Patent Description:
At the moment of their first breath, a baby's lungs are collapsed and filled with fluid. The pressures needed to open their lungs and keep them open are several times that of a normal breath until the fluid is displaced and the lungs have filled with air. To generate these large pressures, the baby must have strong respiratory muscles, as well as a surfactant in their alveoli. The surfactant reduces the surface tension of the fluid within the alveoli, preventing the alveolar walls from sticking to each other.

Neonates have difficulty in opening their lungs and keeping them open. Reasons for this include:.

To alleviate this it is known to apply Positive End Expiratory Pressure (PEEP) during respiration, resuscitation or assisted respiration (ventilation). In applying PEEP, the patient's upper airway and lungs are held open during expiration against a pressure that stops alveolar collapse. Lung fluid is pushed back into the circulating blood, alveolar surfactant is conserved, and a larger area of the lung participates in gas exchange with the blood. As blood oxygenation and carbon dioxide removal improves, more oxygen is delivered to growing tissue, while less oxygen and energy is consumed by respiratory muscles. In the case of resuscitation or ventilation the pressure is varied between a Peak Inspiratory Pressure (PIP) and the PEEP value until the patient is breathing spontaneously.

To provide the PEEP across a range of flow rates, some method is required to regulate the pressure to prevent injury to patients, particularly neonates due to the fragility of their lungs and airway.

It is known to provide a valve near the patient which actuates at a level of pressure (namely, the PEEP value) to allow the gases to vent externally and reduce pressure in the stream delivered to the patient. Such valves may be spring-loaded. These require the use of high quality springs which must be individually tested to give a high tolerance spring constant to ensure that they actuate at a value substantially that of the maximum safe pressure. Both the manufacture and testing of such a spring result in high costs. Also such valves are known to have substantial variation of the relief pressure with flow rate.

To address issues with spring-loaded valves, umbrella valves have been used. Umbrella valves provide a lower variation in delivered pressure.

<CIT>, discloses umbrella valve designs for reducing the variation in delivered pressure that may be experienced with prior art valves. According to particular embodiments, the elastomeric member used to selectively close the vent is adapted such that as the flow rate increases, a larger portion of the flow at the inlet is able to pass through the vent, better regulating the pressure delivered to the patient.

<CIT> further describes an arrangement which enables the PEEP value to be manually adjusted. This arrangement is shown in <FIG>. Referring to <FIG>, gas enters the apparatus <NUM> via inlet <NUM> and generally exits via an outlet (in the base of apparatus <NUM> but hidden in the Figures provided) which couples to a mask or other patient interface (not shown) to deliver air to the patient, typically an infant. The apparatus <NUM> further includes a vent which terminates in an orifice <NUM> in a screw on cap <NUM> which engages with thread <NUM> on the main body of the apparatus <NUM>. Air exits through the vent via nozzle <NUM> and apertures positioned around the nozzle <NUM>. As will be appreciated, due to the position of the nozzle <NUM> in relation to the orifice <NUM>, rotation of the cap on the thread <NUM> will not significantly affect flow through the nozzle <NUM>. However, rotation of the cap <NUM> does affect flow from the apertures around the nozzle <NUM> because as the cap is tightened, the orifice <NUM> becomes partially blocked by the outer wall of the nozzle <NUM>, reducing flow. Thus, rotation of the cap <NUM> enables the PEEP value to be adjusted.

<CIT> describes a relief valve assembly for relieving excess pressure in a manual resuscitator that may result from a user exerting too much force to compress a self-inflating bag type reservoir of the resuscitator. The assembly includes a vent (generally similar to that shown in <CIT>) that is adjacent an outlet for interfacing with a patient. According to one embodiment, as shown in <FIG> herein, the valve assembly includes a threaded portion <NUM> for connecting to the resuscitator. Valve element <NUM> is biased against a seat <NUM> to seal the opening. In the event there is excessive pressure in the resuscitator, the valve element <NUM> moves upwards and away from the seat, allowing gas to be vented through aperture <NUM>.

According to one embodiment described in <CIT>, the valve element <NUM> is mounted on a screw <NUM> via the end wall <NUM> of the cap whereby rotation of the screw <NUM> adjusts the force with which the valve element <NUM> bears against the seat <NUM>, thereby adjusting the adjusting the pressure at which the valve assembly provides relief. While this provides adjustment of the relief pressure, a screwdriver or other like tool is required to do so. Further, overtightening of the screw <NUM> may urge the valve member <NUM> too far downwards such that valve member <NUM> and screw <NUM> become detached from the cap. This could result in portions of the assembly being passed to the patient interface outlet with the potential risk of injury to a patient. Conversely, withdrawing the screw <NUM> too far from the cap may urge the valve member <NUM> into contact with the end wall <NUM> of the cap potentially damaging the valve member <NUM>. This may affect performance of the valve assembly and again potentially result in parts of the apparatus (i.e., fragmented parts of the valve element <NUM>) being passed to the patient interface. <CIT> discloses a pressure regulator for use with breathing assistance apparatus.

It is an object of the invention to provide apparatus which overcomes or ameliorates at least one problem associated with prior art arrangements.

Alternatively, it is an object of the invention to at least provide a useful choice to the public.

According to a first aspect, there is provided a pressure regulating device for use with a breathing assistance and/or resuscitation apparatus which conveys gases along a gases pathway to a patient, particularly an infant or neonate and more particularly a prematurely born neonate but not limited thereto, the device comprising:.

Preferably the control member is capable of manipulation by hand, without the need for use of additional equipment such as a screwdriver.

Preferably the control member is rotatably coupled to the mounting.

Preferably the control member is otherwise fixed relative to the mounting although it may be detachable therefrom.

Preferably the valve member comprises an elastomeric member. More preferably the valve member is integrally molded from liquid silicon.

Preferably the valve member comprises a skirt or at least one flap wherein said selective blocking is performed by movement of the skirt or flap(s). Where multiple flaps are used, these may, for example, take the form of radially extending lobes.

Preferably the valve member comprises a shaft.

Preferably the shaft is joined to or integral with the skirt or flap(s).

Preferably the shaft is substantially perpendicular to the skirt or flap(s) and/or centrally positioned in relation thereto.

Preferably the thickness of the flap proximate to the join with the shaft is less than the thickness of the skirt or flap(s) at the periphery thereof. More preferably the ratio of thicknesses is substantially <NUM>:<NUM>.

Preferably the valve member is an umbrella valve. However, other valve means may be used including membranes otherwise fixed in position to selectively close, at least partially, the first outlet.

Preferably the mounting comprises framework for defining an aperture in which the shaft of the valve member is received and held.

Preferably the valve member is held in a substantially central position in the first outlet with respect to a plane substantially perpendicular to flow through the first outlet when the first outlet is open.

Preferably the pressure regulating device comprises a seat member, the seat member being positioned such that when the pressure of gases is below the selected level, a portion of the valve member sits thereon.

Preferably the seat member comprises a substantially annular surface on which said portion of the valve member sits.

Preferably the seat member is engaged with the control member whereby manipulation of the control member moves the seat member and effects said adjustment of the selected level of pressure.

Preferably the pressure regulating device is configured such that manipulation of the control member moves the seat member in a direction substantially parallel to the normal flow of gases through the first outlet when the first outlet is open.

Preferably the control member is rotatably fixed relative to the seat member. More preferably the seat member comprises at least one projection configured to engage at least one projection or recess in the control member to effect said rotational fixing although alternative arrangements may be used.

Preferably the seat member is threadingly engaged to said mounting whereby rotation of the control member effects said movement of the seat member.

Preferably engagement between the control member and seat member provides for sliding engagement, preferably in a direction substantially parallel to the normal flow of gases through the first outlet when the first outlet is open.

To this end, according to one embodiment, the seat member comprises at least one projection configured to be received in a groove or between elongated teeth provided on the control member, the projection being slidable along the groove or between the teeth but preventing relative rotation between the control member and the seat member. As will be appreciated, alternatively, a groove or grooves in the seat member may similarly engage with projection(s) or teeth on the control member.

Preferably the control member is in the form of a cap and comprises a sidewall that extends from the first outlet when coupled thereto.

Preferably the cap comprises an orifice.

Preferably the orifice is configured to be selectively occluded such as by placement of a finger or thumb of a user thereon. Such operation preferably varies the pressure of gases in the pressure regulating device between a desired PIP and PEEP by occluding or not, respectively the orifice.

Preferably, with the control member in any given position, the pressure of gases inside the gases pathway is substantially independent of the rate of flow of gases along the pathway.

Thus preferred embodiments of the pressure regulating device of the first aspect provide a vent that provides for controlled and adjustable pressure relief so that when coupled to a breathing circuit, the pressure of gases delivered to a patient is substantially constant or independent or gases flow rate but manually adjustable to different levels by manipulation of the control member.

Preferably the pressure regulating device comprises the first outlet.

The mounting may be integral with or coupleable (preferably sealably) to a wall defining the first outlet.

Preferably the pressure regulating device comprises an inlet for receiving gases therethrough.

The inlet is preferably configured to couple to apparatus configured to provide a flow of gas. The apparatus may comprise a pump and/or a humidifier and may be coupled via known conduits.

Preferably the pressure regulating device comprises a second outlet, the second outlet configured to deliver gas to patient.

The second outlet may form part of a patient interface such as a mask.

Alternatively, the second outlet may be configured to couple (preferably sealably) to a patient interface, including via intermediate equipment such as a conduit.

More particularly, the pressure regulating device preferably comprises a housing that defines the inlet, the first outlet and the second outlet.

The inlet and the first and second outlets are all in fluid communication. When the first outlet is blocked or substantially blocked, at least a major portion of the gas entering the inlet is delivered to a patient interface via the second outlet. When the valve member opens, at least a portion of the gas is vented through the first outlet thereby providing pressure relief.

According to particular embodiments, the housing comprises an aperture adapted to allow insertion of equipment therethrough, such as surfactant delivery means or a suction tube.

Preferably the pressure regulating device comprises a sealing means adapted to prevent gas flow through said aperture and allow the equipment to be inserted therethrough while providing breathing assistance.

Preferably the sealing means is a duck billed valve.

Preferably said aperture and said second outlet are substantially aligned or coaxial.

In a further aspect there is provided a pressure regulator for use with a breathing assistance and/or resuscitation apparatus, and which is arranged to regulate pressurised gases supplied to a patient by releasing or exhausting some gases when the pressure exceeds a threshold. This threshold is preferably easily manipulated by manual adjustment of the regulator by a user's digits including fingers and/or thumbs. In an embodiment this is achieved by adjusting the position of a valve seal against which a valve member is biased.

In an embodiment there is provided a pressure regulator for a breathing assistance apparatus and comprising: a mounting having an inlet port for receiving pressurised gases, an outlet port for delivering said pressurised gases to a patient, and a relief port for regulating the pressure of said gases; the relief port including a valve member biased against a valve seat and arranged to open when the pressure of said gases exceeds a selected level in order to release some of the gases out through the relief port; wherein the position of the valve seat is manually adjustable within the relief port in order to adjust the selected level of pressure at which the valve member will open.

In an embodiment the pressure regulator further comprises a control interface adapted to operate under manual digital manipulation by a user, the control interface externally mounted on the mounting and arranged to adjust the position of the valve seat in response to relative movement between the interface and the mounting caused by the digits of the user.

In an embodiment the interface comprises a cap externally mounted over the relief port and which is rotatably moveable thereon.

In an embodiment the cap comprises an orifice for passing the released gases, the orifice being sized to allow its occlusion by a digit of a user.

In another embodiment there is provided a pressure regulator for a breathing assistance apparatus and comprising: a conduit for receiving and delivering pressurised gases, the conduit having a pressure relief valve comprising a valve member and an adjustable valve seat, the valve seat adjustable to vary the pressure at which the relief valve releases some pressurised gas in order to reduce the pressure of the gases in the conduit; wherein the valve seat is arranged to adjust in response to digital pressure by a user of the regulator.

In an embodiment the pressure regulator further comprises a control interface adapted to operate under manual rotation by the user, the control interface externally mounted on the valve and arranged to adjust the position of the valve seat in response to said rotation.

In an embodiment the interface comprises a cap externally mounted over the valve and having an orifice for passing the released gases, the orifice being sized to allow its occlusion by a digit of the user.

In a further aspect there is provided a breathing assistance and/or resuscitation apparatus having a pressure regulator which is arranged to regulate pressurised gases supplied to a patient by releasing or exhausting some gases when the pressure exceeds a threshold. This threshold is preferably easily manipulated by manual adjustment of the regulator by a user's digits including fingers and/or thumbs. In an embodiment this is achieved by adjusting the position of a valve seal against which a valve member is biased.

In embodiments the pressure regulator employed can be as defined above or in the accompanying claims, or substantially as described herein.

Further aspects of the invention, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading of the following description which provides at least one example of a practical application of the invention.

Embodiments of the present invention include a connector for resuscitating a patient, particularly an infant or neonate, more particularly a prematurely born neonate. The delivered pressure is varied between Peak Inspiratory Pressure (PIP) and Peak End Expiratory Pressure (PEEP) by the occlusion of the PEEP outlet. The PEEP outlet provides for variable PEEP, by adjustment. However, at any particular PEEP setting, preferred embodiments of the invention provide for substantially flow independent fixed PEEP. The fixed PEEP valve avoids the need for adjustment as flow changes and provides more effective therapy.

A duck billed valve may be included for suctioning of surfactant delivery during resuscitation.

Preferably, the connector is adapted to one handed use.

Referring now to <FIG> in which a typical application is depicted, a Positive End Expiratory Pressure (PEEP) system is shown in which a patient <NUM>, shown as an infant, is receiving pressurized gases through a mask <NUM> (or endotracheal tube or other interface as are known in the art) connected to an inhalatory conduit <NUM>, preferably for resuscitation. Either the mask <NUM> or the inhalatory conduit <NUM> can include the pressure regulator <NUM> to control the pressure of gas delivered to the patient. The inhalatory conduit <NUM> is connected to the outlet of a resuscitator apparatus <NUM>, which is in turn connected to a flow regulator and air supply <NUM> (which preferably provides gas to the resuscitator at <NUM> psi or thereabouts).

It should be understood that the present invention is not limited to resuscitation, or the delivery of PEEP gases but is also applicable to other types of gas delivery systems, including those adapted to deliver gases to non-infant patients. Further, while embodiments are described showing more sophisticated gas delivery apparatus, it will be appreciated that the invention is not limited to such applications and may also be used with manually powered arrangements, such as those described in <CIT>.

A preferred embodiment of apparatus of the invention is shown in <FIG>. According to preferred embodiments, the apparatus is disposed within or coupled to the mask <NUM> although it will be appreciated that it may form part of a separate assembly provided it is proximate the patient.

Referring to <FIG> and <FIG>, the apparatus <NUM> includes an inlet <NUM> fluidly connected to two outlets <NUM>, <NUM>. The inlet <NUM> receives gases and delivers these to a patient via a mask or other patient interface (not shown) connected to first outlet <NUM>. The gases may be delivered to the inlet <NUM> via a flow regulator and air supply <NUM> and resuscitator <NUM> as shown in <FIG> although other means for delivering pressurised gases may alternatively be used. Further, the gases may simply be air extracted and pumped from the patient's surroundings, and/or may be enriched such as by additionally coupling an oxygen reservoir or supply to the inlet, as is known in the art. Further, the gases may be humidified using known humidifier arrangements.

The second outlet <NUM> provides an external orifice which terminates a pressure regulator <NUM>. The pressure regulator <NUM> may be used to vary the pressure between PIP and PEEP by selective occlusion of the orifice <NUM>, such as by placement of a finger over it. A PEEP valve <NUM> is located between the inlet <NUM> and the second outlet <NUM>.

The PIP may be adjusted at the resuscitator <NUM> to a desired level. The delivered gases are varied between the PIP with the orifice <NUM> near the patient occluded and the PEEP with the orifice <NUM> unoccluded. In this fashion, resuscitation of a patient can be attempted by varying between the PIP and PEEP at the normal rate of breathing.

The purpose of the PEEP valve <NUM> of preferred embodiments is to keep the PEEP at a reasonably constant level independent of changes in flow rate. Further, embodiments of the regulator <NUM> preferably provide for adjustment of the PEEP. Such adjustment may preferably be performed manually without the need for additional equipment or tools, such as a screwdriver.

Desirably for infant respiratory assistance the PEEP value should be approximately <NUM> cmH<NUM>O, independent of the flow rate. Preferably the interface needs to be simple and cost effective, as it is a single-use product. Also, due to the nature of this application, a valve with many small separate parts, such as a spring valve, is not a viable option. Further, as will particularly be appreciated for resuscitation applications, time may be limited and delays caused by complicated adjustment, such as of the PEEP valve described in <CIT>, are preferably avoided. Further, while pressurised gas within apparatus <NUM> will tend to prevent contaminants or debris being passed from the second outlet <NUM> to the first outlet <NUM> (and to the patient), the need to insert a tool into the second outlet, as required by <CIT>, increases the risk of this happening.

As shown in <FIG> and <FIG>, the apparatus <NUM> may include a further inlet <NUM> including a duck billed valve <NUM> which is normally closed and configured for introducing tubes therethrough and down the trachea for suctioning, delivery of surfactant etc. For the avoidance of doubt, the further inlet <NUM> may be omitted.

As described in <CIT>, new born neonates often lack surfactant in their lungs. Embodiments of the invention, as shown in <FIG> and <FIG>, when used with an endotracheal tube, make it easy to administer surfactant to a patient without the need to remove the breathing assistance apparatus from the patient. By using a syringe or other device known in the art the operator can administer surfactant to the neonate by pushing the end of the syringe through the duck billed valve <NUM> located opposite the inlet to the patient (i.e., first outlet <NUM>).

The duck billed valve <NUM> is normally fluidly sealed but upon insertion of the syringe opens to allow the end of the syringe to enter the interior of the apparatus <NUM>. The bills or flaps of the valve <NUM> may be formed from silicone rubber or other suitable materials known in the art and they seal around the end of the syringe keeping the apparatus <NUM> sealed. Because surfactant is a viscous fluid this is advantageous over administering surfactant using multi lumen endotracheal tubes.

The duck billed valve <NUM> can also be used to suction a neonate to remove airway secretions. Suctioning is performed using a catheter inserted through the duck billed valve and down the endotracheal tube. The bills of the valve seal around the inserted catheter thereby maintaining airway pressure. The duck billed valve is retained in a housing in such a way that any instrument inserted into the valve is guided directly into the top of an endotracheal tube (or nasal mask or other interface as are known in the art), fitted at the outlet to the neonate <NUM>. To aid in performing this, a tube guide (not shown) may be provided inside apparatus <NUM> which is aligned with the inlet <NUM> and the first outlet <NUM>. An example arrangement is shown in <FIG> of <CIT>.

The apparatus is preferably shaped to enable ease of use. More particularly, preferred embodiments enable one handed operation. The portion providing the first outlet <NUM> is wide and short and in the embodiment shown, it is cylindrical. A flange (not shown) may be provided at the first outlet <NUM> so that when apparatus <NUM> is used with a mask, the flange enables the operator to apply pressure to fluidly seal the mask to the patient's nose and/or mouth. The construction of apparatus <NUM> enables an operator to use a digit to occlude orifice <NUM> to vary pressure between the PIP and PEEP. The operator may do this by placing their thumb and middle finger about the first outlet <NUM> (or on an associated flange, if present) and use their index finger to seal orifice <NUM>. The second outlet <NUM> is angled to allow the index finger to be in a natural position to occlude orifice <NUM>.

The pressure regulator <NUM> will now be described in more detail with reference additionally to <FIG>, <FIG> and <FIG>.

The PEEP valve <NUM> as shown is in the form of an umbrella valve made of an elastomeric material, positioned on a valve seat <NUM> (see in particular <FIG>). Preferably this valve is included as part of a nasal mask or endotracheal tube or other patient interface. As the flow rate increases, the skirt or flap(s) <NUM> of the umbrella valve lift up, thereby allowing excess pressure to be vented therethrough. Preferred embodiments provide adaptive pressure relief so as to maintain the pressure inside the apparatus <NUM> at a substantially constant level.

While the PEEP valve <NUM> is shown as an umbrella valve, the invention is not limited thereto. Other valve means may be used such as flexible diaphragms. However, umbrella valves are preferred due to the ease with which they may be fitted to or removed from the apparatus and without the need for additional fixing means, the fixing being provided by the stem portion or shaft of the umbrella valve.

While not limited thereto, according to preferred embodiments, the umbrella valve is configured in accordance with embodiments described in <CIT>. More particularly, preferably, the valve is formed from Silastic liquid silicone rubber Q7-<NUM> and/or with dimensions as specified in <FIG> of <CIT> wherein the periphery of the skirt or flap(s) <NUM> at or proximate to the valve seat <NUM> is thicker than at its centre, adjacent the stem. An umbrella valve constructed in this manner does not act as a 'pop-off' valve like most umbrella valves as it is not designed to open at a specific pre-determined pressure known as the 'cracking pressure'. Rather, the valve of <CIT> is designed to open at a predetermined flow rate (e.g. below <NUM> litres/minute) and keep on opening as the flow rate increases causing the pressure to stay around a certain level as the flow increases. Most umbrella valves will open at a certain pressure and not open any further as the flow rate increases, causing the pressure to increase as the flow increases.

According to preferred embodiments of the invention, the tensioning of the skirt or flap(s) <NUM> of the PEEP valve <NUM> is adjustable by adjusting the relative position of the valve seat <NUM> as will be described in more detail below.

The pressure regulator <NUM> shown in <FIG> includes a cap <NUM>, seat member <NUM>, PEEP valve <NUM> and mount <NUM>.

The mount is configured to sealably couple the pressure regulator <NUM> to the second outlet <NUM>. Any known coupling / sealing arrangement may be used and the invention is not limited to the specific arrangement shown. For example, rather than simply being adapted to be pushed on to the second outlet <NUM>, a threaded, snap-fit or other form of engagement may be provided between the mount <NUM> and the second outlet <NUM>. As will be appreciated O-rings and other sealing means may additionally be provided. Further, all or portions of the mount <NUM> may be integral to the second outlet <NUM> although the arrangement shown is easier to manufacture and assemble, as well as readily enabling the complete pressure regulator <NUM> to be removed and replaced with another, if required.

Preferably, the cap <NUM> sealingly engages the mount <NUM> to prevent gases exiting other than through the orifice <NUM>. Preferably, this seal is provided, at least in part, at location <NUM> marked in <FIG>.

The mount <NUM> further positions and holds the PEEP valve <NUM> in position. As shown, preferably, the PEEP valve is fixed in position relative to the mount and consequently the second outlet <NUM>, except for the skirt or flap(s) <NUM> which open and close to allow the PEEP valve <NUM> to operate.

The seat member <NUM> is coupled to the mount <NUM> so as to enable the valve seat <NUM> to move relative to the fixed position of the PEEP valve <NUM>. According to the embodiment shown, an external thread <NUM> on the seat member <NUM> cooperates with an internal thread <NUM> on the mount <NUM> such that rotation of one relative to the other moves the seat member <NUM> as shown by the arrows marked A in <FIG>. While this arrangement is preferred, other means for generating the same or similar relative movement of the valve seat <NUM> relative to the PEEP valve <NUM> are included within the scope of the invention.

In <FIG>, the seat member <NUM> is in the lowermost position with the underside thereof abutting the mounting means <NUM>. It will be appreciated that alternative arrangements may be used to limit the extent of movement in this direction. In <FIG>, the seat member <NUM> is in the uppermost position with the upper side thereof abutting projection or instep <NUM>. Again, alternative arrangements may be used to limit the extent of movement. The seat member <NUM> is positionable between the lowermost and uppermost positions shown in <FIG> and <FIG>. To maintain the position of the seat member <NUM> in use, preferably the threaded engagement between the seat member <NUM> and the mount <NUM> and/or the sliding engagement between the cap <NUM> and the mount and/or the sliding engagement between the cap and the seat member <NUM> generate sufficient friction to substantially prevent unwanted adjustment (i.e., adjustment not directly generated by a user rotating the cap <NUM>). To this end, the threaded engagement may be spring-biased so as to generate forces in the directions marked A in <FIG>, thereby increasing the friction therebetween.

The cap <NUM> in the embodiment shown is configured to snap fit to the mount <NUM>. More particularly, a lip <NUM> of the cap <NUM> engages a lip <NUM> of the mount <NUM>. While not limited thereto, preferably, the cap <NUM> is releasably fitted to enable it to be removed, thereby allowing access inside the regulator <NUM> such as to replace the PEEP valve <NUM>.

The cap <NUM> further includes teeth <NUM> configured to mate with the projections <NUM> on the mount <NUM>. The top or end of cap <NUM> terminates in orifice <NUM> and as shown in the markings thereon in <FIG>, is rotatable to adjust the PEEP. More particularly, when a user rotates the cap <NUM>, the seat member <NUM> also rotates since the projections <NUM> mate with the teeth <NUM> locking the cap <NUM> in position rotationally relative to the seat member <NUM>. The rotation of the cap <NUM> generates movement in the direction A of the seat member <NUM> through action of the thread <NUM> against the thread <NUM>. The movement of the seat member <NUM> is accommodated in the portion of the cap <NUM> that engages the mount <NUM>. As shown, the teeth <NUM> are elongate, allowing the projections <NUM> to move in the direction A relative to the cap <NUM> while rotationally fixing the cap <NUM> relative to the mount <NUM>.

While this arrangement is presently preferred, equivalent arrangements are also included with the scope of the invention. Further, to prevent wear of the skirt or flap(s) <NUM> of the PEEP valve <NUM> caused by rotation of the cap <NUM> and the seat <NUM>, the seat <NUM> may be rotatably isolated from the seat member <NUM> such that it does not rotate.

Further, it will be appreciated that it would be possible to slidably couple the cap <NUM> and seat member <NUM> assembly to mount <NUM>. However, the arrangement shown facilitates greater control of movement as well as providing for smaller adjustments to be made.

Thus, the invention provides a pressure regulator that provides simple, controlled adjustment of the PEEP value by hand without the need for additional equipment.

According to particular embodiments, the device of embodiments of the invention is preset during manufacture or assembly such that the cap <NUM> is in a desired position for generating a selected PEEP pressure or pressure profile. This can avoid the need for users to adjust the setting for more "standard" cases.

Improved results provided by the invention can be seen in <FIG> when compared with the results shown in <FIG> for a device of the type shown in <FIG> (Fisher & Paykel Healthcare Limited product code RD1300-<NUM>). The results shown in <FIG> were generated using a prototype made in accordance with the embodiment shown in <FIG>. Flow was generated using Fisher & Paykel Healthcare Limited's Neopuff™ resuscitator.

Pressure was measured at the base of the T-piece where the paient interface would be attached (i.e., at first outlet <NUM>).

<FIG> shows how the PEEP varied as the flow rate increased from <NUM> to <NUM> litres per minute with the cap <NUM> in six different rotational positions. Note that the "minimum" position corresponds to that shown in <FIG> with the cap <NUM> fully wound to the left and the seat member <NUM> fully down. Conversely, the "maximum" position corresponds to that shown in <FIG>. As can be seen, even at higher flow rates, while the PEEP did increase, the increase was not significant compared to prior art arrangements. The variation in pressure across the range of flow was greatest with the cap <NUM> in the "minimum" position (namely <NUM> cmH<NUM>O) and least when the cap <NUM> was in the "maximum" position (namely <NUM> cmH<NUM>O), ignoring the dip at <NUM> cmH<NUM>O. Further, as can be seen by the lines being substantially parallel and the spacing therebetween being substantially equal, the rotation of the cap <NUM> was shown to vary PEEP substantially proportionally to the amount of rotation of the cap <NUM>, providing a meaningful and intuitive change in the PEEP as a result of rotation of the cap <NUM>.

Thus preferred embodiments of the invention are capable of providing a substantially constant or at least less varied PEEP across a range of flow rates with the PEEP being manually adjustable. Further, since the pressure flow curve at any particular position of the cap <NUM> is relatively flat (i.e., the PEEP does not vary significantly), any leakage between the patient interface or mask and the patient (which is common with masks during resuscitation), does not drop the PEEP in the same way that prior art devices do, preventing collapse of the patient's lungs.

Turning to the results shown in <FIG>, which were generated in a similar manner but with the T-piece switched over, it can be seen that the variation in PEEP across the same range of flow rates was greater for all positions of the cap. Notably, the minimum variation was recorded with the cap in the "minimum position", the PEEP differing across this range by <NUM> cmHzO, which was greater than the maximum variation of <NUM> cmHzO in <FIG> for any given position of the cap. Further, the PEEP increased more sharply when the flowrate exceeded <NUM> LPM, rather than the steady increase shown in <FIG> for the prototype according to the present invention.

The invention may also be said broadly to consist 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, as long as it falls within the definition of the invention in the appended claims.

Claim 1:
A pressure regulating device (<NUM>) for a gas delivery apparatus which conveys gases along a gases pathway to a patient, comprising:
a mounting (<NUM>) having:
an inlet (<NUM>) configured to couple to an apparatus configured to provide a flow of gas;
a first outlet (<NUM>) configured to deliver gas to the patient; and
a second outlet (<NUM>) in fluid communication with the gases pathway, having a valve member that selectively blocks, at least in part, the second outlet (<NUM>); the second outlet (<NUM>) providing an external orifice (<NUM>); and
a control member moveably engaged with the mounting (<NUM>);
wherein the valve member (<NUM>) is biased against a valve seat member (<NUM>) and arranged to open when the pressure of said gases exceeds a selected level to allow at least a portion of said gases to flow out of said second outlet (<NUM>);
characterized in that the manipulation of the control member moves the seat member (<NUM>) to effect adjustment of the selected level of positive end expiratory pressure (PEEP).