Pressure adjustment valve

Abstract

To provide a pressure release or adjustment device used in a respiratory gas system which provides a user with a respiratory gas flow, for example a high flow rate respiratory gas system.SOLUTION: A pressure adjustment or pressure release device includes an inlet and an outlet chamber having an outlet. The inlet fluidly communicates with the outlet chamber. A valve seat is positioned between the inlet and the outlet. A valve member is urged to seal the valve seat, and displaces from the valve seat by an inlet pressure at the inlet that increases over a pressure threshold, and lets a gas flow from the inlet through the outlet chamber to the outlet. The gas flow through the outlet has an inlet pressure and an outlet pressure of the outlet chamber act on the valve member to displace the valve member from the valve seat.SELECTED DRAWING: Figure 12A

Description

[Technical field]

[0001] The present disclosure relates generally to pressure relief or regulation devices, and more particularly to pressure relief or regulation devices for use in breathing gas systems for providing a flow of breathing gas to a user, such as high flow breathing gas systems. [Background technology]

[0002] Respiratory gas supply systems provide gas for delivery to a patient. Respiratory gas supply systems typically include a fluid connection between a gas supply and a patient, which may include an inhalation tube and a patient interface. Such systems may be open, i.e., include a non-sealing patient interface, such as a nasal cannula, or closed, i.e., include a sealing patient interface, such as a face mask that seals against the user's face. Such systems may receive gas from a pressurized gas supply (such as a gas tank or a hospital wall supply), a blower, or a combination thereof.

[0003] Open breathing gas delivery systems may include, for example, those used in nasal high flow therapy. Closed breathing gas delivery systems may include, for example, those used in continuous positive airway pressure (CPAP) or ventilation.

[0004] Respiratory gas delivery systems may be susceptible to accidental or inadvertent flow restriction or obstruction. For example, an inspiratory tube may be accidentally pinched, kinked, or crushed, resulting in a sudden and / or large flow restriction or obstruction. As a result, a large back pressure may be created upstream of the restriction or obstruction.

[0005] It should further be appreciated that sudden and / or large backpressures may occur when a patient presents excessive flow resistance. For example, the shape, size, or anatomy of the patient's nose and / or airways may provide a restriction that creates a large backpressure. Additionally, alternatively and / or simultaneously, large backpressures may be created by the patient exhaling into the incoming gas flow.

[0006] Excessive back pressure within a breathing gas supply system can cause failure of tubing, fluid connections, or other components, particularly causing the tubing, fluid connections, or other components to burst or break.

[0007] Therefore, to avoid or prevent component damage, it is necessary to relieve / regulate the pressure within the breathing gas supply system that is created by the restriction, blockage, or excessive flow resistance.

[0008] Respiratory gas delivery systems, if provided with inadequate or no pressure limiting means, may cause strain on the patient's tissue, which may result in the patient being at risk for barotrauma or gastric distension.

[0009] Therefore, it is also necessary to provide an upper pressure limit for patient safety.

[0010] A pressure relief valve may be used to provide a pressure upper limit to the breathing system. The pressure relief valve may allow the release of gas pressure if the system pressure exceeds a pressure relief threshold provided by the pressure relief valve. As the flow rate increases beyond the pressure relief threshold, the pressure in the system increases progressively approximately proportional to the flow. As a result, the patient and system components may be exposed to increasingly higher pressures as the flow rate increases.

[0011] An example of a pressure relief valve is a plunger and spring type valve. The plunger is displaced when pressure within the valve exerts a force on the plunger that exceeds the return force exerted by the spring. Gas is then allowed to pass through the gap between the plunger and the valve seat until the pressure within the valve is insufficient to generate a force that continues to exceed the return force exerted by the spring, at which point the plunger re-engages the valve seat and closes the gap. This type of valve may naturally vibrate as the above function repeats (as pressure builds and then successively opens). This may be referred to as valve "rattle" or valve "rumble". In some cases, such vibrations may be irregular. Valve vibrations may generate unwanted noise, pressure or flow fluctuations, or wear.

[0012] Plunger and spring type valves also typically require some means of sealing the plunger within the housing in which it moves and / or some means of sealing the plunger against the valve seat. Such means may include additional components such as O-rings. The formation of a tight fluid-tight seal is usually critical. The additional components add complexity to the valve's construction, which in turn increases the valve's susceptibility to breakage and / or wear.

[0013] A respiratory system presents resistance to the flow of respiratory gases within the system. The flow resistance created by individual components of the system, such as humidifiers, conduits, couplings, filters, patient interfaces, and any other system components, accumulates throughout the system, resulting in a total pressure drop within the system. Flow resistance can be due, for example, to flow redirection, restriction, convergence, divergence, and / or permeability barriers (such as filters) within the flow path.

[0014] To increase the flow rate of gas in the system, the pressure provided by the flow source is increased to offset the increased pressure loss in the system caused by the increased flow rate. As the flow increases, the system pressure required to achieve the flow rate (driving pressure) may reach a set opening pressure of the pressure relief valve, e.g., a predetermined safe pressure limit. The set opening pressure of the pressure relief valve thus defines or determines the maximum flow rate that can be delivered to the patient. In prior art pressure relief valves, the maximum flow rate that can be delivered to the patient is limited by the set opening pressure of the pressure relief valve. This can constrain the design of the system components.

[0015] To minimize pressure drop and maximize the flow deliverable to the patient within the set opening pressure of the pressure relief valve, it is usually desirable to design the system to minimize flow resistance. For example, a particular tubing diameter and length may be selected to minimize flow resistance. However, system pressure drop may change during use. For example, tubing may bend, bend, fold, or collapse during use, or different patients may exhibit different airway restriction characteristics.

[0016] References herein to patents, other external documents, or other sources of information are generally for the purpose of providing a context for explaining features of the present invention. Unless otherwise indicated, the reference to such external documents should not be construed as an admission that such documents or such sources are prior art in any jurisdiction or form part of the common general knowledge in the art. Summary of the Invention [Problem to be solved by the invention]

[0017] It is therefore an object of certain embodiments disclosed herein to provide a pressure relief or pressure regulation device that goes at least some way towards addressing the aforementioned challenges or that at least provides the industry with a useful option. [Means for solving the problem]

[0018] In accordance with at least one embodiment disclosed herein, the pressure regulation or relief device comprises: The entrance and an outlet chamber having an outlet, the inlet being in fluid communication with the outlet chamber; a valve seat between the inlet and the outlet; a valve member biased to seal against a valve seat; Including, The valve member is adapted to be displaced from the valve seat by an inlet pressure at the inlet increasing above a pressure threshold to pass gas flow from the inlet through the outlet chamber to the outlet, and together with the inlet pressure, the gas flow through the outlet exerts an outlet pressure (back pressure) in the outlet chamber on the valve member, displacing the valve member (further) from the valve seat.

[0019] In some embodiments, the valve member includes a membrane that is biased against the valve seat.

[0020] In some embodiments, the valve member includes a frame that supports the membrane in tension.

[0021] In some embodiments, the frame includes one or more clipping features for clipping the valve member to the body of the device (without significantly altering the tension in the membrane).

[0022] In some embodiments, the outer periphery of the valve member provides a seal to seal the outlet chamber from the surroundings or the displacement chamber.

[0023] In some embodiments, the membrane is stretched or tensioned over the valve seat such that the tension in the membrane urges the membrane to seal against the valve seat.

[0024] In some embodiments, the periphery of the membrane is supported by the wall of the outlet chamber.

[0025] In some embodiments, the device includes a spring to bias the membrane against the valve seat, the spring compressing and acting on the non-pressurized side of the membrane, or the spring expanding and acting on the pressurized side of the membrane.

[0026] In some embodiments, the membrane is a resilient or elastomeric material, such as a silicone material, which may be either a thermoplastic or a thermoset material.

[0027] In some embodiments, the membrane has a thickness of less than 1 mm, for example, 0.3 mm.

[0028] In some embodiments, the valve seat is centrally located relative to the membrane.

[0029] In some embodiments, the membrane includes a thickened portion for contacting the valve seat, for example, the membrane includes a thickened central portion for acting against the valve seat.

[0030] In some embodiments, the area of ​​the valve member is greater than the area of ​​the valve seat.

[0031] In some embodiments, the inlet pressure acts on the valve member over the valve seat area and, when the valve member is displaced from the valve seat, the outlet pressure acts on the valve member over an area outside the valve seat area.

[0032] In some embodiments, the inlet pressure acts on the valve member over an area outside the valve seat area, and when the valve member is displaced from the valve seat, the outlet pressure acts on the valve member over the valve seat area.

[0033] In some embodiments, the ratio of the valve member area to the valve seat area is in the range of 1.2-1600.

[0034] In some embodiments, the inlet comprises an inlet tube and the valve member is approximately perpendicular to a longitudinal axis of the inlet tube.

[0035] In some embodiments, the inlet includes an inlet tube that extends to the outlet chamber.

[0036] In some embodiments, the valve seat is provided at the outlet end of the inlet tube in the outlet chamber.

[0037] In some embodiments, the outlet comprises at least one aperture in a wall of the outlet chamber and / or at least one aperture in the valve member.

[0038] In some embodiments, at least one aperture is in a wall of the outlet chamber and proximate to the inlet tube.

[0039] In some embodiments, the outlet end of the inlet tube forms the valve seat.

[0040] In some embodiments, the outlet end of the inlet tube is beveled, the beveled edge of the outlet end of the inlet tube forming the valve seat.

[0041] In some embodiments, the outlet is disposed radially between the outer periphery of the valve member and the outer periphery of the valve seat and / or the inlet and / or inlet tube.

[0042] In some embodiments, the device includes an inlet tube surrounding the outlet chamber, with the valve seat provided at the inlet to the outlet chamber.

[0043] In some embodiments, the valve member is supported by or seals against a wall of the outlet chamber, or the valve inlet comprises an inlet tube and the valve member is supported by or forms a seal with the wall of the inlet tube.

[0044] In some embodiments, the device includes a displacement chamber, into which the valve member is displaced when the valve member is displaced from the valve seat.

[0045] In some embodiments, the displacement chamber is open to ambient pressure such that when the valve member is displaced into the displacement chamber the pressure in the displacement chamber remains substantially at ambient pressure; or The displacement chamber is sealed or sealable from the surrounding environment.

[0046] In some embodiments, the displacement chamber is sealed or sealable from the surrounding environment.

[0047] In some embodiments, the device includes a pressure device for varying the pressure in the displacement chamber, for example a foot or hand operated pump for increasing or decreasing the pressure in the displacement chamber.

[0048] In some embodiments, the device includes a pressure reset device, such as a poppet valve, for resetting the pressure in the displacement chamber to ambient pressure.

[0049] In some embodiments, the inlet, valve member, valve seat, and outlet are arranged such that gas flow through the outlet chamber is directed against the valve member as the gas flow enters the chamber, is deflected off the valve member over an angle of greater than 90 degrees, and exits the chamber through the outlet.

[0050] In some embodiments, the outlet comprises at least one aperture in a wall of the outlet chamber opposite the valve member.

[0051] In some embodiments, the outlet chamber surrounds the valve seat (eg, the valve seat is disposed within the outlet chamber).

[0052] In some embodiments, the ambient pressure acts on the non-pressurized side of the valve member.

[0053] In some embodiments, the area of ​​the outlet is variable.

[0054] In some embodiments, the outlet comprises one or more apertures in a wall of the outlet chamber, which may be selectively opened or closed or partially closed to vary the area of ​​the outlet.

[0055] In some embodiments, the relative position of the valve seat and the valve member is adjustable to adjust the bias of the member against the valve seat.

[0056] In some embodiments, the valve member is a plunger or piston and the device includes a biasing member for biasing the valve member to seal against the valve seat. The biasing member may be a spring or a resilient diaphragm or (elastomeric) membrane or other spring element.

[0057] In some embodiments, the outlet comprises a gap between a periphery of the valve member and a wall of the outlet chamber, and / or the outlet comprises one or more apertures in the valve member.

[0058] In some embodiments, the valve member is a piston that includes a sliding seal with the wall of the outlet chamber, and the outlet is one or more apertures in the piston or the wall of the outlet chamber.

[0059] In some embodiments, the biasing member is a spring, and the expansion or compression of the spring is adjustable to vary the amount of bias relative to the plunger or piston to seal against the valve seat.

[0060] In some embodiments, the device is adapted to maintain an opening pressure range of less than 5 cmH2O over a flow range of 30 L / min within the device.

[0061] In some embodiments, the device comprises at least two outlet chambers in series or in parallel.

[0062] In some embodiments, the outlet chamber of claim 1 is a first outlet chamber having a first outlet, and the device includes a second outlet chamber having a second outlet, the second outlet chamber adapted to receive a gas flow from the first outlet; The valve member is adapted to be displaced from the valve seat by inlet pressure at the inlet increasing above a pressure threshold to pass gas flow from the inlet through the first outlet chamber, the first outlet, and the second outlet chamber to the second outlet, the gas flow through the first outlet and the second outlet, together with the inlet pressure, exerting an outlet pressure (back pressure) in the first outlet chamber on the valve member to displace the valve member (further) from the valve seat.

[0063] In some embodiments, the valve member and valve seat provide a dynamically variable flow restriction between the inlet and outlet chambers that depends on the inlet and outlet pressures, the dynamically variable flow restriction decreasing as the inlet and / or outlet pressures increase.

[0064] In some embodiments, the outlet provides an outlet flow restriction that is independent of the inlet pressure and the outlet pressure.

[0065] In some embodiments, the outlet flow restriction is larger than the dynamically variable flow restriction.

[0066] In some embodiments, the valve member is a first valve member and the device includes a second valve member coupled to the first valve member, the first member exhausting the flow of exhaled gas and the second valve member opening and closing the nebulizer port; When expelling exhaled gas, the first valve member is displaced from the valve seat and the second valve member is displaced to close the nebulizer port; When the valve member contacts the valve seat, the second valve member is displaced from the nebulizer port to allow medication to flow from the nebulizer.

[0067] In accordance with at least one embodiment disclosed herein, a patient interface system or respiratory system includes: a patient interface for sealing an airway of the patient; an inlet conduit or flow path to a patient interface that includes a nebulizer port; A device as described above, wherein the inlet is arranged to receive a flow of exhaled gas from a patient interface; Includes.

[0068] In accordance with at least one embodiment disclosed herein, the pressure regulation or relief device comprises: The entrance and The exit, a valve seat between the inlet and the outlet; a valve member biased to seal against the valve seat, the valve member adapted to be displaced from the valve seat by an inlet pressure at the inlet increasing above a pressure threshold to permit gas flow from the inlet to the outlet; Including, The valve member is or includes a diaphragm that is stretched or tensioned over the valve seat such that tension in the membrane urges the membrane to seal against the valve seat.

[0069] In accordance with at least one embodiment disclosed herein, the pressure regulation or relief device comprises: The entrance and The exit, a valve seat between the inlet and the outlet; a valve member biased to seal against the valve seat, the valve member adapted to be displaced from the valve seat by an inlet pressure at the inlet increasing above a pressure threshold to permit gas flow from the inlet to the outlet; a diaphragm stretched or tensioned over the valve member or the valve seat to bias the valve member against the valve seat; Includes.

[0070] A device according to the foregoing description may include the feature or features described in any one or more of the preceding descriptions relating to pressure regulating or pressure relief devices.

[0071] In some embodiments, the valve member is or includes a membrane (diaphragm) that is stretched or tensioned over the valve seat such that tension in the membrane urges the membrane to seal against the valve seat.

[0072] In accordance with at least one embodiment disclosed herein, the pressure relief device comprises: The entrance and an outlet chamber having an outlet, the inlet being in fluid communication with the outlet chamber; a dynamically variable flow restriction between the inlet and outlet chambers; a flow path within the valve from an inlet through a dynamic flow restriction and an outlet chamber to an outlet; Including, an outlet from the outlet chamber includes or provides an outlet flow restriction from the device that creates an outlet pressure (back pressure) in the outlet chamber; The dynamically variable flow restriction is dependent on the inlet pressure at the inlet and the outlet pressure at the outlet chamber, and as the inlet and / or outlet pressure increases the dynamically variable flow restriction decreases, and the outlet restriction is independent of the inlet and outlet pressures.

[0073] A device according to the foregoing description may include the feature or features described in any one or more of the preceding descriptions relating to pressure regulating or pressure relief devices.

[0074] According to at least one embodiment disclosed herein, there is provided a flow compensated pressure regulation or pressure relief device for a system providing a gas flow, the device comprising: a primary inlet for receiving a gas flow from a gas source; and a primary outlet for supplying at least a portion of the gas flow received by the primary inlet to flow from the device; a pressure relief valve adapted to exhaust at least a portion of the gas flow received by the inlet when the pressure of the gas flow increases above a pressure threshold; and a sensing mechanism for dynamically adjusting the pressure threshold based on the rate of gas flow from the primary outlet to the patient.

[0075] In some embodiments, the pressure relief valve comprises: a valve inlet in fluid communication with the main inlet; An exhaust outlet; a valve seat between the valve inlet and the exhaust outlet; a valve member biased to seal against the valve seat and displaced from the valve seat by an inlet pressure at the valve inlet increasing beyond a pressure threshold to exhaust at least a portion of the gas flow from the valve inlet to the exhaust outlet; Including, The sensing mechanism is a sensing member for sensing a differential pressure indicative of a flow rate of the gas flow through the primary outlet; a mechanical link acting between the sensing member and the valve member for transmitting a force applied by the sensing member to the valve member and for adjusting a bias of the valve member against the valve seat in response to a gas flow rate through the primary outlet; Includes.

[0076] In some embodiments, the sensing mechanism includes a flow restriction or constraint for generating a differential pressure sensed by the sensing member and displacing the sensing member in response to the flow rate of gas through the primary outlet.

[0077] In some embodiments, the sensing mechanism comprises: a flow restriction or constriction downstream of the valve inlet; and a sensing chamber, wherein a sensing member located within the sensing chamber divides the sensing chamber into a first chamber and a second chamber, the first chamber in fluid communication with the gas flow upstream of the flow restriction or constriction and the second chamber in fluid communication with the gas flow of the flow restriction or downstream of the flow restriction, and a differential pressure caused by gas flow through the flow restriction or constriction and the primary outlet is sensed by the sensing member.

[0078] In some embodiments, a mechanical link is coupled to the valve member and the sensing member and biases the valve member against the valve seat in response to a flow rate of the flow gas through the primary outlet.

[0079] In some embodiments, the mechanical link is separate from the valve member or the sensing member, or the valve member and the sensing member; the valve member is biased against the valve seat by the absence of gas flow through the primary outlet, and a mechanical link supports the valve member and the sensing member; As gas flow through the main outlet increases, the differential pressure within the sensing member increases and when the gas flow rate through the main outlet increases above a threshold, the force applied to the valve member by the mechanical link decreases and the bias of the valve member against the valve seat is reduced until the mechanical link loses contact with the valve member or the sensing member or both the valve member and the sensing member.

[0080] In some embodiments, the pressure relief valve comprises: an outlet chamber including a discharge outlet; The valve member is adapted to be displaced from the valve seat by an inlet pressure at the valve inlet increasing above a pressure threshold to discharge at least a portion of the gas flow received by the main inlet from the valve inlet through the outlet chamber to a discharge outlet, the gas flow through the discharge outlet acting together with the inlet pressure on the valve member, causing an outlet pressure (back pressure) in the outlet chamber to act on the valve member and displace the valve member (further) from the valve seat.

[0081] In some embodiments, the valve member includes a membrane that is biased against the valve seat.

[0082] In some embodiments, the sensing member includes a membrane.

[0083] In some embodiments, the valve member and / or the sensing member includes a frame that supports the membrane in tension.

[0084] In some embodiments, the frame includes one or more clipping features for clipping the valve member or sensing member to the body of the device (without significantly altering the tension in the membrane).

[0085] In some embodiments, the outer periphery of the valve member provides a seal to seal the outlet chamber from the surroundings or the displacement chamber and / or the outer periphery of the sensing member provides a seal to seal the first sensing chamber from the second sensing chamber.

[0086] In some embodiments, the membrane is stretched or tensioned over the valve seat such that the tension in the membrane urges the membrane to seal against the valve seat.

[0087] In some embodiments, the valve member is a plunger or piston.

[0088] In some embodiments, the area of ​​the valve member is greater than the area of ​​the valve seat.

[0089] In some embodiments, the inlet pressure acts on the valve member over the valve seat area and, when the valve member is displaced from the valve seat, the outlet pressure acts on the valve member over an area outside the valve seat area.

[0090] In some embodiments, the inlet pressure acts on the valve member over an area outside the valve seat area, and when the valve member is displaced from the valve seat, the outlet pressure acts on the valve member over the valve seat area.

[0091] In some embodiments, the valve inlet includes an inlet tube that extends to the outlet chamber.

[0092] In some embodiments, the valve seat is provided at the outlet end of the inlet tube in the outlet chamber.

[0093] In some embodiments, the exhaust outlet comprises at least one aperture in a wall of the outlet chamber and / or at least one aperture in the valve member.

[0094] In some embodiments, the valve member is supported by or forms a seal with a wall of the outlet chamber, or the valve inlet comprises an inlet pipe and the valve member is supported by or forms a seal with a wall of the inlet pipe.

[0095] In some embodiments, the sensing member is disposed within the sensing chamber, the flow restriction is provided by a gap between the sensing member and a sidewall of the sensing chamber and / or the flow restriction is provided by one or more apertures in the sensing member, and the flow path of the gas flow from the main inlet to the main outlet is through the sensing chamber.

[0096] In some embodiments, the sensing member is a piston and the sensing chamber is a cylinder in which the piston moves, the piston pneumatically sealing the first chamber from the second chamber.

[0097] In some embodiments, the mechanical link transmits tension and / or compression.

[0098] In some embodiments, the mechanical link is a rod or shaft, and the device includes a link guide that supports the mechanical link between the valve member and the sensing member, and the primary inlet is in fluid communication with the sensing chamber via an annular space between the link and the link guide.

[0099] In some embodiments, the device includes an opening between the main inlet and the sensing chamber, with the mechanical link extending into the opening, with the mechanical link received within the opening presenting an annular opening between the main inlet and the sensing chamber.

[0100] In some embodiments, the mechanical link is a ribbed rod or shaft.

[0101] In some embodiments, the mechanical link includes a flange at one end for supporting the valve member against the valve seat.

[0102] In some embodiments, the flange has a diameter greater than a diameter of the valve seat so that when the valve member seats on the valve seat, the valve member is supported against the valve seat between the flange and the valve seat.

[0103] In some embodiments, the mechanical link is adjustable in length.

[0104] In some embodiments, the device includes a user interface to allow a user to adjust the length of the mechanical link during use.

[0105] In some embodiments, the device includes a displacement chamber, and the valve member may be displaced away from the valve seat into the displacement chamber.

[0106] In some embodiments, the displacement chamber is sealed or sealable from the surrounding environment.

[0107] In some embodiments, the device includes a pressure device for varying the pressure in the displacement chamber, for example a foot or hand operated pump for increasing or decreasing the pressure in the displacement chamber.

[0108] In some embodiments, the device includes a pressure reset device, such as a poppet valve, for resetting the pressure in the displacement chamber to ambient pressure.

[0109] In some embodiments, the relative position of the valve seat and the valve member is adjustable to adjust the bias of the member against the valve seat.

[0110] In some embodiments, during use, the relative position of the valve seat and valve member is adjustable.

[0111] In some embodiments, the device comprises: a flow restriction and a pressure tap from the flow restriction to the second chamber; or The device includes an orifice flow restriction and a pressure tap downstream of the orifice to the second chamber.

[0112] In some embodiments, the flow restriction or constraint is adjustable.

[0113] In some embodiments, the device is configured to limit the amount of movement or deformation of the sensing member to set an upper pressure limit for a pressure threshold that is independent of flow rate.

[0114] In some embodiments, the device includes mechanical limits to limit the amount of movement or deformation of the sensing member.

[0115] In some embodiments, the mechanical limit is an end stop acting on a mechanical link or sensing member.

[0116] In some embodiments, the walls of the sensing chamber limit the amount of deformation or movement of the sensing member.

[0117] In some embodiments, the sensing mechanism comprises: one or more electronic sensors for detecting the flow rate (e.g., differential pressure) of gas flowing through a primary outlet of the device and the pressure of the gas flow between the primary inlet and the primary outlet; An actuator; and a controller or processor that receives signals from the sensor, drives the actuator, and provides an output to adjust a pressure threshold of the pressure relief valve based on the detected flow rate.

[0118] In some embodiments, the actuator drives a member attached to a valve member of the pressure relief valve to adjust the amount of bias of the valve member against a valve seat of the pressure relief valve.

[0119] In some embodiments, the valve member is a plunger or a diaphragm.

[0120] In some embodiments, the device includes a housing for containing the pressure relief valve and the sensing mechanism.

[0121] In some embodiments, the device includes a body, the body including a primary inlet and a primary outlet and at least an outlet chamber of the device and a first one of the sensing chambers, and a housing substantially encasing the body.

[0122] In some embodiments, the housing provides a space or cavity around the body, and the displacement chamber and / or the exit chamber of the device are in fluid communication with the cavity or space.

[0123] In some embodiments, the housing includes a housing outlet from the housing space.

[0124] In some embodiments, the housing includes a housing exhaust outlet in communication with the exhaust outlet from the outlet chamber, the housing exhaust outlet being coaxial with the main inlet or main outlet.

[0125] In some embodiments, the housing includes an outlet in fluid communication with the displacement chamber, and the aperture is coaxial with the main inlet or the main outlet.

[0126] In some embodiments, the flow restriction or constraint is a first flow restriction or constraint, and the device comprises: a second flow restriction or constriction upstream of the valve inlet; and a first port located between the second chamber and the first flow restriction or adjacent and downstream of the first flow restriction; a second port located between the second chamber and the second flow restriction or adjacent and upstream of the second flow restriction; Including, In the gas flow from the main inlet to the main outlet, the second port is blocked by a conduit or connector; In the gas flow from the main outlet to the main inlet, the first port is blocked by a conduit or connector.

[0127] In some embodiments, the first flow restriction or restriction exhibits a greater pressure differential than the second flow restriction or restriction, or the second flow restriction or restriction exhibits a greater pressure differential than the first flow restriction or restriction.

[0128] In some embodiments, the device includes an indicator to indicate when gas flow is being exhausted from the pressure relief valve.

[0129] In some embodiments, the indicator is visually observable when gas is being vented through the pressure relief valve.

[0130] In some embodiments, the indicator provides a binary indication of draining / not draining, or a proportional indication of drainage indicating the rate of drainage.

[0131] In some embodiments, the indicator includes a movable member, such as a shuttle or plunger or flap, located within a guide or housing, for example a housing that houses a pressure relief valve and a sensing mechanism.

[0132] In some embodiments, the movable member is located near the exhaust outlet of the device.

[0133] In some embodiments, the device includes an indicator to indicate the flow rate of gas or gas delivered from the main outlet of the device.

[0134] In some embodiments, the indicator comprises an impeller or flap located within the main outlet of the device.

[0135] In some embodiments, the device includes a flow restriction downstream of the valve inlet, and the indicator includes a shuttle or plunger received within a guide tube, the inlet end of the guide tube being in fluid communication with a main inlet upstream of the flow restriction, and the outlet end of the guide tube being in fluid communication with a main outlet downstream of the flow restriction.

[0136] According to at least one embodiment disclosed herein, there is provided a flow compensated pressure regulation or pressure relief device for a system providing a gas flow, the device comprising: a primary inlet for receiving a gas flow from a gas source; and a primary outlet for supplying at least a portion of the gas flow received by the primary inlet to flow from the device; A pressure relief valve, a valve inlet in fluid communication with the main inlet; An exhaust outlet; a valve seat between the valve inlet and the exhaust outlet; a valve member biased to seal against the valve seat and displaced from the valve seat by inlet pressure at the valve inlet increasing beyond a pressure threshold to exhaust at least a portion of the gas flow from the valve inlet to the exhaust outlet; a pressure relief valve including: a sensing member for sensing a differential pressure indicative of a flow rate of the gas flow through the primary outlet; a mechanical link acting between the sensing member and the valve member for transmitting a force applied by the sensing member to the valve member and for adjusting the bias of the valve member against the valve seat in response to a flow rate of flow gas through the primary outlet; Includes.

[0137] In some embodiments, the device comprises: a flow restriction or constriction downstream of the valve inlet; and a sensing chamber, wherein a sensing member located within the sensing chamber divides the sensing chamber into a first chamber and a second chamber, the first chamber in fluid communication with the gas flow upstream of the flow restriction or constriction and the second chamber in fluid communication with the gas flow of the flow restriction or downstream of the flow restriction, and a differential pressure caused by gas flow through the flow restriction or constriction and the primary outlet is sensed by the sensing member.

[0138] In some embodiments, the pressure relief valve comprises: an outlet chamber including a discharge outlet; The valve member is adapted to be displaced from the valve seat by an inlet pressure at the valve inlet increasing above a pressure threshold to discharge at least a portion of the gas flow received by the primary inlet from the valve inlet through the outlet chamber to a discharge outlet, the gas flow through the discharge outlet causing an outlet pressure in the outlet chamber together with the inlet pressure to act on the valve member displacing the valve member from the valve seat.

[0139] In accordance with at least one embodiment disclosed herein, a flow compensating pressure regulation or pressure relief device for a system providing a gas flow comprises: a primary inlet for receiving a gas flow from a gas source; and a primary outlet for supplying at least a portion of the gas flow received by the primary inlet to flow from the device; a valve adapted to exhaust at least a portion of the gas flow received by the inlet or to choke the gas flow from the primary inlet to the primary outlet; one or more electronic sensors for detecting the flow rate and pressure of the gas flowing through a primary outlet of the device; An actuator; a controller or processor that receives a signal or signals from the sensor and drives the actuator to provide an output to adjust the valve to exhaust at least a portion of the gas flow received by the inlet or to at least partially occlude the gas flow from the primary inlet to the primary outlet when the detected pressure exceeds a pressure threshold, the pressure threshold being dependent on the detected flow rate; Includes.

[0140] In some embodiments, the valve is adapted to occlude gas flow from the main inlet to the main outlet, and the device includes an exhaust aperture downstream of the valve.

[0141] In some embodiments, the device includes a first valve for exhausting at least a portion of the gas flow received by the inlet, a second valve for occluding the gas flow from the main inlet to the main outlet, a first actuator for driving the first valve, and a second actuator for driving the second valve, the second valve being downstream of the first valve; The controller drives the first and second actuators when the detected pressure exceeds a pressure threshold to adjust the first valve to exhaust at least a portion of the gas flow received by the inlet and the second valve to at least partially block the gas flow flowing from the main inlet to the main outlet, the pressure threshold being dependent on the detected flow rate.

[0142] According to at least one of the embodiments disclosed herein, a breathing gas system including a pressure regulating or pressure relief device or a flow compensated pressure regulating or pressure relief device as described in any one or more of the above descriptions.

[0143] In some embodiments, the system is a bi-level pressure system including said flow compensated pressure regulation or pressure relief device, a pressurized gas source, and a sealed patient interface, wherein the flow compensated pressure regulation or pressure relief device comprises: during inspiration, substantially all of the gas flow received by the primary inlet flows to the primary outlet such that the inspiration pressure is determined by the pressure setting of the pressure source; During exhalation, a portion of the gas flow received by the primary inlet is configured to be exhausted through the exhaust outlet such that the exhalation pressure is determined by the exhaust pressure of the device.

[0144] In some embodiments, the device is positioned adjacent or in close proximity to the patient interface.

[0145] In some embodiments, the pressurized gas source includes a flow gas source and a second pressure regulating or pressure relief device, as described above, where during inspiration and expiration, a pressure relief valve of the second device is adjusted to continuously exhaust a portion of the gas flow received by the main inlet out of the exhaust outlet.

[0146] In some embodiments, the system is a high flow breathing gas system that includes a flow source and a non-sealing patient interface, such as a nasal cannula.

[0147] In some embodiments, the respiratory gas system is a CPAP system including a flow gas source and a sealed patient interface, and the pressure regulating or pressure relief device is arranged such that during inspiration and expiration, the pressure relief valve continuously exhausts a portion of the gas flow received by the main inlet through the exhaust outlet.

[0148] In some embodiments, the breathing gas system is a ventilation or CPAP system, the system including a ventilator or flow gas source and a sealed patient interface, the pressure regulation or pressure relief device being at or adjacent to the patient interface and adapted to operate as an anti-asphyxiation valve; During inspiration, substantially all of the gas flow received by the primary inlet flows to the primary outlet; If the ventilator or pressurized gas source fails or stops, a large portion of the patient's exhaled air will be exhausted through the exhaust outlet.

[0149] In some embodiments, the respiratory gas system is a ventilation or bi-level pressure system, the system including a flow gas source and a sealed patient interface, and the pressure regulation or pressure relief device is adjusted such that during inspiration, the pressure relief valve continuously discharges a portion of the gas flow accepted by the primary inlet from the exhaust outlet at a first pressure threshold, and during expiration, the pressure relief valve continuously discharges a portion of the gas flow accepted by the primary inlet from the exhaust outlet at a second threshold, the first threshold exceeding the second threshold.

[0150] In some embodiments, the system includes an inhalation conduit, a first pressure regulation or pressure relief device as described above in the inhalation conduit, and a second pressure regulation or pressure relief device as described above in the exhalation flow path, the first device configured to provide an inhalation pressure and the second device configured to provide an exhalation pressure.

[0151] In some embodiments, the pressure regulation or pressure relief device includes a significant pneumatic coupling between the main inlet and the sensing member such that the valve provides a rapid response as the pressure in the patient changes rapidly between inhalation and exhalation pressures determined by first and second thresholds.

[0152] According to at least one of the embodiments disclosed herein, an insufflation system includes a flow-compensated pressure regulation or pressure relief device according to any one of the preceding statements, wherein the pressure relief valve is configured to continuously exhaust a portion of the gas flow received by the primary inlet through the exhaust outlet. The system continuously exhausts the patient (peritoneal cavity) during use. The system preferably exhausts the patient through a filter.

[0153] "High flow gas flow" or "high flow gas flows", as used herein, is defined as the volumetric movement of a portion / portion of a gas or gas mixture into the patient's airways at a rate that exceeds the fractional inspired oxygen requirement at peak inspiratory flow demand. In particular, in one embodiment, high flow gas flow (or high flow gas flows) refers to a gas flow rate of greater than 15 L / min (liters per minute), greater than or equal to about 20 L / min, greater than or equal to about 30 L / min, greater than or equal to about 40 L / min, greater than or equal to about 50 L / min, greater than or equal to about 60 L / min, greater than or equal to about 70 L / min, greater than or equal to about 80 L / min, greater than or equal to about 90 L / min, greater than or equal to about 100 L / min, greater than or equal to about 110 L / min, greater than or equal to about 120 L / min, greater than or equal to about 130 L / min, greater than or equal to about 140 L / min, or less than or equal to about 150 L / min. In certain embodiments, the effective range of high flow gas flow may be selected between any of the above flow rates, including, but not limited to, about 40 L / min to about 80 L / min, about 50 L / min to about 80 L / min, about 70 L / min to about 100 L / min, about 70 L / min to about 80 L / min, about 100 L / min to about 150 L / min, and greater than about 15 L / min to about 150 L / min, and about 30 L / min to about 150 L / min. These flow rates may be provided using a patient interface, and in certain embodiments, by a nasal interface. For suitable high flow therapy, an operating flow rate range of 30 to 70 L / min and preferably 30 to 100 L / min is desired for treating adult patients. When treating children, "high flow" therapy may require a flow rate of about 1 to 50 L / min.

[0154] Unless the context indicates otherwise, a flow source provides a gas flow at a set flow rate. The set flow rate may be a constant flow rate or may be a fluctuating flow rate, e.g., a sinusoidal flow rate. Unless the context indicates otherwise, a pressure source provides a gas flow at a set pressure. The set pressure may be a constant pressure or may be a fluctuating pressure, e.g., a sinusoidal pressure.

[0155] The term "comprising" as used herein means "consisting at least in part of." When interpreting each sentence containing the term "comprising" herein, there may be other features present than the feature preceded by the term. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

[0156] Those skilled in the art to which this invention pertains will envision numerous modifications of the structure and widely differing embodiments and applications of the invention without departing from the scope of the invention as defined in the appended claims. The present disclosure and descriptions herein are purely illustrative and are not intended to be limiting in any way.

[0157] The present invention comprises the foregoing and also contemplates the constructions described below by way of example only.

[0158] Preferred embodiments will now be described, by way of example only, and with reference to the drawings in which: [Brief description of the drawings]

[0159] [Figure 1] A high flow breathing system is shown that includes a pressure relief or regulating valve (PRV). [Figure 1A] 1 shows a pediatric resuscitation system including a pressure relief or relief valve (PRV). [Figure 1AA] 1 shows a high flow breathing system including a flow controlled pressure relief valve. [Figure 1B-1] 1 shows a continuous positive airway pressure system including a flow controlled pressure relief valve. [Figure 1B-2] 1 shows a continuous positive airway pressure system including a flow controlled pressure relief valve. [Figure 1B-3] 1 shows a graph of pressure in a Flow Compensating Pressure Relief Valve (FCPR) versus flow rate of gas to a patient. [Figure 1C-1] 1 shows a bi-level pressure breathing system including a flow controlled pressure relief valve. [Figure 1C-2] 1 shows a bi-level pressure breathing system including a flow controlled pressure relief valve. [Figure 1C-3] 1 shows a graph of patient pressure versus flow of gas to the patient. [Figure 1C-4] 1 illustrates the characterization of patient pressure in a system over multiple respiratory cycles. [Figure 1C-5] 1 shows another bi-level pressure breathing system including two flow controlled pressure relief valves. [Figure 1D] 1 shows a surgical insufflation system including a flow controlled pressure relief valve. [Figure 1E-1] 1 illustrates a continuous positive airway pressure system or ventilator system including a flow controlled pressure relief valve configured as an anti-asphyxiation valve. [Figure 1E-2] 1 illustrates a continuous positive airway pressure system or ventilator system including a flow controlled pressure relief valve configured as an anti-asphyxiation valve. [Figure 1F-1] 1 illustrates a system including a flow-controlled pressure relief valve configured to operate as a ventilator. [Figure 1F-2] 1 illustrates a system including a flow-controlled pressure relief valve configured to operate as a ventilator. [Figure 1F-3] 1 shows a graph of pressure in the FCPRV versus flow of gas to the patient. [Figure 2A] 2A and 2B show a cross-section and corresponding schematic diagram of a PRV, respectively: Fig. 2A shows the PRV with the valve member in a sealed position; Fig. 2B shows the valve member displaced from its seat; and Fig. 2C shows the valve member further displaced from its seat. [Figure 2B] 2A and 2B show a cross-section and corresponding schematic diagram of a PRV, respectively: Fig. 2A shows the PRV with the valve member in a sealed position; Fig. 2B shows the valve member displaced from its seat; and Fig. 2C shows the valve member further displaced from its seat. [Figure 2C]2A and 2B show a cross-section and corresponding schematic diagram of a PRV, respectively: Fig. 2A shows the PRV with the valve member in a sealed position; Fig. 2B shows the valve member displaced from its seat; and Fig. 2C shows the valve member further displaced from its seat. [Figure 2D] 1 shows a cross section of a PRV with two output chambers in parallel. [Diagram 3] 1 shows a graph of the inlet and outlet chamber pressure of a PRV versus the exhaust flow rate of the PRV according to embodiments described herein. [Figure 4] 4 shows a graph of inlet pressure and outlet chamber pressure versus PRV discharge flow rate for a PRV of the same configuration as that of FIG. 3, but with an outlet area twice that of the PRV of FIG. [Diagram 5] 4 shows a graph of inlet pressure and outlet chamber pressure versus PRV discharge flow rate for a PRV of the same configuration as that of FIG. 3, but with an outlet area three times that of the PRV of FIG. [Figure 6] 1 is a graphical representation comparing exhaust pressure versus exhaust flow rate for a prior art plunger type valve without an outlet chamber and a PRV with an outlet chamber according to the described embodiments. [Figure 7] 1 is a graphical representation of the effect of different outlet areas on the performance (discharge pressure vs. discharge flow rate) of a PRV according to the described embodiments. [Figure 8] 13 is a graph showing the effect of different tensions in the membrane valve member on the opening or exhaust pressure of the PRV versus the exhaust flow rate of the PRV. [Figure 9A] 9A and 9B show a cross-section and corresponding schematic diagram of a PRV, respectively: Fig. 9A shows the PRV with the valve member in a sealed position; Fig. 9B shows the valve member displaced from its seat; and Fig. 9C shows the valve member further displaced from its seat. [Figure 9B] 9A and 9B show a cross-section and corresponding schematic diagram of a PRV, respectively: Fig. 9A shows the PRV with the valve member in a sealed position; Fig. 9B shows the valve member displaced from its seat; and Fig. 9C shows the valve member further displaced from its seat. [Figure 9C]9A and 9B show a cross-section and corresponding schematic diagram of a PRV, respectively: Fig. 9A shows the PRV with the valve member in a sealed position; Fig. 9B shows the valve member displaced from its seat; and Fig. 9C shows the valve member further displaced from its seat. [Figure 10A] 11A-11C are cross-sectional views of alternative PRVs each having a piston-type valve member. [Figure 10B] 11A-11C are cross-sectional views of alternative PRVs each having a piston-type valve member. [Figure 11A] Each PRV is shown having different amounts of stretch in the inlet tube to change the amount of tension in the membrane valve member. [Figure 11B] Each PRV is shown having different amounts of stretch in the inlet tube to change the amount of tension in the membrane valve member. [Figure 12A] 1 shows a cross-sectional view of a further exemplary embodiment of a PRV. [Figure 12B] 1 shows a cross-sectional view of a further exemplary embodiment of a PRV. [Figure 12C] 1 shows a cross-sectional view of a further exemplary embodiment of a PRV. [Figure 12D] 1 shows a cross-sectional view of a further exemplary embodiment of a PRV. [Figure 12E] 1 shows a cross-sectional view of a further exemplary embodiment of a PRV. [Figure 13A] Each shows a cross section of the PRV: Figure 13A shows the PRV with the valve member in a sealed position, Figure 13B shows the valve member displaced from its seat, and Figure 13C shows the valve member further displaced from its seat. [Figure 13B] Each shows a cross section of the PRV: Figure 13A shows the PRV with the valve member in a sealed position, Figure 13B shows the valve member displaced from its seat, and Figure 13C shows the valve member further displaced from its seat. [Figure 13C] Each shows a cross section of the PRV: Figure 13A shows the PRV with the valve member in a sealed position, Figure 13B shows the valve member displaced from its seat, and Figure 13C shows the valve member further displaced from its seat. [Figure 14A] 14A and 14B are schematic diagrams of a flow compensated pressure relief valve: Figure 14A shows the FCPRV in a no-flow configuration, and Figure 14B shows the FCPRV in a flowing configuration. [Figure 14B] 14A and 14B are schematic diagrams of a flow compensated pressure relief valve: Figure 14A shows the FCPRV in a no-flow configuration, and Figure 14B shows the FCPRV in a flowing configuration. [Figure 15A] The system pressure (pressure drop) vs. flow curve and the opening pressure vs. flow curve of the FCPRV are shown, where flow is the flow rate of gas delivered to the patient or delivered from the main outlet of the FCPRV. [Figure 15B] 1 shows the system pressure (pressure drop) vs. flow curve and the opening pressure vs. flow curve of the FCPRV, illustrating various stages of operation of the FCPRV, where flow is the flow rate of gas delivered to the patient or delivered from the main outlet of the FCPRV. [Figure 16A] 16A and 16B are schematic diagrams of a flow compensated pressure relief valve, showing the FCPRV in a flow exhaust configuration, FIG. 16B in a low flow configuration, and FIG. 16C in a high or high flow pressure restriction configuration. [Figure 16B] 16A and 16B are schematic diagrams of a flow compensated pressure relief valve, showing the FCPRV in a flow exhaust configuration, FIG. 16B in a low flow configuration, and FIG. 16C in a high or high flow pressure restriction configuration. [Figure 16C] 16A and 16B are schematic diagrams of a flow compensated pressure relief valve, showing the FCPRV in a flow exhaust configuration, FIG. 16B in a low flow configuration, and FIG. 16C in a high or high flow pressure restriction configuration. [Figure 16D] The system pressure (pressure drop) vs. flow curve and the opening pressure vs. flow curve of the FCPRV are shown, where flow is the flow rate of gas delivered to the patient or delivered from the main outlet of the FCPRV. [Figure 17] 15B shows the same graph as FIG. 15B, but with two additional flow compensated opening pressure vs. flow curves. [Figure 18] The adjustment routine of FCPRV is shown. [Figure 18A] 1A-1C are schematic diagrams of flow compensated pressure relief valves each including an adjustment mechanism for adjusting the relief valve discharge pressure characteristics of the FCPRV. [Figure 18B] 1A-1C are schematic diagrams of flow compensated pressure relief valves each including an adjustment mechanism for adjusting the relief valve discharge pressure characteristics of the FCPRV. [Figure 18C]1A-1C are schematic diagrams of flow compensated pressure relief valves each including an adjustment mechanism for adjusting the relief valve discharge pressure characteristics of the FCPRV. [Figure 19] 1 shows the system pressure (pressure drop) vs. flow rate curve and the opening pressure vs. flow rate curve for an FCPRV in which the opening pressure is limited to the maximum opening pressure. [Figure 20] A cross-sectional view of the FCPRV is shown. [Figure 21] 4 shows a free body diagram of another FCPRV. [Figure 22] 1 shows a cross-sectional view of another FCPRV. [Figure 23A] 23A is a schematic diagram of the FCPRV of Figure 22. Figure 23A shows a no-flow or low-flow configuration, and Figure 23B shows a flow or high-flow configuration. [Figure 23B] 23A is a schematic diagram of the FCPRV of Figure 22. Figure 23A shows a no-flow or low-flow configuration, and Figure 23B shows a flow or high-flow configuration. [Figure 24] 1 shows a cross-sectional view of another FCPRV. [Figure 25A] 25A-25B are schematic diagrams of the FCPRV of Fig. 24. Fig. 25A shows a no-flow or low-flow configuration, and Fig. 25B shows a flow or high-flow configuration. [Figure 25B] 25A-25B are schematic diagrams of the FCPRV of Fig. 24. Fig. 25A shows a no-flow or low-flow configuration, and Fig. 25B shows a flow or high-flow configuration. [Figure 26A] 26A-26B are schematic diagrams of an FCPRV similar to that of Fig. 24 including a sensing piston with an aperture. Fig. 26A shows a no-flow or low-flow configuration, and Fig. 26B shows a flow or high-flow configuration. [Figure 26B] 26A-26B are schematic diagrams of an FCPRV similar to that of Fig. 24 including a sensing piston with an aperture. Fig. 26A shows a no-flow or low-flow configuration, and Fig. 26B shows a flow or high-flow configuration. [Figure 27A] 27A-27B show cross-sectional views of an alternative FCPRV. These views are cross-sectional views taken along an axis passing through the central axes of the valve member and sensing member of the valve. The cross-sectional plane of FIG. 27A is perpendicular to the cross-sectional plane of FIG. 27B. [Figure 27B]27A-27B show cross-sectional views of an alternative FCPRV. These views are cross-sectional views taken along an axis passing through the central axes of the valve member and sensing member of the valve. The cross-sectional plane of FIG. 27A is perpendicular to the cross-sectional plane of FIG. 27B. [Figure 27C] Figure 27D is a cross-sectional view of the valve or sensing member of Figure 27C, showing a valve or sensing member including a resilient diaphragm or membrane and a rigid frame. [Figure 27D] Figure 27D is a cross-sectional view of the valve or sensing member of Figure 27C, showing a valve or sensing member including a resilient diaphragm or membrane and a rigid frame. [Figure 27E] 1 is a cross-sectional view of a valve body, a valve member, and a sensing member assembly of a flow controlled pressure relief valve. [Figure 27F] 27F is a cross-sectional view of an assembly of a valve body, a valve member, and a sensing member of a flow-controlled pressure relief valve. The assembly of FIG. 27F has increased pneumatic coupling between the main flow path and the sensing chamber compared to the assembly of FIG. 27E. [Figure 28A] FIG. 27C is a diagram of the valve disc of the FCPRV of FIGS. 27A and 27B. [Figure 28B] FIG. 27C is a diagram of the valve disc of the FCPRV of FIGS. 27A and 27B. [Figure 28C] FIG. 27C is a diagram of the valve disc of the FCPRV of FIGS. 27A and 27B. [Figure 29A] 27A and 27B show the mechanical linkages of the FCPRV. [Figure 29B] 27A and 27B show the mechanical linkages of the FCPRV. [Diagram 30] 1 shows a free body diagram of another FCPRV adapted to be reversible. [Figure 31A] 31A and 31B are schematic diagrams of an electromechanical FCPRV: Figure 31A shows the FCPRV in a low-flow configuration, and Figure 31B shows the FCPRV in a high-flow configuration. [Figure 31B] 31A and 31B are schematic diagrams of an electromechanical FCPRV: Figure 31A shows the FCPRV in a low-flow configuration, and Figure 31B shows the FCPRV in a high-flow configuration. [Figure 32A]32A and 32B are schematic diagrams of another electromechanical FCPRV: Figure 32A shows the FCPRV in a low-flow configuration, and Figure 32B shows the FCPRV in a high-flow configuration. [Figure 32B] 32A and 32B are schematic diagrams of another electromechanical FCPRV: Figure 32A shows the FCPRV in a low-flow configuration, and Figure 32B shows the FCPRV in a high-flow configuration. [Figure 33A] 33A and 33B are schematic diagrams of another electromechanical FCPRV: Figure 33A shows the FCPRV in a low-flow configuration, and Figure 33B shows the FCPRV in a high-flow configuration. [Figure 33B] 33A and 33B are schematic diagrams of another electromechanical FCPRV: Figure 33A shows the FCPRV in a low-flow configuration, and Figure 33B shows the FCPRV in a high-flow configuration. [Figure 34A] 1 shows a graph of the inlet and outlet chamber pressure of a PRV versus the discharge flow rate of a PRV adjusted for use as a flow compensating PRV. [Figure 34B] 1 shows the system pressure (pressure drop) versus flow curve and the opening pressure versus flow curve of a PRV adapted for use as an FCPRV. The horizontal axis is the flow delivered to the patient downstream of the PRV inlet. [Figure 35A] FIG. 1 is a schematic diagram of a pressure relief valve configured to exhaust exhaled breathing gas, control the opening and closing of a nebulizer port, and deliver medication to the gas flow to a patient. [Figure 35B] FIG. 1 is a schematic diagram of a pressure relief valve configured to exhaust exhaled breathing gas, control the opening and closing of a nebulizer port, and deliver medication to the gas flow to a patient. [Diagram 36] FIGURES 30-32 show cross-sectional views of a portion of an FCPRV. FIGURES 33 and 34 show cross-sectional views of the body of an FCPRV including a discharge flow indicator. [Figure 37] FIGURES 30-32 show cross-sectional views of a portion of an FCPRV. FIGURES 33 and 34 show cross-sectional views of the body of an FCPRV including a discharge flow indicator. [Figure 38]FIGURES 30-32 show cross-sectional views of a portion of an FCPRV. FIGURES 33 and 34 show cross-sectional views of the body of an FCPRV including a discharge flow indicator. [Figure 39] FIGURES 30-32 show cross-sectional views of a portion of an FCPRV. FIGURES 33 and 34 show cross-sectional views of the body of an FCPRV including a discharge flow indicator. [Diagram 40] FIGURES 30-32 show cross-sectional views of a portion of an FCPRV. FIGURES 33 and 34 show cross-sectional views of the body of an FCPRV including a discharge flow indicator. [Figure 41A] An impeller flow indicator is shown. [Figure 41B] 1 shows an FCPRV including an impeller at its outlet to indicate the flow rate at the outlet of the FCPRV. [Figure 42A] A flap flow indicator is shown. [Figure 42B] Shown is an FCPRV including a flap flow indicator that is invisible in no-flow conditions. [Figure 42C] FIG. 42B shows the FCPRV with gas flow from the outlet of the FCPRV indicated by the flap moved into a flow condition. [Diagram 43] 1 shows an FCPRV that includes a flow indicator that includes a guide tube and a shuttle or plunger. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0160] Various embodiments will be described with reference to the drawings. Throughout the drawings and the specification, the same reference numbers may be used to indicate the same or similar components, and redundant descriptions thereof may be omitted.

[0161] The pressure relief device according to the embodiments described herein is particularly adapted for use in a breathing system such as a CPAP or high flow breathing gas system, e.g., a high flow system for use in anesthesia procedures. Breathing systems in which the pressure relief valve may be particularly useful are CPAP, BiPAP, high flow therapy, variable high flow therapy, low flow air delivery, low flow O2 delivery, bubble CPAP, apneic high flow (i.e., high flow for anesthetized patients), invasive ventilation, and non-invasive ventilation. Additionally, the pressure relief valve described herein may be useful in systems other than breathing systems.

[0162] By way of example, a high flow respiratory system 10 is described with reference to Figure 1. High flow therapy may be used as a means to enhance gas exchange and / or respiratory support by delivery of oxygen and / or other gases and removal of CO2 from a patient's airways. High flow therapy may be particularly useful before, during, or after a medical procedure.

[0163] When used prior to a medical procedure, the high flow gas stream can pre-oxygenate the patient to increase the patient's blood oxygen saturation and lung oxygen content and provide an oxygen buffer during the patient's apneic phase during the medical procedure.

[0164] A continuous supply of oxygen is essential to maintain healthy respiratory function during medical procedures (such as during anesthesia) where respiratory function may be compromised (e.g., reduced or stopped). When this supply is compromised, hypoxia and / or hypercapnia can occur. During medical procedures such as anesthesia and / or general anesthesia where the patient is unconscious, the patient is monitored to detect when this occurs. If oxygen delivery and / or CO2 removal is compromised, the clinician stops the medical procedure and promotes oxygen delivery and / or CO2 removal. This may be accomplished, for example, by manually ventilating the patient with an anesthesia bag and mask or by using a high-flow therapy system to deliver a high-flow gas stream to the patient's airways.

[0165] An additional benefit of high flow gas streams may include that they increase the patient's airway pressure, providing pressure support that opens the airways, trachea, lungs / alveoli, and bronchioles. Opening these structures improves oxygenation and aids in some degree in the removal of CO2.

[0166] The increased pressure can also prevent structures such as the larynx from obstructing the view of the vocal cords during intubation. If humidified, a high-flow gas stream can also prevent the airway from drying out, reduce mucociliary damage, and lower the risk of laryngospasm and the risks associated with a dry airway, such as epistaxis, aspiration (resulting from nosebleeds), and airway obstruction, swelling, and bleeding. Another advantage of a high-flow gas stream is that the flow can remove smoke generated in the airway during surgery. In such an embodiment, the smoke may be generated by a laser and / or cauterization device.

[0167] Pressure relief or regulation devices are particularly desirable for use in respiratory systems, such as high flow systems that include a non-sealing patient interface, to provide an upper pressure limit for the system. Most importantly, the upper pressure limit may be configured to provide a limit for patient safety or to prevent damage to tubing, fluid connections, or other components. Pressure relief or regulation devices may be used in CPAP systems to regulate the pressure delivered to the patient.

[0168] With reference to FIG. 1, the system / apparatus 10 may include an arrangement based on integrated or separate components generally shown within the dashed box 11 in FIG. 1. In some configurations, the system 10 may include a modular arrangement of components. Hereinafter, it is referred to as a system, but this should not be construed as limiting. The system may include a flow source 12, such as an in-wall oxygen source, an oxygen tank, a blower, a flow therapy device, or any other oxygen or other gas source. The system may also include an additive gas source including one or more other gases that may be combined with the flow source. The flow source 12 may provide a pressurized high flow gas flow 13 that may be delivered to a patient 16 through a delivery conduit 14 and a patient interface 15 (such as a nasal cannula). A controller 19 controls the flow source 12 and additive gas through a valve, etc. to control the flow rate of the high flow gas 13 and other characteristics such as any one or more of pressure, composition, concentration, volume, etc. A humidifier 17 may also be provided that may humidify the gas and control the temperature of the gas under the control of the controller. One or more sensors 18a, 18b, 18c, 18d, such as flow sensors, oxygen sensors, pressure sensors, humidity sensors, temperature sensors, or other sensors, may be located throughout the system and / or at, on, or near the patient 16. The sensors may include a pulse oximeter 18d on the patient for determining the oxygen level in the blood.

[0169] A controller 19 may be coupled to the flow source 12, the humidifier 17, and the sensors 18a-18d. The controller 19 may operate the flow source to provide a delivered gas flow. The controller 19 may control the flow rate, pressure, composition (if more than one gas is provided), volume, and / or other parameters of the gas provided by the flow source based on feedback from the sensors. The controller 19 may also control any other suitable parameters of the flow source to meet the oxygen administration requirements. The controller 19 may also control the humidifier 17 based on feedback from the sensors 18a-18d. Using input from the sensors, the controller may determine the oxygen administration requirements and control parameters of the flow source and / or the humidifier as needed. An input / output interface 20 (such as a display and / or input device) is provided. The input device is for receiving information from a user (e.g., a clinician or a patient) that may be used to determine the oxygen administration requirements. In some embodiments, the system may not have a controller and / or an input / output interface. A medical professional, such as a nurse or technician, may provide the necessary control functions (eg, as shown in FIG. 1A).

[0170] The pressure may also be controlled. As mentioned above, the high flow gas stream (which may be humidified) may be delivered to the patient 16 through the delivery conduit 14 and a patient interface 15 or "interface", such as a cannula, a mask, a nasal or oral device, or a combination thereof. A nasal interface, as used herein, is a device such as a cannula, a nasal mask, nasal pillows, or other type of nasal device, or a combination thereof. The patient or nasal interface may be substantially sealed, partially sealed, or substantially non-sealed. A nasal interface may also be used in conjunction with a mask or oral device (such as a tube inserted into the mouth) and / or with a mask or oral device (such as a tube inserted into the mouth) that may be detached from and / or attached to the nasal interface. A nasal cannula is a nasal interface that includes one or more prongs configured to be inserted into the patient's nares. A mask refers to an interface that covers the patient's nares and / or mouth, and may also include devices where the portion of the mask that covers the patient's mouth is removable, or other patient interfaces such as a laryngeal mask airway or an endotracheal tube. Mask also refers to a nasal interface that includes nasal pillows that provide a substantial seal with the patient's nares. The controller controls the system to provide the required oxygen administration.

[0171] The system 10 according to embodiments herein includes a pressure relief or regulation device, or pressure limiting device 100 (herein, pressure relief valve, or PRV). The PRV may be located anywhere in the system between the gas source 12 and the patient 16. Preferably, the PRV is located at the outlet of the flow source 12 or between the flow source 12 and the humidifier 17, e.g., near the inlet of the humidifier. In some embodiments, the PRV may be located at the outlet of the humidifier and / or the inlet of the conduit 14, or anywhere along the conduit 14 through a suitable housing or coupling device. The PRV 100 may be located anywhere in the system, e.g., the PRV may be part of a patient interface assembly. The system may additionally or alternatively include a flow-controlled pressure relief or regulation device (FCPRV) 300, as shown in FIG. 1AA.

[0172] The PRV 100 according to the embodiments described herein regulates the pressure to a nearly constant pressure over a given flow range. The PRV 100 may be used to provide an upper limit for patient safety and / or to prevent damage to system components due to overpressure. For example, a blockage in the system may cause significant backpressure in the system upstream of the blockage, and the PRV may operate to prevent the backpressure from increasing beyond a limit to protect the patient and / or system components from damage. Blockage of the patient's nares or exhalation conduit may lead to an increase in patient pressure. Blockage of the system may be caused, for example, by inadvertently kinking or collapsing the conduit 14, or may be intentionally caused, for example, by blocking the conduit 14 (e.g., by pinching a portion of the conduit closed) to prevent gas flow from reaching the patient.

[0173] 2A and 12A, in some embodiments, the PRV 100 includes an inlet 101, an outlet chamber 102 having an outlet 103, a valve seat 104 between the inlet 101 and the outlet chamber 102, and a valve member 105 biased to seal against the valve seat 104. The valve member is adapted to be displaced from the valve seat by a pressure Pc at the inlet increasing beyond a pressure threshold. The pressure Pc acts on the valve member 105 and forces the member away from the valve seat 104 when the pressure Pc reaches the threshold, for example as shown in FIG. 2B. When the member is displaced from the valve seat, gas flows from the inlet to the outlet chamber 102 and then from the outlet chamber through the outlet 103 to ambient / atmospheric pressure. The outlet from the chamber is configured such that gas flow through the outlet creates a (back pressure) pressure Pb in the outlet chamber, which acts on the valve member 105 and displaces the valve member further from the valve seat, for example as shown in FIG. 2C. As the member is displaced further from the valve seat, the gap 109 between the valve member and the valve seat increases. Further explanation of valve operation is provided below.

[0174] As shown in Figures 2A-2C, in some embodiments, the valve member is an elastomeric membrane 105. The membrane may be suspended in a floating manner across the outlet chamber 102. The membrane is preferably stretched or tensioned over the valve seat 104 such that the tension of the membrane urges it against the valve seat to form a seal with the valve seat and close the flow path from the inlet to the outlet chamber. Alternatively, a separate biasing member or spring may be provided to urge the membrane against the valve seat. For example, a compression spring may be provided to act on the non-pressurized side (non-system pressurized side) of the membrane and push the membrane against or towards the valve seat. Alternatively, a tensioned spring may be provided to act on the system pressurized side of the membrane. The periphery of the membrane may be supported or held by the wall 106 of the outlet chamber with the membrane stretched or tensioned over the valve seat. For example, the valve may include a housing. The housing may include a first housing portion and a second housing portion forming an outlet chamber, with the peripheral edge of the membrane sandwiched between the first housing portion and the second housing portion. The second housing portion may form the displacement chamber 107. The valve member may be bonded / glued or welded to the housing.

[0175] In some embodiments, the PRV may include a displacement chamber 107 into which the valve member may be displaced away from the valve seat. A membrane separates the outlet chamber and the displacement chamber. The PRV may include a housing separated into an outlet chamber and a displacement chamber. The outlet chamber may be considered to be the pressurized side of the housing and the displacement chamber may be considered to be the ambient side of the housing. Preferably, the displacement chamber is open to atmospheric / ambient pressure (e.g., the displacement chamber is not sealed). For example, the displacement chamber may have a relatively large opening (e.g., opening 112 in FIG. 12A) that maintains ambient pressure in the displacement chamber. When the valve member is displaced from the valve seat with the displacement chamber at ambient pressure, the displacement chamber remains at ambient pressure such that displacement of the valve member into the displacement chamber does not result in an increase in pressure in the displacement chamber that acts against the displacement of the membrane away from the valve seat. The displacement chamber may accommodate the membrane but has an opening to maintain atmospheric pressure in the displacement chamber. The opening of the displacement chamber is of sufficient area so that there is no pressure increase in the displacement chamber when the valve member is displaced from the valve seat. Ambient pressure (atmospheric pressure) acts on the non-pressurized side 112 of the valve member. The non-pressurized side is the side of the member opposite the side that seals against the valve seat. The size of the opening to atmosphere may be reduced to reduce valve vibration / change the response of the valve. The smaller the opening, the less the response time of the valve. Alternatively, the displacement chamber may be sealed. One advantage of having a displacement chamber open to atmosphere / ambient is that any leakage of the valve member due to a pressure increase in the displacement chamber will not cause the valve to malfunction.

[0176] In a preferred embodiment, the outlet exhausts the gas flow from the inlet through the outlet chamber to the atmosphere / ambient environment.

[0177] In some embodiments, as shown in Figures 2A-2C, the inlet includes an inlet tube 108 that extends into the outlet chamber 102. A valve seat 104 is preferably provided at the end of the inlet tube. In some embodiments, the end of the inlet tube 108 forms the valve seat. In some embodiments, the membrane 105 is approximately perpendicular to the inlet tube (e.g., perpendicular to the longitudinal axis of the inlet tube). In some embodiments, the inlet tube abuts the membrane, deflecting the elastomeric membrane when it contacts the valve seat, such that the membrane is biased by the tension of the membrane against the valve seat to create a seal with the valve seat.

[0178] The outlet chamber 102 surrounds the valve seat 104. When the valve member (i.e., membrane 105) seals against the valve seat, the inlet pressure acts over a first area or portion of the valve member, determined by the geometry of the valve seat 104. When the valve member is displaced from the valve seat, the inlet pressure Pc acts on the valve member over the valve seat area (first area) and the outlet chamber back pressure Pb acts over a second area, which is the area of ​​the valve member outside the valve seat area. In some embodiments, the second area of ​​the valve member is larger than the first area of ​​the valve member. The pressure difference between the inlet pressure Pc and the back pressure Pb is caused by the pressure loss of the gas flow through the gap 109 between the valve member 105 and the valve seat 104. Because the area of ​​the valve member is larger than the area of ​​the valve seat, when the valve member is displaced from the valve seat, the inlet and outlet pressures act over a larger area of ​​the valve member.

[0179] In some embodiments, the abutting end 104 of the inlet tube 108 is beveled around its periphery to form the valve seat 104. The beveled edge 104a reduces the amount of surface area of ​​the end of the inlet tube that contacts the elastomeric membrane and may help ensure a seal between the valve seat and the membrane. The beveled edge of the tube is not so sharp that it may damage the membrane. The beveled edge may be on the outer periphery of the tube. The abutting end 104 of the tube may be any number of shapes including curved, flat, triangular, beveled, or combinations thereof.

[0180] The membrane (i.e., valve member) 105 may be formed from a suitable elastomeric material, such as a rubber or silicone material or other elastic material. The material may be a thermoplastic or thermoset material, or may be a thermoplastic film. The membrane material may be non-porous, or in some embodiments may be porous, for example, to allow continuous exhaust flow to pass through the valve member at pressures above a threshold. One prototype valve was made using a rubber material with a thickness of approximately 0.4 mm. Other prototypes have thicknesses between 0.1 mm and 0.3 mm, with 0.3 mm being preferred. It should be understood that other membranes of different material compositions and / or geometries may also be used. Different materials may include, for example, rubber, thermoplastic, silicone, etc., each with a different elastic modulus. Different geometries may include membranes of different thicknesses, shapes, or combinations thereof. For example, the membrane may include a thickened region. The thickened region may be formed as a thickened circular center of the membrane or thickened radial ribs. For example, a membrane having a thickened central portion 105a for supporting the valve seat 104 is shown in Figures 12B and 12C. The portion 105b of the membrane extending around the thickened central portion 105a is of a suitable thickness to provide the desired characteristics of the PRV. The thin portion 105b may provide the necessary bias of the valve member 105 against the valve seat 104. In Figure 12B, the cross-sectional thickness of the thin portion 105b is constant over its radial length. In Figure 12C, the thickness of the thin portion 105b decreases along its radial length from the central thickened portion 105a to the outer periphery of the membrane 105 at the wall 106 of the outlet chamber 102. In the exemplary embodiment of Figures 12D and 12E, the membrane 105 is provided with ribs 105c, 105d. In Figure 12D, the ribs 105c are radial ribs 105c. A radial rib may have a constant width along its radial length, or may increase in width along its length toward the membrane's periphery, as shown. In FIG. 12E, rib 105d is a concentric rib 105d. Rib 105d may be applied, for example, to affect the way the membrane elastically deforms to achieve desired properties of the PRV.

[0181] The outlet 103 from the outlet chamber 102 provides resistance to flow from the outlet chamber of the PRV. The flow resistance creates a pressure Pb (back pressure) in the outlet chamber 102 that acts on the valve member to push or force the member away from the valve seat 104. In some embodiments, there may be more than one outlet, or in other words, the outlet 103 may include multiple outlet holes or apertures 103. The chamber pressure Pb is the back pressure created in the outlet chamber 102 by the restriction provided by the flow through the chamber 102 and the configuration of the outlet 103 from the chamber 102. To create a back pressure in the chamber 102, in some embodiments, the outlet 103 from the chamber is configured to have a greater flow resistance than the gap 109 between the valve seat 104 and the valve member 105. The pressure difference between the inlet pressure Pc and the back pressure Pb is created by the pressure loss of the gas flow through the gap 109 between the valve member 105 and the valve seat 104.

[0182] The valve member and valve seat provide a dynamically variable flow restriction 109 between the inlet 101 and the outlet chamber 102. The dynamically variable flow restriction is dependent on the inlet pressure at the inlet of the PRV and the outlet pressure or back pressure at the outlet chamber. As the inlet and / or outlet pressure increases, the dynamically variable flow restriction 109 decreases. The outlet 103 provides a "constant" flow restriction, or a flow restriction that is independent of the inlet and outlet pressures. In other words, the outlet restriction does not change with changing inlet or outlet pressures. However, as described in more detail below, in some embodiments, the outlet restriction may be adjusted by the user.

[0183] 2A-2C, the valve seat is at the end of the inlet 101 such that the inlet pressure Pc acts on the valve member over a valve seat area defined by the diameter of the valve seat (D in FIG. 12A). When the valve member 105 is displaced from the valve seat 104, the inlet pressure continues to act on the valve member 105 over the valve seat area and a back pressure Pb acts on the valve member over an area outside the valve seat. Thus, the back pressure Pb acts on an area of ​​the valve member equal to the valve member area minus the valve seat area.

[0184] 13A-13C show another embodiment in which the valve seat 104 is at the inlet of the outlet chamber 102. An inlet tube surrounds the outlet chamber. The peripheral edge of the valve member membrane 105 may be supported or held by the wall 108 of the inlet tube with the membrane stretched or in tension on the valve seat 104. When the valve member 105 seats on the valve seat 104, the inlet pressure Pc of the inlet 101 acts on the valve member 105 over the area outside the valve seat 104 (i.e. the valve member area minus the valve seat area). When the valve member 105 is displaced from the valve seat 104, the inlet pressure continues to act on the valve member 105 over the area outside the valve seat area and the outlet chamber back pressure Pb generated by the outlet vent 103 acts on the valve member over the valve seat area. The device includes an inlet tube surrounding the outlet chamber and a valve seat is provided at the opening to the outlet chamber.

[0185] It may be desirable for the PRV to achieve a nearly constant opening pressure (within a pressure band) over a range of operating flow rates. The flow range over which the valve can regulate the opening pressure within a predefined pressure band may be referred to as the valve's effective operating range. For example, as shown in FIG. 3, in one embodiment, the PRV achieves a pressure band of about 18-20 cmH2O over a flow range of about 5 L / min-35 L / min. Specific valves may be developed to achieve the desired pressure band and flow range. A further advantage of the described PRV is that it reaches a safe operation by reducing the opening pressure at high flow rates outside the range, even if the system flow is set higher than the desired operating range. Factors that affect the performance of the valve are described in more detail below.

[0186] A substantially constant response is desirable because a constant opening pressure PRV ensures that, for a given operating flow range, the pressure in the system and / or the pressure delivered to the user does not rise above a pressure band. This improves the safety of the user against overpressure when the flow rate delivered by the system is at the upper end of the operating range. PRVs according to embodiments described herein may also allow for a wider operating flow range because pressure remains constant over a range of flow rates compared to prior art valves. This is advantageous because a wider flow range can be used for respiratory treatments such as high flow therapy.

[0187] Operation of a PRV according to embodiments described herein will now be described with reference to Figures 3-6. When the pressure Pc in the inlet 101 is sufficient to overcome the force of the membrane, the membrane 105 is displaced from the valve seat 104, transmitting gas from the inlet 101 through the gap 109 between the valve seat 104 and the valve member 105 to the outlet chamber 102. The gas may then be transmitted from the outlet chamber to atmosphere through the outlet(s) 103 or outlets.

[0188] As gas flows through the outlet chamber 102, a pressure P acts on the membrane 105. B is generated in the outlet chamber. As the flow rate increases, this pressure in the outlet chamber may increase progressively according to a "square law" pressure, i.e., the pressure is approximately proportional to the square of the flow rate. The rate of increase in pressure in the outlet chamber may increase at a slower rate than the square law as the volume of the chamber expands due to movement of the valve member.

[0189] As the flow rate through the valve 100 increases, the pressure in the outlet chamber 102 increases and the gap 109 between the membrane 105 and the valve seat 104 (e.g., the abutting end of the inlet tube) widens further, which has the effect of progressively reducing the flow resistance presented by the gap 109, reducing the pressure Pc in the inlet tube from about 35 L / min to about 80 L / min, as shown in Figure 3. In other words, the total pressure drop in the PRV from inlet 101 to outlet 103 decreases.

[0190] As the flow rate increases further, the gap 109 between the membrane 105 and the valve seat 104 widens even more, and eventually the pressure Pc in the inlet pipe 108 and the pressure Pc in the outlet chamber 102 increase. B At this point, the inlet and outlet chamber pressures begin to become equal. In other words, the pressure drop in the gap 109 between the valve seat 104 and the valve member 105 approaches zero. The inlet and chamber pressures may not actually achieve equalization during operation, but there may be a tendency toward equalization. In FIG. 3, the inlet and outlet chamber pressures are nearly equalized at a flow rate of about 120 L / min. This flow rate is outside the useful "constant" operating range of the PRV.

[0191] As the pressure in the outlet chamber Pb and the inlet pressure Pc tend to equalize, the pressure drop from the inlet 101 to the outlet chamber 102 decreases and the pressure drop in the PRV 100 predominates from the outlet chamber 102 to the outlet 103 to the ambient. In other words, the pressure drop in the PRV predominates from the outlet chamber 102 to the ambient. As the pressure drop from the outlet chamber to the ambient predominates, the inlet pressure Pc increases according to a "square law". In other words, the total pressure drop in the PRV 100 begins to increase according to a "square law" as the pressure Pb in the outlet chamber 102 predominates. For the exemplary valve profile shown in FIG. 3, this occurs at about 100 L / min. The pressure drop in the PRV begins to increase according to a square law outside the effective operating flow range of the valve. The data shown in FIG. 3 is provided for an exemplary valve, and other valves according to embodiments described herein will exhibit different flow / pressure characteristics. The performance of a particular valve, including the point at which the pressure begins to increase according to a square law, will depend on a variety of factors. These elements are discussed in further detail below.

[0192] In prior art valves, the pressure loss of the valve is predominant in the gap between the valve seat and the valve member. When the valve "opens" or opens by the valve member moving away from the valve seat, the pressure loss in the gap between the valve seat and the valve member increases progressively and may increase linearly in proportion to the flow rate. In comparison, the PRV according to the embodiments described herein increases substantially in proportion to the square of the flow rate, but the point at which the pressure loss of the PRV begins to increase is offset. This comparison between the PRV according to the embodiments described herein and the prior art valve is shown diagrammatically in FIG. 6. The valve according to the embodiments described herein (pressure curve 121 in FIG. 4) maintains a substantially constant opening pressure over a wide range of flow rates. The approximate point at which the pressure loss of the valve (Pc) begins to increase according to a square law is indicated by an arrow on the graph. The PRV may be designed such that the point at which the pressure begins to increase according to a square law is outside the effective operating flow range of the valve, and the valve exhibits a relatively constant opening pressure for the intended flow range of the valve. The graph of FIG. 6 is merely illustrative, and the shape of the pressure curve has been exaggerated to highlight the effect of PRV in accordance with the described embodiment.

[0193] The size and number of outlets from the outlet chamber (i.e., the total outlet area) determines the pressure P generated in the outlet chamber. BFor example, with a small exit aperture, the pressure in the exit chamber increases progressively at a faster rate as the flow rate increases. Conversely, with a large exit aperture, the pressure in the exit chamber increases progressively at a slower rate as the flow rate increases. Thus, adjusting the size and / or number of the exit apertures (i.e., the total exit area) has the resulting effect of adjusting the effective operating range of the valve. This mechanism for modifying the characteristics of the PRV is shown in Figures 3-5. In Figure 3, the test PRV included a single exit aperture from the exit chamber. In Figure 4, the test PRV had two exit apertures of the same size such that the exit area of ​​the test PRV in Figure 4 was twice that of the test valve in Figure 3. The larger exit area resulted in a slower progressive increase in the pressure in the exit chamber as the flow rate increases. As a result, the effective flow operating range of Figure 4 is increased, regulating the pressure to a nearly constant pressure over a wider flow range compared to Figure 3. Additionally, in Figure 5, the test PRV included three exit apertures such that the exit area of ​​the test PRV in Figure 5 was three times that of the test valve in Figure 3. The larger exit area, as compared to the valves tested in Figures 3 and 4, resulted in a slower progressive increase in pressure in the exit chamber as flow rate increased, thus further expanding the effective flow operating range and regulating the pressure to a nearly constant pressure over a wider flow range.

[0194] In some embodiments, the PRV may be adjusted at the time of manufacture to a particular useful operating range, such as by assembly with a predetermined number and / or size of exit holes. Alternatively, the valve may be adjusted to a particular useful operating range by an end user, such as by means of selectively adjusting the exit area from the exit chamber. Such means may be, for example, a function of selectively opening / closing some of the exit holes. In one embodiment, the exit chamber may include one or more exit apertures, and a covering member may be movably coupled to the chamber, the covering member including a corresponding one or more apertures. The member may move relative to the exit chamber to align the apertures of the exit chamber with the apertures of the covering member and maximize the exit area from the chamber. The covering member may move relative to the chamber such that the apertures of the chamber and the apertures of the member are partially aligned, resulting in an exit area less than the maximum exit area. For example, the covering member may be a ring member having a hole that is rotatably coupled to rotate relative to the exit chamber and move between a position in which the hole in the member and the exit aperture 103 from the chamber 102 are aligned (maximum exit area) and a second position in which the hole in the member and the exit aperture 103 from the chamber 102 are not aligned (minimum exit area) such that the exit aperture is partially covered. Alternatively, there may be multiple exit apertures 103 with removable covers, where the exit area is variable by removing the cover from one or more of the exit apertures 103.

[0195] A small outlet area creates a relatively high flow resistance, resulting in a relatively high back pressure in the outlet chamber 102, acting on the valve member 105 to "push" it further away from the abutting inlet pipe or valve seat 104. As a result, the valve has a short effective operating range with a pressure curve that includes a relatively short, steep "knee" that indicates how quickly the valve reaches its predetermined maximum opening pressure. Conversely, a large outlet area creates a lower flow resistance, resulting in a lower back pressure that acts on the valve member to "push" it further away from the abutting inlet pipe. A larger outlet area provides a wide effective operating range with a pressure curve that includes a relatively longer, rounder "knee". This concept is further illustrated in FIG. 7. Reference numeral 123 indicates an ideal valve pressure curve with no static leakage, no steep "knee", and a constant opening pressure. Curve 124 shows the pressure curve for a valve including a relatively large outlet area, where the pressure curve has a wide effective flow operating range and a relatively long, rounded "knee. " For comparison, curve 125 shows the pressure curve for a valve including a relatively small outlet area, where the pressure curve has a shorter effective flow operating range and a relatively short, less rounded "knee.

[0196] The outlet or outlets 103 from the outlet chamber 102 provide an amount of resistance to flow from the chamber 102 and therefore affect the amount of pressure within the chamber acting to move the valve member from the valve seat. The effect of the area of ​​the outlet has been discussed above. Also, the length of the outlet from the outlet chamber can affect the pressure within the outlet chamber. For example, as shown in Figures 2A-2C, in some embodiments, the outlet may include one or more apertures in the wall of the outlet chamber. In some embodiments, the PRV may include an outlet tube (not shown) extending from the outlet chamber. The length of the outlet tube may provide flow resistance that may affect the pressure level generated within the outlet chamber.

[0197] The location of the outlet from the outlet chamber can also affect the gas flow dynamics of the PRV. Thus, the location of the outlet may provide some flow resistance that can subsequently affect the amount of pressure created in the outlet chamber. The shape of the outlet can also affect the performance of the PRV.

[0198] As shown in the embodiment of Figures 2A-2C and 12A, preferably the outlet is located radially between the outer periphery of the valve member and the outer periphery of the valve seat and / or the inlet and / or the inlet tube. Locating the outlet between the outer periphery of the valve member and the valve seat helps to create a flow path in the outlet chamber to the valve member. In some embodiments, the inlet, valve member, valve seat, and outlet are arranged such that as the gas flow enters the chamber, the gas flow through the outlet chamber is directed against the valve member, bounces off the valve member over an angle of more than 90 degrees, and exits the chamber through the outlet. In some embodiments, as shown, the inlet is arranged to direct the gas flow into the outlet chamber perpendicular to the valve member. The direction of flow entering the chamber may be substantially opposite to the direction of gas flow exiting the outlet chamber (e.g., the direction of flow from the outlet is about 180 degrees to the direction of flow from the inlet). In some embodiments, the outlet is in a wall of the outlet chamber opposite the valve member. In some embodiments, the outlet vent 103 may be provided in the outlet tube concentric with the inlet tube 101. In some embodiments, the exit vent may be located near the periphery of the valve member. Alternatively or additionally, in some embodiments, the exit vent or vents 103 may be located within the valve member (e.g., an aperture in the valve member) or the valve member may be porous, e.g., porous or have one or more apertures within the valve member in an area outside the valve seat area. The entire valve member may be porous, resulting in some leakage flow through the valve member even when it is against the valve seat.

[0199] Additionally, the size of the outlet chamber 102 may affect the performance of the valve. For example, a very large outlet chamber may take longer to pressurize, resulting in a valve characteristic with a "soft" opening characteristic. In contrast, a small volume outlet chamber may be pressurized more quickly, resulting in a membrane lifting off the valve seat more quickly. In some embodiments, the outlet chamber may have zero volume when the valve member is against the valve seat and a volume greater than zero when the valve member is away from the valve seat. In a zero volume chamber, when the valve member 105 is against the valve seat 104, the valve member may rest against a wall of the chamber 102. The wall may be curved or flat. As the valve member 105 lifts, it may expose an outlet hole such that the outlet area is variable depending on the pressure generated in the outlet chamber. Alternatively or additionally, the valve member may change the flow resistance of the outlet from the outlet chamber as the valve member 105 lifts away from the valve seat 104 to allow gas flow into the outlet chamber 102. For example, the gap between the valve member and the outlet from the outlet chamber may change as the valve member moves away from the valve seat to change the flow resistance of the outlet. In preferred embodiments, the valve chamber has a sufficient volume such that the velocity of gas flow within the chamber is substantially lower than the velocity of gas flow through the gap between the valve seat and the valve member. In some embodiments, the velocity of gas flow within the chamber is substantially lower than the velocity of gas flow through the outlet from the chamber.

[0200] As mentioned above, in some embodiments, the inlet tube 108 extends into the outlet chamber 102 such that the membrane abuts the end of the tube and provides a valve seat. An alternative or additional means by which the valve characteristics can be adjusted is by varying the distance the inlet tube extends into the chamber, and therefore how much the membrane is stretched or tensioned on the valve seat. The inlet pressure required to lift the membrane away from the valve seat is directly related to the amount the membrane is tensioned on the valve seat. In some embodiments, the inlet tube 108 may be movably coupled to the outlet chamber 102, for example in a sliding engagement, so that the inlet tube, and therefore the valve seat 104, can move relative to the membrane 105 and outlet chamber 102 to adjust the tension of the membrane when abutting the valve seat 104. FIG. 11A shows the inlet tube positioned in a first, less stretched position, where the membrane 105 is in a less tensioned state, and FIG. 11B shows the inlet tube positioned in a second, extended position, where the membrane is in a more tensioned state. Experimental data for different amounts of tube extension into the outlet chamber is shown in FIG. 8. Pressure curve 126 is the inlet pressure (Pc) of the PRV with the inlet tube in a non-extended position, curve 127 is the inlet pressure (Pc) of the PRV with the inlet tube initially extended beyond a first position, curve 128 is the inlet pressure (Pc) of the PRV with the inlet tube extended beyond a first extended position, curve 129 is the inlet pressure (Pc) of the PRV with the inlet tube extended beyond a second extended position, and curve 130 is the inlet pressure (Pc) of the PRV with the inlet tube extended beyond the second extended position to a further extended position. FIG. 8 shows that a greater opening pressure is obtained when the membrane tension is increased by the extension of the inlet tube into the outlet chamber. In practice, movement of the inlet tube relative to the chamber 102 or valve member 105 may be achieved by moving the chamber 102 and / or the valve member relative to the tube, i.e., the position of the inlet tube is fixed relative to other system or valve components. For example, the valve member may be attached to the chamber by a threaded interface, and adjusting the position of the valve member within the chamber adjusts the relative position of the valve member with respect to the valve seat. For example, as shown in FCPRV of FIG. 18B, the chamber 102 may include an adjustment mechanism for moving the valve member with respect to the valve seat.

[0201] In some embodiments, the inlet tube may be fixed to the breathing gas supply system, and the membrane, along with the outlet chamber, may be moved relative to the tube, which remains attached in place to the gas supply system, to adjust the relative position of the membrane and the valve seat.

[0202] As discussed above, the valve member may be fixed to the chamber 102, which may be in sliding engagement with the inlet tube 108, although other configurations may be possible. For example, in some embodiments, the inlet tube may engage the outlet chamber by a threaded mechanism or a bayonet fitting. A user may rotate the outlet chamber relative to the inlet tube, causing the membrane to press further onto the abutting end of the inlet tube, thereby moving the outlet chamber and membrane longitudinally relative to the inlet tube. The adjustment mechanism may provide discrete adjustment steps (e.g., corresponding to known pressure settings) or a continuous adjustment range without steps.

[0203] The inlet pipe cross-sectional area and / or valve seat area may affect the performance of the PRV. For example, the smaller the inlet pipe area or valve seat area, the smaller the area of ​​the membrane over which the inlet pressure acts, and the smaller the area, the more inlet pressure is required to lift the membrane away from the valve seat. Also, the ratio of the inlet pipe or valve seat area to the total membrane area may affect the performance of the PRV at a given membrane tension, and changes in membrane size may also result in changes in tension, further altering valve performance.

[0204] In the embodiments described herein, the area of ​​the valve member against which the pressure in the outlet chamber acts is greater than the area of ​​the valve seat / inlet (the area against which the inlet pressure acts when the valve member is seated on the valve seat). The larger the area of ​​the valve member, the greater the force that the pressure in the outlet chamber Pb exerts on the valve member, and therefore the greater the effect that the pressure in the outlet chamber has to push the valve member off the seat. The shape of the inlet pipe cross section or valve seat may also affect the performance of the PRV.

[0205] The material and / or geometry of the membrane may be determined to achieve particular valve characteristics. For example, the geometry, cross-sectional shape, and area of ​​the membrane all together determine the spring constant or tension of the membrane. Furthermore, the amount of tension in the membrane may be set during manufacture by setting the amount of stretch of the membrane during assembly of the PRV. Additionally, the amount of tension of the membrane against the valve seat affects the performance of the PRV, as discussed above in connection with the movable inlet tube.

[0206] In the above embodiment, the valve member is a membrane. In another embodiment, the valve member may comprise a plunger type valve member. Referring to Figures 9A-9C, the PRV 200 shown includes an inlet 201, an outlet chamber 202, a valve seat 204 between the inlet and outlet, and a plunger type valve member 205 biased to seal against the valve seat 204. The plunger type valve member is biased by a biasing member 210 (spring) to seal against the valve seat. An outlet 203 from the outlet chamber is provided between the periphery of the valve member 205 and a wall 206 of the outlet chamber. The outlet 203 is open to ambient or atmospheric pressure, i.e., the open or displacement side 207 of the chamber towards which the valve member faces can be referred to as the displacement chamber 207, and the displacement chamber is open to atmospheric pressure. The PRV 200 may include a housing 206. The outlet chamber may be considered to be the pressurized side 202 of the housing, and the displacement chamber may be considered to be the circumferential side 207 of the housing. The boundary between the pressurized and ambient sides of the housing moves as the plunger moves. Ambient pressure (atmospheric pressure) acts on the non-pressurized side 212 of the plunger. The non-pressurized side is the side of the plunger opposite the side that seals against the valve seat. The inlet 201 may include an inlet tube 208 that extends into the outlet chamber, for example as described with reference to previous embodiments including a membrane valve member.

[0207] The valve member 205 is adapted to be displaced from the valve seat by an inlet pressure Pc increasing beyond a pressure threshold. The pressure Pc acts on the valve member and forces the member away from the valve seat 204 when the pressure Pc reaches the threshold, for example as shown in FIG. 9B. As the member is displaced from the valve seat 204, gas flow flows from the inlet 201 to the outlet chamber 202 and then from the outlet chamber through an outlet 203 defined between the plunger 205 and a wall 206 of the chamber. The outlet 203 from the chamber 202 is configured such that the gas flow through the outlet 203 creates a (back pressure) pressure Pb in the outlet chamber 202 that acts on the valve member 205 and further displaces the valve member 205 from the valve seat 204, for example as shown in FIG. 9C. As the flow in the PRV increases, the back pressure in the outlet chamber increases and the gap 209 between the valve seat 204 and the valve member 205 further increases. Finally, the pressure Pc in the inlet pipe 208 and the pressure Pc in the outlet chamber 202 B tend to be equal. When the pressure in the outlet chamber Pb and the inlet pressure Pc tend to be equal, the pressure drop from the inlet 201 to the outlet chamber decreases and the pressure drop in the PRV becomes predominant at the outlet 203 from the outlet chamber 202. In other words, the pressure drop in the PRV becomes predominant from the outlet chamber 202 to the ambient. Once the pressure drop from the outlet chamber to the ambient becomes predominant, the pressure Pc at the inlet of the PRV (i.e. the pressure drop in the PRV) then increases progressively according to a "square law". The embodiments of Figures 9A-9C are therefore able to achieve the properties described above with reference to Figures 3-5.

[0208] 10A and 10B, in another plunger type pressure relief valve, the outlet from the PRV may be provided by one or more apertures 203b (FIG. 10A) in the valve member 205, or the PRV may include an outlet 203c from the outlet chamber 202. In the embodiment of FIGS. 10A and 11B, the plunger valve member 205 is a piston forming a sliding seal with the wall 206 of the outlet chamber 202. However, in an embodiment that includes a piston in a sliding relationship with a cylinder housing, there may be a flow path between the piston and the cylinder, for example, by a channel in the cylinder wall or by a cutout or notch in the periphery of the piston. Such a flow path between the piston and the cylinder may be in addition to the apertures in the piston.

[0209] Other features of the membrane valve described above may equally apply to plunger-type valves such as the PRV described with reference to Figures 9A-10B. For example, one end of the spring may be fixed relative to the chamber 202 and the inlet tube 208 may be adjustable relative to the chamber 202 to change the tension that the spring 210 exerts on the plunger 205. With reference to the embodiment of Figures 10A and 10B, the area of ​​the outlet apertures 203b, 203c in the plunger or in the chamber wall may be adjustable. Additionally or alternatively, the tension or compression of the biasing member (e.g., spring) may be adjustable. In the figures, the spring 210 is shown as a tensioned spring (which may be a coil spring or a diaphragm member or any other spring element connected to the valve member), but in another embodiment, a compressed spring (a compressed coil spring, a rubber block, or a leaf spring, or any other spring element) may act on the opposite side of the valve member.

[0210] 12A is a cross-sectional view of a prototype valve, as an example of a valve according to some described embodiments, having the following dimensions:

[0211] The seat diameter and / or inlet diameter is 20 mm. In some embodiments, the seat diameter and / or inlet diameter may be in the range of 5 mm to 100 mm. Note that the seat area is considered to be the area bounded by the seat diameter (D in FIG. 13A). Thus, at a seat diameter of 20 mm, the seat area is approximately 315 mm. 2 It is.

[0212] Thus, at a valve seat diameter of 20 mm and a valve member diameter of 60 mm, the ratio of valve member area to valve seat area is approximately 9.

[0213] The outer diameter of the membrane is 60 mm. In some embodiments, the membrane diameter may be in the range of 10 mm to 200 mm.

[0214] The exit area from the chamber is 54 mm 2 , 108mm 2 , and 162mm 2 (8.3 mm diameter aperture). The aperture does not have to be round / circular. These areas correspond to the valves that provided the data shown in Figures 3, 4 and 5, respectively. In some embodiments, the exit area is 12 mm 2 ~200mm 2 may be in the range.

[0215] For a silicone film or material with comparable properties, the film thickness is 0.3 mm. In some embodiments, the film thickness may be in the range of 0.05 mm to 1 mm.

[0216] The volume of the outlet chamber is 32 mL.

[0217] The volume of the displacement chamber is 55 mL (which should be sufficient so as not to restrict the valve member unless restriction is desired).

[0218] In some embodiments, the ratio of membrane diameter to membrane thickness may be in the range of 20 to 2000 (e.g., membrane diameter 20 mm and thickness 1 mm to membrane diameter 200 mm and thickness 0.1 mm). Another representative ratio of membrane diameter to membrane thickness is 50 at a diameter of 10 mm and thickness of 0.5 mm.

[0219] In some embodiments, the ratio of the area of ​​the valve member 105, 205 to the area of ​​the inlet or valve seat 104, 204 may be in the range of 1.2 to 1600 (eg, membrane diameter 20 mm and inlet diameter 18 mm to membrane diameter 200 mm and inlet diameter 5 mm).

[0220] In some embodiments, the PRV is adapted to maintain an opening pressure range of less than 5 cmH2O over a flow range of 100 L / min through the PRV.

[0221] In some embodiments, the PRV may include at least two outlet chambers in series. For example, in some embodiments, the PRV may include a first outlet chamber having a first outlet and a second outlet chamber having a second outlet. The second outlet chamber receives the gas flow from the first outlet.

[0222] The valve member may be displaced from the valve seat by the inlet pressure at the inlet increasing above a pressure threshold to allow the gas flow from the inlet to the first outlet chamber. The gas flow is then routed from the first outlet chamber through the first outlet to the second outlet chamber and then through the second outlet to the second outlet chamber. The first and second outlets may each include multiple apertures in the wall of the respective first or second outlet chamber. The outlet pressure (back pressure) in the first outlet chamber acts on the valve member with the inlet pressure by the gas flow through the first and second outlets, further displacing the valve member from the valve seat. Having two or more outlet chambers in series may provide additional advantages in tuning the PRV to achieve a desired pressure release profile. The outlet resistance provided by each of the first and second outlets may be adjustable in some embodiments, as described above with reference to the single outlet chamber embodiment.

[0223] In some embodiments, the PRV may include at least two outlet chambers, for example, in parallel as shown in FIG. 2D. When the valve member 105 lifts from the first valve seat 104-1, the exhaust flow may first flow through the exhaust outlet(s) 103-1 of the first chamber 102-1. When the pressure Pb-1 in the first chamber builds up to a threshold, the valve member may then lift from the second valve seat 104-2 and flow to the second outlet chamber 102-2 and be exhausted through at least one exhaust outlet 103-2 of the second outlet chamber 102-2. Alternatively or additionally, the valve may include an aperture or flow passage 102a between the first and second outlet chambers. The flow through the first exhaust outlet 103-1 creates a back pressure Pb-1 in the first chamber 102-1 acting on the valve member. Flow through the second exhaust outlet 103-1 creates a back pressure Pb-2 in the second chamber 102-2 acting on the valve member.

[0224] A PRV according to the embodiments described above may have several advantages over prior art valves. In prior art valves, once a pressure release threshold is exceeded and as the flow rate increases, the pressure in the system increases progressively in proportion to the flow. As a result, the patient and system components may be exposed to increasingly higher pressures as the flow rate increases. In a PRV according to the embodiments described herein, as the valve member lifts off the valve seat, a pressure P B is generated, acting on the valve member to further reduce the flow restriction of the valve seat. This can have the beneficial effect of offsetting the point at which the pressure drop across the PRV begins to increase. Thus, the "useful operating range" of the valve can be extended over a wider range of flow rates than those of prior art valves.

[0225] In embodiments including a membrane valve member, the membrane has a low spring constant that acts similarly to a very long, soft spring. A low spring constant may be desirable to substantially reduce the flow resistance of the valve. Additionally, the membrane provides design flexibility, allowing, for example, valves of shorter length to achieve a low spring constant compared to valves that use longer springs.

[0226] Additionally, the membrane advantageously serves simultaneously as a valve member, a valve actuation or biasing member (e.g., replacing the need for a spring in addition to the valve member and sealing member). As a result, manufacturing costs may be significantly reduced, no lubrication of moving parts is required, which is useful for preventing contamination, and the membrane provides a reliable seal under tension (even at low tensions).

[0227] In use, the low mass of the membrane (i.e., it is lightweight) results in minimal vibration of the membrane. In particular, the low mass of the membrane provides low inertia in the movement of the membrane compared to prior art valves having plunger-type valve members that can vibrate or rattle / rattle. Low inertia also means that gravity, and therefore orientation, has minimal effect on the operation of the valve.

[0228] In some embodiments described herein, the characteristics of the PRV may be adjusted or tuned. For example, the outlet area of ​​the outlet chamber and / or the tension of the membrane of the biasing member may be adjusted (e.g., by adjusting the relative position of the inlet tube / valve seat and the valve member) to tune the performance of the valve. It may be desirable to tune the valve so that the pressure release characteristics of the valve are approximately constant over a range of flow rates. Adjustability gives the user of the system more flexibility. In some embodiments, two or more features of the valve may be adjusted simultaneously. For example, adjusting the membrane tension by screwing a portion of the valve body against the valve seat may simultaneously change the size of the exhaust outlet from the valve body. For example, when setting a higher pressure, the operating flow range may also be extended by increasing the outlet area. In a further example, changing the membrane tension by translating the position of the valve seat by moving the inlet tube 101 may simultaneously change the size of the flow restriction 152.

[0229] In the above described embodiments, a back pressure Pb acts on the valve member. The back pressure is created by a flow restriction provided by the exhaust outlet(s) or exhaust outlets 103. In some embodiments, the exhaust outlet may be large enough that little or no back pressure is created on the valve member, in which case the ambient pressure acts on the valve member outside the valve seat area (FIG. 2A) or on the valve seat area (FIG. 13A). In such valves, the pressure required to lift the valve member is determined by the bias of the valve member against the valve seat. In preferred embodiments including a membrane valve member, the membrane exhibits a low spring constant so that a relatively "flat" or "constant" exhaust pressure can be achieved. Furthermore, a low spring constant is achieved with a low valve height. In some embodiments, the valve member may be biased against the valve seat by a diaphragm membrane, or the valve member is or includes a diaphragm / membrane. Such a valve may be configured as shown in FIG. 12A, but with a large outlet discharge aperture 103 such that flow from the outlet 103 does not create a back pressure Pb.

[0230] The valve may be adjusted or set to a "safe" pressure for different patient populations (i.e. adults, neonates, etc.) that may exhibit different airway flow restrictions. This may be set by medical personnel at the time of manufacture or prior to use. Additionally, adjustment of the valve characteristics may allow the valve to be used in other (non-respiratory) systems.

[0231] In some embodiments, the PRV may be adapted for use as a pressure regulating device to provide peak end expiratory pressure (PEEP) and peak inspiratory pressure (PIP), for example, for use in pediatric resuscitation. FIG. 1A shows a system including a flow source 12, an optional PRV 100-1 providing a patient safety pressure limit, a pressure gauge to indicate pressure to a medical professional (e.g., a nurse), and a PRV 100-2 configured to provide PEEP and PIP provided at or near a mask 115. The PRV 100 configured to provide PEEP and PIP includes at least one outlet vent 103a that can be occluded by the professional, i.e., by a finger, and at least one outlet vent 103b that cannot be occluded. There may be a cover or baffle 103c on the vent 103b to prevent the professional from blocking / occluding the vent 103b. The flow diagram depicted in FIG. 1A describes a method for adjusting or configuring the valves to provide PEEP and PIP. In step 41, a mask seal with the mask 115 is created, and in step 42, an input flow rate is set for the flow source to provide a gas flow to the mask 115. In step 43, the professional blocks the accessible / occludable outlet vent 103a with a finger, acting to reduce the opening pressure of the valve by back pressure against the valve member. The valve is then adjusted in step 44 to achieve the desired PEEP, for example by adjusting the valve member bias and / or adjusting the size of the non-occludable outlet vent 103b. In step 45, the outlet vent 103a is unblocked, and in step 46, the occludable outlet vent 103a is adjusted to achieve the desired PIP pressure. Thus, in use, the medical professional blocks the occludable exhaust outlet to provide PEEP and unblocks the occludable vent to provide PIP. A PRV adapted for use to provide PEEP and PIP may replace prior art devices used for this purpose, such as those described in WO 03 / 066146.

[0232] In the valves of the present invention, leakage from the valve may have little effect on the operation of the valve, since leakage only provides the equivalent of additional outlet area. Therefore, leakage contributes more to the effect of the outlet hole. That is, leakage from the outlet chamber reduces the resistance to flow out of the outlet chamber, reducing the amount of back pressure acting on the valve membrane, "pushing" it further away from the abutting inlet tube. Examples of "leaks" may include, although unlikely, small fluid passages around the edges of the membrane that are unintentionally formed during assembly (i.e., where the membrane is pinched between the halves of the valve chamber), or leaking valve members, or leaking bayonet / screw features for providing pressure adjustment.

[0233] Flow Compensated Pressure Relief Valve (FCPRV) 300 The maximum pressure, and therefore the flow rate that can be delivered to the patient, is limited by the set opening pressure of the pressure relief valve. The pressure loss in the system may vary for a given flow rate during use. For example, the tube may bend, bend, fold, or collapse during use, or different patients may exhibit different airway restriction characteristics. If the tube is folded or collapsed or otherwise partially occluded, the partial occlusion presents an additional flow restriction to the system. An additional pressure loss is created at the partial occlusion, and the flow rate in the system is reduced. In a system configured to deliver a specific flow rate (rather than a specific pressure), e.g., a high flow rate system, the flow source may increase the system pressure to offset the additional pressure loss due to the partial occlusion and maintain a set or desired flow rate. The amount by which the system pressure or driving pressure can be increased to maintain a desired flow rate is limited by the opening pressure provided by the PRV. It may be desirable to provide a pressure relief valve that compensates for the pressure loss in the system, so that the maximum flow rate in the system is not limited by the opening pressure of the PRV. Such a valve extends the range of flow rates that can be delivered to the patient. Thus, in some embodiments, it may be desirable to have a PRV with an opening pressure that is dependent on the flow rate in the system, such that the opening pressure increases as the flow rate increases to offset additional or variable pressure losses in the breathing system. In some embodiments, the pressure relief valve compensates for pressure losses in the system so that the maximum flow rate in the system is not limited by the opening pressure of the PRV and ensures that the patient is protected from overpressure.

[0234] 14A and 14B show a flow-compensated pressure relief valve or device 300 (FCPRV) that dynamically adjusts its opening pressure in proportion to the flow rate in the system. An exemplary characteristic of the FCPRV 300 is shown in FIG. 15A. Referring to FIG. 15A, an ideal open valve opening pressure may be 20 cmH2O, as shown by line 140. A breathing system, for example, the system 10 of FIG. 1, has a system pressure loss versus flow characteristic shown by curve 141 in FIG. 15A, where the pressure loss in the system increases as the flow rate in the system (e.g., from the flow source to the patient and surroundings) increases. The pressure loss curve 141 shows the system pressure loss (without any occlusion) from the FCPRV to the nasal cannula, or in other words, the pressure at the FCPRV (Pc). For an opening pressure of 20 cmH2O, the maximum flow rate that the system can deliver to the patient is about 75 L / min, as shown by the point where the system pressure versus flow curve 141 intersects the 20 cmH2O opening pressure line 140. If there are additional occlusions in the system, the pressure loss in the system will increase beyond curve 141 and the maximum flow rate deliverable to the patient for a given maximum opening pressure of 20 cmH2O will decrease.

[0235] In FIG. 15A, pressure vs. flow curve 142 shows an exemplary pressure release vs. flow curve for an FCPRV configured as shown in FIG. 14A and FIG. 14B. As shown, in the configuration shown in FIG. 14A and FIG. 14B, the opening pressure (curve 142) increases with increasing flow rate. In FIG. 15A, the opening pressure 142 tracks the opening pressure of the system pressure vs. flow curve 141. This shows that the valve is matched to the system pressure loss due to flow resistance. In the illustrated embodiment, the pressure release level is consistently 20 cmH2O above the system pressure loss. As will be explained in more detail below with reference to FIG. 15B, the offset between curve 141 and curve 142 (20 cmH2O in FIG. 15A) is the maximum pressure to which the patient can be exposed.

[0236] The FCPRV 300 shown in Figures 14A and 14B includes the PRV 100 as previously described. The FCPRV 300 further includes a pressure sensing mechanism 150 for dynamically adjusting the pressure threshold at which the PRV 100 vents pressure based on the flow rate of gas passing through the FCPRV 300. In the illustrated embodiment, the sensing mechanism 150 includes a flow restriction or flow restriction 152 between the primary inlet 151 and primary outlet 153 of the FCPRV. For ease of reference, the term "flow restriction" may be used herein to describe both flow restrictions such as orifice plates and flow restrictions such as those used in venturis. In operation, gas flow in the breathing system flows through the device 300 from the primary inlet 151 to the primary outlet 153. The flow restriction 152 is downstream of the valve inlet 101 of the pressure relief valve 100 and therefore senses flow to the patient or through the primary outlet of the valve. The sensing mechanism 150 also includes a sensing chamber 154 and a sensing member 155 located within the sensing chamber 154. The sensing member 155 divides the sensing chamber 154 into a first chamber 154a and a second chamber 154b. The first chamber 154a is in fluid communication with the gas flow upstream of the flow restriction 152, e.g., the first chamber 154a is in fluid communication with the main inlet 151 and the valve inlet 101 upstream of the restriction 152. The second chamber 154 is in fluid communication with the gas flow at or downstream of the flow restriction 152. In the illustrated embodiment, the device includes a flow restriction configured as a venturi, and the second chamber 154b is in fluid communication with the restriction via a pressure "tap" or passageway 156. However, in alternative configurations, the device may include a flow restriction 152, e.g., an orifice plate, and the first and second chambers may be connected remotely on opposite sides of the orifice plate. The pressure difference may be generated in any other suitable manner, e.g., by a permeable membrane or filter with a known pressure drop (flow restriction).

[0237] The pressure drop caused by the flow of gas from the primary inlet 151 to the primary outlet 153 of the device and through the restriction 152 is thus sensed by a sensing member 155 located in the sensing chamber 154. To increase the flow rate in the respiratory system, the pressure provided by the flow source 12 is increased, increasing the pressure at the PRV inlet 101 and also the pressure in the first chamber 154a of the sensing chamber 154. This pressure is shown in Figure 14A as Pc. Furthermore, as the flow rate increases, the increased velocity of the gas passing through the restriction 152 creates a larger pressure drop through the restriction 152 and the pressure Pv in the second chamber 154b of the sensing chamber 154 decreases. Thus, an increase in flow rate through the device 300 from the primary inlet 151 to the primary outlet 153 results in an increase in the pressure differential across the sensing member 155, with the first chamber 154a becoming the high (higher) pressure side of the sensing chamber 154 and the second chamber 154b becoming the low (lower) pressure side of the sensing chamber 154. This causes the sensing member 155 to move away from the pressure relief valve 100 and towards the low pressure side of the sensing chamber 154.

[0238] The sensing member 155 is mechanically coupled to the valve member of the pressure relief valve such that as the sensing member 155 moves towards the lower pressure side of the sensing chamber 154, the sensing member 155 pulls or biases the valve member 105 of the PRV 100 against the valve seat 104. Thus, the sensing member 155 biases the valve member 105 against the valve seat 104 in response to the flow rate of gas flow through the device 300 from the primary inlet 151 to the primary outlet 153. In some embodiments, the sensing member 155 is coupled to the valve member 105 by a mechanical link 157, e.g., a flexible member such as a cord or wire (e.g., nylon line) or a rigid member such as a rod or shaft. In some embodiments, the mechanical link can transmit only tension (e.g., a wire or separate shaft) or both tension and compression (e.g., a shaft).

[0239] In a preferred embodiment, the sensing member is a membrane 155 that may be constructed in a manner similar to the valve member 105 of the pressure relief valve described above, but without a valve seat or inlet tube within the sensing chamber 154. Alternatively, the sensing member 105 may be a plunger or piston that pneumatically separates the first and second chambers and moves within the sensing chamber 154 due to a pressure differential provided by a flow restriction or constriction.

[0240] In a preferred embodiment including a membrane sensing member, an increasing pressure differential between the first chamber 154a and the second chamber 154b causes the sensing membrane 155 to expand or expand toward the low pressure side of the sensing chamber, tensioning the PRV valve member 105, via a mechanical link 157 with the valve member 105, as shown in FIG. 14B, such that the opening pressure provided by the PRV 100 increases proportional to the flow rate in the FCPRV from the primary inlet 151 through the restriction 152 to the primary outlet 153.

[0241] 15B, four operational stages of the FCPRV 300 are described. In stage 1, indicated by point 1 on the system pressure loss line 141, the breathing system is providing gas flow to the patient, and all (or substantially all) flow provided from the flow source 12 to the primary inlet 151 of the FCPRV 300 is delivered to the system from the primary outlet 153 of the FCPRV 300. At point 1, the total pressure in the system drops, so that very low or ambient pressure is delivered to the patient. As the flow rate delivered to the patient is adjusted, for example by the user, up or down, the pressure release threshold of the PRV 100 changes along the release pressure vs. flow rate curve 142, and as the flow rate to the patient increases, the increasing differential pressure sensed by the sensing member 155 acts on the valve member 105 to increase the PRV vent threshold pressure 142.

[0242] At a given flow rate setting (90 L / min in FIG. 15B), the flow rate may decrease instantaneously in stage 2 in the event that a flow rate restriction is introduced into the system 12, for example, by a partial blockage of the patient inhalation conduit 14, or by crushed nasal prongs of the nasal cannula patient interface 15, or more importantly, by a blockage in the patient between the nasal prongs and the patient's nares. However, in a set flow system, the flow source 12 adjusts (rapidly) to increase the pressure in the system to maintain the flow rate at the desired level. The decrease in flow rate and the subsequent increase in pressure due to the flow source's response to maintain the set flow rate of the FCPRV may be substantially instantaneous, i.e., very quickly, and therefore negligible. As the flow rate is maintained, the pressure differential created by the flow restriction or restriction 152 of the FCPRV 300 remains constant, the bias applied to the valve member 105 by the sensing member 155 remains constant, and therefore the opening pressure threshold of the PRV 100 remains constant. However, as the system pressure increases (e.g., due to increased pressure in the patient's airway / nose), the pressure Pc acting on the valve member 105 (and the sensing member 155 on the high pressure side of the sensing chamber 154) increases toward the opening pressure of the PRV 100. This situation is illustrated by vertical arrow 2 in FIG. 15B. If partial occlusion is maintained and an equilibrium condition is reached, a higher system pressure vs. flow curve will result, illustrated by curve 141b in FIG. 15B, and the offset between the higher system pressure vs. flow curve 141b and the PRV opening pressure vs. flow curve 142 will be smaller. For example, at partial occlusion between the nasal prongs and the patient's nose resulting in an increase in system pressure 141b, the pressure created in the patient's nose is the offset between curve 141b and curve 141.

[0243] In stage 3, an introduced flow restriction (e.g., a collapsed conduit 14 or a blockage in the patient's nose) increases the system pressure required to maintain the desired flow rate for a given flow rate (approximately 90 L / min in FIG. 15B) to a level that exceeds the opening pressure 142 of the flow compensation relief valve. When the system pressure (e.g., Pc) of the FCPRV 300 exceeds the flow compensation relief pressure 142, the PRV 100 begins to drain and a portion of the flow provided to the primary inlet 151 is drained through the PRV 100 and a portion of the flow that passed through the restriction 152 is drained through the primary outlet 153. The flow source maintains the set flow rate at the primary inlet of the FCPRV. Thus, as the PRV 100 begins to drain, the flow rate in the suppression or restriction 152 decreases and the differential pressure acting on the sensing member 155 decreases. This reduces the bias applied by the sensing member 155 to the valve member 105 via the mechanical link 157 and therefore reduces the pressure relief threshold of the PRV 100. This situation is indicated by arrow 3 on the pressure relief versus flow curve 142 in Figure 15B. In an ideal situation, an equilibrium state is reached where the patient receives as much flow as possible without exceeding the pressure relief threshold or exceeding the maximum delivery pressure of the patient interface.

[0244] In stage 4, indicated by point 4 in FIG. 15B, a flow restriction introduced into the system may completely (or substantially completely) block the system, for example, the conduit 14 is completely occluded (completely crushed or pinched shut) or the patient's nose is completely blocked. All flow delivered to the primary inlet 151 of the FCPRV 300 is exhausted through the PRV 100. With no flow through the device 300 from the inlet 151 to the outlet 153, and therefore no flow through the restriction / constraint 152, the pressures in the first chamber 154a and the second chamber 154b are equal and the sensing member 155 exerts a minimal bias on the valve member 105. Changes in pressure Pc do not change the differential pressure across the sensing membrane 155. The PRV 100 operates as described above in connection with the previous embodiment without the sensing mechanism 150 (e.g., with reference to FIGS. 2A-2C), but may have a higher pressure threshold due to coupling to the sensing member 155. In this state, the two membranes act as two springs in series.

[0245] Thus, in a situation where the patient's nose is blocked, the maximum pressure the patient can receive is the offset between the opening pressure curve 142 and the system pressure loss curve 141, protecting the patient from overpressure. For example, in FIG. 15B, this maximum patient pressure is 20 cmH2O. Thus, the FCPRV provides a flow-dependent exhaust pressure threshold, but simultaneously sets an upper pressure limit to which the patient can be subjected. The FCPRV 300 must be able to exhaust the maximum flow provided by the flow source 12 to reliably exhaust the system to return the flow to the patient along curve 142 to zero, otherwise a patient pressure higher than the offset pressure shown may result.

[0246] The operation of the FCPRV described above is for a system that delivers a gas flow to a user through a non-sealing patient interface, such as a nasal cannula that does not seal against the patient's nose. The source of gas in such a system may be a compressed gas tank, or a hospital wall flow meter supply, or a blower capable of delivering sufficient flow rate, or other suitable source capable of providing rapid response to changes in system resistance and maintaining the set flow rate of the system. A system including the FCPRV 300, a humidifier 17, a filter 5, and a flow meter 12 that delivers a set flow rate of gas to a patient through a non-sealing nasal cannula 15 is shown in FIG. 1AA. Such a system may be particularly adapted for the delivery of nasal high flow therapy.

[0247] The FCPRV may also be used in conjunction with a flow source to provide continuous positive airway pressure in a respiratory system. A CPAP system including an FCPRV is shown in Fig. 1B-1 and Fig. 1B-2, and the characteristics of the FCPRV in such a system are shown by the graph in Fig. 1B-3. The system includes a flow source 12, such as a compressed gas tank or a hospital wall flow meter supply, an FCPRV 300, a humidifier, and a sealing patient interface, such as a face mask that seals over the patient's mouth and nose, and an interconnecting hose or conduit. The sealing mask allows a bias flow of gas from the mask and has a bias flow hole to flush CO2 / exhaled gas. In the CPAP system, the input flow is set to exceed the peak inspiratory demand and mask leakage and the bias flow, and the FCPRV is configured to continuously exhaust a portion of the gas supplied by the flow source. The flow rate provided by the flow source 12 provides a pressure Pc of the PRV sufficient to lift the valve member 105 from the valve seat and allow the exhaustion of a portion of the gas during normal CPAP therapy. Therefore, the pressure (Pc) of the FCPRV during CPAP therapy is the FCPRV discharge pressure shown by line 142 in FIG. 1B-3. When the patient inhales, as shown in FIG. 1B-1, the flow in the main flow path of the FCPRV and to the patient is at its maximum, and a relatively high differential pressure is sensed by the sensing member 155, causing a corresponding higher opening pressure of the FCPRV. Since the FCPRV is adjusted so that there is a nearly consistent offset pressure between the flow resistance of the system and the discharge pressure of the FCPRV, the pressure at the patient remains constant, which is shown by the pressure difference between line 141 and line 142 in FIG. 1-B3. In FIG. 1-B3, curve 141 shows the pressure loss from the FCPRV to the patient interface. During inhalation, a relatively low flow is discharged in the FCPRV, and the pressure FCPRV is directed to the right end of the arrow on line 142 in FIG. 1B-3.

[0248] When the patient finishes inhaling, the flow rate in the valve decreases to a low level equal to the bias flow and / or leakage flow at the patient interface. The discharge pressure of the FCPRV decreases due to the reduced pressure difference across the sensing member caused by the low flow rate. The system pressure loss also decreases due to the reduced flow rate. Thus, a relatively high flow rate is discharged at the FCPRV, and the pressure at the FCPRV moves toward the left end of the arrow on line 142 in FIG. 1B-3. Toward the left end of the arrow on line 142, nearly all of the flow accepted by the main inlet of the FCPRV is discharged at the FCPRV, and only a small flow exits the main outlet of the FCPRV due to the bias flow and / or leakage in the system.

[0249] When the patient exhales, flow reverses within the FCPRV as well as exiting through the biasing holes / mask leaks as appropriate. The result of exhalation reversal flow in the FCPRV can cause a pressure increase in the primary outlet that offsets any pressure reduction by the FCPRV venturi, resulting in a low differential pressure at the sensing member and causing a relatively high flow rate to exit the FCPRV such that the pressure in the FCPRV is toward the left end of the arrow on line 142.

[0250] Thus, a set flow gas source may be used with the FCPRV described herein that is adjusted to continuously discharge to provide a constant pressure to the patient. The pressure to the patient, shown as the difference between lines 141 and 142 in FIG. 1B-3, is maintained as the valve cycles pressure along line 142, as shown by the arrow. Changes in the discharge flow of the FCPRV result in changes in flow to the patient to achieve a constant patient pressure during the respiratory cycle.

[0251] In a CPAP system, the flow source must be able to deliver more than the maximum inspiratory flow rate, otherwise the pressure at the FCPRV will drop below the set exhaust pressure, reducing pressure to the patient. The vertical dashed lines in Figure 1B-3 indicate the boundaries of the FCPRV required by the maximum flow rate delivered by the flow source and the minimum flow rate, which is the bias flow and / or leakage from the system, i.e., leakage at the patient interface. The FCPRV opening pressure cycles between these boundaries.

[0252] The FCPRV may also be used in a respiratory system to provide bi-level continuous positive airway pressure. A bi-level pressure system including an FCPRV is shown in Fig. 1C-1 and Fig. 1C-2, and the characteristics of the FCPRV in such a system are shown by the graph in Fig. 1C-3. The system includes a CPAP source gas source 12a (i.e., a constant pressure source CPAP blower), an FCPRV 300, a humidifier, a sealing patient interface such as a face mask that seals over the patient's mouth and nose, and an interconnecting hose or conduit. The sealing mask may have a bias flow hole to allow a bias flow of gas from the mask and to flush CO2 / exhaled gas. The FCPRV is located near the patient interface so that there is low flow resistance between the FCPRV and the patient.

[0253] Unlike the system of Figures 1B-1 and 1B-2, in which the FCPRV is adjusted to achieve a consistent offset between the FCPRV opening pressure 142 and the system pressure loss 141 from the FCPRV to the patient, in the system of Figures 1C-1 and 1C-2, the FCPRV is adjusted so that the opening pressure curve 142 diverges from the system pressure loss curve 141 as flow rate increases, as shown in Figure 1C-3.

[0254] As the patient inhales, flow through the FCPRV causes the sensing member to keep the valve member sealed against the valve seat, preventing the FCPRV from expelling, and providing the patient with an inspiratory positive airway pressure equal to the CPAP pressure provided by the gas source. This pressure level is indicated by the top horizontal pressure line in Figure 1C-3.

[0255] When the patient inhales, the maximum inhalation flow occurs first, achieving IPAP at the patient. As the patient continues to inhale, the flow at the patient naturally decreases, and therefore the flow in the valve decreases. The discharge pressure of the FCPRV decreases due to the decrease in flow through the flow restriction of the FCPRV and the decrease in the differential pressure at the sensing member caused by the discharge of flow by the FCPRV. The pressure at the FCPRV is therefore the discharge pressure, which is the curve between the vertical pressure axis and the horizontal IPAP line in Figure 1C-3.

[0256] Towards the end of inspiration, the flow rate in the FCPRV to the patient decreases even further to a low level equal to the bias flow and / or leakage flow at the patient interface, and the pressure in the FCPRV, and therefore the pressure at the patient, continues to move to the left towards the vertical pressure axis in FIG. 1C-3, and the FCPRV exhausts more flow from the pressure gas source. As exhalation begins, there is no flow through the FCPRV as exhalation counteracts the bias flow, and the pressure in the FCPRV is shown by the crossing of the vertical pressure axis in FIG. 1C-3, and the FCPRV continues to exhaust flow from the system. As the patient continues to exhale, the pressure in the FCPRV, and therefore the pressure at the patient in effect (because the FCPRV is in close proximity to the patient) becomes the exhaust pressure of the FCPRV. Thus, the exhaust pressure of the FCPRV sets the expiratory positive airway pressure level of the bi-pressure system. Such a system may be used for patient resuscitation, for example, pediatric resuscitation.

[0257] A breath beginning with an inhalation and ending with an exhalation moves from right to left in Fig. 1C-3. A display of the pressure at the patient interface for multiple breaths is shown in Fig. 1C-4, where the time axis runs from right to left.

[0258] A further system configured for bi-level pressure therapy is shown in Figure 1C-5, in which the CPAP constant pressure source of the system of Figures 1C-1 and 1C-2 is replaced by a flow source 12 in combination with an FCPRV 300 to provide a constant pressure source for the CPAP system as described above with reference to Figures 1B-1 and 1B-2.

[0259] An FCPRV tuned or configured for use in a bi-level pressure system may also be configured to act as an anti-asphyxiation valve if flow to the patient stops, e.g., if the flow or pressure source becomes inoperable. The EPAP pressure level may be set for a particular flow rate in the FCPRV to the patient (i.e., communicated as a bias flow level) and may also be set to allow patient exhalation in the absence of flow in the FCPRV to the patient.

[0260] The FCPRV may also be used with a flow source to provide continuous positive pressure in surgical insufflation. A surgical insufflation system is shown in FIG. 1D. The system includes a flow source 12, such as a compressed gas tank or a hospital wall flow meter supply, an FCPRV 300, a humidifier 17, a trocar 215 for providing a humidified gas flow from the system to the patient's abdominal cavity, and a filter 216 for the gas flow exiting the abdominal cavity. The combination of the set flow source and the FCPRV provides a constant pressure as described above in the CPAP system, and a sealed patient interface as described above with reference to FIG. 1B-1, with flow characteristics as shown in FIG. 1B-3.

[0261] The FCPRV may also be used as an anti-asphyxiation valve in a breathing system. A ventilation or CPAP system including an FCPRV as an anti-asphyxiation valve is shown in Fig. 1E-1 and Fig. 1E-2. The system includes a CPAP source gas source (i.e., a constant pressure source CPAP blower) or a ventilator for providing a flow of gas to a user through a patient interface, such as a face mask that seals over the patient's mouth and nose. The sealing mask has a bias flow hole for flushing CO2 / exhaled gases through a bias flow of gas from the mask. The FCPRV 300 is preferably located near the patient interface so that there is low flow resistance between the FCPRV and the patient. During treatment, the ventilator or CPAP gas source provides a continuous positive pressure or alternating bilevel pressure. The valve is adjusted to remain closed during at least a portion of the normal inspiration period. When the patient exhales, the valve operates as described above for the bilevel system with reference to Fig. 1C-2. Alternatively or additionally, an expiratory limb may be provided. In the event that the ventilator or CPAP source breaks or fails, the CPAP source or ventilator flow path is opened, allowing the patient to "pull" inhaled air through the ventilator / CPAP source, the delivery conduit, and the patient interface, as shown in FIG. 1E-1. Because the FCPRV is located near the patient interface, the flow resistance from the patient to the FCPRV (R1) is lower than the flow resistance from the FCPRV to the CPAP source or ventilator (R2). Thus, as shown in FIG. 1E-2, when the patient exhales, most of the patient's exhaled air is exhausted from the FCPRV. Prior art breathing systems may include an anti-asphyxiation valve, e.g., a valve in the patient interface. Prior art anti-asphyxiation valves may include a flap valve mechanism that opens in the absence of pressure, and such valves may be affected by gravity depending on the orientation of the mask. The FCPRV according to the present invention is not affected by gravity or orientation.

[0262] Another system configuration for providing bilevel pressure for apneic (i.e., not spontaneously breathing) patients or for operating as a ventilator system is shown in Figures 1F-1 and 1F-2, and the FCPRV characteristics of such a system are shown by the graph in Figure 1F-3. The system includes a flow source 12, such as a compressed gas tank or a hospital wall flow meter supply, an FCPRV 300, a humidifier 17, a sealing patient interface 115, such as a face mask that seals over the patient's mouth and nose or a laryngeal mask airway (LMA) or an endotracheal intubation, and an interconnecting hose or conduit. The sealing mask 115 may have a bias flow hole to flush CO2 / exhaled gases through a bias flow of gas from the mask. The FCPRV is located near the patient interface so that there is low flow resistance between the FCPRV and the patient. However, the FCPRV may be located upstream of the humidifier or anywhere in the system.

[0263] In the system of Figures 1F-1 and 1F-2, the FCPRV functions in much the same way as the FCPRV used in the system for delivering constant pressure as described above in the CPAP system of Figures 1B-1, 1B-2, and 1B-3. In the system of Figures 1F-1 and 1F-2, the FCPRV is adjusted to be continuously discharged such that the pressure at the FCPRV is the discharge pressure and the patient pressure is equal to the FCPRV discharge pressure minus the system pressure loss from the FCPRV to the patient, i.e., the difference between curves 142 and 141 in Figure 1F-3. However, unlike the systems of 1B-1 and 1B-2, in which the FCPRV is adjusted to achieve a consistent offset between the FCPRV opening pressure 142 and the system pressure loss 141, in the system of Figures 1F-1 and 1F-2, the FCPRV is adjusted such that as the flow rate increases, the opening pressure curve 142 diverges from the system pressure loss curve 141, as shown in Figure 1F-3. Thus, as the system pressure at the FCPRV cycles back and forth along the pressure flow curve 142 of FIG. 1F-1, the pressure to the patient cycles between a relatively low pressure P1 and a relatively high pressure P2. As described with reference to FIG. 1B-3, when the patient inhales, the flow to the patient is at its maximum and a relatively high differential pressure is sensed by the sensing member 155, resulting in a corresponding higher opening pressure at the FCPRV. A relatively low flow is exhausted at the FCPRV, and the pressure at the FCPRV moves toward the right end of the arrow on the line 142 of FIG. 1F-3. The FCPRV pressure moves toward the left end of the arrow on the opening valve pressure curve 142 of FIG. 1F-3 as the patient finishes inspiration and begins expiration. The diverging FCPRV pressure curve causes the patient to experience high pressure during inspiration and low pressure during expiration to assist ventilation. The inventors have also discovered that by providing a significant pneumatic coupling between the sensing member 155 and the main gas flow path 158, the FCPRV can be made to operate in a relatively rapid response configuration such that the pressure in the FCPRV changes rapidly from the inspiratory pressure P2 and expiratory pressure P1, which is particularly useful for ventilating an apneic patient. The pneumatic coupling between the sensing member and the main gas flow path is described in more detail below with reference to Figures 27E and 27F.

[0264] An FCPRV configured for bilevel pressure as described with reference to Figures 1F-1-3 may also be used with a pediatric resuscitation PEEP / PIP device, such as those described in WO 03 / 066146. As described above, the FCPRV 300 is adjusted to continuously discharge. To provide a positive end-expiratory pressure, the medical professional blocks the discharge outlet of the patient interface (face mask) of the resuscitation device (e.g., Fisher and Paykel Healthcare's Neopuff® device). This serves to increase flow resistance and reduce the opening pressure of the FCPRV so that the FCPRV discharges and reduces the flow rate to the child to obtain a positive end-expiratory pressure (e.g., P1 in Figure 1F-3). To provide an inspiratory peak airway pressure, the medical professional unblocks the discharge outlet of the Neopuff® device to reduce the opening pressure of the FCPRV, for example, to obtain pressure P2 in Figure 1F-3. To adjust the FCPRV for this application, the patient interface face mask is sealed and the input flow rate from the flow source is set. The Neopuff® vent is occluded and the FCPRV is adjusted, for example, by adjusting the valve member bias to achieve the desired PEEP. The Neopuff® vent is then unoccluded and adjusted to achieve the desired PIP pressure.

[0265] In some embodiments, the flow compensating pressure relief valve 300 may be matched to the system's pressure loss under normal operating conditions, e.g., without any additional flow resistance added to the system, such as a blocked conduit. Such an arrangement is illustrated by the characteristics shown in Figures 15B and 1B-3. This ensures that the valve opening pressure is consistently offset from the system pressure loss, such that the pressure relief line 142 is consistently 20 cmH2O above the system pressure loss line 141, as shown, for example, in Figure 15B.

[0266] For example, as described above with reference to FIG. 1C-3 for a bilevel pressure system and FIG. 1F-3 for a ventilator system, in some applications a consistent offset may exist between the system pressure vs. flow curve 141 and the opening pressure vs. flow curve 142.

[0267] FIG. 17 provides a further example of the FCPRV characteristic of a set flow rate non-sealing patient interface system with no consistent offset between system pressure loss 141 and FCPRV opening pressure 142. In FIG. 17, curves 143 and 144 show FCPRV opening pressures that do not match the system pressure loss. The upper line 143 shows a dynamic adjustment opening pressure that progressively increases as flow rate increases. Such a characteristic may be desirable to compensate for anticipated partial circuit occlusions, such as bends. The lower line 144 shows a dynamic adjustment opening pressure that progressively decreases as flow rate increases, which eventually intersects with the system pressure loss (Pc) sensed by the FCPRV 300. In this example, the system is limited to delivering a flow rate of approximately 105 L / min, and at any flow rate higher than this the FCPRV will eject flow through the outlet vent. This is a practical option when the flow resistance of the systems cannot be matched. For example, if a single valve configuration is used in a variety of different systems, each with different flow resistances, matching the valve to the flow resistance of these systems may not be achievable. Thus, the lower curve maintains a safe pressure but limits the flow rate. This is acceptable when the flow rate limit exceeds the desired therapeutic flow rate. In either case, the mismatched opening pressure vs. flow rate curves 143 and 144 may be less desirable than the matched curve 142. In some embodiments, a dynamically adjusted opening pressure that progressively decreases as the flow rate from the inlet to the outlet of the FCPRV increases may be desirable. As the delivered flow rate increases, the pressure in the system (i.e., pressure-flow curve 141) increases. If the pressure in the system continues to increase, the system components (such as seals, humidifier chambers, tubing, or circuit connections, etc.) may eventually break due to overpressure. Therefore, it is desirable to have some upper limit to protect the system. More importantly, the point where curve 144 intersects with pressure-flow curve 141 provides a pressure upper limit for limiting the flow to the patient and therefore limiting the patient pressure to a safe level. The pressure-flow curve 141 is different in different systems. For example, a system with an adult cannula has a lower flow resistance compared to a pediatric cannula.Thus, the pressure-flow curve for a system with a pediatric cannula is "steeper" than the pressure-flow curve for a system with an adult cannula. Thus, the system pressure drop characteristics of a particular system must be determined to determine an appropriate upper limit for FCPRV (i.e., the shape of the pressure relief vs. flow threshold curve 142 must be adjusted so that the pressure relief vs. flow curve 142 intersects the system pressure vs. flow curve 141 for a particular system at a desired upper pressure limit).

[0268] Several factors related to the configuration of the FCPRV affect the operating characteristics of the FCPRV. For example, the venturi or orifice of the flow restriction 152 causes a pressure difference that is sensed by the sensing member 155, so the shape of the opening pressure versus flow curve 142 may be determined by the size of the venturi throat or orifice diameter.

[0269] To adjust the opening pressure characteristics, the FCPRV 300 may be provided with any one or more of a variety of features described below.

[0270] The flow compensated pressure relief valve device 300 may be used in a system of known flow resistance. In such a situation, the venturi or orifice may be of a fixed size and may be determined for use with the system having the known flow resistance of that particular system.

[0271] Alternatively, if the system in which the FCPRV will be used is unknown, the FCPRV may be provided with an adjustable venturi or orifice (e.g., adjustable area and / or length) to allow the user to "tune" the FCPRV for a particular application. For example, the FCPRV 300 may be provided with a variety of different orifice plates, each with a different sized orifice. The orifice plates are interchangeable, each with a known resistance. For example, a nasal high flow system may be interchangeable between "adult" and "pediatric" cannulas. Each cannula exhibits a different known flow resistance. One orifice may, for example, "tune" the flow compensated pressure relief valve to a system configured for an "adult" cannula, and another orifice may "tune" the flow compensated pressure relief valve to a system configured for a "pediatric" cannula. The different orifices may be located on a slidable plate that may slide each orifice into the flow path of the flow compensated pressure relief valve. Other means for adjusting the size of the venturi throat or orifice / flow restriction may be used. For example, an orifice sized to be the maximum flow restriction (i.e., the smallest orifice size) may be provided, which may be opened to achieve a large orifice size / small flow restriction. Alternatively, a large orifice size may be provided, and an insert or inserts, each with a small orifice size, may be provided to fit or abut the large orifice. The flow restriction may be provided by a valve arrangement, for example, a gate valve type arrangement. In a gate valve type arrangement, the valve may have a screw adjustment to move the gate of the valve to adjust the size of the flow restriction. The screw may provide many turns to relatively fine adjustment to perform precise adjustment of the FCPRV. Alternatively or additionally, a variety of different patient interfaces may be provided, each with the same flow resistance, so that all patient interfaces of the various interfaces can be used with the same FCPRV setup.For example, a flow restriction may be provided at each patient interface of the various interfaces such that each patient interface has the same total flow restriction. The flow restriction may be provided by a filter, an orifice, a narrow section of tubing, or any other suitable arrangement.

[0272] In some embodiments, the FCPRV may include more than one flow restriction in series and / or in parallel. In some embodiments, the flow restriction may be configured to provide a first flow resistance in a first flow direction within the restriction and a second flow resistance in a second opposite flow direction within the flow restriction. For example, the flow restriction may include an angled inlet to the channel or a funnel flow to the orifice, which has the effect of making the orifice larger. An angled inlet provides the advantage of flattening the negative flow response. In some embodiments, the flow restriction 152 may include an angled outlet, which also has the effect of making the orifice larger by gently guiding the flow away from the orifice. This has the advantage of flattening the positive flow response. In general, an outlet has a greater effect on the flow response than an inlet. An inlet may be particularly beneficial in bilevel PAP, since an inlet becomes an outlet when the patient exhales (negative flow).

[0273] The effect of flow resistance in the system on the FCPRV may also depend on the location of the FCPRV in the system. Therefore, the FCPRV is preferably tailored to a particular location in the system. In a humidified system, the FCPRV is preferably located upstream of the humidifier in the system to avoid the possibility of condensation in the FCPRV. However, the FCPRV can be located elsewhere in the system, for example downstream of the humidifier.

[0274] FIG. 18 illustrates a method of adjusting a flow compensated pressure relief valve as described herein. In step 160, the system is pressure tested to determine the system flow rate (e.g., flow rate delivered to the patient) versus the system's pressure drop response curve. In step 161, a desired opening pressure versus flow rate curve is determined, for example, by adding an offset pressure to the system pressure versus flow rate curve. In step 162, an FCPRV according to an embodiment as described herein is installed in the system. In step 163, flow restrictions are continuously added to the system downstream of the FCPRV 300, and the resulting opening pressures for various flow rates are determined. In step 164, the actual pressure relief versus flow rate curve is compared to the desired curve. In step 165, if the actual curve does not match the desired curve, the size of the flow restriction is adjusted and steps 163 and 164 are repeated again until the desired pressure relief characteristics are obtained, at which point the FCPRV has been successfully adjusted. The flow restriction can be adjusted continuously, i.e., with a tapered plug in a hole that can move back and forth to continuously change the restriction, or dynamically by changing the position of a valve, for example a gate valve having a gate actuated by a screw adjustment as described above.

[0275] Alternatively or additionally, the vent pressure threshold may be adjusted by adjusting any one or more of the features described above in connection with the PRV 100, 200. For example, the tension of the valve membrane 105 may be adjusted, for example, by adjusting the relative position of the valve inlet tube 108 with respect to the valve member 105, or the size of the exhaust outlet 103. In the PRV 100, the size of the exhaust outlet determines the shape of the pressure relief valve opening pressure vs. flow rate curve as shown in Figures 3-5 and 7, and thus the vent pressure threshold across various flow rates. When the system is completely shut off / occluded, the FCPRV operates as the PRV 100 described above, except that the sensing member may provide some additional bias to the valve member 105. Also, the biasing force provided by the sensing member 155 to the valve member 105 may be adjustable. For example, the length of the mechanical link 157 between the sensing and valve member may be adjustable, with a shorter length of the link increasing the biasing force and therefore the vent pressure.

[0276] Further adjustment mechanisms for adjusting the opening valve discharge pressure are shown in Figures 18A-18C. In some embodiments, the displacement chamber 107 may be sealed or sealable from the surrounding environment, as shown in Figure 18A. In the illustrated embodiment, the FCPRV is provided with a device 107a for changing the pressure in the displacement chamber. Such a device may also be provided with the PRV 100 (i.e., not flow controlled). For example, the device 107a may be a foot or hand operated pump for increasing or decreasing the pressure in the displacement chamber. The effective volume of the displacement chamber may include the volume of the displacement chamber 107 and the volume of the device 107a. For example, the device 107a may be an air-filled syringe or other cylinder and plunger arrangement, or may be an air-filled bag / balloon. By reducing the volume of the device, the effective volume of the displacement chamber is reduced, resulting in an increase in the pressure in the displacement chamber 107. The changed pressure in the displacement chamber changes the opening pressure of the PRV of the FCPRV, with an increase in the pressure of the displacement chamber increasing the opening pressure and a decrease in the pressure of the displacement chamber decreasing the opening pressure. The device 107a should be adapted not to lift the valve member from the valve seat 104 unless lifting the valve member from the valve seat 104 is desired. The pressure regulating device 107a may be located on the displacement chamber, i.e. the FCPRV, or may be connected to the displacement chamber by a hose or conduit and may be separate. The device 107a may be adjustable by hand or foot, or may be actuated by electromechanical means such as a solenoid, or may be an electrically powered mechanical pump. The PRV 100 may also be provided with a reset device 107b for resetting the pressure in the displacement chamber to ambient pressure. The reset device may be a manual or electrically powered release valve, such as a poppet valve or other similar device. In FIG. 18A, the FCPRV 300 is shown in a no-flow state in which the valve member 105 is biased against the valve seat 104 by the pressure in the displacement chamber.

[0277] In some embodiments, the relative position of the valve member 104 and the valve seat may be adjustable to adjust the opening pressure. As described above, the position of the valve inlet relative to the valve seat may be adjustable. Alternatively or additionally, in some embodiments, the position of the valve member relative to the valve seat is adjustable. As shown in FIG. 18B, the valve member may be supported by a housing portion, and the position of the housing portion relative to the inlet is adjustable, for example, by a threaded mechanism 102a between the housing of the displacement chamber 107 and the housing of the outlet chamber 102. Alternatively or additionally, the sensing member 155 may be adjustable relative to the valve inlet to adjust the bias that the sensing member exerts against the valve member against the valve seat. For example, the sensing chamber housing may include a threaded mechanism for moving the relative position of the sensing member relative to the valve seat 104. A user may manipulate the threaded mechanism, for example, by manually turning the housing portion, to adjust the opening pressure. The housing may provide an indication of the housing position relative to the opening pressure setting.

[0278] As previously mentioned, the mechanical link 157 connecting between the sensing member and the valve member may be adjustable in length. In some embodiments, the length of the mechanical link may be adjusted during use of the FCPRV. For example, as shown in FIG. 18C, in some embodiments, the mechanical link may include a first portion 157a, a second portion 157b, and a threaded engagement 157c between the first portion 157a and the second portion 157b for adjusting the overall length of the link 157. A control handle or knob 157d may be provided to allow a user to rotate one portion 157a relative to the other link portion 157b to adjust the overall length of the link 157 via the threaded engagement 157c.

[0279] In some embodiments, the FCPRV may include or provide a pressure limit. The pressure limit may correspond to a safe pressure limit of the system to protect the system components. The pressure limit may be set by limiting the amount of movement of the sensing member, for example, by limiting the deformation of the sensing membrane or by limiting the amount of movement of the sensing plunger or piston. Limiting the amount of movement of the sensing member limits the amount of tension the sensing member can exert on the valve member, which in turn provides an upper limit on the effect that the flow through the flow restriction of the FCPRV has on the valve member. In some embodiments, the second chamber may limit the deformation of the sensing membrane or may limit the movement of the sensing plunger or piston. For example, the sensing membrane may be limited to a maximum expanded configuration when the membrane expands and contacts the wall of the second chamber. Alternatively, the maximum travel of the sensing piston or plunger may be set by the piston or plunger bearing against the wall of the second chamber, or by a mechanical stop in the second chamber (e.g., a shoulder or protrusion extending from the wall of the second chamber as shown by item 271 in FIG. 21). Alternatively, the mechanical stop may be provided to engage the mechanical link 157, 257 between the sensing member and the valve member. An illustration of this embodiment is provided in FIGS. 14A and 14B, where a shoulder 272 protruding from the wall of the FCPRV is adapted to engage a shoulder provided by a flange or protrusion 273 on the mechanical link to limit travel of the sensing member.

[0280] The effect of limiting the travel of the sensing member or mechanical link is shown in Figure 19. As the flow rate delivered to the patient increases, the pressure loss 141 in the system increases and the pressure differential across the sensing member increases, thus increasing the opening pressure 142 of the FCPRV. However, once the travel of the sensing member reaches a maximum travel, the effect of any further increase in flow rate and the resulting increase in pressure differential across the sensing member is not transmitted to the valve member, and thus the opening pressure reaches a maximum pressure. In Figure 19, the maximum opening pressure is shown by line 145 and is less than 50 cmH2O.

[0281] 19, i.e., limiting the movement or deformation of the sensing member to a maximum level, may be advantageous since a system maximum pressure limit can be achieved regardless of the type or type of system the FCPRV is used in. While manually setting the system maximum pressure requires knowledge of the flow resistance within the system, the configuration as described allows for limiting the system pressure regardless of the type of system the FCPRV is used in.

[0282] In some embodiments, the mechanical link operates only in compression by being decoupled from the valve member or the sensing member or both the valve member and the sensing member. One such embodiment is illustrated by the schematic diagram shown in FIGS. 16A-16C, in which the ends of the mechanical link 157 are not coupled to the valve member 105 and the sensing member 155. In a state where there is no gas flow in the primary flow path of the valve 158 (i.e., zero flow to the FCPRV inlet 151), one end of the mechanical link 157 supports the valve member 105 and the other end of the mechanical link 157 supports the sensing member. The length of the mechanical link is greater than the distance between the valve member and the sensing member when in its undeflected state. The valve member has a greater bias than the sensing member such that the valve member supports the valve seat 104. For example, in an embodiment including a membrane valve member and a membrane sensing member, the valve member membrane has a greater tension than the sensing member membrane such that the valve member is biased against the bias of the sensing member against the valve seat. As the flow in the FCPRV from inlet 151 to outlet 153 increases, the pressure difference in the sensing member increases and acts against the bias of the sensing member, reducing the force applied to the valve member by mechanical link 157. As the flow continues to increase, the force exerted by the mechanical link on the valve member is progressively reduced and therefore the opening pressure is progressively increased. FIG. 16B shows the state of the valve where the flow in the main flow path and flow restriction 152 reduces the force exerted by mechanical link 157 on the valve member 105 and the mechanical link supports both the valve member 105 and the sensing member 155. As the flow continues to increase, the sensing member is deflected such that the mechanical link loses contact with either the sensing member 155, the valve member 105, or both. FIG. 16C shows the high flow state where the link is no longer in contact with the valve member and the sensing member. At this stage, the bias of the sensing member no longer exerts any force on the valve member 105 through the mechanical link. Thus, above a certain flow threshold, the opening pressure is determined solely by the bias of the valve member against the valve seat 104, and the FCPRV functions as a PRV without flow compensation. The bias of the valve member against the valve seat sets a pressure limit for the system that is independent of flow, as indicated by the dashed horizontal line in the flow versus pressure curve of FIG. 16D.As shown in FIG. 16D, the opening pressure increases progressively as the flow rate increases until contact between the mechanical link and one or both of the valve and sensing members is lost (as shown in FIG. 16C), at which point the pressure limit set by the biasing of the valve member is reached.

[0283] If a flow restriction (e.g., a partially collapsed conduit) is introduced into the system downstream of the FCPRV, the flow source (reference number 12 in FIG. 1AA) will maintain a set flow rate to the FCPRV and the pressure Pc in the FCPRV will increase without a corresponding increase in the differential pressure across the sensing member. In this situation, the pressure Pc will increase until it reaches the opening pressure indicated by the vertical line in FIG. 16D, and the sensing member, mechanical linkage, and valve member will move in a direction that causes the valve member to lift off the valve seat and expel flow through the outlet chamber and outlet vent opening 103.

[0284] FIG. 16A illustrates a complete shutoff downstream of the FCPRV causing all flow provided to the FCPRV inlet 151 to be discharged through the PRV discharge outlet 103.

[0285] In some embodiments, the valve member is biased against the valve seat by tension in the membrane valve member or biasing spring member, for example as described with reference to Figures 9A and 10A. An additional bias (positive or negative) is provided by the sensing member via a mechanical link to modify the pressure required to lift the valve member away from the valve seat. In some embodiments, the valve member is not biased against the valve seat other than by the bias provided by the sensing member, for example as shown in Figure 23A. The membrane valve member may not be stretched over the valve seat such that the membrane is not biased against the valve seat until it is pulled into contact with the valve seat by the sensing member. In some embodiments, the sensing member provides a positive bias to the valve member, i.e. the sensing member pulls the valve member against the valve seat. In some embodiments, the sensing member provides a negative bias to the valve member, i.e. the sensing member pushes the valve member away from the valve seat, as described with reference to Figures 16A-16D. Unless the context indicates otherwise, bias or biasing of a valve member against a valve seat is intended to mean the overall bias of the valve member against the valve seat provided by the tension of the valve member membrane, or by a spring element, or by a sensing member via a mechanical link.

[0286] The representation of Figures 14A and 14B shows one possible configuration of an FCPRV, in which the valve inlet 101 and first chamber 154a of the sensing chamber 154 are connected to a primary flow path 158, which includes a primary inlet 151, a primary outlet 153, and a flow resistor 152, via a "T" with the legs of the T connected to the primary flow path and the PRV 100 and sensing chamber 154 arrangement connected on opposite sides of the top of the "T".

[0287] Another embodiment of a flow compensated pressure relief valve is shown in Figure 20. Compared to the configuration of Figures 14A and 14B, the embodiment of Figure 20 is configured into a single valve unit 400 that occupies less space and has a more aesthetic appearance.

[0288] In FIG. 20, the valve body 110 defines a first chamber 154a and an outlet chamber 102 of the sensing chamber 154. The first chamber 154a and the outlet chamber 102 are separated by a wall 106b. The main inlet 151 and the main outlet 153 are formed in or with the body 110 in direct communication with the first chamber 154a, such that the gas flow from the main inlet 151 to the main outlet 153 passes through the first chamber 154a. An orifice 152 is provided in the wall 106 of the body 110 at the main outlet 153, and a pressure tap 156 is provided downstream of the outlet and / or orifice in communication with a second chamber 154b provided by a cap 110a attached to the end of the body 110. The first chamber 154a and the second chamber 154b define a sensing chamber 154 having a sensing member 155 therein. In the illustrated embodiment, the sensing member 155 is a membrane secured between a cap 110a forming a second chamber 154b and a body 110 forming a first chamber 154a. A valve inlet tube 108 extends from the first chamber 154a to the outlet chamber 102, with an end 104 of the inlet tube providing a valve seat 104 against which the valve member 105 seals. The valve member 105 is secured to the body 110 by a second cap 110b attached to the body 110. An outlet aperture 103 is provided in a wall 106 of the body 110, forming the outlet chamber 102. The valve member 105 and the sensing member 155 are connected by a rigid rod 157.

[0289] Figure 21 is a free body diagram of an embodiment of an FCPRV 500 similar to that of Figure 20, but where the sensing member 155 is a piston 280 that moves within a cylinder that forms the sensing chamber 154. In this embodiment, the valve member 105 is a membrane.

[0290] FIG. 22 shows yet another embodiment of the FCPRV 600. The embodiment of FIG. 22 is similar to the embodiment of FIG. 20, except that in FIG. 22 the valve member 205 is a non-sealing plunger 205 rather than a membrane, meaning that the plunger does not form a seal with the wall 206 of the outlet chamber 202. In this embodiment, the valve member 205 is similar to the valve member described with reference to FIGS. 9A-9C. In FIG. 22, the mechanical link 257 between the valve member 205 and the sensing member 155 is of adjustable length and may, for example, include a telescoping component. Adjusting the length of the link adjusts the amount of force that the sensing member 155 exerts on the valve member 205 in addition to the force caused by the pressure difference between the first chamber 154a and the second chamber 154b. Flow from the primary inlet 151 to the primary outlet 153 is through a conduit 167. The conduit 167 intersects the first chamber 154a (e.g., the conduit may be tangential to the first chamber) such that gas flow from the primary inlet to the primary outlet communicates with the first chamber 154a through an opening 170 in the wall of the first chamber 154a. A communication passage (not shown) may connect from downstream of the flow restriction (a flow restriction such as an orifice or venturi downstream from the opening 170) to the second chamber 154b via a nipple 159 or other suitable connection.

[0291] Schematic diagrams of the FCPRV of FIG. 22 are provided in FIGS. 23A and 23B. FIG. 23A illustrates a no-flow or low-flow configuration where there is no or low pressure differential across the sensing membrane. FIG. 23B illustrates an increased or high-flow configuration where there is a pressure differential across the sensing member such that the sensing member 155 is deformed toward the second chamber 154b of the sensing chamber. The deformation of the sensing member causes the sensing member to bias the sealing member 205 against the valve seat 204 via the mechanical link 257. FIG. 23A illustrates the sensing membrane 155 being deformed from a neutral point (undeformed or unstretched) when in the no-flow or low-flow configuration. For example, as described above for the PRV 100 according to some embodiments, this deformation is an initial deformation or preload that provides the valve member 205 with an initial or minimal biasing force against the valve seat 204.

[0292] FIG. 24 shows yet another embodiment of the FCPRV 700. The FCPRV has a primary inlet 251 and a primary outlet 253 for receiving a gas flow from a gas source and delivering the gas flow to a system, such as the respiratory system 12 of FIG. 1. To release pressure above a pressure threshold, a PRV 100 is provided, which in the illustrated embodiment includes a membrane valve member 105 and other features as described with reference to the previous embodiment, including a valve inlet 101, an outlet chamber 102, and a valve seat 104. An exhaust outlet from the outlet chamber 102 (e.g., exhaust outlet 103 of FIG. 2A) is hidden from view in FIG. 24 but is provided in a wall 206 of the outlet chamber 102. The FCPRV 700 includes a sensing mechanism for dynamically adjusting the pressure threshold of the PRV 100 based on the flow rate of the gas flow delivered from the primary inlet 251 to the primary outlet 253. The sensing mechanism includes a sensing chamber 254 in which a sensing member 255 is disposed. The body 210 of the FCPRV 700 defines both the sensing chamber 254 and the exit chamber 102, with a partition 206b separating the two.

[0293] Unlike the previous embodiment, in the embodiment of FIG. 24, the gas flow from the main inlet 251 to the main outlet 253 flows through the sensing chamber 254 from the first chamber 254a to the second chamber 254b, and the main outlet 253 is from the second chamber 254b. The sensing member 255 is a non-sealing plunger, meaning that the plunger does not form a seal with the wall 206c of the sensing chamber. The sensing plunger 255 is mechanically coupled to the valve member 105 by a mechanical link 257. In the illustrated embodiment, the link 257 includes two telescoping members for adjustable length. An annular gap 252 between the outer circumference of the plunger 255 and the wall 206c of the sensing chamber provides a restriction for the gas flow from the main inlet to the main outlet. Additionally, in some embodiments, the plunger may include an aperture (not shown) in the plunger such that the aperture in the plunger and the annular gap 252 between the plunger and the chamber wall provide a desired flow resistance. In another embodiment, the plunger may be a piston, for example, that forms a seal with the wall of the sensing chamber, but where one or more apertures in the piston provide the flow restriction 252. The gap or flow restriction 252 is downstream of the valve inlet 101 since the valve inlet 101 receives the gas flow from the main inlet 251 before the gas flow passes through the flow restriction 252, or in other words, the valve inlet 101 is upstream of the flow restriction 252 since the valve inlet 101 does not experience a pressure drop created by the restriction 252. As the flow passes through the annular gap 252, a pressure drop is created such that the pressure in the sensing chamber on the downstream side 254b of the plunger 255 is lower than the pressure in the sensing chamber 254 on the upstream side 254b of the plunger 255. The upstream side of the sensing member 255 may be referred to as the first chamber 254a of the sensing chamber 254, and the downstream side of the sensing member 255 may be referred to as the second chamber 254b. The sensing plunger 255 separates the first chamber 254a and the second chamber 254b, but does not pneumatically separate the two chambers from the gas flow passing from the first chamber to the second chamber.The first chamber 254a is in fluid communication with the gas flow upstream of the flow restriction 252 provided by the gap between the sensing member 255 and the sensing chamber wall 206c, and the second chamber 254b is in fluid communication with the gas flow downstream of the flow restriction 252 provided by the gap 252 between the sensing member 255 and the chamber wall 206c. A pressure differential within the sensing member 255 causes the sensing member 255 to move away from the valve inlet 101 in response to the flow of gas through the sensing chamber 254 from the primary inlet to the primary outlet, urging the valve member 101 towards the valve seat 104 via link 257.

[0294] Schematic diagrams of the FCPRV of FIG. 24 are provided in FIG. 25A and FIG. 25B. FIG. 25A shows a no-flow or low-flow configuration where there is no or low pressure differential on the sensing plunger 255. FIG. 25B shows an increased or high-flow configuration where there is a pressure differential on the sensing plunger such that the sensing plunger 255 is forced towards the second chamber 254b of the sensing chamber. Movement of the sensing plunger causes it to bias the sealing member 105 against the valve seat 104 via the mechanical link 257, and flow through the FCPRV from the primary inlet 251 to the primary outlet 253 passes through a flow restriction provided by the annular gap 252 between the plunger 255 and the wall of the sensing chamber 254.

[0295] Schematic diagrams of an FCPRV similar to that of FIG. 24 are provided in FIG. 26A and FIG. 26B. In this embodiment, the sensing member is a piston 280 that forms a seal with the wall of the sensing chamber. The piston includes an aperture 281. The aperture 281 provides a flow restriction in the sensing chamber. FIG. 26A shows a no-flow or low-flow configuration where there is no or low pressure differential across the sensing piston 280. FIG. 26B shows an increased or high-flow configuration where there is a pressure differential across the sensing piston such that the sensing piston 255 is forced towards the second chamber 254b of the sensing chamber. Movement of the sensing piston causes the sensing piston to bias the sealing member 105 against the valve seat 104 via the mechanical link 257, and flow through the FCPRV from the primary inlet 251 to the primary outlet 253 passes through the flow restriction provided by the aperture 281 in the piston 280. Further, in an embodiment including a piston sensing member 255 in sliding relationship with a cylinder housing 254, there may be a flow path between the piston 255 and the cylinder 254, for example, by a channel in the cylinder wall or by a cutout or notch in the outer periphery of the piston. Such a flow path between the piston and the cylinder may be in addition to an aperture in the piston. In further embodiments, the arrangements of Figures 26A and 26B may be implemented by using a membrane sensing member, an aperture in a membrane, or a porous membrane. A flow path may be provided in the mechanical link and an aperture in the sensing member, for example, a hollow mechanical link having an end that extends into the sensing member.

[0296] In some embodiments, the FCPRV includes an outer housing or housing enclosure for housing the components of the FCPRV, such as the membranes 105, 155. Figures 27A and 27B show an FCPRV 800 including a housing 180. The housing houses the valve member 105 and the sensing member 155. The FCPRV has a body 110. In some embodiments, the body provides or forms the outlet chamber 102 and the first chamber 154a of the sensing chamber 154. In some embodiments, the body also includes a primary inlet 151 and a primary outlet 153, for example, in an integrally formed body 110. The body 110 of the embodiment shown in Figure 27a is shown in Figures 28A and 28B. In some embodiments, the housing 180 includes two mating parts 180a, 180b (e.g., two halves). The two housing parts may be secured together by a complementary tongue and groove configuration or using a screw or bolt type configuration, or may be welded together, for example, by ultrasonic welding or any other suitable method. A sealing member, e.g., a gasket, may be provided between the two housing parts, although a seal is not deemed necessary since ambient pressure exists inside and outside the housing. The body 110 and the valve and sensing members are received within and contained by the two housing parts. In some embodiments, one of the housing parts 180a (the first housing part) provides the displacement chamber 107, and the valve member is displaced into the displacement chamber 107 from the valve seat 104. In some embodiments, one of the housing parts 180b (the second housing part) provides the second chamber 154b of the sensing chamber 154. In some embodiments, the valve member and / or the sensing member also provide or act as a sealing member for sealing the outlet chamber 102 or the first chamber 154a of the sensing chamber. For example, the housing (e.g., the first housing part 180a) includes an annular member 182 extending inwardly from a sidewall of the housing.The annular member 182 supports the outer periphery of the valve member 105 (diaphragm) so that the valve member is sandwiched between the housing and the body 110, sealing the outlet chamber 102 from the surroundings or displacement chamber 107 (other than any flow passages that may be provided in the valve member). The body may include an annular shoulder or flange 183 and the valve member sandwiched between the body annular flange and the housing annular member. In some embodiments, the valve member may include a radially inward facing channel or groove that receives the outer edge of the annular flange 183. The housing annular member 182 and the radially inner housing wall of the annular member 182 form the displacement chamber. The annular member 182 and the body flange 183 may be circular or other shapes. The second chamber 154b of the sensing chamber may be similarly formed, with the body 110 including an annular flange 184 and the housing annular member 182 extending from the side wall of the housing 180, with the sensing member captured / sandwiched between the annular flange 184 and the housing annular member 182.

[0297] In some embodiments, the body 110 is clamped between two housing portions. As best shown in FIG 27B, the body 110 is clamped between the annular walls 182 of the housing portions 180a, 180b. The valve member and the sensing member are also clamped between each housing portion 180a, 180b and the body 110.

[0298] In some embodiments, the valve member and / or sensing member includes a rigid frame and a diaphragm or membrane. The rigid frame supports or holds the periphery of the diaphragm or membrane, or is bonded to the periphery of the diaphragm or membrane. As previously described, in some embodiments, the membrane 105, 155 is an elastomeric membrane. With reference to Figures 27C-27E, the membrane 105 may be held in tension by a frame 105e such that the membrane has a predetermined tension. The rigid frame 105e may be overmolded to the membrane 105, or in a preferred embodiment, the membrane is overmolded to the frame. In the overmolding process, the rigid frame may be held in a mold cavity and uncured material may be injected into the mold cavity to form a membrane that is overmolded to the frame. As the membrane material cures, it shrinks, for example by 2-3%, creating a pretension of the membrane within the frame. The frame 105e engages the valve body 110 to assemble the membrane to the body. The frame may include a clipping interface 105f for clipping the frame to the body. The frame will ensure that the proper tension of the membrane is achieved and maintained during assembly of the FCPRV. Additional pretension may be applied using features on the body 110 that cause the membrane 105 and membrane 155 to flex. Bonding the frame 105e to the valve body ensures that the proper tension is maintained since the membrane does not need to be stretched to assemble to the valve body. In an embodiment without a frame (e.g. as shown in FIG. 27B), the membrane may need to be stretched or deformed to attach to the valve body, which may cause changes in the membrane tension after assembly to the valve body, resulting in performance changes between different valves. If ports are provided in the valve member, such as pressure port 156 and pressure port 185 shown in FIG. 27A, the ports may extend into the rigid frame or into the frame and membrane material overmolded to the frame. Such an arrangement of the ports means that the ports do not interfere with the membrane tension. An area 105g of membrane material overmolded onto the frame may form a seal with a chamber wall of the valve, for example the sensing chamber or the outlet chamber or the displacement chamber.

[0299] The relatively rigid frame 105e of the valve member 105 and the sensing member 155 may be formed from any suitably rigid material, such as metal or a plastic material, such as polycarbonate or other plastic materials known in the art. The body 110 may also be made from a relatively rigid material and may be made from the same material as the frame and sensing member of the valve or other rigid materials known in the art. Preferably, the housing may also be made from a relatively rigid material and may be made from the same material as the valve body or other materials known in the art. Components of the valve, such as the valve membrane or valve body, may be made from a vapor permeable material.

[0300] The housing 180 extends outside the outer periphery of the valve member 105 and the annular wall 182, creating a cavity or space 186 (first space) within the housing and outside the displacement chamber. In some embodiments, the housing space 186 within the housing 180 surrounds the displacement chamber and the outlet chamber 102. In some embodiments, the housing space 186 within the housing 180 surrounds the displacement chamber 107, the outlet chamber 102, and the sensing chamber 154. A communication conduit or line 185 may be provided between the displacement chamber 107 and the housing space 186. The space 186 is open to the surrounding environment through the aperture 112 and the aperture 188. In some embodiments, the communication conduit is in direct fluid communication with the surrounding environment. In some embodiments, the aperture 112 is coaxial with one of the main inlet and the main outlet. 27a, the aperture in fluid communication with the displacement chamber 107 is coaxial with the main outlet 153, such that the aperture 112 is an annular aperture. In some embodiments, a port 185 fluidly connecting the displacement chamber 107 with the housing space 186 extends into the valve member 105 near the outer periphery of the valve member 105 and radially inward of the annular wall 182 of the housing 180.

[0301] In some embodiments, a communication port or line 156 is provided between the main outlet 153 and the second chamber 154b of the sensing chamber 154. In some embodiments, the port 156 extends fluidly into the sensing member 155 near the outer periphery of the sensing member 155 and radially inward of the annular wall 182 of the housing 180. The pressure downstream of the main outlet or flow restriction or orifice 152 is sensed at location 156a (FIG. 27A). This may also be the case for a flow restriction. Since this pressure extraction point is in the main gas flow, the pressure sensed by the sensing member 155 in the second chamber of the sensing chamber 154 may be subject to turbulence / dynamic pressure. The FCPRV may include a baffle to shield the port 156 from the main gas flow path and to stabilize pressure fluctuations sensed by the sensing member. The FCPRV may include a baffle to shield the flow path from the main gas flow path and the sensing chamber and to stabilize pressure fluctuations sensed by the sensing member.

[0302] In some embodiments, the housing 180 provides a cavity or space 187 (second space) outside the outlet chamber 102. An exhaust outlet 103 may be provided in the wall 106 (shown in FIG. 27A ) of the body 110 so that gas passing through the pressure relief valve 100 can be exhausted from the outlet chamber 102 to the housing space 187 when the valve member lifts off the valve seat 104. The outlet chamber 102 may be a first outlet chamber and the housing space 187 may be a second outlet chamber, the first and second outlet chambers being arranged in series, and the exhaust gas passes through the first and second outlet chambers and is exhausted to the ambient environment. The outlet(s) 188 or outlets from the vent or housing space 187 to the surrounding ambient environment may also be described as exhaust outlets. The exhaust outlet 103 and exhaust outlet 188 may be tailored to achieve specific valve characteristics. In some embodiments, the exhaust outlet 103 may be sufficiently large relative to the exhaust outlet 188 so that there is a significant pressure drop at the exhaust outlet 103 from the outlet chamber 102, or in some embodiments, the exhaust outlet 103 may be sufficiently small so that there is a significant pressure drop at the exhaust outlet 103 from the outlet chamber 102. In some embodiments, the housing spaces 186, 187 described above are joined as a single housing space surrounding the sensing chamber 154, the outlet chamber 102, and the displacement chamber 103. In some embodiments, the housing provides two separate housing spaces 186, 187. In some embodiments, the body or housing includes a shroud or duct 189 extending between the exhaust outlet 103 and the housing exhaust outlet 188 for directing gases exhausting from the outlet chamber to the housing exhaust outlet 188. The duct may be disposed with the housing space 186 in fluid communication with the displacement chamber. The interior of the duct 189 may provide the housing space 187 into which gases are exhausted from the outlet chamber. The duct may substantially separate gas exiting the outlet chamber from the housing space 186 which communicates with the displacement chamber. In the embodiment shown, the duct 189 extends from the body.

[0303] In some embodiments, the housing exhaust outlet 188 from the housing volume 187 to the surroundings is coaxial with one of the primary inlet and the primary outlet. In the illustrated embodiment of Figure 27A, the exhaust outlet 188 is coaxial with the primary inlet 151 such that the exhaust outlet 188 is annular.

[0304] In some embodiments, the primary inlet and primary outlet are aligned, as best shown in Figure 27 A. As mentioned above, in some embodiments, the displacement chamber outlet 112 (first housing outlet) and the exhaust outlet 188 (second housing outlet) are coaxial with each one of the primary inlet and primary outlet.

[0305] As shown in Figure 27A, in some embodiments, the valve includes a bend in the flow path between the main inlet 151 and the valve seat 104. In the embodiment of Figure 27A, the bend is a 90 degree bend. Pressure sensed by the valve member 105 is extracted downstream of the bend, at location 151a in Figure 27A. The bend may reduce turbulent pressure at the extraction point 151a acting on the valve member 105. The extraction point 151a is outside of the main gas flow path 158, which is a direct flow path from the main inlet 151 to the main outlet 153.

[0306] As described above with reference to the previous embodiment, the valve member and the sensing member may be coupled by a mechanical link 157. The mechanical link 157 may be a rigid rod or shaft or a flexible member such as a wire or cord. The mechanical link is received in a guide, for example, a tubular guide 181. In the embodiment of FIG. 27A, the link is a rigid rod or shaft that slides in the tubular guide 181. In some embodiments, the first chamber 154a of the sensing chamber 154 is in fluid communication with the main inlet through the mechanical link guide 181 so that the sensing member can sense the pressure in the main inlet through the mechanical link guide. The guide 181 positions the link 157 and provides fluid communication between the main inlet 151 and the sensing chamber 154a. The main inlet or main flow path is in fluid communication with the sensing chamber through the annular space between the link 157 and the link guide 181. The space may have a relatively small cross-sectional area and a relatively long path from the main gas flow path to the sensing chamber 154. The small area of ​​space between the link and the link guide provides a deliberate flow resistance that delays the time it takes for pressure fluctuations in the main gas flow path 158 to reach the sensing chamber and the sensing member 155. As a result, the time constant of the valve's response is extended, making the valve less responsive to pressure fluctuations. This is beneficial in some applications, such as CPAP. In some embodiments, the link 157 includes a ribbed exterior surface. The ribs create a turbulent flow path to generate additional flow resistance between the inlet and the sensing chamber. The ribs can generate turbulent flow resistance while maintaining adequate space between the link and the link guide to generate the desired flow resistance, i.e., without requiring a close tolerance fit between the shaft and the shaft guide.

[0307] In some embodiments, the mechanical link is a rigid shaft or rod that includes a ribbed structure as shown in Figures 29A and 29B. The ribs provide sufficient rigidity to the shaft with a reduced amount of material. A flange 157b is provided on one end of the shaft. A locking washer 157c or other means for coupling the link to the sensing member is provided on the opposite end. The locking washer includes several projections that extend inward from the outer periphery. The radially inner ends of the projections engage the end of the shaft. The washer is held on the end of the shaft by a shoulder or washer receiver. The washer and flange support each one of the valve member 105 and the sensing member 155 as shown in Figure 29B, coupling the two members together. In some embodiments, the washer may be overmolded onto the valve member or sensing member so that the member clips onto the link. In some embodiments, the washer or locking washer may be provided on both ends of the shaft. The washer may include a flange 157b as described below.

[0308] In some embodiments, the mechanical link includes a flange 157b for supporting the valve member 105 against the valve seat. In some embodiments, as shown in Figures 27E and 27F, the flange 157b has a diameter larger than the diameter of the valve seat, so that when the valve member seats on the valve seat, the valve member is supported against the valve seat between the flange and the valve seat. When the sensing member pulls the valve member against the valve seat, the flange supports and pulls the valve member over an area greater than that defined by the outer diameter of the valve seat, as shown in Figures 27E and 27F. The flange functions to maintain a flat area of ​​the valve member on the valve seat. In some embodiments, the flange supports the valve member on a side of the valve member opposite the side that contacts the valve seat 104. In some embodiments, the flange may be overmolded into the valve member. The flange diameter may be less than (Figures 27A and 27B), greater than (Figures 27E and 27F), or equal to the diameter of the valve seat. In some embodiments, the flange may seat on the valve seat, in which case the flange is part of the valve member.

[0309] The embodiment of FIG. 27E includes a relatively restricted pneumatic coupling between the main gas flow path 158 and the sensing member 155. As discussed above with reference to FIG. 27A, this provides a damping effect to pressure fluctuations in the main gas flow path 158 reaching the sensing member 155, and therefore provides stable valve operation. However, in some applications, a smaller time constant / faster responding valve may be desirable. A faster response characteristic may be achieved by providing an increased or significant pneumatic coupling between the main gas flow path (i.e., the main inlet) upstream of the flow restriction and the sensing member 155. FIG. 27E illustrates an embodiment including an increased pneumatic coupling between the main gas flow path 158 and the sensing member 155. The FCPRV of FIG. 27F is identical to the embodiment of FIG. 27E, but without the mechanical link guide tube 181. An opening 158a is provided between the main inlet or main gas flow path 158 and the sensing chamber through which the mechanical link extends. Thus, with the link received within the opening, the opening 158 provides an annular space between the main gas flow and the sensing chamber, and hence the sensing member. The increased area of ​​the annular space of the opening 158a compared to the annular space between the link guide 181 and the link in FIG. 27E provides a faster response such that the valve of FIG. 27F responds more quickly to pressure changes in the main gas flow path 158. Alternatively, the guide tube can provide a larger clearance between the guide tube 181 and the kink 157. The increased area of ​​the opening 158a provides a reduced flow restriction between the main gas flow and the sensing chamber. The resulting rapid response valve is particularly useful for use with a set flow source such as a compressed gas tank or hospital wall flow meter supply that functions as a ventilator, for example, in the system described above with reference to FIGS. 1F-1, 1F-2 and 1F-3. In a rapid response valve, the system pressure in the FCPRV, and therefore in the patient, tends to change rapidly between the bilevel pressure P1 and the bilevel pressure P2 shown in FIG. 1F-3.A valve configured in this manner advantageously provides a very low cost portable ventilator that may be useful in situations where conventional ventilators are not available, such as ambulance transport, mass patient situations where only a limited number of conventional ventilators are available, field hospitals, and in developing countries.

[0310] In the embodiment of FIG. 27F, the flow restriction between the main gas flow 158 and the first chamber 154a of the sensing chamber 154 is reduced and the pneumatic coupling between the main gas flow 158 and the first chamber is increased. Alternatively or additionally, to achieve a rapid response valve, the pneumatic coupling between the main gas flow 158 and the sensing chamber 154 may be increased by increasing the pneumatic coupling between the main gas flow 158 and the second chamber 154b of the sensing chamber 154. For example, the area of ​​the pressure port 156 between the main flow path 158 and the second chamber 154b may be increased and / or the length of the pressure port 156 may be reduced. A rapid response valve may also be achieved by increasing the area of ​​the pressure port 185 from the displacement chamber 107 or by reducing the volume of the first and / or second chambers of the sensing chamber.

[0311] Various FCPRV embodiments have been described above. Two preferred embodiments of the valve disc 110, valve member 105, and sensing member 155 are shown in Figures 27E and 27F. Some exemplary approximate valve dimensions for these embodiments are listed below.

[0312] Valve seat diameter 20 mm / PRV inlet pipe 101 area 315 mm2 (i.e. the area of ​​valve member 105 exposed to inlet pressure Pc when the valve member seats on valve seat 104). The valve member and the sensing member are made of a rubber material having a thickness of 0.3 mm, for example, an elastic modulus of about 0.1 GPa (for example, silicone rubber). The valve member and sensing member have a diameter of approximately 60 mm. The bias of the valve member against the valve seat is approximately 1 mm. The sensing member bias is approximately 1 mm, ie with the valve member in contact with the valve seat, the sensing member is displaced approximately 1 mm. The area of ​​the flow restriction orifice 152 is 37 mm2. The exit discharge aperture 103 in the direction of flow is 80 mm2 (eg, two holes of 40 mm2 each).

[0313] In some embodiments, the FCPRV may be configured to be reversible such that the FCPRV may be connected in the system with a first connection of the primary flow path 158 as the inlet 151 and a second connection of the primary flow path 158 as the outlet 153 in a first configuration, and with the first connection of the primary flow path 158 as the outlet 153 and the second connection of the primary flow path 158 as the inlet 151 in a second configuration. As shown in FIG. 30, the FCPRV is connected with a first connection 158a of the primary flow path 158 connected to the system as the primary inlet 151. A second connection 158b of the primary flow path 158 connects as the primary outlet 153. The reversible valve 500' includes a first pressure port or passageway 156-1 between the first connection 158a of the primary flow path and the sensing chamber 154b, and a second pressure port or passageway 156-2 between the second connection 158b of the primary flow path 158 and the sensing chamber 154b. The reversible FCPRV is also provided with a first flow restriction 152-1 (e.g., an orifice or venturi) proximate the first connection 158a of the primary flow path 158 and a second flow restriction 152-2 (e.g., an orifice or venturi) proximate the second connection 158b of the primary flow path 158. The inlet and outlet conduits of the system are adapted such that the first pressure port 156-1 or the second pressure port 156-2 is blocked by the inlet conduit when the inlet conduit is attached to the primary flow first connection 158a or the primary flow second connection 158b. Alternatively, the FCPRV may be provided with a connector 168 that may be attached to either the primary flow path first connection 158a or the primary flow path second connection 158b and that blocks the respective pressure port 156-1 or pressure port 156-2 and configures the first connection 158a or the second connection 158b as the inlet 151 to the primary flow path. The other of the first main flow connection 158a and the second main flow connection 158b is configured as a main outlet 153, and the respective first or second pressure port 156-1, 156-2 is not blocked. For example, when the inlet conduit or connector 168 is connected to the first main flow connection 168a as shown in FIG. 30, the first pressure port 156-1 is blocked and no pressure loss across the first restriction 152-1 is detected by the sensing member 280.The sensing member 280 senses the differential pressure through the second pressure portion 156-2 adjacent the primary flow connection 158b configured as the primary outlet 153. If the system conduits are configured as inlet and outlet conduits such that the inlet conduit blocks the pressure ports 156-1, 156-2 and the outlet conduit does not block the pressure ports 156-1, 156-2, the FCPRV may be installed in the system in either orientation and may achieve the same performance characteristics if the FCPRV is configured to have the same flow path from the first connection 158a to the valve seat 104 and from the second connection 158b to the valve seat 104 (i.e., the first flow restriction 156-1 and the second flow restriction 156-2 are identical). Such an arrangement avoids unintentionally connecting the FCPRV in the wrong orientation within the system. Alternatively, the FCPRV may be configured to provide different characteristics depending on the direction of the primary flow within the valve. For example, in the embodiment of Figure 30, the first flow restriction 156-1 may be different from the second flow restriction 156-2 such that the direction of valve connection may select the first or second flow restriction sensed by the sensing member. The reversible valve shown in Figure 30 shows the embodiment of Figure 21 including a piston sensing member 280. However, the reversible configuration including the first and second restrictions 152-1, 152-2 and first and second pressure ports 156-1, 156-2 described with reference to Figure 30 may be implemented in any FCPRV according to any of the embodiments described herein, for example, an FCPRV including a membrane sensing member 155.

[0314] In some embodiments, the FCPRV is provided with a tube or conduit, such as a conduit for providing a flow of gas from the FCPRV to the patient. The conduit may be permanently attached to the FCPRV. By providing the FCPRV with a conduit, the risk of unintentionally connecting the FCPRV in the wrong orientation in the system is reduced.

[0315] In some embodiments, the PRV or FCPRV described herein may be adapted for use in a system including a humidifier and / or may be placed in the system near the patient. Thus, in some applications, humidified gas or condensation from the patient's breath may accumulate in the PRV or FCPRV. To reduce or prevent condensation accumulation, in some embodiments, the PRV or FCPRV may include a heater to heat the device or a portion of the device to reduce or remove condensation that forms in the PRV or FCPRV. For example, the valve body 110 may be heated by an electric heater, such as a wire or other resistive element provided in or on the body. The valve may include a water catcher or other means for removing condensation. In some embodiments, the PRV or FCPRV may be used in a system without a humidifier.

[0316] In yet another embodiment, the FCPRV may include a sensing mechanism that is an electrical sensing device that includes one or more electronic sensors for detecting the flow rate of gas (e.g., the pressure loss of flow through a flow restriction or restriction) from the primary inlet to the primary outlet of the FCPRV. Some examples of sensors that may be suitable are hot film sensors or ultrasonic sensors, or any other suitable sensors, including the use of pressure sensors or differential pressure sensors to measure flow through an orifice or venturi. An electrical controller / processor that receives signals from the sensors may provide an output to drive an actuator and control the PRV of the FCPRV to adjust the opening pressure threshold of the PRV of the FCPRV. For example, the actuator may include a servo that drives a member, such as a link 157, 257 attached to the valve member 105, 205 of the PRV to adjust the amount of bias of the member 105, 205 against the valve seat 104, 204 of the PRV. A solenoid may be controlled to move the valve member.

[0317] Various PRV and FCPRV embodiments have been shown having circular valves and sensing members, however, other shapes may be desirable to achieve desired characteristics.

[0318] 31A and 31B show an FCPRV 901 including an electrical sensing device. The electrical sensing device includes a flow and / or pressure sensing mechanism 950, a processor or controller 951 (e.g., digital and / or analog electronics and / or electromechanical devices), and an actuator 952. The sensing mechanism may include a venturi and first and second pressure sensors to measure the flow rate at and near the venturi throat, or may include an orifice with upstream and downstream pressure sensors or any other flow sensing mechanism known in the art. The controller 951 receives a signal from the sensor 950 and controls the actuator 952 to vary the amount of force or load applied to the valve member 205 (i.e., plunger) against the valve seat 104, for example via a mechanical link 157, based on the flow rate of gas flowing through the primary outlet 153. In the embodiment of FIG. 31A and FIG. 31B, the valve member is a plunger adapted to support the valve seat 104. The actuator may be connected to the valve member 205 via a biasing member or element 953, such as a spring 953. The actuator may be driven by the controller to adjust the amount of bias provided by the biasing member 953 to adjust the pressure required to lift the valve member 205 off the valve seat 104 in response to the flow rate determined by the controller from the signal provided by the sensor 950. FIG. 31B shows the actuator driven to increase the bias by stretching the biasing member 953 to increase the opening pressure of the PRV. The coupling member 157 may also be rigid, such that the actuator opens and closes the valve member directly. In one such embodiment, the sensor measures both pressure and flow rate and opens the exhaust valve based on the relationship between pressure and flow rate. For a measured flow rate and a measured pressure, the valve opens a predetermined amount to control the pressure at the patient and achieve the characteristics shown in FIG. 15B.

[0319] 32A and 32B show an FCPRV including an electrical sensing device. The electrical sensing device includes a flow and / or pressure sensor 950, a processor or controller 951 (e.g., digital and / or analog electronics), and an actuator 952. The controller 951 receives a signal from the sensor 950 and controls the actuator 952 to vary the amount of force or load applied to the valve member 105 against the valve seat 104, for example, via a mechanical link 157. In the embodiment of FIGS. 32A and 32B, the valve member 104 is a flexible diaphragm adapted to support the valve seat 104. The actuator may be driven to adjust the amount of force or load applied to the valve member in response to a flow rate determined by the controller via a signal provided by the sensor 950, to vary the amount of bending of the flexible diaphragm as it is pulled against the valve seat, and to adjust the pressure required to lift the valve member 105 off the valve seat 104. The bias against the valve seat is provided by the resiliency of the flexible diaphragm. Figure 32B shows the actuator actuated to increase the bias by pulling the diaphragm against the valve seat 104.

[0320] 33A and 33B show flow-controlled pressure regulation devices that control pressure at a patient to a safe level based on the relationship between pressure and flow rate provided to the patient. Each device includes an electrical sensing device. The electrical sensing device includes a flow and pressure sensor 950, a processor or controller 951 (e.g., digital and / or analog electronics), and an actuator 952. The controller 951 receives a signal from the sensor 950 and controls the actuator 952 to change the size of the restriction or opening / orifice and regulate the amount of flow to the patient. The sensor 950 is located downstream (i.e., on the patient side) of a variable flow restriction 954 (e.g., a valve) to provide an indication of the pressure to the patient. Turbulence can occur behind the variable restriction or valve 954. To reduce the effect of turbulence on the sensing device 950, baffles or vanes may be provided and / or the sensor may be located sufficiently downstream of the variable flow restriction / valve. In Figure 33A, a variable flow restriction 954 is in the primary flow path from the primary inlet 151 to the primary outlet 153. If a flow restriction is introduced into the system downstream of the variable restriction 954 (or, for example, in the patient's nares), the controller may sense an increase in pressure for a given flow rate and reduce the flow restriction 954 by moving actuator 952 to increase the size of the orifice or opening 954 to maintain a set flow rate in the system (e.g., as shown by the vertical line in the graph of Figure 15B). If the flow restriction causes the pressure in the device to reach a pressure limit based on the pressure vs. flow relationship (i.e., curve 142 in Figure 15B), the controller may then begin to increase the flow restriction 954 by moving actuator 952 to decrease the size of the orifice or opening, limiting the pressure in the device and therefore the flow rate and pressure at the patient (i.e., the flow restriction is controlled such that the pressure and flow at the device are at point 3 in Figure 15B). Thus, the valve or variable flow restriction 954 is controlled based on the relationship between pressure and flow. An additional vent 955 may be used to reduce pressure in the outlet line in the event of a rapid shutoff where the actuator cannot respond quickly enough.

[0321] In FIG. 33B, a variable flow restriction 954 is in the exhaust path to exhaust a portion of the flow from the system. If a flow restriction is introduced into the system downstream of the valve or variable restriction 954, the controller will sense an increase in pressure and move the actuator 952 to increase the size of the orifice or opening 954, thereby reducing the flow restriction 954 and exhausting the flow from the system, maintaining the maximum set pressure in the pressure regulating device and therefore the patient. Thus, the valve or variable flow restriction 954 is controlled based on the relationship between pressure and flow. In some embodiments, the device of FIG. 33A may include a second actuator and valve 954 to control the flow rate of gas exhausting through the aperture 955. For example, the exhaust aperture 955 of FIG. 33A may be controlled by a valve arrangement as shown in FIG. 33B. The controller may control a (first) actuator and valve to occlude flow from the main inlet to the main outlet as shown in Figure 33A, and a second actuator and valve downstream of the first valve to control vent flow from aperture 955 as shown in Figure 33B. The first valve may be controlled as described above, but the second valve may operate to vent flow and pressure if the first valve is unable to respond to a quick pressure increase.

[0322] Various embodiments of FCPRVs have been described that include a sensing mechanism for adjusting the opening pressure of the valve in response to flow. However, PRVs without flow sensing mechanisms, such as the embodiments described above with reference to Figures 2A-12E, may be configured to operate as flow-compensated pressure relief valves for fixed input flows. Referring to the graph of Figure 34A, the PRV may be adjusted to have a "knee" as described above with reference to Figures 3-8. The Pc pressure drops from the knee of the Pc curve, for example between points A and B in Figure 34A, as the exhaust flow increases. When the flow to the patient is equal to the flow to the PRV minus the exhaust flow, the negative slope of the exhaust flow curve between points A and B corresponds to the positive slope of the flow to the patient within the same pressure band (in this example, from about 18 cmH2O to about 30 cmH2O).

[0323] FIG. 34B shows the opening pressure flow curve 142b of the flow to the patient, which is the flow to the PRV minus the PRV exhaust flow curve 142a. Thus, as the valve system pressure Pc increases for flow to the patient, the opening pressure 142b also increases. Because the PRV is adjusted so that the valve continuously exhausts within the valve's operating range, the PRV system pressure Pc is equal to the PRV exhaust pressure 142b. The pressure to the patient at any flow rate to the patient is equal to the exhaust pressure Pc (curve 142b) minus the system pressure loss from the PRV to the patient (curve 141) at that flow rate, i.e., the offset between curve 142b and curve 141. For a known flow resistance 141 of the system and a fixed input flow, the valve response required to achieve the drive pressure 142a required to exhaust the excess flow and achieve a safe patient pressure can be designed. The exhaust pressure 142b at a given flow rate x to the patient is equal to the system flow resistance 141 at that flow rate plus the safe patient pressure (Ppatient). The patient pressure at a given flow rate for the patient can be determined as the exhaust pressure 142a at a certain exhaust flow rate (which is equal to the input flow rate minus the patient flow rate) minus the flow resistance of the system at that patient flow rate.

[0324] Various embodiments of the PRV 100 have been described above with respect to exhaust pressure from the gas flow provided to the user through the patient interface. Further uses and arrangements of the PRV according to the embodiments described herein are shown in Figs. 35A and 35B. As shown, the valve member 105-1 of the PRV 100 is coupled to the second valve member 105-2 via a mechanical link 157. The second valve member 105-2 is configured to seal a port of the nebulizer 116 located in the respiratory gas flow to the patient. As shown in Fig. 35A, when the patient exhales, the exhaled gas flows from the patient interface 115 through the PRV 100 and is exhausted from the exhaust outlet 103 of the PRV 100. When exhausting the exhaled gas through the PRV 100, the valve member lifts off the valve seat 104, and the displacement of the valve member 105-1 holds the second valve member 105-2 against the valve seat 104-2 of the nebulizer 116. Thus, when the patient exhales, the medication delivered by the nebulizer 116 is sealed from being released into the gas stream to the patient. As shown in Figure 35B, when the patient inhales, the PRV is in a closed or non-discharge configuration with the valve member 105-1 abutting the valve seat 104-1. Displacement of the valve member 105-1 against the valve seat 104-1 lifts the second valve member 105-2 off the nebulizer valve seat 104-2, thereby discharging medication from the nebulizer 116 into the gas stream delivered to the patient via the patient interface 115. The above arrangement thus prevents the discharge of medication to atmosphere, thus preventing medication from being wasted.

[0325] In some embodiments, the PRV (e.g., PRV100) or FCPRV (e.g., FCPRV800) includes a vent indicator to indicate when flow is being discharged from the PRV or FCPRV through the outlet chamber 102 and outlet vent 103. Some vent indicator embodiments are described below with reference to Figures 36-40.

[0326] 36, the FCPRV includes a guide or sight tube 1001 and a shuttle 1002 that moves along the tube 1001 in response to gas flow exiting the exit chamber 102. The tube 1001 may be aligned with the exit exhaust aperture 103. As the shuttle moves due to flow through the exhaust aperture 103, the shuttle becomes visible from outside the housing 180, for example, through a transparent portion of the housing and / or the sight tube.

[0327] 37, the FCPRV includes a flap 1003 that moves about a hinge axis in response to gas flow exiting the outlet chamber 102, e.g., in the direction indicated by arrow A. The flap 1003 is located adjacent to or near the outlet vent 103. The housing may have a viewing aperture 1004, which when the flap bends in response to flow from the vent 103, covers the viewing aperture so as to be visible from outside the housing. Through the aperture 1004, the flap appears as a colored "dot" when in a bent or exhausting configuration.

[0328] In some embodiments, as shown in FIG. 38, the FCPRV includes a plunger or shuttle received in a guide for movement in response to the gas flow exiting the outlet chamber 102. The shuttle 1005 may include an annular portion or cuff received in the housing outlet 188, e.g., coaxially received in the housing outlet 188. The annular housing outlet 188 may guide the shuttle. In the exhaust configuration, the shuttle may move visible from outside the housing, e.g., extend out of the housing, or may be visible through a transparent portion of the housing. For example, the housing outlet 188 may be transparent. The remainder of the housing may be opaque. FIG. 39 shows a similar embodiment including a shuttle 1005 that moves in response to the gas exiting the outlet chamber. In the embodiment of FIG. 39, the shuttle includes a member received in the outlet chamber exhaust outlet 103, e.g., there are two elongated members 1006, each elongated member received in each exhaust outlet 103.

[0329] In some embodiments, as shown in FIG. 40, the FCPRV includes a plunger or shuttle 1007 received in a guide, e.g., a guide tube 1008, for movement in response to pressure in the outlet chamber. The pressure in the outlet chamber 102 is proportional to the flow of gas exiting the outlet chamber, and thus an indication of the flow rate of gas exiting the FCPRV. As the shuttle moves along the guide, it becomes visible from outside the housing 180, e.g., through a transparent portion of the housing and / or the sight tube / guide 1008. As shown in FIG. 40, the guide tube may be marked with graduations relating the position of the shuttle along the guide tube to the flow rate. An annular space may be formed between the exterior surface of the shuttle and the interior surface of the guide 1008. Exhaust gas may enter the sight tube 1008 through the outlet vent 103, travel along the guide and around the shuttle 1007, and exit the guide through the outlet end of the tube. A cap 1008a may be attached to the outlet end of the tube, the cap including a hole or aperture 1008b. The holes may be smaller than the cross section of the guide 1008 and may be sized to calibrate the shuttle to indicate the flow rate of the exhaust gases.

[0330] The described exhaust indicator mechanisms may provide a binary indication of exhaust flow from the PRV / FCPRV, for example indicating exhausting or no exhaust (above a threshold). Such mechanisms may be described as "pop-up" indicators that include a member that "pops up" to be visible from outside the housing when flow is being exhausted from the valve. Alternatively, in some embodiments, the exhaust indicator may provide a proportional indication of exhaust, indicating the flow rate of gas being exhausted from the outlet chamber. For example, the housing or shuttle guide 1001, 1008, or a portion of the housing 180 may include markings or indicia indicating the amount of shuttle travel that is indicative of the exhaust flow rate.

[0331] In some embodiments, the PRV or FCPRV may include an indicator to display the flow of gas delivered to the patient or user from the outlet of the PRV / FCPRV. For example, referring to FIG. 41A and FIG. 41B, in some embodiments, the flow indicator includes an impeller 1009 disposed at the outlet 153 of the FCPRV. As the flow of gas travels along the outlet 153, the flow causes the impeller to rotate to indicate the flow. The impeller may be visible from the end of the outlet 153, or the outlet 153 may be transparent so that the impeller is visible through the wall of the outlet. The impeller 1009 may be rotatably mounted within an impeller housing 1010, which may be received within the outlet 153.

[0332] 42A-42C, in some embodiments, the flow indicator may include a flap 1011 disposed within the outlet 153 of the PRV. The flap is movable between a closed position at least partially occluding the outlet and an open position. Flow causes the flap to move to the open position, providing an indication of flow through the outlet and toward the patient. The flap may be visible from the end of the outlet 153, or the outlet 153 may be transparent so that the flap is visible through a wall of the outlet.

[0333] As shown in FIG. 43, in some embodiments, the flow indicator may include a plunger or shuttle 1012 received within a guide tube 1008. The inlet end 1008c of the guide tube may be in fluid communication with the inlet 151 of the FCPRV and the outlet end 1008d may be in fluid communication with the outlet 153 of the FCPRV such that the guide tube senses a differential pressure at the flow restriction 152 (e.g., as shown in FIG. 27A) between the inlet 151 and outlet 153 of the FCPRV. The shuttle 1012 is adapted to move within the guide tube in response to the differential pressure at the flow restriction 152 to provide an indication of flow through the FCPRV to the patient. As shown in FIG. 43, the guide tube may be calibrated to relate the position of the shuttle along the guide tube to the flow rate. A spring (not shown in FIG. 43) may bias the shuttle or plunger against movement in response to an increasing flow rate. In other words, the spring may bias the plunger or shuttle to a zero flow indication. As the flow increases, it moves a shuttle or plunger against the bias of a spring, indicating the flow rate in the FCPRV.

[0334] In some embodiments, the PRV as described above with reference to Figures 2A-12E may include a damper. In some embodiments, the FCPRV as described above with reference to Figures 14A-26B may include a damper. In some embodiments, a damping member (damper) may be disposed or located in contact with the sensing member 155, 255, 280 and / or the valve member 105, 205. In some embodiments, the damper is disposed in contact with the valve member 105, 205. The damper may be attached to the valve member 105, 255. The damper may be disposed in the displacement chamber 107, 207 or, if in contact with the sensing member, in the second chamber 154b, 254b. The damper may include a damping material such as foam, or a cotton pad, sponge, or tissue. In some embodiments, the damper is preferably formed from a soft, sponge-like material. In some embodiments, the damper includes a porous material having a plurality of holes. In some embodiments, the damper acts as a muffler configured to attenuate or muffle noise from various valve moving components. In some embodiments, the damper also increases valve stability over a wider operating flow range. In some embodiments, the damper dampens mechanical vibrations of the moving parts of the PRV or FCPRV, which may further reduce noise and / or increase valve stability over a wider operating flow range.

[0335] In some embodiments, the pressure relief valve of the flow compensated pressure relief valve may not have an outlet chamber.

[0336] In some embodiments, the PRV or FCPRV described herein may be provided as a disposable or consumable item that is discarded after a short period of use so that cleaning of the PRV or FCPRV is not necessary. If a conduit is provided with the PRV or FCPRV, the conduit may also be disposable along with the PRV or FCPRV. Alternatively, the PRV or FCPRV described herein may be provided as a reusable device. Such an article is preferably washable and can be sterilized, for example, by autoclaving. The device may be disassembled for cleaning, for example, by a medical professional, and reassembled after cleaning.

[0337] The above description of the invention includes preferred forms thereof. Modifications may be made thereto without departing from the scope of the invention.

[0338] Where in the foregoing description reference is made to integers or components having known equivalents, these integers are incorporated herein as if individually set forth.

[0339] The present invention may also be considered to be broadly comprised of the components, elements and features referred to or shown in the specification of this application, either individually or collectively, in any or all combinations of two or more of the elements or features.

Claims

1. A flow-compensating pressure regulator or pressure release device for a gas flow supply system, A main inlet for receiving a gas flow from a gas source, and a main outlet for supplying at least a portion of the gas flow received by the main inlet to flow out of the device, A pressure relief valve is provided, which is adapted to release at least a portion of the gas flow received by the main inlet when the pressure of the gas flow increases above a pressure threshold. A sensing mechanism including one or more sensors for detecting the flow rate of gas flowing from the main outlet of the device to the main outlet, and a controller configured to receive signals from the sensors and provide an output for adjusting the pressure threshold of the pressure relief valve based on the detected flow rate, A device that includes this.

2. The device according to claim 1, wherein the sensor is configured to detect the pressure of the gas flow from the main inlet to the main outlet.

3. The device according to claim 1, wherein the sensor is an electronic sensor such as a hot film sensor, an ultrasonic sensor, or a pressure sensor.

4. The device according to claim 1, wherein the sensing mechanism includes an actuator configured to adjust the pressure threshold of the pressure relief valve in accordance with the output from the controller.

5. The aforementioned pressure relief valve is A valve inlet that communicates with the main inlet, Discharge outlet and The valve seat between the valve inlet and the discharge outlet, A valve member that is biased to seal the valve seat, is displaced from the valve seat by the inlet pressure of the valve inlet which increases beyond a pressure threshold, and discharges at least a portion of the gas flow from the valve inlet to the outlet, The device according to claim 4, including the device described in claim 4.

6. The device according to claim 5, wherein the sensing mechanism includes a mechanical link that acts between the actuator and the valve member in accordance with the flow rate of the gas flow from the main inlet to the main outlet, transmits the force applied by the actuator to the valve member, and adjusts the biasing of the valve member with respect to the valve seat.

7. The device according to claim 6, wherein the mechanical link is coupled to the valve member by a biasing member, and biases the valve member with respect to the valve seat in accordance with the flow rate of the gas flow from the main inlet to the main outlet.

8. The device according to claim 7, wherein the biasing member is a spring.

9. The device according to claim 6, wherein the mechanical link is rigid, and the actuator is configured to directly open and close the valve member.

10. The device according to claim 6, wherein the valve member is a flexible diaphragm configured to support the valve seat.

11. The device according to claim 10, wherein the controller is configured to drive the actuator in accordance with the detected flow rate to adjust the amount of force applied to the valve member, to change the amount of bending of the flexible diaphragm, and to provide an output for adjusting the pressure required to lift the valve member from the valve seat.

12. The device according to claim 11, wherein the biasing force on the valve seat is provided by the elasticity of the flexible diaphragm, and the actuator is driven in response to the output from the controller and is configured to increase the biasing force by pulling the diaphragm against the valve seat.

13. The aforementioned pressure relief valve is A discharge path that is in fluid communication with the aforementioned main inlet, A variable flow rate limiting unit in the discharge path, wherein the variable flow rate limiting unit is configured to discharge a portion of the flow from the system, and the controller is configured to reduce the flow rate limit within the variable flow rate limiting unit by moving the actuator in accordance with the pressure threshold to increase the size of the opening of the variable flow rate limiting unit, The device according to claim 4, including the device described in claim 4.

14. A flow-compensating pressure regulator or pressure release device for a gas flow supply system, A main inlet for receiving a gas flow from a gas source, and a main outlet for supplying at least a portion of the gas flow received by the main inlet to flow out of the device, A variable flow rate limiting unit in the main flow path from the main inlet to the main outlet, A sensing device located downstream of the variable flow rate limiting unit, One or more sensors that detect the pressure of the gas flow to the patient, A controller configured to provide an output that changes the size of the variable flow limiter based on the detected pressure display, The sensing device includes, A device that includes this.

15. The device according to claim 14, wherein the variable flow rate limiting unit includes an actuator configured to adjust an opening in the variable flow rate limiting unit in accordance with the output from the controller.

16. The device according to claim 14, wherein the one or more sensors include a flow sensor and / or a pressure sensor.

17. The device according to claim 14, wherein the device includes an exhaust path configured to discharge at least a portion of the gas flow from the main inlet and the main outlet.

18. The device according to claim 16 or 17, wherein the discharge path is located downstream of the variable flow rate limiting unit.

19. The device according to claim 14, wherein the sensor is an electrical sensing device.

20. The device according to claim 14, further comprising a baffle or vane configured to reduce the effects of turbulence on the sensing device.

21. The device according to claim 14, wherein the controller is configured to maintain a set flow rate in the system, and the controller adjusts the size of the variable flow limiter by moving the actuator based on pressure.

22. The device according to claim 15, wherein when the controller detects an increase in pressure relative to a given flow rate, the controller moves the actuator to increase the size of the variable flow rate limiting unit to maintain the set flow rate in the system.

23. The device according to claim 15, wherein, when the pressure of the device reaches a pressure limit based on the pressure-to-flow ratio due to the restriction of gas flow, the controller moves the actuator to reduce the size of the variable flow limiting unit, thereby limiting the pressure of the device and the flow rate and pressure in the patient.

24. A flow-compensating pressure regulator or pressure release device for a gas flow supply system, A main inlet for receiving a gas flow from a gas source, and a main outlet for supplying at least a portion of the gas flow received by the main inlet to flow out of the device, A variable flow rate limiting unit is located within a discharge path, and the discharge path is configured to discharge at least a portion of the gas flow, the variable flow rate limiting unit and A sensing device located downstream of the aforementioned discharge path, One or more sensors that detect the pressure of the gas flow to the patient, A controller configured to provide an output that changes the size of the variable flow limiter based on the detected pressure display, The sensing device includes, A device that includes this.

25. The device according to claim 24, wherein the variable flow rate limiting unit includes an actuator configured to adjust an opening in the variable flow rate limiting unit in accordance with the output from the controller.

26. The device according to claim 24 or 25, wherein the one or more sensors include a flow sensor and / or a pressure sensor.

27. The device according to claim 24, further comprising an actuator disposed within the discharge channel, wherein the controller is configured to operate the actuator to control the gas discharged from the discharge path.

28. The device according to claim 24, wherein the sensing device is an electrical sensing device.

29. The device according to claim 24, further comprising a baffle or vane configured to reduce the influence of turbulence on the sensing device.

30. The device according to claim 24, wherein the controller is configured to maintain a set flow rate in the system, and the controller moves the actuator based on pressure to adjust the opening of the variable flow limiter.

31. The device according to claim 24, wherein when the controller detects an increase in pressure, the controller reduces the variable flow limiter, discharges the gas flow, and maintains the maximum set pressure in the device and therefore in the patient.

Images