Description:DESCRIPTION

Technical Field
[001] This disclosure relates generally to non-invasive and invasive ventilators capable of assisting physiological respiration, and more particularly to ventilators and methods for simultaneously maintaining positive end expiratory pressure (PEEP) and maintaining fraction of Oxygen (FiO2) in the Oxygen-air mixture in the inspiratory line.

Background
[002] Ventilators are medical devices used to provide supplemental oxygen support to patients. The ventilators may include a source of pressurized Oxygen and an air source fluidly connected to the patient through a conduit, to supply Oxygen-air mixture to the patient. During a controlled inhalation phase, respiratory gas (for example, Oxygen and air mixture) is supplied to the patient.
[003] Positive end expiratory pressure (PEEP) is the positive pressure that remains in the airways at the end of the respiratory cycle (end of exhalation). The PEEP should be maintained greater than the atmospheric pressure in mechanical ventilators being used with mechanically ventilated patients. A passive PEEP valve may be used to maintain a predetermined minimum pressure during a controlled exhalation phase. Further, it may be important to to maintain a predetermined fraction of Oxygen (FiO2) in the Oxygen-air mixture in the inspiratory line of the mechanical ventilators.
[004] Some conventional techniques attempt to maintain both the necessary PEEP and the FiO2 simultaneously in the ventilator circuit. However, these techniques rely on bulky electronically controlled valves at the expiratory end and require pre-determination of resistance and compliance to derive mathematical equations to maintain the PEEP. As such, these conventional techniques are inefficient, costly, and difficult to implement. Moreover, these conventional techniques do not take into consideration the Hammer effect, thereby introducing other complications in the process of using ventilators.
[005] Therefore, it is desired to provides a method and system for simultaneously maintaining the PEEP and the FiO2 in the ventilator circuit while considering the Hammer effect to prevent the undesired variation in the pressure in the ventilator circuit.

SUMMARY
[006] A ventilator circuit for maintaining a positive end expiratory pressure (PEEP) is disclosed. The ventilator circuit may include an Oxygen source, an air source, and a mixing chamber fluidically coupled to the Oxygen source and the air source. The mixing chamber may be configured to mix a supply of Oxygen from the Oxygen source and a supply of air from the air source, to generate Oxygen-air mixture. The ventilator circuit may further include an inspiratory line configured to supply the Oxygen-air mixture from the mixing chamber to a user and an expiratory line. The expiratory line may include a flow control valve configured to fluidically couple to the inspiratory line. The first flow control valve may be configurable between at least a first state and a second state. The expiratory line may further include an exhalation membrane valve. In the first state, the flow control valve may allow flow of Oxygen-air mixture from the inspiratory line to the exhalation membrane valve. In the second state, the flow control valve may prevent flow of Oxygen-air mixture between the mixing chamber and the exhalation membrane valve.
[007] In another embodiment, a method of maintaining a positive end expiratory pressure (PEEP) in the ventilator circuit is disclosed. The method may include detecting one of an inspiratory and an expiratory phases. Further, the method may include, in response to the detection of the inspiratory phase or the expiratory phase of the ventilator cycle, configuring a flow control valve between at least a first state and a second state. The flow control valve may be provided on an expiratory line and may be configured to be fluidically coupled to an inspiratory line. The inspiratory line may be configured to supply Oxygen-air mixture from a mixing chamber to a user. The expiratory line may further include an exhalation membrane valve. In the first state, the flow control valve may allow flow of Oxygen-air mixture from the inspiratory line to the exhalation membrane valve. In the second state, the flow control valve may prevent flow of Oxygen-air mixture between the mixing chamber and the exhalation membrane valve. A predetermined fraction of Oxygen (FiO2) in the Oxygen-air mixture may be maintained in the inspiratory line.
[008] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS
[009] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles.
[010] FIG. 1 illustrates a schematic diagram of a ventilator circuit for maintaining a positive end expiratory pressure (PEEP), in accordance with an embodiment of the present disclosure.
[011] FIG. 2 illustrates a graphical representation of flow respect to time in the ventilator circuit of FIG. 1 and the corresponding gas pressure in the ventilator circuit with respect to time, in accordance with some embodiments of the present disclosure.
[012] FIG. 3 illustrates a flowchart of a method of maintaining the PEEP in the ventilator circuit of FIG. 1, in accordance with another embodiment of the present disclosure.

DETAILED DESCRIPTION
[013] Exemplary embodiments are described with reference to the accompanying drawings. Wherever convenient, the same reference numbers are used throughout the drawings to refer to the same or like parts. While examples and features of disclosed principles are described herein, modifications, adaptations, and other implementations are possible without departing from the spirit and scope of the disclosed embodiments. It is intended that the following detailed description be considered as exemplary only, with the true scope and spirit being indicated by the following claims. Additional illustrative embodiments are listed below.
[014] The present subject matter discloses techniques for simultaneously maintaining PEEP and FiO2 in the ventilator circuit using a simple electronically controlled valve at the expiratory end. Further, the ventilator circuit and methods of the present subject matter take in to account the Hammer effect to prevent any undesired variation in the pressure in the ventilator circuit.
[015] A 3/2 electronically controlled proportional valve is used which lessens the complexity of the pneumatic assembly. Further, the techniques of the present subject matter sense the flow rate during the exhalation phase to maintain the PEEP at a predefined level. Maintaining the PEEP at the predefined level helps in maintaining the natural exhalation process of the patient. Further, the techniques help in maintaining the PEEP at the predefined level without requiring any complicated mathematical calculations. Further, the techniques work on the principle of reducing the Hammer effect by addressing abrupt stopping of the flowing fluid during the transition from inspiration to expiration phase. This is achieved by allowing the patient to exhale naturally till a certain limit above the required PEEP pressure and then introducing the air flow and the required oxygen flow through the inspiratory line to maintain FiO2 percentage. An expiratory valve controls the opening of the expiratory membrane when the pressure drops within a PEEP tolerance range. As a result, the expiratory valve is switched ON proportionally, based on feedback from proportional–integral–derivative (PID) control. Once the flow is reduced to a desired level, the expiratory valve is switched ON completely, thereby preventing further gas leakage, and hence maintaining the PEEP level. The proportional control to the expiratory valve reduces the Hammer effect and also there is no rise in the PEEP after closing the system.
[016] In one embodiment, a schematic diagram of a ventilator circuit 100 is illustrated in FIG. 1, in accordance with some embodiments of the present disclosure. The ventilator circuit 100 may include an Oxygen source 102, an air source 104 and a mixing chamber 106. The mixing chamber 106 may be fluidically coupled to the Oxygen source 102 and the air source 104. The mixing chamber 106 may be configured to receive a supply of Oxygen from the Oxygen source 102 and a supply of air from the air source 104. The mixing chamber 106 may mix the supply of Oxygen and the supply of air to generate Oxygen-air mixture. To this end, the mixing chamber 106 may be Y-shaped member which may include two input ports to receive the supply of Oxygen and the supply of air respectively. The supply of Oxygen and the supply of air may be mixed inside the Y-shaped member to generate Oxygen-air mixture and the Oxygen-air mixture may be outputted via a single output port. The output port may be connected to the patient to supply the Oxygen-air mixture.
[017] Additionally, in some embodiments, the ventilator circuit 100 may further include a humidifier (not shown in FIG. 1). As will be appreciated by those skilled in the art, the Oxygen-air mixture may cause dryness in the respiratory tract of the patient if supplied directly to the patient as is. Therefore, the Oxygen-air mixture may be passed through the humidifier before it is supplied to the patient. The humidifier may add humidity to the air Oxygen-air mixture, to reduce the dryness effect which may be otherwise caused by the dry Oxygen-air mixture. The construction and working of the humidifier may be same as is being used in those already known in the art. Thereafter, the Oxygen-air mixture upon humidification may be supplied to the patient 114 (also referred to as user 114 in this disclosure). It should be noted that the various fluidic couplings, i.e., the fluidic coupling between the Oxygen source 102 and the mixing chamber 106, the fluidic coupling between the air source 104 and the mixing chamber 106, etc. may be implemented via various associated tubes.
[018] Further, in some embodiments, the ventilator circuit 100 may include an Oxygen pressure regulator 124 positioned between the Oxygen source 102 and the mixing chamber 106, that may regulate the pressure of the Oxygen being supplied by the Oxygen source 102. Furthermore, an air pressure regulator (not shown in FIG. 1) may be provided and positioned between the air source 104 and the mixing chamber 106, that may regulate the pressure of the air being supplied by the air source 104, when the air source 104 is compressed air. However, the air pressure regulator may not be required in case an air blower is used as the air source 104, as the pressure can be regulated by controlling the air blower's speed. By regulating the both the Oxygen pressure and the air pressure, an over-pressure situation may be prevented. Further, the pressure regulators may provide an indication when the respective pressure falls below a predefined pressure threshold.
[019] The ventilator circuit 100 may further include an Oxygen control proportional valve 126 positioned between the Oxygen pressure regulator 124 and the mixing chamber 106. Further, the ventilator 100 may include an air control proportional valve (not shown in FIG. 1) positioned between the air pressure regulator (not shown in FIG. 1) and the mixing chamber 106, when the air source 104 is compressed air. However, no air control proportional valve may be required when an air blower is used as the air source 104.
[020] The ventilator circuit 100 may further include a pressure sensor 122 which may be configured to measure the gas pressure within the inspiratory line 110. It should be noted that the pressure sensor 122 may be selected from any conventional pressure sensors already known in the art.
[021] Further, the ventilator circuit 100 may include a Y-shaped member 108 which may be fluidically coupled to the mixing chamber 106, via an inspiratory line 110. The Y-shaped member 108 may include multiple ports, for example, a port coupled with the inspiratory line, a port coupled with an expiratory line 112, and another port coupled with a user 114 (a patient). The inspiratory line 110 ay be therefore configured to supply the Oxygen-air mixture from the mixing chamber 106 to the user 114.
[022] The expiratory line 112 may include a flow control valve 116. The flow control valve 116 may be configured to be fluidically coupled to the inspiratory line 110. The flow control valve 116 may be configurable between at least a first state and a second state. In some example embodiments, the flow control valve 116 may be 3/2 normally closed (NC) proportional valve. The expiratory line 112 may further include an exhalation membrane valve 118.
[023] The exhalation membrane valve 118 may be configured to close during inspiratory phase due to pressure differential across the exhalation membrane valve 118. The exhalation membrane valve 118, in some example embodiments, may include an air pressure sensitive membrane, which depending on the pressure across it, may cause the open or close the flow of gas across the exhalation membrane valve 118.
[024] In the first state, the flow control valve 116 may allow flow of the Oxygen-air mixture from the inspiratory line 110 to the exhalation membrane valve 118. In the second state, the flow control valve 116 may prevent flow of the Oxygen-air mixture between the mixing chamber 106 and the exhalation membrane valve 118. It should be noted that in the second state of the flow control valve 116, the prevention of the flow of Oxygen-air mixture from the inspiratory line to the expiratory line may cause the exhalation membrane valve 118 to open, thereby allowing exhalation gases (generated during the expiratory phase of breathing) to escape to the ventilator circuit 100 into the atmosphere.
[025] In order to perform the above functionalities, the flow control valve 116 may include multiple ports – a first port 116A, a second port 116B, and a third port 116C. In some embodiments, the first port 116A may be fluidically coupled with the inspiratory line 110. In particular, for example, the first port 116A may be fluidically coupled with the mixing chamber 106 to receive the Oxygen-air mixture therefrom. The second port 116B may be fluidically coupled with the exhalation membrane valve 118 of the expiratory line 112. The third port 116C may be configured to be open to the atmosphere. The first port 116A, the second port 116B, and the third port 116C may be selectively and individually opened and closed, for example based on a control signal. In an embodiment, first control valve may be configured to proportionally distributed the Oxygen-air mixture received from the first port 116A between the second port 116B and the third port 116C based on a control signal. The proportional distribution of the Oxygen-air mixture helps in controlling the amount of Oxygen-air mixture supplied from the inspiratory line 110 to the exhalation membrane valve 118.
[026] Therefore, in the first state, both the first port 116A and the second port 116B are open to thereby allow flow of the Oxygen-air mixture from the inspiratory line 110 to the exhalation membrane valve 118. It should be noted that the flow control valve 116 may be configured in the first state during inspiratory phase of ventilator cycle. It should be further noted that the flow control valve 116 may be configured to switch from the first state to the second state, in response to transition of the ventilator cycle from the inspiratory phase to an expiratory phase. In the second state, at least one of the first port 116A and the second port 116B may be closed to thereby prevent flow of the Oxygen-air mixture between the mixing chamber 106 and the exhalation membrane valve 118. In other words, in the second state, the flow of Oxygen-air mixture from the mixing chamber 106 to the exhalation membrane valve 118 is prevented. In an embodiment, in the second state, the flow control valve 116 may be configured to direct the flow of entire Oxygen-air mixture received at the first port 116A to the third port 116C and thereby prevent flow of the Oxygen-air mixture between the mixing chamber 106 and the exhalation membrane valve 118.
[027] In some embodiments, the flow control valve 116 may be configured to further switch from the second state to the first state at a variable switching rate during the expiratory phase. The switching from the second state to the first state may be in response to pressure in the expiratory line 112 falling below a predetermined pressure level.
[028] Further, in some embodiments, the flow control valve may be configured to switch between the second state and the first state in two phases. A first of the two phases (i.e., a first phase) may be based on a first switching rate. A second of the two phases (i.e., a second phase) may be based on a second switching rate. Further, in some embodiments, the second phase may occur after the first phase. Furthermore, the second switching rate may be faster than the first switching rate. In other words, the rate of switching from the second state to the first state may vary such that the rate of switching may be slower initially (i.e., during the first phase) and the rate of switching may later become faster (i.e., during the second phase). This change in the rate of switching prevents the Hammer effect, as well as reduces the pressure drop thereby increasing the rate of recovery of the PEEP.
[029] The above variable switching rate may be based on a proportional–integral–derivative (PID) controller feedback, corresponding to the PEEP as measured by a pressure sensor 122. The pressure sensed by the pressure sensor may be used to control the PID controller feedback to the flow control valve 116 and thereby, vary the switching rate of the flow control valve 116.
[030] Alternately, the above switching may be controlled by control signals at the inspiratory line 110 and the expiratory line 112. To this end, the ventilator circuit 100 may include a first flow sensor 120-1 provided near the Oxygen source 102, a second flow sensor 120-2 provided near the air source 104, and a third flow sensor 120-3 provided at the expiratory line 112. In particular, the first flow sensor 120-1 may sense the flow rate of Oxygen gas supplied by the Oxygen source 102. The second flow sensor 120-2 may sense the flow rate of air supplied by the air source 104. The third flow sensor 120-3 may sense the flow rate of expiratory gases exiting the expiratory line via the exhalation membrane 118. Corresponding to the flow rate sensed, each of the first flow sensor 120-1, the second flow sensor 120-2, and the third flow sensor 120-3 may generate a signal. These signals may be then used to control the switching of the flow control valve 116. Thus, the signals at the inspiratory line 110 and the expiratory line 112 may be used to proportionally increase the flow of the Oxygen-air mixture through the expiratory line 112. The proportional increase in the flow of the Oxygen-air mixture causes gradual closure of the exhalation membrane 118 and thus preventing the Hammer effect. As will be appreciated by those skilled in the art, the Hammer effect may cause abrupt pressure rise in the ventilator circuit 100. Therefore, by avoiding the Hammer effect, there is lesser need of the corrections in both the inspiratory line 110 and the expiratory line 112, and hence lesser fluctuations in the PEEP.
[031] Further, a non-return valve 128 may be provided that when activated may prevent flow in the direction from the mixing chamber to the air source 104. Similarly, a non-return valve (not shown in FIG. 1) may be provided that when activated may prevent flow in the direction from the mixing chamber to the Oxygen source 102.
[032] It may be desirable to maintain a predetermined fraction of Oxygen (FiO2) in the Oxygen-air mixture in the inspiratory line 110. To this end, the ventilator circuit 100 may include at least one inspiratory flow sensor (i.e., at least one of the first flow sensor 120-1 and the second flow sensor 120-2) configured to maintain a predetermined fraction of Oxygen (FiO2) in the Oxygen-air mixture in the inspiratory line. As such, the predetermined FiO2 in the Oxygen-air mixture is maintained in the inspiratory line 110 simultaneously with maintaining the PEEP, by controlling supply of Oxygen from the Oxygen source 102 and supply of air from the air source 104.
[033] Referring now to FIG. 2, a graphical representation 200 of the flow with respect to time in the ventilator circuit 100 and the corresponding gas pressure in the ventilator circuit 100 with respect to time is illustrated, in accordance with some embodiments of the present disclosure. In particular, the graph 200A depicts the pressure (along y-axis) with respect to time (along x-axis). The graph 200B of the graphical representation 200 depicts inspiratory flow and expiratory flow (along y-axis) with respect to time (along x-axis). The graphical representation 200 is obtained based on the operation of the flow control valve 116.
[034] The invention uses a single 3/2 electronically controlled proportional valve which lessens the complexity of the pneumatic assembly. The algorithm senses the flow rate during the exhalation while maintaining the PEEP, which helps to maintain the natural exhalation process of the patient with no use of pre-determined equations. It works on the principle to reduce the hammer effect which is caused when a flowing fluid is stopped abruptly during the transition from exhalation to PEEP maintaining phase.
[035] This is achieved by allowing the patient to exhale naturally till a certain limit above the required PEEP pressure and then introducing the air flow and required oxygen flow through the inspiratory line to maintain balance the sudden reduction in pressure as well as to maintain the FiO2%. The control is given to the 3/2 proportional valve which controls the opening of the expiratory membrane when the pressure drops within a PEEP tolerance range. Thus, the 3/2 proportional valve is switched ON proportionally using feedback sense PID control. When the flow is reduced to a predefined level below PEEP, the 3/2 proportional valve is switched ON completely thus preventing the further leakage and maintaining the PEEP. This proportional control of the 3/2 proportional valve reduces the hammer effect. Thus, there is no rise in PEEP after closing the system. Herein, the switching ON the 3/2 proportional valve refers to the configuration of the valve where the Oxygen-air mixture received at the port 116A of the valve is directed towards the port 116B of the valve.
[036] As shown in FIG. 2, the inspiration phase extends from time t2 to time t3, during which the pressure in the system (i.e., the ventilator circuit 100) gradually rises, as per the curve between time t2 to time t3, in the graph 200A. During the inspiration phase, the flow control valve 116 is configured to operate in the first state. In the first state, the entire flow of the Oxygen-air mixture received at the port 116A of the valve is directed towards the exhalation membrane 118 via port 116B. This flow of the Oxygen-air mixture may cause the membrane to close and thus prevent leakage of gases from the system. Once the inspiration phase is over, at time t3, the expiration phase starts. At time t3, the flow control valve 116 may be configured to switch OFF i.e., switch to the second state from the first state. In the second state, the entire flow of the Oxygen-air mixture received at the port 116A of the valve is directed towards port 116C. This results in reduction in a pressure drop across the exhalation membrane 118 causing the exhalation membrane 118 to open. The opening of the exhalation membrane 118 causes the exhalation gases (from the user 114) to freely escape the ventilation circuit 100 in the atmosphere resulting in a sudden drop in the pressure in the ventilation circuit 100. The outflow of the gases from the system is depicted by Peak Expiratory flow on negative y-axis at the time t3 in the graph 200B. Due to this sudden drop, the pressure in the system tends to fall below a predefined PEEP. As mentioned above, it is desirable to maintain the minimum pressure in the system at the predefined PEEP, during the expiration phase.
[037] At point A (time tA), the pressure in the system may be just above PEEP. At this point, the inspiration line may be activated. As such, supply of the Oxygen-air mixture to the user 114 via the inspiratory line 110 may be started such that a desired FiO2% is maintained in the supplied Oxygen-air mixture. At point A, the first flow control valve 116 may be configured to operate in the second state (i.e., preventing the flow of Oxygen-air mixture to the exhalation membrane valve 118).
[038] At point B, when the pressure in the system has fallen below the predefined PEEP, the flow control valve 116 (3/2 proportional valve) may be activated. The activation of the flow control valve 116 may take place based on signals received from one or more pressure sensors provided in the ventilator circuit 100. As such, when the pressure in the system falls below the predefined PEEP, the one or more pressure sensors may detect the same and generate a corresponding control signal which is sent to the flow control valve 116 to activate the flow control valve 116. Once activated, the process of proportionally switching the flow control valve 116 into the first state may start. Thus, once activated, the flow control valve directs a certain proportion of the Oxygen-air mixture received at the port 116A towards the exhalation membrane 118 via the port 116B. The supply of Oxygen-air mixture causes the exhalation membrane 118 to gradually close. Once the exhalation membrane valve 118 starts closing, the dropping of pressure stops, and the pressure starts rising (as is depicted by the curve between time tB to time tD). As stated earlier, in the first state, the flow control valve 116 allows entire flow of Oxygen-air mixture from the inspiratory line 110 to the exhalation membrane valve 118. This supply of the Oxygen-air mixture from the inspiratory line 110 may cause the exhalation membrane valve 118 to close.
[039] It should be noted that the before time tB, the flow control valve 116 may be configured in the second state, wherein the flow control valve 116 prevents flow of Oxygen-air mixture from the inspiratory line 110 to the exhalation membrane valve 118. At point B (time tB), the process of configuring (switching) the flow control valve 116 from the second state to the first state may begin, wherein the flow control valve 116 allows flow of Oxygen-air mixture from the inspiratory line 110 to the exhalation membrane valve 118, thereby closing the exhalation membrane valve 118.
[040] In some embodiments, the flow control valve 116 may be switched from the second state to the first state at a variable switching rate during the expiratory phase, in response to pressure in the expiratory line falling below a predetermined pressure level. In particular, the flow control valve 116 may be switched between the second state and the first state in two phases. In the first phase, the transition of the flow control valve 116 from the second state to the first state may take place at a first switching rate. The first phase may last from time tB to time tC.
[041] At point C (time tC), the second phase of the transition of the flow control valve 116 from the second state to the first state may start. The second phase may take place at a second switching rate. The second phase may extend from time tC to time tD. As such, the second phase occurs after the first phases. In some embodiments, the second switching rate may be faster than the first switching rate. In other words, the switching of the flow control valve 116 from the second state to the first state may first take place via a slower transition (first phase, first switching rate) followed by a faster transition (second phase, second switching rate).
[042] At point D (time tD), the switching of the flow control valve 116 from the second state to the first state may be complete. In the first state, the flow control valve 116 may therefore keep the exhalation membrane valve 118 closed, thereby preventing the drop of the pressure in the system. The pressure at time tD onwards is therefore maintained at the predefined PEEP. (It should be noted that the illustrated graph between point A and point D is merely for the purpose of explanation and the scale of the illustrated graph may not be in exact correspondence with actual use-case scenario graph.)
[043] By proportionally controlling the flow of the gas through expiratory line 112, the Hammer effect is minimized if not eliminated. As mentioned above, the Hammer effect may cause pressure rise in the ventilator circuit 100. Therefore, by avoiding the Hammer effect, there is lesser need of the corrections in both the inspiratory line 110 and the expiratory line 112, and hence lesser fluctuations in the PEEP.
[044] Referring now to FIG. 3, a flowchart of a method 300 of maintaining a positive end expiratory pressure (PEEP) in the ventilator circuit 100 is illustrated, in accordance with some embodiments. The method 300 is explained in conjunction with FIGs. 1-2. The method 300 may be performed in association with the flow control valve 116.
[045] At step 302, one of an inspiratory phase or an expiratory phase of a ventilator cycle may be detected. For example, the inspiratory phase or an expiratory phase may be detected using one or more flow sensors 120-1, 120-2, 120-3 provided in the ventilator circuit 100.
[046] At step 304, in response to the detection of the inspiratory phase or the expiratory phase of the ventilator cycle, the flow control valve 116 may be configured between the first state and the second state. As mentioned above, the flow control valve 116 may be provided on the expiratory line 112, and may be configured to be fluidically coupled to the inspiratory line 110. The inspiratory line 110 may be configured to supply Oxygen-air mixture from the mixing chamber 106 to the user 114. The expiratory line 112 may further include the exhalation membrane valve 118. The exhalation membrane valve 118 may be closed during inspiratory phase due to pressure differential across the exhalation membrane valve 118.
[047] In the first state, the flow control valve 116 may allow flow of Oxygen-air mixture from the inspiratory line 110 to the exhalation membrane valve 118, thereby closing the exhalation membrane valve 118. In the second state, the flow control valve prevents flow of Oxygen-air mixture between the mixing chamber 106 and the exhalation membrane valve 118. Once the flow of Oxygen-air mixture from the inspiratory line 110 to the exhalation membrane valve 118 stops, the exhalation membrane valve 118 may open under the effect of exhalation gases during the expiration phase.
[048] By way of an example, the flow control valve 116 may switch from the first state to the second state, in response to transition of the ventilator cycle from the inspiratory phase to the expiratory phase. The exhalation membrane valve 118 may be closed during inspiratory phase due to pressure differential across the exhalation membrane valve 118. When the flow control valve 116 starts switching to first state, the flow control valve 116 may allow flow of Oxygen-air mixture from the inspiratory line 110 to the exhalation membrane valve 118, thereby closing the exhalation membrane valve 118, and thereby stopping the leakage of the exhalation gases from the ventilator circuit 100 and therefore maintaining the PEEP.
[049] It should be noted that a predetermined fraction of Oxygen (FiO2) in the Oxygen-air mixture is maintained in the inspiratory line 110, simultaneously with the maintaining of the predefined PEEP. To this end, the at least one inspiratory flow sensor may be provided in the ventilator circuit 100 to maintain the predetermined FiO2 in the Oxygen-air mixture in the inspiratory line 110. In particular, two inspiratory flow sensors may be provided in the ventilator circuit 100 to maintain the predetermined FiO2 in the Oxygen-air mixture in the inspiratory line 110. The predetermined FiO2 in the Oxygen-air mixture may be maintained in the inspiratory line 110 simultaneously with maintaining the PEEP, by controlling supply of Oxygen from the Oxygen source 102 and supply of air from the air source 104.
[050] The present subject matter discloses one or more techniques for maintaining PEEP and the predetermined FiO2 in the Oxygen-air mixture, using a simple 3/2 NC proportional valve through an exhalation membrane valve. The above techniques do away with the requirements of using complex electronically controlled valves, pistons, motors, or bulky pneumatic assemblies, to provide for simultaneously maintaining the PEEP and the FiO2% during the expiratory phase. Moreover, the single electronically controlled 3/2 NC proportional valve addresses the Hammer effect. Further, the rise in the PEEP level once the system is closed is addressed. As such, the techniques provide for controlling the inspiratory and expiratory phases proportionally, while reducing or eliminating the Hammer effect. Further, the techniques do away with the requirement of corrections at the inspiratory line which avoids the fluctuations in the system during the expiratory phase. The techniques allow a patient to breathe naturally without any pre-determined equation.
[051] Some conventional techniques use a single breathing circuit for inhalation and exhalation, which can cause infection. The above techniques of the present subject matter use two separate lines for inhalation and exhalation (i.e., the inspiratory line 110 and the expiratory line 112), and therefore minimize the chances of infection.
[052] It is intended that the disclosure and examples be considered as exemplary only, with a true scope and spirit of disclosed embodiments being indicated by the following claims.
, Claims:CLAIMS

We claim:
1. A ventilator circuit (100) for maintaining a positive end expiratory pressure (PEEP), the ventilator circuit (100) comprising:
an Oxygen source (102);
an air source (104);
a mixing chamber (106) fluidically coupled to the Oxygen source (102) and the air source (104) and configured to mix a supply of Oxygen from the Oxygen source (102) and a supply of air from the air source (104), to generate Oxygen-air mixture;
an inspiratory line (110) configured to supply the Oxygen-air mixture from the mixing chamber (106) to a user (114); and
an expiratory line (112) comprising:
a flow control valve (116) configured to be fluidically coupled to the inspiratory line (110), the flow control valve (116) being configurable between at least a first state and a second state,
an exhalation membrane valve (118),
wherein in the first state, the flow control valve (116) allows flow of Oxygen-air mixture from the inspiratory line to the exhalation membrane valve (118), and
wherein in the second state, the flow control valve (116) prevents flow of Oxygen-air mixture between the mixing chamber (106) and the exhalation membrane valve (118).

2. The ventilator circuit (100) as claimed in claim 1, wherein the flow control valve (116) is a 3/2 normally closed (NC) proportional valve.

3. The ventilator circuit (100) as claimed in claim 1, wherein the flow control valve (116) is configured in the first state during inspiratory phase of ventilator cycle.

4. The ventilator circuit (100) as claimed in claim 3, wherein the flow control valve (116) is configured to switch from the first state to the second state, in response to transition of the ventilator cycle from an inspiratory phase to an expiratory phase.

5. The ventilator circuit (100) as claimed in claim 3, wherein the flow control valve (116) is configured to further switch from the second state to the first state at a variable switching rate during the expiratory phase, in response to pressure in the expiratory line (112) falling below a predetermined pressure level.

6. The ventilator circuit (100) as claimed in claim 5, wherein the flow control valve (116) is configured to switch between the second state and the first state in two phases,
wherein a first of the two phases is based on a first switching rate and a second of the two phases is based on a second switching rate,
wherein the second of the two phases occurs after the first of the two phases, and
wherein the second switching rate is faster than the first switching rate.

7. The ventilator circuit (100) as claimed in claim 5, wherein the variable switching rate is based on PID control feedback, corresponding to the PEEP as measured by a pressure sensor.

8. The ventilator circuit (100) as claimed in claim 1, further comprising:
at least one inspiratory flow sensor configured to maintain a predetermined fraction of Oxygen (FiO2) in the Oxygen-air mixture in the inspiratory line (110).

9. The ventilator circuit (100) as claimed in claim 8, wherein the predetermined FiO2 in the Oxygen-air mixture is maintained in the inspiratory line (110) simultaneously with maintaining the PEEP, by controlling supply of Oxygen from the Oxygen source (102) and supply of air from the air source (104).

10. The ventilator circuit (100) as claimed in claim 1, wherein the exhalation membrane valve (118) is configured to close during inspiratory phase due to pressure differential across the exhalation membrane valve (118); and
wherein in the second state of the flow control valve, the prevention of the flow of Oxygen-air mixture from the inspiratory line to the expiratory line causes the exhalation membrane valve (118) to open.

11. A method (300) of maintaining a positive end expiratory pressure (PEEP) in the ventilator circuit (100), the method (300) comprising:
detecting one of an inspiratory and an expiratory phases of a ventilator cycle; and
in response to the detection of the inspiratory phase or the expiratory phase of the ventilator cycle, configuring a flow control valve (116) between at least a first state and a second state,
wherein the flow control valve (116) is provided on an expiratory line (112) and is configured to be fluidically coupled to an inspiratory line (110), the inspiratory line (110) configured to supply Oxygen-air mixture from a mixing chamber (106) to a user (114), and the expiratory line (112) further comprising an exhalation membrane valve (118),
wherein in the first state, the flow control valve (116) allows flow of Oxygen-air mixture from the inspiratory line (110) to the exhalation membrane valve (118),
wherein in the second state, the flow control valve (116) prevents flow of Oxygen-air mixture between the mixing chamber (106) and the exhalation membrane valve (118), and
wherein a predetermined fraction of Oxygen (FiO2) in the Oxygen-air mixture is maintained in the inspiratory line (110).