WO2025075514A1

WO2025075514A1 - A resuscitator and a patient interface for a resuscitator

Info

Publication number: WO2025075514A1
Application number: PCT/NZ2024/050112
Authority: WO
Inventors: Richard Anthony Mcculloch; Gilbert Jacobus Kuypers; Enrico Haemmerle
Original assignee: Km Medical Ltd
Current assignee: Km Medical Ltd
Priority date: 2023-10-06
Filing date: 2024-10-05
Publication date: 2025-04-10
Anticipated expiration: 2026-04-06

Abstract

A resuscitator for delivering a pressurised gas flow to a patient, the pressurised gas flow comprising a controlled volume gas flow, and the resuscitator comprising a controlled volume gas flow generator for generating the controlled volume gas flow, and optionally a patient interface for use with the resuscitator.

Description

A RESUSCITATOR AND A PATIENT INTERFACE FOR A RESUSCITATOR

FIELD OF THE INVENTION

The invention relates to the field of emergency resuscitator devices.

BACKGROUND

Emergency resuscitators are used for delivering a flow of pressurised gas (such as air or oxygen) to a patient in circumstances where the patient is unable to breath unassisted. This could occur when there is a blockage in a patient's airway, or, for example, when the lungs of a newborn baby are unable to inflate to take its first breath.

If the pressure at which air is delivered to the patient is excessively high, or causes the pressure in the patient's airway to change too suddenly, this can cause damage to the patient (pulmonary barotrauma) leading to complications such as collapsed lungs, emphysema, arterial gas embolisms, or in some cases fatality.

Similarly, if the volume of air delivered to the patient is excessive, this can cause damage to the patient (volutrauma) by overinflating the lungs. This is especially a risk for newborn infants with very delicate lungs, and given that lung compliance increases during the transition to extrauterine life, from fluid-filled to air-filled. The equation of compliance¹ states that lung compliance is equal to the change in lung volume divided by the change in transpulmonary pressure:

Therefore even resuscitation equipment which provides a degree of control over the pressure of air delivery can still cause lung and brain injury due to an inadequate control of the rate of air delivery and/or delivery of excessive volume.

These risks can be addressed to some degree by employing complex and expensive medical equipment of the type that is typically installed for ventilation in an intensive care unit, but resuscitation and breathing assistance is frequently required prior the patient arriving in a unit with such equipment. Therefore there is a need for lightweight and portable resuscitator devices that can be used in emergency settings where the device must be brought to the patient and/or used during transit of the patient. There is further a need for such portable devices to be fast to set up and easy to operate, as there will often be limited time available in which to deploy the device and begin delivering air to the

¹ Jay P. Desai; Fady Moustarah 'Pulmonary Compliance'. National Library of Medicine NBK538324 (2022) https://www.ncbi.nlm.nih.gov/books/NBK538324 patient. There is further a need for such portable devices to be efficient to sterilise between use with subsequent patients.

For the delivery of air in emergency settings, portable self-inflating or flow-inflating bag resuscitators are known, as are "T-piece" resuscitators for delivering a continuous positive airway pressure. However such devices are pressure-driven and provide poor control of the volume of airdelivered to the patient. They also provide poor feedback to the operator, who may not be able to detect airway blockages or changes in lung compliance of the patient and react in time to mitigate injury.

US11285281 describes a portable resuscitator suitable for delivering to a patient both a source of air which is controlled as to volume and a secondary source of air which may be controlled as to pressure. However the device employs a custom hydraulic cylinder comprising a complex valve arrangement in order to deliver air from the two alternative sources, which leads to significant cost and complexity associated with manufacture and maintenance of the device.

It is therefore an object of the present invention to provide an improved resuscitator and/or patient interface for a resuscitator which goes at least some way toward addressing one or more of the abovementioned needs and/or ameliorating one or more of the abovementioned problems, or at least provides the public with a useful choice.

SUMMARY OF THE INVENTION

In a first aspect the invention can be said to broadly reside in a patient interface for use with a resuscitator for delivering a pressurised gas flow to a patient, the patient interface comprising: a body defining an interior volume with a first interior zone and a second interior zone; and further defining at least a first port and a second port which each allow for fluid communication between an exterior of the body and the first interior zone; and further defining an orifice which allows for fluid communication between an exterior of the body and the second interior zone; and further comprising a first valve located intermediate of the first interior zone and the second interior zone, which valve can open allow gas to flow from the first interior zone into the second interior zone; and further comprising a second valve at the second port that can open to allow gas from the exterior of the body to enter the first interior zone. In some embodiments either or both of said first and second ports are integral with, connected to, or adapted for connection with a pressurised gas delivery conduit, and optionally wherein both of the first and second ports are integral with, connected to, or adapted for connection with a respective pressurised gas delivery conduit.

In some embodiments both ports are adapted for a detachable connection with a respective pressurised gas flow delivery conduit.

In some embodiments either or both of the first and second valves are unidirectional valves, and optionally wherein both of the first and second valves are unidirectional valves.

In some embodiments either of both of the first and second valves are passively actuated, and optionally wherein both of the first and second valves are passively actuated.

In some embodiments said first and second valves are the only valves which the patient interface comprises.

In some embodiments the body further defines one or more exhaust outlets through which gas can exit the second interior zone of the interior volume.

In some embodiments the first valve is configured to move to selectively allow fluid communication between the orifice and the exhaust outlets via the second interior zone.

In some embodiments the first valve comprises a diaphragm able to seat against a structure internal to the body, and is adapted to move between: a seated condition in which fluid communication between the orifice and the exhaust outlets is prevented or restricted, and an unseated condition in which fluid communication between the orifice and the exhaust outlets is allowed.

In some embodiments the patient interface further comprises one or more sensors for sensing one or more of:

The pressure of the pressurised gas flow delivered to the patient, and

The volume and/or flowrate of the pressurised gas flow delivered to the patient, and

The pressure, volume and/or flowrate of airflow exhaled by the patient.

In a further or alternative aspect the invention can be said to broadly reside in a resuscitator for delivering a pressurised gas flow to a patient, the pressurised gas flow comprising a controlled volume gas flow and the resuscitator comprising a controlled volume gas flow generator for generating the controlled volume gas flow.

In some embodiments the controlled volume gas flow generator comprises one or more of:

A cylinder or piston pump,

A bellows, and

A rolling diaphragm

In some embodiments the controlled volume gas flow generator is a single-acting cylinder or piston pump.

In some embodiments the resuscitator further comprises a controller for controlling the controlled volume gas flow generator.

In some embodiments the controlled volume gas flow generator is a volume-controlled device.

In some embodiments the controlled volume gas flow generator and controller are housed within a unit housing that is compact enough to be carried by hand.

In some embodiments the controller controls the controlled volume gas flow generator dependant on feedback derived from one or more sensors.

In some embodiments the pressurised gas flow further comprises a continuous positive pressure gas flow, and wherein the resuscitator further comprises a continuous positive pressure gas flow generator to generate the continuous positive pressure gas flow.

In some embodiments the continuous positive pressure gas flow generator comprises one or more of:

A fan, and

A blower

A compressed gas cylinder and

A compressor.

In some embodiments the resuscitator further comprises a controller for controlling the continuous positive pressure gas flow generator.

In some embodiments both the controlled volume gas flow generator, the continuous positive pressure gas flow generator and controller are housed within a unit housing that is compact enough to be carried by hand. In some embodiments the controller controls the continuous positive pressure gas flow generator dependant on feedback derived from one or more sensors.

In some embodiments the resuscitator further comprises one or more sensors for sensing one or more of:

The pressure of the pressurised gas flow delivered to the patient, and

The pressure, volume and/or flowrate of airflow exhaled by the patient.

In some embodiments the resuscitator further comprises a patient interface as previously described

In some embodiments the controlled volume gas flow generator is in fluid communication with the patient interface via the first port.

In some embodiments the patient interface, or at least a portion of it, is configured to be detachable.

In some embodiments at least a portion of the patient interface comprising both of the first and second valves is configured to be detachable.

In some embodiments the resuscitator further comprises a controlled volume gas flow delivery conduit via which the controlled volume gas flow generator is in fluid communication with the patient interface, and which is optionally a flexible elongate conduit.

In some embodiments the continuous positive pressure gas flow generator is in fluid communication with the patient interface via the second port.

In some embodiments the resuscitator further comprises a continuous positive pressure gas flow delivery conduit via which the continuous positive pressure gas flow generator is in fluid communication with the patient interface, and which is optionally a flexible elongate conduit.

In some embodiments the resuscitator further comprises one or more valves located intermediate of the controlled volume gas flow generator and the first valve of the patient interface which can be selectively opened to allow the discharge of pressurised gas to a purge line.

In some embodiments said one or more valves are selected from:

A safety valve which can be opened to mitigate over-pressurisation in the event that gas is not desired or able to exit through the patient interface, and a bleed valve which can be opened to regulate the pressure inside of the patient interface so that the pressure within the first interior zone upstream of the first valve remains less than the pressure within the second interior zone that develops on the downstream side of the closed valve as the patient exhales into the interface. .

In a further or alternative aspect the invention can be said to broadly reside in a resuscitator for delivering a pressurised gas flow to a patient, the pressurised gas flow comprising a controlled volume gas flow, the resuscitator comprising: a controlled volume gas flow generator for generating the controlled volume gas flow and further comprising a patient interface, the patient interface comprising: a body defining an interior volume with a first interior zone and a second interior zone; and further defining at least a first port and a second port which each allow for fluid communication between an exterior of the body and the first interior zone; and further defining an orifice which allows for fluid communication between an exterior of the body and the second interior zone; and further comprising a first valve located intermediate of the first interior zone and the second interior zone, which valve can open allow gas to flow from the first interior zone into the second interior zone; and further comprising a second valve at the second port that can open to allow gas from the exterior of the body to enter the first interior zone; and wherein the controlled volume gas flow generator is in fluid communication with the patient interface via the first port.

In some embodiments the wherein the pressurised gas flow further comprises a continuous positive pressure gas flow, and wherein the resuscitator further comprises a continuous positive pressure gas flow generator to generate the continuous positive pressure gas flow, and wherein the continuous positive pressure gas flow generator is in fluid communication with the patient interface via the second port.

A cylinder or piston pump,

A bellows, and

A rolling diaphragm

In some embodiments the continuous positive pressure gas flow generator comprises one or more of: A fan, and

A blower

In some embodiments the resuscitator further comprises a controller for controlling the controlled volume gas flow generator, and also the continuous positive pressure gas flow generator (if present).

In some embodiments the controlled volume gas flow generator, the continuous positive pressure gas flow generator (if present), and the controller are housed within a unit housing that is compact enough to be carried by hand.

In some embodiments the controller controls the controlled volume gas flow generator and the continuous positive pressure gas flow generator (if present) dependant on feedback derived from one or more sensors.

The pressure of the pressurised gas flow delivered to the patient, and

The flowrate of the pressurised gas flow delivered to the patient.

In some embodiments the resuscitator further comprises a patient interface as previously described.

In some embodiments the resuscitator further comprises one or more gas flow delivery conduits via which the controlled volume gas flow generator and the continuous positive pressure gas flow generator (if present) are in fluid communication with the patient interface, and which are optionally flexible elongate conduits.

In some embodiments each of the controlled volume gas flow generator and the continuous positive pressure gas flow generator are in fluid communication with the patient interface via two separate gas flow delivery conduits.

In some embodiments said one or more valves are selected from: safety valve which can be opened to mitigate over-pressurisation in the event that gas is not desired or able to exit through the patient interface, and bleed valve which can be opened to regulate the pressure inside of the patient interface so that the pressure within the first interior zone upstream of the first valve remains less than the pressure within the second interior zone that develops on the downstream side of the closed valve as the patient exhales into the interface.

It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.

In this specification the term "comprising" means "consisting at least in part of". When interpreting a statement in this specification and claims that includes "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted similarly.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the disclosure. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.

The disclosure may also be said broadly to comprise in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

To those skilled in the art to which the disclosure relates, many changes in construction and widely differing embodiments and applications of the disclosure will suggest themselves without departing from the scope of the disclosure. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting. Where specific integers are mentioned herein which have known equivalents in the art to which this disclosure relates, such known equivalents are deemed to be incorporated herein as if individually set forth. The disclosure comprises the foregoing and also envisages constructions of which the following gives examples only. BRIEF DESCRIPTION OF DRAWINGS

The invention will be described with respect to the Figures in which:

Figure 1 shows, diagrammatically, an example of a resuscitator of the present invention;

Figure 2 shows, diagrammatically, an example of a patient interface to be used with or as part of the resuscitator shown in Figure 1;

Figure 2A shows, diagrammatically, an alternative embodiment of a patient interface shown in Figure 2;

Figure 3 shows a specific embodiment of the resuscitator shown in Figure 1;

Figure 4 shows a specific embodiment of an arrangement of first and second valves in a patient interface of or for the resuscitator shown in Figure 3;

Figure 5 shows the resuscitator and patient interface of Figures 3 and 4 in operation during the inhalation phase of breathing, to deliver a controlled volume gas flow to a patient;

Figure 6 shows the resuscitator and patient interface of Figures 3 and 4 in operation during the exhalation phase of breathing, to recharge the supply of gas to a controlled volume gas flow generator while permitting the exhalation of air from the patient via the patient interface;

Figure 7 shows the resuscitator and patient interface of Figures 3 and 4 in operation during the inhalation phase of breathing, to deliver a continuous positive pressure gas flow to a patient; and

Figure 8 shows the resuscitator and patient interface of Figures 3 and 4 in operation during the exhalation phase of breathing, to cease delivery of the continuous positive pressure gas flow while permitting the exhalation of air from the patient via the patient interface.

DETAILED DESCRIPTION

Various embodiments of the invention will now be described with reference to the Figures, in which corresponding reference numerals represent corresponding features of the invention.

Pressurised Gas Delivery

Breathing of a patient may be characterised in: a) an inhalation phase, in which gas enters the patient's airway via the nose and/or mouth and travelling in a direction towards the lungs, and b) an exhalation phase, in which gas in the patient's airway is expelled in the opposite direction, again exiting via the nose and/or mouth.

Breathing may be initiated or induced in a non-breathing patient by the delivery of pressurised gas during the inhalation phase, which may, for example clear blockages of the airway and/or inflate (or at least partially inflate) the lungs. Exhalation may be mechanically assisted, for example by pressing on the patient's diaphragm to expel gas. The delivery of pressurised gas may be ceased or reduced during exhalation.

Even for a patient who is able to breath autonomously, the delivery of pressurised gas may be continued to assist breathing and/or to maintain at least a minimum positive pressure (positive end expiratory pressure PEEP) within the patient's airways to mitigate the risk of airway collapse. .

As shown schematically in Figure 1, in some embodiments the invention is a resuscitator 101 configured for delivering a pressurised gas flow 111 to a patient 112. The pressurised gas flow may comprise of at least pressurised gas from a controlled volume gas flow 114. However, in some embodiments, the pressurised gas flow may comprise of both pressurised gas from a controlled volume gas flow 114 and pressurised gas from a continuous positive pressure gas flow 113. For example, the continuous positive pressure gas flow 113 may be a continuous flow at a constant or substantially constant pressure, (a relatively low pressure, for example at 5 - 15 cm/H20), whereas the controlled volume gas flow 114 may periodically deliver a controlled volume of gas at a higher pressure (i.e. a pressure relatively higher than that of the continuous positive pressure flow, of, for example, in the range of 5 - 30 cm/H20, and optionally 20 - 30cm/H2O).

At some time points the pressurised gas flow 111 delivered to the patient 112 may be comprised entirely of pressurised gas from the continuous positive pressure gas flow 113, at some time points the pressurised gas flow 111 may be comprised entirely of pressurised gas from the controlled volume gas flow 114, and at some time points the pressurised gas flow 111 may be comprised of both.

In this manner it is possible to deliver to the patient, initially, a controlled volume of gas to initiate breathing while mitigating the risk of volutrauma, and subsequently a continuous and/or pressure controlled flow to support continued breathing and mitigate the risk of lung collapse, atelectasis and associated lung scarring. The resuscitator 101 can assist an operator in quickly transitioning between the two delivery modes and/or may facilitate an automated transition between delivery modes at the appropriate time.

In some embodiments the pressurised gas flow 111 is delivered to the patient via a patient interface 15. The patient interface 15 may comprise a first valve 13 that opens to allow the delivery of the pressurised gas flow 111 to the patient (for example during the inhalation phase) and closes to cease or reduce delivery of the pressurised gas flow 111 (for example during the exhalation phase) and to prevent gas exhaled by the patient 112 from being recycled into the delivery gas.

As used herein "pressurised gas" is used to describe pressurised air or oxygen or a mix of these, or any other gas suitable for assisting ventilation of a human or animal patient.

Resuscitator

Referring to the diagram of Figure 1, in some embodiments the controlled volume gas flow 114 may be generated by a controlled volume gas flow generator 10 of or connected to the resuscitator 101. The controlled volume gas flow generator 10 can be a device that is able to displace a predetermined volume of gas in the direction of the patient 112, for example, a positive displacement pump. The tidal volume is the amount of air that moves in or out of the lungs with each respiratory cycle. In some embodiments the controlled volume gas flow generator 10 is configured to displace a tidal volume of gas for delivery to the patient during the inhalation phase, while the supply of gas to the controlled volume gas flow generator 10 is recharged or replenished during the exhalation phase. Bellows, cylinders/piston pumps and rolling diaphragms are examples of suitable devices for generating the controlled volume gas flow 114.

The resuscitator 101 may further comprise a controlled volume gas flow delivery conduit 11 via which the controlled volume gas flow generator 10 is in fluid communication with the patient interface 15. The controlled volume gas flow 114 may travel from the controlled volume gas flow generator 10 to the patient interface 15 along the controlled volume gas flow delivery conduit 11.

Referring further to the diagram of Figure 1, in some embodiments the resuscitator 101 may also facilitate delivery of a continuous positive pressure gas flow 113 generated by a continuous positive pressure gas flow generator 4 of or connected to the resuscitator 101. Blowers or fans are examples of suitable devices for generating the continuous positive pressure gas flow 113. Although in some embodiments the continuous positive pressure gas flow 113 may come from a compressed gas supply and/or the continuous positive gas flow generator 10 may be a compressor or compressed gas cylinder.

The resuscitator 101 may further comprise a continuous positive pressure gas flow delivery conduit 9 via which the continuous positive pressure gas flow generator 4 is in fluid communication with the patient interface 15. The continuous positive pressure gas flow 113 may travel from the continuous positive pressure gas flow generator 4 to the patient interface 15 along the continuous positive pressure gas flow delivery conduit 9.

In some embodiments, either or both (and preferably both) of the delivery conduits 9, 11 may be flexible and elongate to allow for convenient positioning of the patient interface 15. The continuous positive pressure gas flow delivery conduit 9 and the controlled volume gas flow delivery conduit 11 may be separate conduits connected or connectable to the unit housing 21, for example as shown at connection points 31.

In embodiments where the controlled volume gas flow generator 10 is, for example, a cylinder or bellows, it may be necessary to recharge a gas supply of, or internal to, the controlled volume gas flow generator 10 between subsequent deliveries of the controlled volume gas flow 114. The pressure in the controlled volume gas flow delivery conduit 11 may drop as the controlled volume gas flow generator 10 is recharged. Therefore, in some embodiments the resuscitator 101 may comprises a second valve 8 which can be opened to permit an intake of gas for balancing the pressure drop and/or recharging the gas supply of the controlled volume gas flow generator 10. In some embodiments this second valve 8 is also located at the patient interface 15 (along with the first valve 13), rather than at the controlled volume gas flow generator 10 itself.

As further shown in Figure 1, in some embodiments the resuscitator 101 may comprise a controller 18 to control either or both of the continuous positive pressure gas flow generator 4 and the controlled volume gas flow generator 10. For example, in embodiments where the continuous positive pressure generator 4 is a blower, the controller 18 may control the generation of the continuous positive pressure gas flow 113 by controlling the rotational speed of an electric motor that drives rotation of a fan or impeller of the blower. And in embodiments where the controlled volume gas flow generator 10 is a cylinder or piston pump, the controller 18 may control the driving of an electric motor or actuator to control the volume of gas displaced by the cylinder.

In particular, the controller 18 may control the controlled volume gas flow generator so that the volume of air delivered to the patient meets a target volume. For example, the volume and/or volumetric delivery rate could be pre-determined, or selected or input by an operator of the resuscitator. The controller may be configured to control the controlled volume gas flow generator 10 to achieve operation within a specified threshold of the target (for example 10%, or between 5 - 10%). In some embodiments the controlled volume gas flow generator 10 is a volume - controlled device (i.e. delivery of the desired tidal volume is achieved by directly controlling the volume of gas delivered) as opposed to a pressure-controlled device (i.e. delivery of the desired tidal volume is indirectly controlled by controlling the pressure of gas delivered), as the former has been found to deliver the desired tidal volume with greater accuracy. However in some embodiments the continuous positive pressure gas flow 113 may be delivered at a target pressure and/or the continuous positive pressure gas flow generator 4 may be a pressure-controlled device.

In some embodiments the resuscitator 101 may comprise or communicate with one or more sensors 14 for sensing flow characteristics. In particular, the resuscitator may comprise or communicate with one or more sensors 14 for sensing characteristics of the pressurised gas flow 111 delivered to the patient 112. For example, as shown in Figure 1, the sensors 14 may be positioned downstream/patient side of the first valve 13. Characteristics such as the pressure and volumetric flow rate of the flow may be sensed. The sensed values may be fed back to the controller 18 for controlling either or both of continuous positive pressure gas flow generator 4 and the controlled volume gas flow generator 10.

In some embodiments the controller may be configured to control either or both of the continuous positive pressure gas flow generator 4 and the controlled volume gas flow generator 10. to effect an automatic transition between delivery of the controlled volume gas flow 114 (which may, for example, be suitable for initiating breathing in a non-breathing patient) and the delivery of the continuous positive pressure gas flow 113 (which may, for example, be suitable for supporting continued breathing of an autonomously breathing patient). For example, an automatic transition between delivery modes could be made based on information derived by the sensors, or at set time intervals.

In some embodiments one or more of the controller 18, the continuous positive pressure gas flow generator 4 and the controlled volume gas flow generator 10 are contained within a unit housing 21, and in preferred embodiments all of these are contained within the unit housing 21. The the unit housing may be a portable housing, for example, to the extent that the housing and its contents are compact enough (e.g. in size and weight) to be hand-carried. The housing 21 may include features such as a handle, and feet for balancing the unit on a surface. Thus the resuscitator 101 can be transported to and deployed at various locations as required for emergency patients.

An advantage of the embodiments described by Figure 1 is that the resuscitator 101 can deliver to the patient 112 a pressurised gas flow 111 comprising of either or both of the controlled volume gas flow 114 and the continuous positive pressure gas flow 113, and makes it easy to switch between controlled volume and continuous pressure delivery modes without disturbing the patient 112. The requisite valving arrangements to achieve such a delivery (namely the first valve 13 and the second valve 8) can be assembled as a single or unitary component of the patient interface 15. In this manner complex valving arrangements along the gas flow delivery conduits and/or at the controlled volume gas flow generator 10 and continuous positive gas flow generator 4 are avoided and the unit 101 can be manufactured using standard or "off the shelf" delivery conduits and gas movers (e.g. cylinders, bellows, blowers etc) of the smallest possible size.

Patient Interface

The pressurised gas flow 111 may be delivered to the patient 112 via a patient interface 15.

Figure 2 shows an embodiment of a suitable patient interface 15. The patient interface 15 may comprise a body 30 defining an interior volume, for example, generally as indicated by the dotted enclosure 29. The interior volume 29 can be conceptualised as comprising a first interior zone 29a on the upstream side of the valve 13, and a second interior zone 29b on the downstream/patient side of the first valve 13. The body 30 may further define at least two ports 22a, 22b which each allow for fluid communication between an exterior of the body and the first interior zone 29a. The body 30 may further define an orifice 23 which allows for fluid communication between an exterior of the body and the second interior zone 29b. In this configuration, when the first valve 13 is open, pressurised gas (for example the controlled volume gas flow 114 and/or the continuous positive pressure gas flow 113) is able to enter the patient interface 15 via the ports 22, and exit (for example as a pressurised gas flow 111 comprising of either or both of the continuous positive pressure gas flow 113 and the controlled volume gas flow 114) through the orifice 23 for delivery to the patient.

In some embodiments, the patient interface 15 may be adapted to receive or fit against the face of the patient, with at least a portion of the interface 15 encircling the patient's mouth and optionally also nose. For example, in the embodiment shown in Figure 2, there is a mask portion 24 of the body 30 adapted for this purpose, with an edge 23a of the mask defining the orifice 23 through which gas is delivered. At least a portion of the patient interface 15 (e.g. the mask portion 24) may be formed of a compliant material (e.g. rubber or flexible plastic) to fit comfortably against the patient's face. In some embodiments it is desirable for the patient interface 15 to at least partially seal against the patient's face so that pressurised gas (or at least a significant volume of pressurised gas) does not escape the patient interface 15 without delivery to the patient.

In some embodiments, the controlled volume gas flow generator 4 may be in fluid communication with the patient interface 15, and specifically with the first interior zone 29a of the interior volume 29, via the first port 22a. Similarly, the continuous positive pressure gas flow generator 4 may be in fluid communication with the patient interface 15, and specifically with the first interior zone 29a of the interior volume 29, via the second port 22b.

The patient interface 15 may comprise a first valve 13 located intermediate of the first interior zone 29a and the second interior zone 29b, which can open to allow gas to flow from the first interior zone 29a into the second interior zone 29b. This configuration can selectively allow the flow of pressurised gas from the ports 22 where the gas enters the interface 15 through to the orifice 23 where the gas exits. In this manner the flow of pressurised gas 111 can be delivered to the patient during the inhalation phase, while the flow of gas can be ceased or restricted by closing of the valve 13 during the exhalation phase. As the patient exhales into the patient interface 15 the closed valve 13 stops the exhaled air from travelling back into the pressurised gas delivery conduits 9, 11. A second valve 8 may also be located at the patient interface 15, and specifically at the second port 22b.

The second valve 8 may open to allow gas from the exterior of the body 30 to enter the first interior zone 29a through the port 22b. For example, in the embodiment shown in Figures 2, the second valve 8 may be located at the port 22b connected with the continuous positive pressure gas flow delivery conduit 9, so that if the pressure inside of the first interior zone 29a drops below the pressure inside of the gas flow delivery conduit 9, the second valve 8 can open to allow gas from the delivery conduit 9 to flow into the patient interface 15 and balance out the pressure drop. In this embodiment, even if the continuous positive pressure gas flow delivery conduit 9 was not connected with the body 30 of the the patient interface 15, the second valve 8 could still open to draw in ambient gas from the exterior of the patient interface 15.

In some embodiments, either or both of the first 13 and second 8 valves are unidirectional valves that permit the flow of pressurised gas in one direction and prevent or restrict flow in the other direction. Examples of suitable unidirectional valves include duckbill valves, check valves, and diaphragm valves. The valves may be passively actuated - that is, they can be caused to open and close at the desired time due to changing pressure differentials across the valve rather than a powered actuation by, for example, electronic means.

An advantage of the described embodiments which employ passive, unidirectional valves is that such valves can be compact and lightweight in form. This minimises the overall weight of the patient interface 15 component and makes it easier to manipulate during use with a patient. A further advantage of the design in general is that the patient interface requires only these two valves (the first and second valves) to facilitate the delivery of gas from both of the controlled volume and continuous positive pressure gas flows, which is less complex and expensive to assemble and manufacture than other designs that employ numerous valves to achieve the same result.

During the exhalation phase, air exhaled from the patient's airway may enter the patient interface 15 through the orifice 23. Therefore, in some embodiments, the body 30 of the patient interface 15 may define one or more exhaust outlets 12 on the downstream/patient side of the first valve 13 through which gas can exit the second interior zone 29b of the interior volume 29. In this manner, air exhaled by the patient can escape through the patient interface 15 while the first valve 13 is closed.

Sensors 14 may be located at or near the patient interface 15 to sense characteristics of the gas flow through the interface. For example the sensors could be mounted on the body 30 and positioned proximate the flow path in order to sense characteristics of the pressurised gas flow 111 exiting the orifice 23 and/or characteristics of the flow from the patient's airway as it enters through the orifice 23 during the exhalation phase. For example, sensors could be mounted at or near the orifice 23, or at or near either or both of the ports 22.

Attaching and Detaching the Patient Interface

In some embodiments the patient interface 15 is configured for a detachable connection with the resuscitator 101.

For example, in some embodiments the controlled volume gas flow delivery conduit 11 and/or the continuous positive pressure gas flow delivery conduit 9 may be integral with the patient interface 15, so that the patient interface 15 can be detached by disconnecting the gas flow delivery conduits from the controlled volume gas flow generator 10 and/or continuous positive pressure gas flow generator 4 respectively. As a further example, the diagram of Figure 1 shows connection points 31 of the unit housing, which could be threaded or barbed connectors, where the gas flow delivery conduits could be connected and disconnected in order to attach and detach the patient interface 15.

In other embodiments, the connection between the gas flow delivery conduits 9, 11 and the body 30 of the patient interface 15 may be detachable. Again, many common types of threaded or "quick connect" coupling would suffice. For example, in embodiments such as shown in Figure 2, the controlled volume gas flow delivery conduit 11 and the continuous positive pressure delivery conduit 9 may be provided as separate gas delivery conduits, each with a separate detachable connection to body 30 of the patient interface 15. The first port 22a may be connected with the controlled volume gas flow delivery conduit 11, while the second port 22b may be connected with the continuous positive pressure gas flow delivery conduit 9. In this embodiment, the patient interface comprising the body 30, first valve 13 and second valve 8, can be conveniently detached for sterilisation between patients and/or may be provided as a detachable single-use component to be discarded after use.

In a further embodiment, it may be only a portion of the patient interface 15 that is detachable - for example a portion comprising the mask portion 24 and first valve 13 (as these may be the more important portions to be sterilised between patients). An example is shown in Figure 2A, wherein the two gas delivery conduits 9,11 are shown in a conjoined condition with a junction between them. In this embodiment the interior volume 29 defined by the body 30 of the patient interface 15 is shown by the dotted lines, the gas delivery conduits 9, and 11 being integral with the first and second ports 22a, 22b at the junction. The second valve 8 is located at the second port 22b, while a single (e.g. threaded) connection 31 allows detachment of the lower portion of the body 30 comprising the first valve 13, mask portion 24 and orifice 23. Description of Specific Embodiments

Further specific embodiments of a resuscitator and/or patient interface according to the present invention will now be described with reference to Figures 3 through to 8.

Referring to Figure 3, in this embodiment, the controlled volume gas flow generator 10 is a cylinder or piston pump comprising a rigid cylinder body 25 for holding a charge/supply of gas and a piston 16 enclosed within the cylinder body 25 and able to travel along its length. The controlled volume gas flow 114 is generated as the piston 16 advances toward an outlet 20 at an end of the body 25, with the volume of gas displaced (per unit time, and total volume) being accurately controllable by controlling the speed and distance of the piston stroke.

In this embodiment the cylinder is single acting, such that the piston 16 drives in only one direction to deliver the desired tidal volume of gas. For small patients, the cylinder body 25 may contain sufficient gas to deliver an entire tidal volume with a single driving stroke of the piston 16 (or by moving the piston 16 at least a part of the way along its maximum stroke distance). However for larger patients it may be necessary for the tidal volume to be delivered over several cycles of the piston 16.

Gas is displaced through the cylinder outlet 20 in the direction of the patient, and travels along the controlled volume gas flow delivery conduit 11. The controlled volume gas flow delivery conduit 11 is connected at a first port 22a of the patient interface 15, via which pressurised gas can be delivered to the patient.

In this embodiment the piston 16 is driven by a linear motor 17 coupled to or comprising a rod 26. The rod 26 can be actuated for linear motion for example electromagnetically, or on a screw thread. However the skilled person will appreciate alternative arrangements for accurate driving of the piston. to generate a controlled volume gas flow 114, for example by using alternative types of electric motor, such as a stepper motor, or using alternative couplings depending on the configuration of the motor. Further examples of suitable motors, couplings and controls for driving a cylinder or piston pump for the generation of a controlled volume gas flow are described in US 11285281, the entirety of which is incorporated herein by reference.

The controller 18 may control operation of the motor 17 to deliver to the patient a desired volume of gas and/or to deliver gas at a desired volumetric delivery rate. To this end, the controller 18 may communicate with one or more sensors 14 that are mounted on the patient interface 15 in order to measure flow characteristics, such as the volumetric flowrate, of the exiting pressurised gas flow 111. If the characteristics of the exiting pressurised gas flow 111 need to be adjusted, this can be achieved by controlling, for example, the speed at which the motor 17 drives the advance of the piston 16. Referring further to Figure 3, in this embodiment the continuous positive pressure gas flow generator 4 is a blower which draws air through an intake 2 and forces it along the continuous positive pressure gas flow delivery conduit 9. The continuous positive pressure gas flow delivery conduit 9 is connected at a second port 22b of the patient interface 15, via which pressurised gas can be delivered to the patient. The resuscitator 101 may comprise or connect with entrainment valves (such as overpressure valve 1 and under-pressure valve 3) that regulate the pressure upstream of the blower 4. The intake 2 may be connected with a supply of gas such as oxygen, but the under-pressure valve 3 can open to permit the intake of ambient gas if the gas supply pressure drops too low.

Referring further to Figure 3, in this embodiment, almost all components of the resuscitator 101 (excluding the pressurised gas delivery conduits 9,11 and the patient interface 15) are provided within a portable unitary housing denoted by the dotted box 21. The resuscitator 101 may further comprise a display 19a and/or control panel 19b, and these may be mounted on the housing 21. For example, the display 19a may show information derived from the sensed flow characteristics (such as Volume (Vt), Pressure (Pmax), Respiratory Rate (RR), Inspiratory / Expiratory Ratio (l:E), Flow Rate, PEEP, Continuous Positive Airway Pressure (CPAP) and the changes in these parameters over time). The control panel 19b may facilitate, for example, the input of information (e.g. patient weight and age) or commands (e.g. the target volume for controlled volume gas delivery) by an operator of the resuscitator.

Referring further to Figure 3, in this embodiment the patient interface 15 comprises a body 30 defining an interior volume 29 and two ports 22a and 22b for connection, respectively, to the controlled volume gas flow delivery conduit 11 and continuous positive pressure gas flow delivery conduit 9. The first and second ports 22a, 22b allow for fluid communication between the first interior zone 29a of the interior volume 29 and the gas delivery conduits 9, 11 at the exterior of the body 30. The patient interface 15 further comprises a first valve 13 located intermediate of the first and second interior zones 29a, 29b and configured to selectively allow fluid communication between them so that pressurised gas can flow through the patient interface 15 from the ports 22a and 22b to the orifice 23. The patient interface further comprises a second valve 8 which, in this embodiment, is located at port 22b that connects with the continuous positive pressure gas flow delivery conduit 9. The second valve 8 can open to allow gas from the exterior of the body 30 to enter the first interiors zone 29a. In this embodiment both valves are one-way valves configured for passive actuation as a result of the pressure differentials that develop during operation of the resuscitator.

More detail of suitable first and second valves can be seen in Figure 4. Although it will be appreciated that other valve arrangements, and especially other passive one-way valve arrangements, could alternatively be used. As shown in Figure 4, the first valve 13 may be a diaphragm valve comprising a diaphragm body 13a with a central duckbill opening 13b. The duckbill 13b can be forced open when the upstream pressure exceeds the pressure on the downstream/patient side of the valve 13.

Referring further to Figure 4, in this embodiment the body 30 of the patient interface 15 defines one or more (and optionally a series of) exhaust outlets 12 about the second interior zone 29b of the interior volume 29 through which gas can exit. The first valve 13 is configured to move to selectively allow fluid communication between the orifice 23 and the exhaust outlets 12 via the second interior zone 29b. To this end the entire diaphragm body 13a (including the duckbill portion 13b) of the first valve 13 may be configured to move between a seated condition in which the body 13a seats against one or more seating surfaces 1 provided by a structure internal to the body 30 and located within the interior volume 29 as shown in the Figure. However the diaphragm body 13a may be moveable to an unseated condition, for example by rising in the direction of the arrow labelled A, when the pressure downstream/patient side of the valve 13 exceeds the upstream pressure. Movement to the unseated condition opens a passageway around the edge of the seating surface 1 (generally as shown by the dashed arrow labelled B) to allow gas to escape through the one or more exhaust outlets 12. This can mitigate a build up of pressure inside of the patient interface 15 on the downstream side of the valve 13.

Referring further to Figure 4, in this example, the second valve 8 comprises a rigid disc shaped body 8a which over-lies the port 22b. The body 8a has one or more apertures 8b which gas can pass through. The second valve 8 further comprises an elastomeric flap 8c which closes the apertures 8b, but can be forced open to allow the passage of gas when the upstream pressure (e.g. in the continuous positive pressure gas flow delivery conduit 9) exceeds the downstream pressure inside of the patient interface 15.

Referring again to Figure 3, in some embodiments there is a safety valve 6 which can be opened to allow the discharge of pressurised gas to a purge line 5 to mitigate the risk of over-pressurisation in the event that gas is not able to exit through the patient interface 15 as intended - for example, if the first valve 13 were to jam without opening, or if the orifice 23 was covered or obstructed. This could be, for example, a solenoid actuated valve. Similarly, if it is desired to move the piston 16 without delivering the full volume of gas inside of the cylinder 10 to the patient (e.g. if the operator resets the target delivery volume from a larger volume to a smaller volume while failing to disconnect the interface 15 with the patient) then the safety valve 6 can be automatically opened to purge a certain volume of gas.

The operation of the embodiment shown in Figures 3 and 4 will now be described with reference to Figures 5 through 8. Operation is described firstly in respect of delivering a controlled volume gas flow 114 to the patient during the inhalation and exhalation phases, and secondly in respect of operation in a "monitoring mode" wherein only a continuous positive pressure gas flow 113 is delivered to the patient during the inhalation and exhalation phases.

Referring to Figure 5: For controlled volume gas flow delivery during the inhalation phase, the cylinder 10 forces gas along the controlled volume gas delivery conduit 11 and into the patient interface 15 through the first port 22a. At this time, the second valve 8 is closed to close off the other port 22b of the patient interface 15 so that the pressurised airflow cannot escape the patient interface 15 through that port 22b. The pressurised gas flow presses the diaphragm body 13a of the first valve 13 into its seated condition and forces the duckbill 13b to open. The gas flows through the first valve 13 and exits the patient interface 15 via the orifice 23 where it is delivered to the patient.

Referring to Figure 6: During the exhalation phase delivery of the controlled volume gas flow 114 may cease, and the gas supply inside of the cylinder 10 may be recharged ahead of the next inhalation phase. To this end, the piston 16 inside of the cylinder 10 may be retracted in the direction of the arrow labelled C to draw gas from inside of the patient interface 15 along the controlled volume gas flow delivery conduit 11 and into the cylinder body 25. This develops a low pressure condition inside the patient interface 15 and upstream of the first valve 13 so that the first valve 13 is caused to close while the second valve 8 is caused to open. With the second valve 8 (and hence the second port 22b) open there is fluid communication between the continuous positive pressure gas flow delivery conduit 9 and the controlled volume gas delivery conduit 11. In this manner, gas to recharge the cylinder 10 can be drawn in through the blower intake 2, and along the path of the arrows labelled A

As the piston 16 retracts, some gas inside of the cylinder body 25 (being gas contained on the opposite side of the piston 16 to the outlet 20) may be expelled to the purge line 5 through a secondary outlet 28 of the cylinder body 25. The purge line 5 sends the expelled gas to a connection upstream of the blower 4 where the gas may be exhausted via an overpressure valve 1 or drawn back into the blower 4. At the connection point there is also an under-pressure valve 3 which can allow gas into the system to mitigate a low pressure/vacuum condition upstream of the blower 4 during the driving stroke of the piston 16.

Also during the exhalation phase, and optionally simultaneously with recharging of the cylinder, the patient may exhale air into the patient interface 15. The exhalation airflow from the patient (arrows labelled B) enters the patient interface 15 through the orifice 23 downstream of valve 13, and causes the diaphragm body 13a of the first valve 13 to move into its unseated condition. In the unseated condition, a passageway opens (as described with respect to Figure 4) to permit fluid communication between the orifice 23 and the exhaust ports 12. In this manner, the exhalation airflow from the patient can travel through the patient interface 15 and exit through the exhaust ports 12 following the path of the arrows labelled B. In some embodiments the exhaust outlets 12 may be closed with unidirectional valves 32 that prevent or restrict air from being drawn into the patient interface other than through the port(s) 22 connected to the pressurised gas flow.

Referring to Figure 7: For continuous positive pressure gas flow delivery during the inhalation phase, the blower 4 generates a continuous positive pressure gas flow 113 and forces it along the continuous positive pressure gas flow delivery conduit 9 to the second inlet port 22b of the patient interface 15. Because this develops a high pressure condition upstream of the patient interface 15 both the elastomeric flap 8c of the second valve 8 is caused to open (in the manner described with respect to Figure 4) and the duckbill 13a of the first valve 13 is caused to open ( also in the manner described with respect to Figure 4). In this manner pressurised gas can flow along the path of the arrows labelled D and out of the orifice 23 for delivery to the patient.

Referring to Figure 8: During the exhalation phase, the patient may exhale air into the patient interface 15. The exhalation airflow from the patient (arrows labelled E) enters the patient interface 15 through the orifice 23 downstream of valve 13, and causes the diaphragm body 13a of the first valve 13 to move into its unseated condition. In the unseated condition, a passageway opens (as described with respect to Figure 4) to permit fluid communication between the orifice 23 and the exhaust ports 12. In this manner, the exhalation airflow from the patient can travel through the patient interface 15 and exit through the exhaust ports 12 following the path of the arrows labelled E.

The pressure inside of the patient interface 15 should be regulated so that the pressure within the first interior zone 29a upstream of the first valve 13 remains less than the pressure within the second interior zone 29b that develops on the downstream side of the closed valve 13 as the patient exhales into the interface 15. This is because the airflow E of the exhaling patient must be able to move the diaphragm body 13a the first valve 13 into its unseated condition to permit the exhaust of gas. For this purpose, the resuscitator 101 may comprise a bleed valve 7 located intermediate of the controlled volume gas flow generator 10 and the first valve 13 to bleed off pressure on the upstream side of the valve. For example, the bleed valve 7 may be located along the controlled volume gas flow delivery conduit 11 and set to remain open while the resuscitator operates in "monitoring mode" so that upstream pressure can bleed to the purge line 5 as the patient exhales.

The foregoing describes the invention including preferred forms thereof. Modifications and alterations as will be obvious to those skilled in the art may be made without departing from the spirit and scope of the invention.

Claims

1. A patient interface for use with a resuscitator for delivering a pressurised gas flow to a patient, the patient interface comprising: a body defining an interior volume with a first interior zone and a second interior zone; and further defining at least a first port and a second port which each allow for fluid communication between an exterior of the body and the first interior zone; and further defining an orifice which allows for fluid communication between an exterior of the body and the second interior zone; and further comprising a first valve located intermediate of the first interior zone and the second interior zone, which valve can open allow gas to flow from the first interior zone into the second interior zone; and further comprising a second valve at the second port that can open to allow gas from the exterior of the body to enter the first interior zone.

2. The patient interface of claim 1 wherein either or both of said first and second ports are integral with, connected to, or adapted for connection with a pressurised gas delivery conduit, and optionally wherein both of the first and second ports are integral with, connected to, or adapted for connection with a respective pressurised gas delivery conduit.

3. The patient interface of claim 2 wherein both ports are adapted for a detachable connection with a respective pressurised gas flow delivery conduit.

4. The patient interface of any one of claims 1 to 3 wherein either or both of the first and second valves are unidirectional valves, and optionally wherein both of the first and second valves are unidirectional valves.

5. The patient interface of any one of claims 1 to 4 wherein either of both of the first and second valves are passively actuated, and optionally wherein both of the first and second valves are passively actuated.

6. The patient interface of any one of claims 1 to 5 wherein said first and second valves are the only valves which the patient interface comprises.

7. The patient interface of any one of claims 1 to 6 wherein the body further defines one or more exhaust outlets through which gas can exit the second interior zone of the interior volume.

8. The patient interface of claim 7 wherein the first valve is configured to move to selectively allow fluid communication between the orifice and the exhaust outlets via the second interior zone.

9. The patient interface of claim 8 wherein the first valve comprises a diaphragm able to seat against a structure internal to the body, and is adapted to move between: a. a seated condition in which fluid communication between the orifice and the exhaust outlets is prevented or restricted, and b. an unseated condition in which fluid communication between the orifice and the exhaust outlets is allowed.

10. The patient interface of any one of claims 1 to 9 further comprising one or more sensors for sensing one or more of: a. The pressure of the pressurised gas flow delivered to the patient, and b. The volume and/or flowrate of the pressurised gas flow delivered to the patient, and c. The pressure, volume and/or flowrate of airflow exhaled by the patient.

11. A resuscitator for delivering a pressurised gas flow to a patient, the pressurised gas flow comprising a controlled volume gas flow and the resuscitator comprising a controlled volume gas flow generator for generating the controlled volume gas flow.

12. The resuscitator of claim 11 wherein the controlled volume gas flow generator comprises one or more of: a. A cylinder or piston pump, b. A bellows, and c. A rolling diaphragm

13. The resuscitator of claim 12 wherein the controlled volume gas flow generator is a single-acting cylinder or piston pump.

14. The resuscitator of any one of claims 11 to 13 further comprising a controller for controlling the controlled volume gas flow generator.

15. The resuscitator of any one of claims 11 to 14 wherein the controlled volume gas flow generator is a volume-controlled device.

16. The resuscitator of any one of claims 11 to 15 further comprising a controller.

17. The resuscitator of claim 16 wherein the controlled volume gas flow generator and controller are housed within a unit housing that is compact enough to be carried by hand.

18. The resuscitator of claim 16 or claim 17 wherein the controller controls the controlled volume gas flow generator dependant on feedback derived from one or more sensors.

19. The resuscitator of any one of claims 11 to 18 wherein the pressurised gas flow further comprises a continuous positive pressure gas flow, and wherein the resuscitator further comprises a continuous positive pressure gas flow generator to generate the continuous positive pressure gas flow.

20. The resuscitator of claim 19 wherein the continuous positive pressure gas flow generator comprises one or more of: a. A fan, and b. A blower c. A compressed gas cylinder and d. A compressor.

21. The resuscitator of claim 19 or claim 20 further comprising a controller for controlling the continuous positive pressure gas flow generator.

22. The resuscitator of claim 21 wherein each of the controlled volume gas flow generator, the continuous positive pressure gas flow generator and controller are housed within a unit housing that is compact enough to be carried by hand.

23. The resuscitator of any one of claims 20 to 21 wherein the controller controls the continuous positive pressure gas flow generator dependant on feedback derived from one or more sensors.

24. The resuscitator of any one of claims 11 to 23 further comprising one or more sensors for sensing one or more of: a. The pressure of the pressurised gas flow delivered to the patient, b. The volume and/or flowrate of the pressurised gas flow delivered to the patient, and c. The pressure, volume and/or flowrate of airflow exhaled by the patient.

25. The resuscitator of any one of claims 11 to 24 further comprising a patient interface as claimed in any one of claims 1 to 10; and wherein the controlled volume gas flow generator is in fluid communication with the patient interface via the first port.

26. The resuscitator of claim 25 wherein the patient interface, or at least a portion of it, is configured to be detachable.

27. The resuscitator of claim 26 wherein at least a portion of the patient interface comprising both of the first and second valves is configured to be detachable.

28. The resuscitator of any one of claims 25 to 1 further comprising a controlled volume gas flow delivery conduit via which the controlled volume gas flow generator is in fluid communication with the patient interface, and which is optionally a flexible elongate conduit.

29. The resuscitator of any one of claims 25 to 28 wherein the continuous positive pressure gas flow generator is in fluid communication with the patient interface via the second port.

30. The resuscitator of claim 29 further comprising a continuous positive pressure gas flow delivery conduit via which the continuous positive pressure gas flow generator is in fluid communication with the patient interface, and which is optionally a flexible elongate conduit.

31. The resuscitator of any one of claims 25 to 30 further comprising one or more valves located intermediate of the controlled volume gas flow generator and the first valve of the patient interface which can be selectively opened to allow the discharge of pressurised gas to a purge line.

32. The resuscitator of claim 31 wherein said one or more valves are selected from: a. a safety valve which can be opened to mitigate over-pressurisation in the event that gas is not desired or able to exit through the patient interface, and b. a bleed valve which can be opened to regulate the pressure inside of the patient interface so that the pressure within the first interior zone upstream of the first valve remains less than the pressure within the second interior zone that develops on the downstream side of the closed valve as the patient exhales into the interface.

33. A resuscitator for delivering a pressurised gas flow to a patient, the pressurised gas flow comprising a controlled volume gas flow, the resuscitator comprising: a controlled volume gas flow generator for generating the controlled volume gas flow and further comprising a patient interface, the patient interface comprising: a body defining an interior volume with a first interior zone and a second interior zone; and further defining at least a first port and a second port which each allow for fluid communication between an exterior of the body and the first interior zone; and further defining an orifice which allows for fluid communication between an exterior of the body and the second interior zone; and further comprising a first valve located intermediate of the first interior zone and the second interior zone, which valve can open allow gas to flow from the first interior zone into the second interior zone; and further comprising a second valve at the second port that can open to allow gas from the exterior of the body to enter the first interior zone; and wherein the controlled volume gas flow generator is in fluid communication with the patient interface via the first port.

34. The resuscitator of claim 33 wherein the wherein the pressurised gas flow further comprises a continuous positive pressure gas flow, and wherein the resuscitator further comprises a continuous positive pressure gas flow generator to generate the continuous positive pressure gas flow, and wherein the continuous positive pressure gas flow generator is in fluid communication with the patient interface via the second port.

35. The resuscitator of claim 33 or claim 34 wherein the controlled volume gas flow generator comprises one or more of: a. A cylinder or piston pump, b. A bellows, and c. A rolling diaphragm

36. The resuscitator of claim 35 wherein the controlled volume gas flow generator is a single-acting cylinder or piston pump.

37. The resuscitator of any one of claims 34 to 37 wherein the continuous positive pressure gas flow generator comprises one or more of: a. A fan, and b. A blower

38. The resuscitator of any one of claims 33 to 37 further comprising a controller for controlling the controlled volume gas flow generator, and also the continuous positive pressure gas flow generator (if present).

39. The resuscitator of any one of claims 33 to 38 wherein the controlled volume gas flow generator is a volume-controlled device.

40. The resuscitator of any one of claims 33 to 39 wherein the controlled volume gas flow generator, the continuous positive pressure gas flow generator (if present), and the controller are housed within a unit housing that is compact enough to be carried by hand.

41. The resuscitator of any one of claims 33 to 40 wherein the controller controls the controlled volume gas flow generator and the continuous positive pressure gas flow generator (if present) dependant on feedback derived from one or more sensors.

42. The resuscitator of any one of claims 33 to 41 further comprising one or more sensors for sensing one or more of: a. The pressure of the pressurised gas flow delivered to the patient, and b. The volume and/or flowrate of the pressurised gas flow delivered to the patient, and c. The pressure, volume and/or flowrate of airflow exhaled by the patient.

43. The resuscitator of any one of claims 33 to 42 further comprising a patient interface as claimed in any one of claims 1 to 10.

44. The resuscitator of claim 43 wherein the patient interface, or at least a portion of it, is configured to be detachable.

45. The resuscitator of claim 44 wherein at least a portion of the patient interface comprising both of the first and second valves is configured to be detachable.

46. The resuscitator of any one of claims 43 to 45 further comprising one or more gas flow delivery conduits via which the controlled volume gas flow generator and the continuous positive pressure gas flow generator (if present) are in fluid communication with the patient interface, and which are optionally flexible elongate conduits.

47. The resuscitator of any one of claims 43 to 46 wherein each of the controlled volume gas flow generator and the continuous positive pressure gas flow generator are in fluid communication with the patient interface via two separate gas flow delivery conduits.

48. The resuscitator of any one of claims 43 to 47 further comprising one or more valves located intermediate of the controlled volume gas flow generator and the first valve of the patient interface which can be selectively opened to allow the discharge of pressurised gas to a purge line.

49. The resuscitator of claim 48 wherein said one or more valves are selected from: a. safety valve which can be opened to mitigate over-pressurisation in the event that gas is not desired or able to exit through the patient interface, and b. bleed valve which can be opened to regulate the pressure inside of the patient interface so that the pressure within the first interior zone upstream of the first valve remains less than the pressure within the second interior zone that develops on the downstream side of the closed valve as the patient exhales into the interface.