connector for gaseously connecting the one way inlet valve to a source of the gas under pressure; a venturi nozzle in gaseous communication with the connector; and one or more air inlet ports for allowing entrained air to be drawn through the one way inlet valve by the flow of the gas through the venturi nozzle.

[0019] Certain embodiments of the present disclosure provide a positive pressure ventilation device for a patient, the device comprising a one way inlet valve as described herein.

[0020] Certain embodiments of the present disclosure provide a Mapleson circuit type breathing apparatus, the apparatus comprising: a gas inlet for delivering the gas under pressure to the apparatus, the gas inlet comprising a venturi nozzle venting into a chamber for mixing the gas with air; a one way air inlet valve in gaseous communication with the chamber to allow entrained air to be drawn into the chamber and mixed with the gas, the entrained air being drawn into the chamber by the flow of the gas through the venturi nozzle into the chamber; an outlet for delivering the gas mixed with air to the patient, the outlet being in gaseous communication with the chamber for mixing the gas with air; and a reservoir bag for collecting or venting expired gas from the subject, the reservoir bag being in gaseous communication with the outlet.

[0021] Other embodiments are described herein.

[0022] This summary is not intended to be limiting with respect to the embodiments disclosed herein and other embodiments are disclosed in this specification. In addition, limitations of one embodiment may be combined with limitations of other embodiments to form additional embodiments.

BRIEF DESCRIPTION OF THE FIGURES

[0023] For a better understanding of the present disclosure, and to show more clearly how the present disclosure may be carried into effect according to one or more embodiments thereof, reference will be made, by way of example, to the accompanying figures.

[0024] Figure 1 shows a schematic representation of the cross section of a positive pressure ventilation device for delivering a gas mixed with air to a patient according to one embodiment.

[0025] Figure 2 shows a schematic representation of a cross-sectional view of the device shown in Figure 1, where gas is provided under pressure to the device.

[0026] Figure 3 shows an elevated view of a positive pressure ventilation device according to one embodiment rendered in three dimensions.

[0027] Figure 4 shows a schematic representation of a positive pressure ventilation device according to one embodiment used in conjunction with a Mapleson F circuit breathing apparatus. DETAILED DESCRIPTION

[0028] The present disclosure relates, at least in part, to devices and components for mixing a gas with air for delivery to a patient, and to methods for mixing a gas with air for delivering to a patient.

[0029] Certain embodiments of the present disclosure provide a device for mixing a gas with air for delivery to a patient.

[0030] In certain embodiments, the present disclosure provides a device for mixing a gas with air for delivery to a patient, the device comprising: a gas inlet for delivering the gas under pressure to the device, the gas inlet comprising a venturi nozzle venting into a chamber for mixing the gas with air; a one way air inlet valve in gaseous communication with the chamber to allow entrained air to be drawn into the chamber and mixed with the gas, the entrained air being drawn into the chamber by the flow of the gas through the venturi nozzle into the chamber; and an outlet for delivering the gas mixed with air to the patient, the outlet being in gaseous communication with the chamber for mixing the gas with air.

[0031] In certain embodiments, the device is configured for use in a breathing apparatus.

[0032] In certain embodiments, the device is configured for use in a Mapleson type circuit. In certain embodiments, the device is configured for use in a Mapleson F type circuit.

[0033] In certain embodiments, the device is configured to deliver gas to an anaesthetic circuit, such as a circle breathing system.

[0034] In certain embodiments, the patient is a human patient. In certain embodiments, the patent is a paediatric patient. In certain embodiments, the patient is a neonatal patient. Veterinary uses of the present disclosure are also contemplated.

[0035] In certain embodiments, the patient is a paediatric patient susceptible to bronchopulmonary dysplasia and/or retinopathy of prematurity.

[0036] In certain embodiments, the patient is susceptible to absorption atelectasis.

[0037] In certain embodiments, the patient is suffering from a heart condition, such as a congenital heart condition.

[0038] Other types of patients are contemplated.

[0039] In certain embodiments, the gas comprises oxygen. In certain embodiments, the gas is pure oxygen. Other types of gases (or mixture of gases) for mixing with air are contemplated. Sources of gas for delivering the gas under pressure to the device are known in the art. In certain embodiments, the source of gas is bottled gas under pressure.

[0040] In certain embodiments, the gas is delivered to the device at a flow rate of 1 to 6 1/min.

[0041] Venturi nozzles are known in the art. In certain embodiments, the venturi nozzle comprises a minimum throat diameter of 0.3 mm to 1 mm.

[0042] In certain embodiments, the air inlet valve comprises one or more air inlet ports. In certain embodiments, the air inlet valve comprises a plurality of air inlet ports.

[0043] In certain embodiments, the air inlet valve comprises one or more air inlet ports and the one or more air inlet ports are located adjacent to the gas inlet. In certain embodiments, the air inlet valve comprises a plurality of air inlet ports and the air inlet ports are located around the gas inlet. In certain embodiments, the plurality of air inlet ports are located around the gas inlet, which is centrally located.

[0044] In certain embodiments, the venturi nozzle and the air inlet valve are collocated. In certain embodiments, the gas inlet, the venturi nozzle and the air inlet valve are collocated.

[0045] In certain embodiments, the gas inlet, the venturi nozzle and the one way air inlet valve are located in a single component for connection to the chamber, thereby forming a one way valve for providing gas under pressure to a breathing device.

[0046] In certain embodiments, the air inlet valve is a diaphragm type of valve. Diaphragm valves and their production are known in the art. Other valve types are contemplated.

[0047] In certain embodiments, the air inlet valve comprises a seal for sealing the air inlet ports. In certain embodiments, the air inlet valve comprises a seal for sealing the air inlet ports made from a resilient material. Suitable resilient materials may be selected. In certain embodiments, the seal comprises a thermoplastic elastomer. Elastomers are commercially available or may be produced by a method known in the art. Other types of material are contemplated.

[0048] The chamber for mixing the gas with air comprises a void in gaseous communication with the air inlet valve which permits entrained air to enter the device. The chamber may be of a suitable size and configuration to enable mixing of entrained air with the gas.

[0049] In certain embodiments, the outlet for delivering the gas mixed with air to the patient is connected to a connector for connection to a face mask or other component, such as a supraglottic airway or an endotracheal tube.

[0050] In certain embodiments, the device comprises a further inlet/outlet in gaseous communication with the outlet for delivering the gas mixed to the patient, the inlet/outlet permitting flow of expired gas from the patient.

[0051 ] In certain embodiments, the outlet for delivering gas mixed with air to the patient and the inlet/outlet are connected in a linear arrangement and the gas mixed with the entrained air is delivered laterally to the outlet and the inlet/outlet.

[0052] In certain embodiments, the gas mixed with the entrained air is delivered substantially at a right angle to the outlet and the inlet/outlet.

[0053] In certain embodiments, the gas mixed with the entrained air is delivered obliquely. In certain embodiments, the gas mixed with the entrained air is delivered at an angle of 10° to 45° to the outlet and the inlet/outlet.

[0054] In certain embodiments, the device comprises a two-ended bag in gaseous connection with the inlet/outlet, such as in a Mapleson F type circuit.

[0055] In certain embodiments, the device is configured for use in a breathing apparatus. In certain embodiments, the device is adapted for gaseous attachment to a breathing apparatus, such as a Mapleson type circuit.

[0056] In certain embodiments, the device is used to adjust the concentration of a gas to be provided to a patient.

[0057] In certain embodiments, the device is used to deliver a gas mixed with air under positive pressure to a patient.

[0058] Certain embodiments of the present disclosure provide use of a device as described herein to mix a gas with air for delivery under positive pressure to a patient.

[0059] Certain embodiments of the present disclosure provide a method of providing a gas mixed with air to a patient, the method comprising use of a device as described herein to provide gas mixed with air for delivery to the patient.

[0060] Certain embodiments of the present disclosure provide a positive pressure ventilation device as described herein for delivering a gas mixed with air to a patient.

[0061] In certain embodiments, the present disclosure provides a positive pressure ventilation device for delivering a gas mixed with air to a patient, the device comprising: a gas inlet for delivering the gas under pressure to the device, the gas inlet comprising a venturi nozzle venting into a chamber for mixing the gas with air; a one way air inlet valve in gaseous communication with the chamber to allow entrained air to be drawn into the chamber and mixed with the gas, the entrained air being drawn into the chamber by the flow of the gas through the venturi nozzle into the chamber; and an outlet for delivering the gas mixed with air to the patient, the outlet being in gaseous communication with the chamber for mixing the gas with air. [0062] The components of the device, and its use to deliver a gas mixed with air to a patient, are as described herein.

[0063] Certain embodiments of the present disclosure provide use of a positive pressure ventilation device as described herein to deliver a gas under positive pressure to a patient.

[0064] Certain embodiments of the present disclosure provide a method of ventilating a patient, the method comprising use of a device as described herein to ventilate the patient.

[0065] In certain embodiments, the method for ventilating a subject comprises use of a breathing apparatus for the patient.

[0066] In certain embodiments, the breathing apparatus is a Mapleson type circuit. In certain embodiments, the breathing apparatus is a Mapleson F type circuit.

[0067] Certain embodiments of the present disclosure provide a method of providing a gas mixed with air to a patient, as described herein.

[0068] In certain embodiments, the present disclosure provides a method of providing a gas mixed with air to a patient, the method comprising: delivering the gas under pressure via a gas inlet comprising a venturi nozzle venting into a chamber; introducing entrained air into the chamber via a one way air inlet valve to mix with the gas delivered under pressure, the entrained air being drawn into the chamber by the flow of the gas through the venturi nozzle into the chamber; and delivering the gas mixed with the entrained air to the patient, thereby providing the gas mixed with air to the patient.

[0069] Gases and the components used in the method are as described herein.

[0070] Certain embodiments of the present disclosure provide a device for delivering gas mixed with air to a patient, the device using a method as described herein.

[0071] Certain embodiments of the present disclosure provide a method of adjusting the concentration of a gas to be provided to a patient.

[0072] In certain embodiments, the present disclosure provides a method of adjusting the concentration of a gas to be provided to a patient, the method comprising: delivering the gas under pressure via a gas inlet comprising a venturi nozzle venting into a chamber; introducing entrained air into the chamber via a one way air inlet valve to mix with the gas delivered under pressure, the entrained air being drawn into the chamber by the flow of the gas through the venturi nozzle into the chamber; and adjusting the flow rate of the gas delivered to the chamber so as to adjust the concentration of the gas mixed with air to be delivered to the patient.

[0073] Methods for assessing the concentration of gas mixed with air are known in the art. Gases and components used in the method are as described herein.

[0074] Certain embodiments of the present disclosure provide a component of the device as described herein.

[0075] Certain embodiments of the present disclosure provide a one way inlet valve for providing gas under pressure to a breathing device.

[0076] In certain embodiments, the present disclosure provides a one way inlet valve for providing gas under pressure to a breathing device, the inlet valve comprising: a connector for gaseously connecting the one way inlet valve to a source of the gas under pressure; a venturi nozzle in gaseous communication with the connector; and one or more air inlet ports for allowing entrained air to be drawn through the one way inlet valve by the flow of the gas through the venturi nozzle.

[0077] Components of the one way inlet valve are as described herein.

[0078] In certain embodiments, the one way inlet valve is adapted for attachment to a breathing apparatus. [0079] In certain embodiments, the one way inlet valve is adapted for attachment to a component for use in a breathing apparatus, for example a T-piece for use in a Mapleson type circuit.

[0080] In certain embodiments, the one way inlet valve is a component for use in a breathing apparatus.

[0081] Certain embodiments of the present disclosure provide a product comprising a one way inlet valve as described herein and a T-piece for use in a breathing apparatus. In certain embodiments, the one way valve and the T-piece are separate components.

[0082] Certain embodiments of the present disclosure provide a positive pressure ventilation device for a patient, the device comprising a one way inlet valve as described herein.

[0083] In certain embodiments, the device is a breathing apparatus. Breathing apparatus are as described herein.

[0084] In certain embodiments, the breathing apparatus is a Mapleson type circuit breathing apparatus. Mapleson type circuit breathing apparatus are as described herein.

[0085] Certain embodiments of the present disclosure provide a Mapleson circuit type breathing apparatus, the apparatus comprising a one way inlet valve as described herein to deliver gas under pressure to the apparatus.

[0086] In certain embodiments, the present disclosure provides a Mapleson circuit type breathing apparatus, the apparatus comprising: a gas inlet for delivering the gas under pressure to the apparatus, the gas inlet comprising a venturi nozzle venting into a chamber for mixing the gas with air; a one way air inlet valve in gaseous communication with the chamber to allow entrained air to be drawn into the chamber and mixed with the gas, the entrained air being drawn into the chamber by the flow of the gas through the venturi nozzle into the chamber; an outlet for delivering the gas mixed with air to the patient, the outlet being in gaseous communication with the chamber for mixing the gas with air; and a reservoir bag for collecting or venting expired gas from the subject, the reservoir bag being in gaseous communication with the outlet.

[0087] In certain embodiments, the present disclosure provides a Mapleson circuit type breathing apparatus, the apparatus comprising: a one way air inlet valve comprising a connector for gaseously connecting the one way inlet valve to a source of the gas under pressure and a venturi nozzle for venting into a chamber for mixing the gas with air, the one way inlet valve further comprising one or more air inlet ports to allow entrained air to be drawn into the chamber and mixed with the gas; an outlet for delivering the gas mixed with air to the patient, the outlet being in gaseous communication with the chamber for mixing the gas with air; and a reservoir bag for collecting or venting expired gas from the subject, the reservoir bag being in gaseous communication with the outlet.

[0088] The present disclosure is further described by the following examples. It is to be understood that the following description is for the purpose of describing particular embodiments only and is not intended to be limiting with respect to the above description.

EXAMPLE 1 - Development of a positive pressure ventilation device

[0089] The present disclosure arises from the recognition of the problem of high concentrations of oxygen being routinely administered to paediatric patients in the perioperative period. This includes a subset of particularly high risk patient groups, while also likely representing lower level harm in a wider patient cohort.

[0090] The provision of oxygen-air mixtures to anaesthetic circuits usually requires pressurised gas supplies (piped or in cylinders) and a gas blender. This equipment is bulky and expensive. Additionally, at some sites there is no piped medical air available in the anaesthetic rooms or in theatre recovery. As a result, there is often no other option than to provide 100% oxygen to patients in these areas.

[0091] Initially, in the current studies, attempts were made to solve this problem by using a high velocity jet of pressurised oxygen to entrain air into the anaesthetic circuit. However, when positive pressure was applied to the circuit, it was not possible to ventilate the patient due to gas leaking back out the Venturi air inlet.

[0092] Subsequently, it was found that placing a valve in the circuit stopped leakage, however this prevented fresh gas flow into the circuit in the presence of elevated pressure within the circuit. It was subsequently recognised that this problem could be solved by placing a valve “upstream” of the oxygen jet. As a result, an oxygen-air mix could be delivered, with fresh gas continuing to flow into the circuit even when the pressure within the circuit rose significantly.

[0093] A series of 3D printed prototypes were then produced, the first of which did not work as expected, as the valve did not have adequate clearance to open adequately. A second prototype was designed to fit a standard 22 mm connector, which allowed it to be trialled in different positions within the breathing circuit. Several different sizes of Venturi jet were trialled, with the optimum diameter in these studies was found to have a diameter of approximately 400 microns. A modified T-piece was developed to allow the device to fit into the standard Mapleson F T-pieces, replacing the fresh gas inlet. A further modification allowed the switching between pure gas, as on a standard T-piece and a “gas-air mixture”. Further iterations of prototypes refined the design, making it easier to manufacture, smaller, and more ergonomic.

[0094] The valves used were initially hand-cut from plastic film, but then redesigned to be more accurately 3D printed from a flexible thermoplastic elastomer (TPE). A 20 degree offset angle was also added to preferentially direct flow towards the patient end of the T-piece, while maintaining the ergonomic feel of the device.

[0095] Preliminary data obtained using the device indicated that delivering 2 litres per minute of oxygen at 4 BAR entrained approximately 10 litres of room air, to provide 35% oxygen in spontaneous ventilation.

[0096] Without being bound by theory, when ventilation is assisted, the pressure within the circuit rises and therefore air entrainment falls, leading to a gradual increase in the oxygen concentration. The oxygen concentration increase is proportional to the pressure in the circuit and only reaches high levels (80-100%) after a prolonged period of continuous positive pressure. This property of increasing oxygen concentrations with increasing pressure is desirable, as there are often circumstances where increased oxygen delivery is warranted.

EXAMPLE 2 - A positive pressure ventilation device utilising venturi mixing

[0097] An example of a positive pressure ventilation device 100 developed as described herein for delivering a gas mixed with air according to one embodiment is shown in Figures 1 and 2.

[0098] Figure 1A shows a schematic representation of the cross-section of the device 100

[0099] In the embodiment shown, the device 100 comprises a T-shaped connector 105 for connecting the device to a breathing apparatus, such as a Mapleson F type circuit breathing apparatus. The connector 105 comprises an outlet 110 for delivering gas mixed with air to the patient using a one-way air inlet valve 115, typically by way of a facemask, a supraglottic airway or an endotracheal tube. The other end of the connector 105 comprises a reservoir outlet 120, in gaseous communication with the outlet 110, the reservoir outlet permitting flow of expired gas from the patient. Typically, the reservoir outlet is attached to a reservoir bag, which may be closed (Mapleson B, C and D circuits) or open ended (Mapleson F circuit), although in some embodiments the reservoir outlet is not attached to a reservoir bag and is open ended itself (Mapleson E circuit).

[00100] Typically, the device 100 is made from a suitable plastic polymer, such as a polyamide (eg Nylon), a polyethylene tetraphthalate (PET), an acrylonitrile butadiene styrene (ABS), or a polylactic acid (PLA). Other types of polymer plastics are contemplated.

[00101] In the embodiment shown, the device comprises a gas inlet 125 for delivering the gas to the device 100 under pressure. The gas inlet 125 also comprises a venturi nozzle 130, typically having a diameter of around 0.4 mm, which provides a jet of gas entering the chamber 135. The chamber 135 is in gaseous communication with the outlet 110 and the inlet/outlet 120. [00102] In the embodiment shown, the one way air inlet valve 115 is a diaphragm type valve, comprising a diaphragm seal 140, typically made from a resilient material such as a thermoplastic elastomer, which when in the closed position shown in Figure 1 acts to seal multiple air inlet ports 145. The diaphragm seal 140 comprises a central hole 150 which allows the gas provided to enter the chamber 135 via the venturi nozzle 130.

[00103] In the embodiment shown, the one way air inlet valve 115 is a separate component which is held in the wall 155 of the T-shaped connector 105. The valve 115 is typically made from a ductile plastic such as a polyamide (eg Nylon), a polyethylene tetraphthalate (PET), an acrylonitrile butadiene styrene (ABS), or a polylactic acid (PLA), which allows for a snap fit of the components. Other types of polymer plastics are contemplated.

[00104] In the embodiment shown, the valve 115 comprises the gas inlet 125, the venturi nozzle 130, and 6 air inlet ports 145 located around the central gas inlet 125. The diaphragm seal 140 closes the air inlet ports 145.

[00105] Figure 1 B shows a schematic of a top or a bottom view of the diaphragm seal 140 located in the valve 115. The diaphragm comprises a central hole 150, which permits gas to flow into the device 110 through the venturi nozzle 130 without obstruction. The region 160 of the diaphragm seal 140 acts to close the air inlet ports shown in Figure 1 A.

[00106] Turning to Figure 2, there is provided a schematic representation of a cross- sectional view of the device shown in Figure 1, where the gas 265 is provided under pressure to the device 200.

[00107] In the embodiments shown, the gas being delivered to the device (for example oxygen) is provided from a source 270 of the gas. For example, for paediatric patients being provided with an oxygen/air mix, the oxygen may be provided at a pressure of 4 BAR, and a flow rate of 2L/min.

[00108] The gas 265 travels through the gas inlet 225 and passes through a venturi nozzle 230 venting gas 275 into the chamber 235. As the gas 265 passes through the constricted venturi nozzle 230 and expands into the chamber 235, there is a subsequent drop of pressure. The drop of pressure causes the diaphragm seal 240 to open, thereby allowing atmospheric air 280 to enter the device through the air inlet ports 245 by entrainment. The entrained air 280 enters the chamber 235 and mixes 290 with the gas 275.

[00109] In the embodiment shown, the stem 295 of the T shaped connector 205 is disposed obliquely at an angle of 20° to the vertical, which results in the gas/air mixture being delivered laterally and assisting with delivery of the mixture to the patient.

[00110] It should be noted that under increased flow rates, the Venturi velocity of the gas increases and thereby leads to increased entrainment of atmospheric air in the device.

[00111] As such, the device 200 is able to deliver varying concentrations of the input gas 265 to the patient, depending upon the flow rate of gas delivered to the device 200, and can be used to adjust the concentration of the gas mixed with air

[00112] Turning to Figure 3, there is an elevated perspective view of the device 300 rendered in three dimensions according to one embodiment.

[00113] In the embodiment shown, the device 300 comprises a T-shaped connector 305 for connecting the device 300 to a breathing apparatus. The connector 305 comprises an outlet 310 for delivering the gas mixed with air to the patient. The other end of the connector 305 comprises a reservoir outlet 320, in gaseous communication with the outlet 310, the reservoir outlet permitting flow of expired gas from the patient. Typically, the reservoir outlet is attached to a reservoir bag (not shown), which may be closed (Mapleson B, C and D circuits) or open ended (Mapleson F circuit), although in some embodiments the reservoir outlet is not attached to a reservoir bag and is open ended itself (Mapleson E circuit).

[00114] In the embodiment shown, the device 300 comprises a gas inlet 325 for delivering the gas to the device under pressure.

[00115] The device also comprises a one way inlet valve 315. The one way inlet way valve 315 is a separate component to the connector 305 and comprises multiple inlet ports 345, which in the embodiment shown are arranged around the central gas inlet 325. The one way inlet valve 315 also comprises a diaphragm seal 340, which in the closed position acts to seal the inlet ports 345, thereby preventing gas escaping from the circuit and preventing flow of atmospheric air into the device when closed.

EXAMPLE 3 - A positive pressure ventilation device used in a Mapleson F circuit

[00116] Figure 4 shows a schematic representation of a positive pressure ventilation device 400 according to one embodiment used in conjunction with a Mapleson F circuit breathing apparatus.

[00117] In the embodiment shown, the device 400 comprises a gas inlet 425 for delivering oxygen to the device 400 under pressure. The device comprises a T shaped connector 405, which at the inlet 410 connects via a connector 496 to a face mask 497 or other component, such as a supraglottic airway or an endotracheal tube. The device 400 is also connected at the reservoir outlet 420 to a reservoir bag 421, which is open ended 422. The device uses the one way air inlet valve 415 to produce an oxygen/air mixture 466 which is delivered to the patient via the connector 496 connected to the face mask.

[00118] Without being bound by theory, it has been recognised that in standard venturi inlet systems, which act as open systems, the oxygen delivered depends on a number of variables including oxygen jet velocity, oxygen jet diameter, oxygen gas flow rate and air inlet aperture. Many devices alter the air entrainment ratio by modifying these variables. However, in these open systems, downstream pressure is insignificant and/or constant and therefore has minimal-to-no effect on the oxygen concentration delivered.

[00119] The device of the present disclosure acts as a semi-closed system, and it has been found that downstream pressure is the main determinant of the entrainment ratio and is highly variable depending on how the device is used - spontaneous ventilation, CPAP, assisted ventilation.

[00120] The device of the present disclosure has been developed to entrain as much air as possible when the pressure in the circuit approximates atmospheric pressure - e.g. with spontaneous ventilation.

[00121] In the embodiment where the device is used in conjunction with Mapleson F breathing circuit, the T-piece allows for the generation of positive pressure by partial or full occlusion of the reservoir bag exhaust. When the reservoir bag exhaust is occluded, the pressure rises within the circuit as it fills with gas and the reservoir distends. This allows the application of CPAP (partial obstruction of the exhaust) or assisted ventilation (partial - full obstruction of the exhaust). In the case of the device of the present disclosure, it also causes the air inlet valve to close.

[00122] The state of the inlet valve - open vs closed, is dependent on the balance between the negative pressure generated by the Venturi jet and the positive pressure created by the anaesthetist occluding the reservoir bag exhaust.

[00123] If the exhaust is fully occluded, the pressure in the circuit will rise until the valve closes fully.

[00124] Further, with positive pressure (assisted) ventilation, the pressure in the circuit varies with the respiratory cycle, such that the pressure is highest during inspiration and lowest in expiration. The position of the air inlet valve may therefore be anywhere from fully open to fully closed depending on the pressure in the circuit at different points in the respiratory cycle. Hence, air entrainment will mostly occur during expiration.

[00125] In practice, when the anaesthetist provides more respiratory support, more oxygen is provided to the circuit.

EXAMPLE 4 - Provision of oxygen to a paediatric patient

[00126] A 4 year-old boy may be booked for a CT scan under general anaesthesia. Pre oxygenation is achieved using a face mask and a standard paediatric T-piece (Mapleson F). This is connected to the wall oxygen supply at 6 litres per minute to supply 100% oxygen to the circuit. Anaesthesia is induced and maintained intravenously. Following induction, the standard gas inlet on the T-piece is exchanged for the air-entrainment device described herein and oxygen flow is reduced to 2 litres per minute. This provides oxygen-enriched air, with oxygen concentrations of 35-60% with spontaneous or gently assisted ventilation.

[00127] At the end of the procedure, the device is connected to a portable oxygen cylinder, again at 2 litres per minute, to provide supplementary oxygen for transport from the radiology department to recovery. Once in recovery, the device is again connected to the wall oxygen. Oxygenation and ventilation are supported with the device until the patient is fully awake and ready to be discharged from recovery.

[00128] In this case, the use of the air-entrainment device described herein will prevent the patient from prolonged exposure to high oxygen concentrations, while also reducing the hospital oxygen consumption by two thirds during its use, compared to the standard T-piece.

[00129] Although the present disclosure has been described with reference to particular embodiments, it will be appreciated that the disclosure may be embodied in many other forms. It will also be appreciated that the disclosure described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications. The disclosure also includes all of the steps, features, compositions and compounds referred to, or indicated in this specification, individually or collectively, and any and all combinations of any two or more of the steps or features.

[00130] Also, it is to be noted that, as used herein, the singular forms “a”, “an” and “the” include plural aspects unless the context already dictates otherwise.

[00131] Throughout this specification, unless the context requires otherwise, the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.

[00132] When the antecedent term "about" is applied to a recited range or value it denotes an approximation within the deviation in the range or value known or expected in the art from the measurement method. For removal of doubt, it shall be understood that any range or value stated herein that does not specifically recite the term “about” before the range, before any value within the stated range or value inherently includes such term to encompass the approximation within the deviation noted above.

[00133] Reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in any country.

[00134] The subject headings used herein are included only for the ease of reference of the reader and should not be used to limit the subject matter found throughout the disclosure or the claims. The subject headings should not be used in construing the scope of the claims or the claim limitations.

[00135] The description provided herein is in relation to several embodiments which may share common characteristics and features. It is to be understood that one or more features of one embodiment may be combinable with one or more features of the other embodiments. In addition, a single feature or combination of features of the embodiments may constitute additional embodiments.

[00136] The methods described herein can be performed in one or more suitable orders unless indicated otherwise herein or clearly contradicted by context. The use of examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the example embodiments and does not pose a limitation on the scope of the claimed invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential.

[00137] Future patent applications may be filed on the basis of the present application, for example by claiming priority from the present application, by claiming a divisional status and/or by claiming a continuation status. It is to be understood that the following claims are provided by way of example only, and are not intended to limit the scope of what may be claimed in any such future application. Nor should the claims be considered to limit the understanding of (or exclude other understandings of) the present disclosure. Features may be added to or omitted from the example claims at a later date.