Field of the Invention

[0001] The present invention relates to a positive pressure ventilation device. Particularly, although not exclusively, a positive pressure neonate resuscitation device and a mobile bedside trolley comprising the same.

Background of the Invention

[0002] The lungs of neonates are filled with fluid at birth which must be cleared and replaced with air. Apnoea, the temporary cessation of breathing, is common at birth, with around 5% of babies requiring the provision of air or other respiratory gasses e.g. 100% air or an air/0 ₂ mix, under pressure from a respirator via positive pressure ventilation (PPV). PPV is mechanical ventilation, i.e. the application of respiratory gasses under pressure to the patient's lungs via the trachea. Typically, PPV is administered to neonates via a positive end-expiratory pressure (PEEP) device which provide sufficient pressure to keep the neonate’s lung inflated, this may also be referred to as continuous positive airway pressure (CPAP).

[0003] Resuscitation of a patient typically requires delivery of a mixture of air and oxygen. The resuscitation of neonates is particularly complex because there is a need to vary the oxygen concentration and flow rate to suit different newborn clinical situations. Moreover, neonates are often unable to thermoregulate and are more susceptible to temperature changes which may be experienced as a result of the delivery of cool respiratory gasses from compressed sources.

[0004] Originally, neonates were resuscitated with 100% oxygen but it is now recognized that this level of oxygen may be toxic and air (21 % oxygen) is the recommended gas to use for the initial resuscitation. This has led to a central supply of pressurised air being available in maternity delivery rooms where neonatal resuscitation may be required. However, a central supply of pressurized air is not available in many older units and a cylinder is needed to provide the air, while a central supply of oxygen is usually available. At present only compressed sources of oxygen and air are used for neonate resuscitation which may be supplied via a wall outlet from a central cylinder or an individual cylinder of compressed gas associated with the resuscitation equipment. The use of compressed gasses in neonate resuscitation is problematic because compressed gasses expand during administration, causing the gas temperature to drop which is undesirable for babies who are vulnerable to temperature changes.

[0005] If during the initial resuscitation, a neonate fails to respond satisfactorily to PPV with air alone, an increased concentration of oxygen is provided. It is essential that the supplementation with pressurised oxygen is accurately monitored as too much oxygen is known to be toxic. Routinely, supplementary oxygen is provided by mixing a flow of air with a flow of oxygen using an oxygen blender. Blenders are mechanical devices which control the rate of flow of the air and the oxygen to provide the oxygen concentration set by the user and may be used with gas supplied by hospital wall outlets or cylinders of compressed gas. They are very sensitive devices needing regular servicing and maintenance and are calibrated using an oxygen meter. The blender mechanically adjusts the flow of the two gases to set the required concentration of oxygen. However, the mechanical alternation of flow is not recorded. Therefore, there is no real time documentation of the supplemental oxygen concentration used. Oxygen administration records are therefore dependent upon the retrospective documentation and memory of the clinicians.

[0006] Recent research has shown that it is advantageous to conduct neonatal resuscitation at the side of the mother with the placental circulation continuing through the umbilical cord intact. Thus, the neonate can be resuscitated whilst still experiencing placental circulation. This requires the resuscitation equipment is mobile enough to come right up to the mother and several trollies have been designed to provide this. These mobile resuscitation trollies have a supply of oxygen and air which may be provided from wall outlets connected to a centralize supply and/or cylinders of compressed gas e.g. oxygen and/or air. [0007] Figure 1a shows a representative prior art mobile resuscitation trolley 100a. The trolley is supplied by pressurised gas from a wall outlet/mains supply 101 and requires a first length of high pressure hose 102 for air and a second length of high pressure hose 103 for oxygen. The two lengths of high pressure hose 102 and 103 run from the wall 101 to the resuscitation trolley. The wheeled trolley may be further supplied with an oxygen blender 104 and a humidifier 105. Gasses from the wall outlet/mains supply are pressurised and consequently delivered under positive-end expiratory pressure via a T-piece resuscitator 106 to an infant situated on the upper padded surface of the trolley 107. The level of air flow and oxygen delivered to the neonate are displayed by a flowmeter 108. The whole trolley 100a is powered by a cable running to a mains power supply 109. It is often impractical to run compressed gas tubing from wall outlets to mobile trollies because the arrangements are cumbersome. The need to run two length of high pressure hose from the outlet to the trolley can present a trip hazard, whilst the inflexibility of the tubing often restricts the mobility of the trollies and thus the ability to effectively administer resuscitation at the mother’s bedside.

[0008] A commercially available bedside resuscitation trolley is known which has been adapted to carry oxygen and air cylinders. The size and weight of these cylinders is a significant restriction on a mobile mother-side resuscitation trolley. Figure 1b illustrates a representative prior art mobile resuscitation trolley 100b, which is supplied by pressurised gas from pre-filled cylinders of gas 110 and air 111, when the same are connected to the pressure regulator 108. The wheeled trolley may be further supplied with an oxygen blender 104. Gas from the cylinders is pressurised and administered under positive-end expiratory pressure via a T-piece resuscitator 106 to an infant situated on the upper padded surface of the trolley 107. The level of air flow and oxygen delivered to the neonate are displayed by flowmeter 108.

[0009] Gas cylinders which are small enough to be mounted on a trolley are inevitably small, the capacity is finite and there is a risk that they will run out during use. Consequentially, such apparatus requires the cylinders to be checked regularly. For safety, the apparatus is often fitted with a full cylinder between uses to prevent running out mid use, even when a significant amount of gas is still available from the previous use.

[0010] In anticipation of the need for resuscitation, the air supply of both described prior art bedside resuscitation trollies must be running into the positive end-expiratory pressure (PEEP) equipment such as the commercially available Neopuff™ at a typical rate of 10 litres/min while awaiting the birth of the baby. Even when the birth is imminent the exact timing is quite variable. Thus, a considerable amount of gas can be expended and wasted during this time, this is particularly problematic for the finite supplies of gas cylinders. Therefore, in addition to the aforementioned problems, the known devices shown in Figures 1a and 1b are neither environmentally friendly nor economical.

[0011] Oxygen concentrators present an alternative method of oxygen supplementation and are widely available mainly for home use when supplemental oxygen is medically necessary. They provide oxygen enriched air for patients with for example, respiratory problems. Whilst such concentrators avoid the need for cylinders which have to be renewed frequently, they typically have a fixed high level oxygen concentration at any given flowrate. An oxygen concentrator works by the Pressure Swing Adsorption (PSA) principle, in which a mixture of gasses under pressure may be separated according to the individual gas’ affinity for an adsorbent material. When the pressure swings to low pressure, any adsorbed material are desorbed or purged. Specifically, in oxygen concentrators, air is taken in, the nitrogen component of air is more easily adsorbed by certain solid surfaces (e.g. zeolite) than oxygen, nitrogen is removed from the air and hence zeolite adsorption may be employed to increase the oxygen content of pure air.

[0012] Oxygen concentrators cannot delivery gas without oxygen enrichment, i.e. oxygen concentrators do not provide pressurised air (i.e. 21% oxygen). Typically 30% 0 ₂ supplementation is the lowest level of 0 ₂ supplementation available but this varies according to the specifications of the machine.

[0013] The use of an oxygen concentrator for neonatal resuscitation is therefore not appropriate because it cannot meet the requirement to change between the delivery of air and air supplemented with oxygen so that ventilation is initiated with a pressurised air supply, followed by a pressurised 0 ₂ supply if required.

[0014] It will be readily understood that the ventilation device of the present invention which provides a variable supply of oxygen which may be useful in other clinical applications, for example Chronic Obstructive Pulmonary Disease (COPD) or asthma.

Summary of the Invention

[0015] The present invention relates to a ventilation device. Particularly, although not exclusively, a positive pressure neonate resuscitation device and a mobile bedside trolley comprising the same. The positive pressure ventilation device comprises a housing; an air inlet and a gas outlet, each located in said housing, said air inlet and said fluid outlet being in fluid communication; an oxygen concentrator, located between said air inlet and said gas outlet operable to receive air from said air inlet via said motorised pump and to increase the concentration of oxygen present in said fluid which is delivered to said fluid outlet; said oxygen concentrator comprising: a compressor having a motorised pump to draw air into said air inlet; two or more chambers, each containing a nitrogen adsorbent operable and to extract nitrogen from ambient air entering said two or more chambers to provide oxygen-enriched gas to said gas outlet; and at least one valve to alternate the flow of air between said two or more chambers; wherein the device further comprises means to regulate the frequency at which said at least one valve alternates the flow of air between said two or more chambers of said oxygen concentrator to alter the composition of gas delivered to the gas outlet. [0016] It will be readily understood that the term “valve” includes any device suitable for controlling or regulating the passage of fluid, particularly gas through the device.

[0017] Preferably, the at least one valve comprises first and second electrically controlled valves.

[0018] It is envisaged that the first and second electrically controlled valves are associate with said first and second chambers of the oxygen concentrator respectively.

[0019] The at least one valve may comprise a first and second solenoid valve or a single four-way solenoid valve.

[0020] Preferably, the means to regulate the flow of air through said oxygen concentrator to alter the composition of gas delivered to the gas outlet comprises an electronic control means.

[0021] The means to regulate the flow of air through said oxygen concentrator to alter the composition of gas delivered to the gas outlet comprises a computerised control unit, preferably a microprocessor.

[0022] It is envisaged that the computerised control unit further comprises data storage means.

[0023] Preferably, the device further comprises means to extract data stored on said data storage means from the device.

[0024] The composition of gas delivered to the gas outlet varies between ambient air and air supplemented with oxygen, preferably between 21% and 100%, more preferably between 21% and 95% 0 ₂ . The maximum value of oxygen concentration which can be achieved will be determined by the efficacy of the oxygen concentrator. [0025] Preferably, the nitrogen adsorbent of each of said two or more chambers is selected from any combination of the following adsorbents: zeolite, activated carbon, molecular sieves and lithium. [0026] The device may further comprise a humidifier and/or a warmer.

[0027] The gas outlet comprises a positive-end expiratory pressure T- piece. [0028] It is envisaged that the device further comprises an oxygen sensor to measure the oxygen concentration dispensed by said gas outlet.

[0029] The oxygen sensor may be an oximeter. [0030] Preferably, data obtained from the oxygen sensor or oximeter is received by said electronic control means, computerised control means or microprocessor and is used to modify the gas output of the device. Advantageously this provides a positive feedback loop to automatically adjust the gas composition delivered to the gas outlet according to the oxygen concentration determined by an oxygen sensor at the outlet or an oximeter on the patient. Thus, the device automatically alters the gas composition delivered in order to meet the 02 concentration set by the clinician.

[0031] The device may further comprise a battery to power the device.

[0032] It is envisaged that the device may be incorporated into a mobile trolley.

[0033] Advantageously, the device may comprise a voltage protector to ensure that the device can function uninterrupted during current/power surges.

[0034] The invention also claims a method of controlling the gas composition delivered by a positive pressure ventilation device comprising the steps of: filling a ventilation device with ambient air via an air inlet; alternating the flow of air from said air inlet between two or more chambers, each chamber containing an nitrogen adsorbent operable to extract nitrogen from said ambient air to increase the concentration of oxygen delivered to a gas outlet of the ventilation device; and regulating the frequency at which the flow of air alternates between said two or more chambers to vary the gas composition delivered by the ventilation device between ambient air and air supplemented with oxygen.

[0035] The frequency at which airflow is alternated between first and second chambers of the device is typically measured at a rate of alternations/second. The range of frequency values is typically between 0.25 and 4 alternations per second. Typically, higher oxygen concentrations are achieved at lower alternating frequencies which provided sufficient time for the chambers to adsorb nitrogen from ambient air. At higher frequencies of alternation, there is insufficient time for nitrogen to be expunged by the first chamber before airflow is switched to the second chamber, the first chamber is therefore unable to adsorb as much nitrogen on the next alternation, thus at increasing frequencies the oxygen concentration in the chamber outlet is reduced.

[0036] When the rate of alternations/second is 0 between each cylinder the gas outlet delivers air. The size of the chambers and the pressure of the pump used in the compressor determine the optimal frequency range required to achieve oxygen concentration. The means to regulate the frequency of alternation between first and second chambers is an electronic control means, preferably a computerised control means, even more preferably a microprocessor.

[0037] It is an object of the present invention to provide a neonate or resuscitation device which addresses the problems outlined above. Specifically, to provide a neonate or infant resuscitation device whose mobility is not restricted by connection to wall mounted supplies; which is not vulnerable to running out as a result of finite cylinder supplies of pressurised gas and which can interchangeably deliver pressurised air and pressurised air which is supplemented with 0 ₂ .

[0038] It is a further object of the invention to provide a positive pressure neonate or infant resuscitation device which is capable of recording the level and duration of supplemental 0 ₂ administered to the neonate. [0039] Advantageously, the present invention does not require an external (compressed cylinder) or integrated gas supply and only an electrical supply is required. This can be either a mains supply (readily available and necessary for other equipment used for neonatal or infant resuscitation) and/or a battery supply within the trolley.

[0040] Unlike gas cylinder fed devices, there is no risk that the gas supply of the present invention will be exhausted.

[0041] Advantageously, the present invention uses oxygen concentrators in a novel way to provide air with a higher oxygen concentration suitable for the resuscitation of newborn babies and young infants.

[0042] The device according to the invention provides air for the initial positive pressure ventilation of a neonate requiring resuscitation at birth and can optionally provide additional oxygen if required without using a source of pure oxygen (100% O2) and a blender. The advantage of this approach is that there will be an immediate supply of air (and followed by an increased concentration of oxygen if required) without any heavy cumbersome compressed gas cylinders or tubing to a wall source.

[0043] The invention does not require the use of an oxygen blender to combine the air and oxygen to provide an oxygen concentration above 21 %, the normal concentration of 0 ₂ in air.

[0044] The present invention does not use compressed gasses and the air or air and oxygen mixture is thus advantageously delivered at ambient temperature.

[0045] It is envisaged that the device of the present invention can be incorporated into a mobile resuscitation trolley. It needs only a mains power supply or an onboard battery supply. It will not run out of oxygen or air and can run continuously without attention. Thus, a trolley incorporating the invention provides mobile resuscitation equipment which does not require a source of pure oxygen.

[0046] The mobility of a trolley incorporating a device according to the present invention is advantageous as it allows resuscitation of babies at birth immediately next to the mother whilst the placenta is still attached.

[0047] It is envisaged that the device of the present invention allows the operator to vary the flow rate and oxygen concentration independently of one another.

[0048] Advantageously, the device of the present invention can deliver gaseous mixtures under positive pressure ranging from pure air (typically 78.1% nitrogen, 20.9% oxygen and a 1% mix of argon, hydrogen, methane, nitrous oxide, xenon, krypton, helium and neon) to air supplemented with additional oxygen in the range of >20.9% to 100% 0 ₂ .

[0049] Preferably, the control of the oxygen supplement is microprocessor controlled and the oxygen level is recorded and stored as an electronic recording.

[0050] The invention incorporates an oxygen sensor to measure the oxygen concentration dispensed; this allows the user to validate the oxygen concentration administered to the patient and to adjust the device as required.

[0051] It is a further advantage of the present invention that the gas entering the oxygen concentrator is at room temperature, it warms slightly with the compression and then cools again as it expands but ultimately, it leaves the concentrator at room temperature. The gas may also be humidified to meet the requirement of the neonate as it leaves the concentrator. The device may further comprise a warmer or heating means to heat the gas expelled by the device to meet the requirements of the neonate or infant.

[0052] Advantageously, the device of the present invention comprises an initial self-calibration period to stabilize the oxygen concentration and avoid delivery of excess oxygen levels. The device will only administer air until the self-calibration is complete or when an oxygen concentration is selected by a user. The calibration procedure has a duration of up one minute. Oxygen blenders used in traditional neonatal resuscitation trollies need to be calibrated regularly by technical staff during regular maintenance.

[0053] The device of the present invention monitors the flowrate and oxygen concentration to automatically determine when the adsorbent needs replacing.

[0054] It is envisaged that the device will automatically adjust the switching rate between the two or more chambers in response to changes in the flow rate to ensure that the oxygen concentration is maintained at the desired concentration. The device may regulate the frequency at which said at least one valve alternates the flow of air between said two or more chambers of said oxygen concentrator to alter the composition of gas delivered to the gas outlet in response to data received from oxygen sensors which may be integral to the device or an oximeter which is in contact with a limb of a patient being treated with the ventilation device. For example, in the case of neonate resuscitation, oxygen levels from an oxygen sensor at the gas outlet or an oximeter attached to the foot of a neonate may be fed back to the computerised control unit, to indicate whether higher of lower oxygen supplementation is required.

[0055] Optionally, the device may include a humidifier to humidify the gas expelled by the device. The device may also include a warmer or heating means to heat the gas expelled by the device.

[0056] Optionally, the device will be able to store the oxygen concentration values during any resuscitation procedure or use of the device.

[0057] It is envisaged that the stored oxygen concentration data may be downloaded to an external drive.

[0058] Optionally, the oxygen concentration in the gas outlet is maintained according to the input from an oximeter present on the neonate. The control and target oximetry blood oxygen saturation level ( Sp0 ₂ ) of the neonatal blood is decided by the clinician. The Sp0 ₂ level can be manually read from the oximeter and the oxygen output of the device can be adjusted manually or alternatively the Sp02 level can be read electronically by the computerised control unit of the device which adjusts the gas output of the device accordingly in an automated feedback loop.

[0059] The device may further comprise a fraction of inspired oxygen (Fi0 ₂ ) dial which displays the volumetric fraction of oxygen in the air delivered by the ventilation device. Ambient air containing approximately 21% oxygen, has a Fi0 ₂ of 0.21, whereas oxygen-enriched air has a Fi0 ₂ value between 0.21 and 1 .00. A Fi0 ₂ value of 1 .0 is the equivalent of 100% oxygen.

[0060] The device may be fitted with air filters to remove any contaminants from the pump outlet or PEEP equipment. Preferably, filters are present at the entry air inlet to valve 1 and valve 2 of chambers 1 and 2 of the oxygen concentrator respectively; and also at the gas outlet to filter contaminants from air on the way into the device and gas on the way out of the device.

[0061] Other aspects are as set out in the claims herein.

Brief Description of the Drawings

[0062] For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which:

Figure 1a shows a perspective view of a prior art resuscitation trolley supplied by pressured gas from a wall/mains supply.

Figure 1 b shows a front view of a prior art resuscitation trolley supplied with pressured gas from pre-filled cylinders. Figure 2a shows a perspective view of a positive pressure ventilation device according to a first embodiment of the present invention in a clinical setting.

Figure 2b shows a graphical representation of the relationship between the frequency of alteration between first and second chambers of the oxygen concentrator the device and the O2 concentration delivered by the gas outlet of a device according to the present invention.

Figure 3 shows a perspective view of the oxygen concentrator component of the ventilation device according to the present invention.

Figure 4 shows an internal view of the oxygen concentrator component of the ventilation device according to the present invention.

Figure 5a shows a schematic diagram of a user interface controlling the frequency of alternating airflow between first and second chambers of the oxygen concentrator of the device according to the present invention.

Figure 5b shows a typical user interface of the ventilation device according to the present invention.

Figure 6 shows an alternative schematic diagram of the oxygen concentrator component of the ventilation device according to the present invention.

Figure 7 shows a schematic software flow diagram for the microprocessor of the device according to the present invention.

Detailed Description of the Embodiments

[0063] There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the description.

[0064] Referring to Figure 2 there is shown a perspective view 200 of a positive pressure ventilation device according to a first embodiment of the present invention in a clinical setting. The figure illustrates that ventilation may be administered whilst the neonate still experiences placental transfusion via the umbilical cord 201 . The device 200 comprises an oxygen concentrator 202 which generates supplemental oxygen from air and which can interchangeably switch between air and air supplemented with oxygen which is delivered via tubing 203 under positive-end expiratory pressure (PEEP) device to a T-piece mouthpiece 204 to an infant situated on the upper padded surface of the trolley 205. The level of oxygen delivered to the neonate or infant can be selected, displayed and recorded by a control unit 206 and visual indicator 207 which are components of the oxygen concentrator 202. The ventilation device 200 is powered by a cable running to a mains power supply 208. The output gas generated by the device is delivered by tubing to the mouthpiece 204. The device may further comprise a humidifier, and/or a warmer, a CPAP or PEEP controller and any combination thereof 209 located between the mouthpiece 204 and the oxygen concentrator 202. The CPAP and PEEP controllers limit and regulate the pressure of gas being supplied to the infant or neonate.

[0065] The trolley unit itself comprises a wheeled base unit 210, a central support tower 211 and an upper padded surface 205 which receives a neonate thereon. It will be readily understood that the positive pressure ventilation device may be supplied without the trolley components (210, 211 and 205) for retrofitting to existing mobile trolleys or for mobile use for example at home births or in an ambulance.

[0066] The device of the present invention uses the Pressure Swing Adsorption (PSA) principle to adsorb nitrogen from air to increase the oxygen concentration. The oxygen concentrator comprises a condenser having a pump which draws ambient air into the device, via the chambers of the oxygen condenser to deliver air or air supplemented with oxygen, (as determined by the frequency of alternation between the first and second chamber so the device) under positive pressure. The device allows the user to adjust the flow rate and the level of supplemental oxygen delivered by the device. The device regularly switches the flow of air between the two or more chambers containing zeolite or another suitable nitrogen adsorbent. The frequency of alternating airflow between the first and second chambers determines the oxygen concentration present in the gas delivered to the gas outlet. When the frequency of alternating airflow between first and second chambers is 0, no switching occurs; the valve(s) controlling airflow into the first and second chambers are open and air flows to the gas outlet without oxygen being condensed and ambient air is received by the gas outlet.

[0067] The frequency at which airflow is alternated between first and second chambers of the device is typically measured at a rate of alternations/second. A typical range of alternating frequency values is 0.25 to 4.00 alternations per second. Higher oxygen concentrations are achieved at lower alternating frequencies as this provides sufficient time for the chambers to adsorb nitrogen from ambient air. At higher frequencies of alternation, less nitrogen is adsorbed by each chamber of the oxygen concentration before airflow passes to another chamber of the concentrator, thus less oxygen is saturated. Less nitrogen can be adsorbed because the zeolite within the initial chamber is still partially saturated as there is insufficient time for the nitrogen to be expunged.

[0068] As illustrated in Figure 2b, the concentration of oxygen delivered by the device is variable. When the alternating frequency is 0 between each cylinder the said gas outlet delivers air under positive pressure. When the alternating frequency is increased from 0 there is an increase in mean oxygen concentration delivered to the gas outlet (see A on Figure 2b), until the optimal frequency (* on Figure 2b) for oxygen concentration is reached. When the alternating frequency is increased beyond the optimal mean oxygen concentration (see B on Figure 2b), there is insufficient time for nitrogen to be expunged by the first chamber before airflow is switched to the second chamber; the adsorbent remains partially saturated and is unable to adsorb as much oxygen and thus, the level of oxygen which is concentrated is reduced. At high frequencies of alternation, for example values of greater than 2.5 alternations per second on the example shown in Figure 2b, airflow is so rapidly alternated between the chambers of the oxygen concentrator that the rapid alternation has an effect which is the equivalent of the valve to both chambers of the concentrator being opened. At such particularly high frequencies of alternation, ambient air is released at the gas outlet. It will be readily understood that the values illustrated in Figure 2b are for illustrative purposes only. The rise in the means oxygen concentration may be more gradual or may feature further along the x axis. The precise frequency for achieving maximum oxygen concentration is determined by the number and size of chambers (or sieve beds) present in the oxygen concentrator and also the pressure of the pump used in the condenser.

[0069] Referring to Figure 3 there is shown a perspective view of the oxygen concentrator component 202 of the ventilation device 200 according to the present invention. The oxygen concentrator 202 is a self-contained unit which can be powered electrically via a mains cable 301 , or powered by an internal battery (not shown). The visual appearance of the unit may vary but comprises an air inlet 302 through which atmospheric air is drawn into the device by an internal oil free compressor pump driven by a motor. The compressor includes a cooling fan. The compressor pump compresses atmospheric air which is concentrated into a continuous stream and delivered to the at least first and second chambers containing nitrogen adsorbents including but not limited to activated carbon, molecular sieves and lithium, preferably, zeolites. It will be readily understood that the terms first and second chambers may be interchangeably referred to as first and second sieve beds, which function to deplete nitrogen levels from ambient air. More than two chambers or sieve beds may be used to enable a continuous supply of oxygen if so required. [0070] The device may be fitted with air filters to remove any contaminants from the compressor pump before it is concentrated and delivered to the first and second chambers and ultimately, the PEEP equipment.

[0071] Once ambient air is compressed and delivered to the first and second chambers, the device may either utilise adsorbent within the chambers to remove nitrogen from the air to increase the oxygen concentration of pressurised gas delivered to the outlet 303.

[0072] The device according to the invention allows a user to set a required oxygen concentration from >21% digitally on the user display interface 304 using buttons, dials, a control knob or equivalent 305, and controls the switching period to deliver the selected 0 ₂ concentration. The switching period will be readily understood to be the frequency with which the device alternates pumping in turn through the chambers comprising an adsorbent. The device automatically controls the switching period so that oxygen concentration can be varied at any given flow rate.

[0073] The device measures the 02 concentration being delivered from the adsorption chambers using an oxygen sensor 306 and uses this as feedback to allow control of the switching period to deliver the required oxygen concentration.

[0074] Referring to Figure 4 there is shown an internal view 400 of the oxygen concentrator 202 of the positive pressure ventilation device illustrated in Figure 3, according to the present invention. Atmospheric air (typically 78.1% nitrogen, 20.9% oxygen and a 1% mix of argon, hydrogen, methane, nitrous oxide, xenon, krypton, helium and neon) is drawn into the device housing 401, through air inlet 403 which is a filtered vent in the side of the housing. Air enters the air inlet 403 under the action of a motorized pump 402 of an oil free compressor 404 which is located within the housing 401. The compressor draws in ambient air, increases the air pressure to approximately 2-3 atmospheres to deliver a continuous stream of compressed (pressurised) air to the first 405 and second 406 chambers each containing the microporous, six-sided aluminosilicate, zeolite, or any other suitable material, which provides a molecular sieve bed that adsorbs nitrogen from atmospheric air so that the relative quantities of oxygen leaving the chamber are higher than those entering the chamber. The sieve beds function to increase the oxygen concentration of gas leaving the chamber.

[0075] Once air has been forced through the first chamber 405, the first sieve bed is filled up with adsorbed nitrogen and oxygen rich air is expelled from the device. Subsequently, when the first sieve bed is saturated, the gas flow is switched and compressed air is moved to the second sieve bed. The first chamber (sieve bed) is vented to allow it to return to atmospheric pressure, this drop in pressure causes the zeolite adsorbent to release the adsorbed nitrogen to the atmosphere and the sieve bed is reset and capable of adsorbing further nitrogen. The compressor 404 is connected to first 405 and second 406 chambers by large bore high pressure piping 407. The control of flow between first and second chambers (interchangeably called sieve beds) is regulated by two solenoid valves 408 and 409, or alternatively a four-way solenoid valve, each controlled by an electronic control unit 411 . The first 409 and second 410 solenoid valves control compressed gas flow from the compressor 404 into the first 405 and second 406 chambers of the oxygen condenser respectively. Each of said first 408 and second 409 solenoid valve has two positions. In a first position the valve is open to allow flow from the compressor to the chambers 405 and 406; in a second position the valves 408 and 409 are closed, preventing gas flow from the compressor to the chambers 405 and 406, when the valves are closed and gas is vented to the atmosphere via nitrogen vents 410. The outlets 412 from each zeolite chamber 405 and 406 are pinhole narrow bores having a diameter sufficient to maintain a pressure of 2-3 atmospheres when the venting valves are closed, but also sufficient enough to allow sufficient flow of gas to the outlet.

[0076] The presence of two of more chambers 405 and 406 permits the near continuous production of concentrated oxygen if so required. This arrangement also allows pressure equalization between the two chambers. The first 408 and second 409 valves alternate so that the first 405 and second 406 chambers are filled sequentially. At any given time, one chamber receives pressurised air from the compressor pressure in the first chamber 405 increases to approximately pressure to approximately 2-3 atmospheres, preferably 2.36) at this increased pressure, the zeolite adsorbs nitrogen from the pressurised air supply. The increased oxygen concentration in the outlet is detected by an oxygen sensor 413 which may be independent or integral with the control unit 411. The frequency of alternating between first and second chambers using the pressure swing adsorption (PSA) controls the level of oxygen delivered to the gas outlet.

[0077] The control unit 411 adjusts the valves 408 and 409 to provide air or a set concentration of 0 ₂ as determined by the clinical situation. The control unit 411 may be a microprocessor, CPU or any other suitable interface which maintains the frequency of the PSA to maintain the selected oxygen concentrations. The microprocessor may be a commercially available microprocessors for example the Raspberry Pi or an open sourced electronics platform such as Arduino. An example coding programme for the device is shown in Annex 1 .

[0078] Increasing the frequency of switching between the first and second chambers (swinging the pressure) above the optimal level (area B in Figure 2b) results in a reduction in the mean oxygen concentration. The maximum level of oxygen which the device is capable of delivering (* in Figure 2b) is determined by the size of the zeolite chambers and the pressure of the pumped air. The quality of the zeolite is also critical and the zeolite does have a limited life and will require replacing periodically. The control unit 411 is capable of detecting when the zeolite needs replacing. The control unit 411 further comprises a realtime clock and data storage facilities so that the level of oxygen administered can be recorded at regular time intervals. Documentation of the levels of oxygen used during resuscitation of a neonate is particularly important for audit purposes and during civil litigation (medico-legally). The control unit 411 may have data entry facilities to enable data for patient identification to be stored. The inbuilt timestamp ensures that readings are recorded ‘real-time’ providing a record of the oxygen/air levels used for that specific patient. [0079] When initially turned on i.e. at ‘start-up’, the device operates at an initial high frequency as selected by the microprocessor controller 411 (the equivalent to infinity alternations/second). At this value, nitrogen cannot be expunged from the chambers, oxygen is not concentrated and instead the device delivers pressurised air to the fluid outlet 303. During this initial ‘start-up’ period the oxygen concentration at the gas outlet is the same as the oxygen concentration at the inlet e.g. 21 % O2 (ambient air). The calibration period lasts for approximately 30 seconds after the start-up of the device. The device continues to deliver 21% 0 ₂ until a higher oxygen concentration is selected by the user/clinician.

[0080] When a user or clinician selects an oxygen concentration higher than ambient air, the frequency of alternation between first 405 and second 406 chambers of the concentrator must be altered. The device further comprises a means 417 to regulate the frequency at which valves 408 & 409 alternate switching of the flow of air between first 405 and second 406 chambers of the oxygen concentrator to vary the gas composition delivered to outlet 416. The means to regulate the frequency of alternation 417 comprises a computerised control unit, preferably a microprocessor located within the control unit 411 .

[0081] In use, in resuscitation of a neonate or infant, initially, the switching of pressurised air flow between first 405 and second 406 chambers is off; both nitrogen vents 410 are closed and neither chamber 405 or 406 can purge adsorbed nitrogen. Consequentially, the first 408 and second 409 valves remain in an open position, pressurised air is pumped into both chambers 405 and 406 and nitrogen is adsorbed. Once both adsorbents are occupied with their maximum nitrogen adsorption, the adsorbent cannot be purged back to the atmosphere. Further nitrogen cannot be removed from the highly pressurised air the compressor is feeding into the device and the initially concentrated oxygen flow is returned to normal atmospheric oxygen levels. Thus, during initial use, when the device is first switched on a high concentration of oxygen reaches the outlet which is detected by an oxygen sensor 413 at the outlet 303. The control unit displays a message to the user to notify them that the device is not yet ready for use on neonate resuscitation which should as explained previously be initiated with air. Therefore there is an initial calibration/adjustment period which correlates to the time taken for both adsorbents to be concentrated with their maximum nitrogen capacity. Practically this is a very short period of time, approximately 30 seconds, until the oxygen sensor 413 detects an oxygen level of 21% at the gas outlet 416/303 indicting the device is suitable for use to begin resuscitation using pressurised air delivered by a T-piece resuscitator (see 204 figure 2).

[0082] Referring to Figure 5, there is shown a flow chart to illustrate use of the device when additional oxygen supplementation is required. The clinician sets the required concentration using the visual display (304 of Figure 3) and adjusting buttons (305 of Figure 3) of a user interface 501 located on the device housing. Interactions at the user interface 501 are received by the microprocessor of the control unit 502/411 which in turn acts via first 503 and second 504 solenoid switches or drivers to control first 506/408 and second 507/409 valves of the first and second chamber respectively. The microprocessor 502 regulates the frequency at which first 506/408 and second 507/409 solenoid valves are opened and closed to regulate the flow of air between the first and second chambers of the oxygen concentrator. When one valve 506/408 is opened the second valve 507/409 is closed. The rate of frequency of alternation refers to the frequency/second of alternating between the two valves 506/408 and 507/409. This may also be interchangeably referred to as the rate of switching airflow between the first and second chambers of the oxygen condenser. The frequency of the switching solenoid valves 506/408 and 507/409 is under the control of microprocessor 502 with a closed loop feedback from an oxygen sensor (413/601). The oxygen sensor may be located at the device outlet (303 figure 3) or may be located remotely as an oximeter on a neonate or infant (see 701 figure 7). The valves 506/408 and 507/409 have to control high pressure and the solenoids therefore require a high current to switch, much higher than is available from the microprocessor digital output. The digital output of the microprocessor 502 is fed into a solenoid switch or driver 503/504 which provides the output for the solenoid valves. [0083] A typical user interface and the likely displayed information is shown in Figure 5b.

[0084] Figure 6 shows an alternative schematic diagram of a ventilation device according to the present invention with like numerals denoting like parts. The device has an oxygen sensor 413 the output 416 of the gas flow. The software for the sensor to provide the percentage of oxygen in the output is integrated into the microprocessor of the control unit 411 or can be provided separately in a remote sensor or oximeter 601. Optionally, the closed loop feedback controlling the oxygen concentration in the gas output can be determined by the oxygen saturation of the tissues using an oximeter 602 which measured the tissues oxygen saturation (SpO¾, typically in the a hand or foot of the infant or neonate. Alternatively, feedback can be provided by near-infrared spectrometry (NIRS) measuring the oxygen saturation in the brain 603. The software sensors for the Sp0 ₂ and NIRS can be integrated into the control unit 411 or provided separately. The parameter and required range for the feedback is selectable by the clinician using the equipment. The switching software uses a value from the sensor 413, 601, 602 or 603 which represents the oxygen concentration (or Sp0 ₂ or NIRS) to modify the switching frequency until the oxygen concentration falls within the selected and desired range.

[0085] Filters 604 are present at the point of entry of valves 408 and 409 in first and second chamber 405 and 406 respectively. The filters 604 function to remove particulate matter and water vapour from ambient air entering the device and ensure that gas delivered from the device to the patient is free from microparticles for example adsorbent particles. . At the outlets 412 from each zeolite chamber 405 and 406 are pinhole narrow bores having a diameter sufficient to maintain a pressure of 2-3 atmospheres when the venting valves are closed. The outlets 412 comprise pressure nozzles 605 which control the pressure of the gas delivered to the device outlet (303 Figure 3).

[0086] Referring to Figure 7, there is shown a schematic software flow diagram for the microprocessor of the device according to the present invention. When the equipment is first switched on, the microprocessor enters a set up mode, where the switching frequency is set to zero. Both valves are open, representing a switching frequency of infinity. When the oxygen sensor detects 20.9% oxygen in the output (after about 30 seconds), the display indicates that the equipment is ready for use. At this stage the operator can select the required range of oxygen concentration 701 or alternatively, feedback 702 from the oxygen sensor at the gas outlet, an oximeter or NIRS is received and recognized by the software algorithm.

[0087] The detected oxygen values 703 are computed by the microprocessor and appropriate action selected 704. The software enters a feedback loop which detects the analogue input from the oxygen sensor, oximeter or NIRS. If the input data is below the required mean oxygen concentration, the frequency of the switching/alternating is adjusted accordingly. The positive feedback loop continues and a second sensor reading is detected by the microprocessor, if necessary the alternating frequency is further adjusted. If the detected mean oxygen concentration data received from the oxygen sensor at the gas outlet, an oximeter or NIRS is within the required clinical range no change in the switching frequency is made. If the mean oxygen concentration is still too low a further adjustment to the alternation of frequency/switching is made until the required oxygen concentration is reached. This process is repeated until the optimal frequency switching is reached for the required oxygen concentration. If the input is higher than the required range the switching frequency is increased. If the required oxygen concentration is set to the maximum - representing close to 100% oxygen, switching frequency decreases until the optimal frequency is reached. This varies according to the machine, the size of the sieves and the pressure of the pump, and can be limited by the software to prevent the frequency falling below the optimum. If the oxygen concentration is below the maximum possible (practically approximately 95%) a warning is given to indicate that the zeolite or molecular sieve may need to be changed.

[0088] It will be understood that various modifications of the invention will be apparent to those skilled in the art. For example, the zeolite adsorbent may be substituted with any other suitable nitrogen adsorbent including but not limited to activated carbon, molecular sieves and lithium.

[0089] The device of the present invention may also be applicable to other applications in other areas of medicine. Currently, home oxygen concentrators are commonly used by those with chronic obstructive disease of the lungs (COPD) but the level of oxygen is not adjusted to any exact requirement of the patient. This could provide a customized level of oxygen, avoiding the risk of hyperoxia i.e. cells, tissues and organ damage caused by exposure to an excess supply of oxygen.

Annex 1 :