Patent Publication Number: US-2016243330-A1

Title: Respiratory Ventilation System with Gas Sparing Valve Having Optional CPAP Mode and Mask for Use with Same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 13/680,793, filed Nov. 19, 2012, entitled “Respiratory Ventilation System with Gas Sparing Valve having Optional CPAP Mode and Mask for Use with Same,” which application claims benefit of priority of U.S. Provisional Application No. 61/561,465, filed Nov. 18, 2011. Each of the above-identified related applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates, generally, to a respiratory ventilation system that controls gas delivery to a patient and, particularly, to a respiratory ventilation system that utilizes a gas sparing valve to conserve gas. More particularly, the present invention relates to a pneumatically controlled respiratory ventilation system that utilizes a pilot circuit to control gas flow in a main gas supply circuit to thereby conserve gas supplied to a patient. 
     BACKGROUND OF THE INVENTION 
     Ventilation is the physiologic process of moving a gas into (inspiration) and out of (expiration) the lungs of a patient, thereby delivering oxygen to organs of the patient and excreting carbon dioxide. During spontaneous ventilation, i.e. unassisted breathing, negative (sub-atmospheric) pressure is created within the chest of the patient. As a result, gas moves into the lungs of the patient. 
     In the practice of medicine, there is often a need to substitute mechanical ventilatory support for the spontaneous breathing of a patient. Mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator. Alternatively, the breathing of the patient may be assisted by a physician or other suitable person compressing a bag or set of bellows. In positive pressure ventilation, air (or another gas mix, e.g., oxygen mix) is pushed into the trachea of the patient. The positive pressure forces air to flow into the airway to expand and fill the lungs until the inspiration breath is terminated. Subsequently, the airway pressure drops, and the elastic recoil of the chest wall and lungs push the tidal volume, the breath, out through passive expiration or exhalation. 
     Mechanical ventilation may be necessary during respiratory failure or when patients are placed under anesthesia. Particular examples are patients with acute lung injury, including acute respiratory distress syndrome (ARDS); apnea with respiratory arrest, including cases from intoxication; chronic obstructive pulmonary disease (COPD); acute respiratory acidosis; respiratory distress; hypoxemia; hypotension including sepsis; shock; congestive heart failure; and neurological diseases such as Muscular Dystrophy and Amyotrophic Lateral Sclerosis; etc. 
     SUMMARY OF THE INVENTION 
     In accordance with an exemplary aspect of the present invention, there is provided a system for delivering gas to a patient. The system includes a gas control unit, a breathing circuit, a pilot control switch, and a patient interface. The gas control unit includes an outlet having a main gas line outlet. The gas control unit further includes a gas sparing circuit having a primary branch coupled to the main gas line outlet. The primary branch includes a gas sparing valve for controlling a flow of gas through the primary branch. The breathing circuit includes a main gas line having a first end and a second end. The first end of the main gas line is coupled to the main gas line outlet. The pilot control switch is for selectively causing the gas sparing valve to provide the flow of gas to the main gas line via the main gas line outlet. The patient interface is coupled to the second end of the main gas line of the breathing circuit. 
     In accordance with another exemplary aspect of the present invention, there is provided a pneumatic system for delivering gas to a patient. The pneumatic system includes a gas control unit, a breathing circuit, a pilot control switch, and a patient interface. The gas control unit includes an outlet having a pilot control line outlet and a main gas line outlet. The breathing circuit includes a pilot control line having a first end and a second end. The breathing circuit also includes a main gas line having a first end and a second end. The first end of the pilot control line is coupled to the pilot control line outlet, and the first end of the main gas line is coupled to the main gas line outlet. The pilot control switch allows a user to selectively cause the gas control unit to provide gas to the main gas line via the main gas line outlet. The patient interface is coupled to the second end of the main gas line of the breathing circuit. 
     In accordance with a further exemplary aspect of the present invention, there is provided a pneumatic system for delivering gas to a patient. The pneumatic system includes a gas control unit, which includes an outlet having a pilot control line outlet and a main gas line outlet and a gas sparing circuit. The gas sparing circuit includes a primary branch coupled to the main gas line outlet, a pilot control branch coupled to the pilot control line outlet, a pneumatic control valve disposed in the primary branch, the pneumatic control valve comprising a control input, and a timer circuit comprising an output coupled to the control input of the pneumatic control valve. The pneumatic system also includes a breathing circuit having a pilot control line a main gas line. The pilot control line includes a first end and a second end, and the main gas line includes a first end and a second end. The first end of the pilot control line is coupled to the pilot control line outlet, and the first end of the main gas line is coupled to the main gas line outlet. The pneumatic system further includes a pilot control switch for selectively causing the pneumatic control valve to open to provide gas to the main gas line via the main gas line outlet and for activating the pneumatic timer to close the pneumatic control valve after a predetermine amount of time. A patient interface is coupled to the second end of the main gas line of the breathing circuit. 
     In accordance with still another exemplary aspect of the present invention, there is provided a pneumatic system for delivering gas to a patient. The pneumatic system includes a gas control unit having an outlet including a pilot control line outlet and a main gas line outlet. The pneumatic system also includes a breathing circuit, a pilot control switch, and an endotracheal hand piece configured to couple the breathing circuit to an endotracheal tube. The breathing circuit includes a pilot control line having a first end and a second end and a main gas line having a first end and a second end. The first end of the pilot control line is coupled to the pilot control line outlet, and the first end of the main gas line is coupled to the main gas line outlet. The pilot control switch allows for a user to selectively cause the gas control unit to provide gas to the main gas line via the main gas line outlet. 
     In accordance with yet another exemplary aspect of the present invention, there is provided a pneumatic system for delivering gas to a patient. The pneumatic system includes a gas control unit, a breathing circuit, a pilot control switch, and a patient interface. The gas control unit includes a pilot branch, a primary branch, a continuous positive airway pressure (CPAP) branch, and an outlet having a pilot control line outlet coupled to the pilot branch and a main gas line outlet coupled to the primary branch and the CPAP branch. The gas control unit further includes a directional flow control valve for selecting for gas to flow to the main gas line outlet via the primary branch or the CPAP branch. The breathing circuit includes a pilot control line having a first end and a second end and a main gas line having a first end and a second end. The first end of the pilot control line is coupled to the pilot control line outlet, and the first end of the main gas line is coupled to the main gas line outlet. The pilot control switch allows a user to selectively cause the gas control unit to provide gas to the main gas line via the main gas line outlet. The patient interface is coupled to the second end of the main gas line of the breathing circuit. 
     In accordance with another aspect of the present invention, there is provided a gas control unit. In one embodiment, the gas control unit includes an outlet having a main gas line outlet, and a gas sparing circuit including a primary branch coupled to the main gas line outlet and a gas sparing valve for controlling a flow of gas through the primary branch in response to a selective control. In another embodiment, the gas control unit includes an inlet line, an outlet port having a pilot control line outlet and a main gas line outlet, and a gas sparing circuit. The gas sparing circuit includes a primary branch coupled to the inlet line and the main gas line outlet, a pilot control branch coupled to the inlet line and the pilot control line outlet, and a pneumatic control valve disposed in the primary branch. The pneumatic control valve includes an input coupled to the inlet line, an output coupled to the main gas line outlet, and a control input coupled to the pilot branch. The pneumatic control valve is configured to be actuated after occlusion of the pilot control branch to allow gas to flow through the primary branch to the main gas line outlet. 
     In accordance with yet another embodiment of the present invention, there is provided a valve system having a one-way breathing valve for providing primary gas from a source system to a patient upon inhalation, a one-way exhaust valve for exhausting gas from the patient upon exhalation, and an air inlet valve for inletting gas from atmosphere when demand for gas from the patient during inhalation exceeds the gas from the source system. 
     In accordance with yet another embodiment of the present invention, there is provided a patient interface for use with a gas sparing circuit. The patient interface may include a patient mask interface or an endotracheal tube connection. The patient interface may also include a vent port for exhalation by a user of the patient interface during a continuous positive airway pressure (CPAP) mode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For the purpose of illustration, there are shown in the drawings certain embodiments of the present invention. In the drawings, like numerals indicate like elements throughout. It should be understood, however, that the invention is not limited to the precise arrangements, dimensions, and instruments shown. In the drawings: 
         FIG. 1  illustrates an exemplary embodiment of a system for delivering gas to a patient, the system comprising a gas control unit, a disposable breathing circuit, and a mask, the gas control unit comprising a gas sparing circuit comprising a primary branch and a pilot control branch, the primary branch comprising a gas sparing valve, in accordance with an exemplary embodiment of the present invention; 
         FIG. 2  illustrates an exemplary embodiment of an alternative system for delivering gas to a patient, the alternative system comprising a gas control unit, a disposable breathing circuit, and a mask, the gas control unit comprising a gas sparing circuit comprising a primary branch, a pilot control branch, and a continuous positive airway pressure (CPAP) branch, the primary branch comprising a gas sparing valve, in accordance with an exemplary embodiment of the present invention; 
         FIG. 3  illustrates an exemplary block diagram of the exemplary embodiment of the system of  FIG. 1 , in accordance with an exemplary embodiment of the present invention; 
         FIG. 4  illustrates an exemplary block diagram of the exemplary embodiment of the system of  FIG. 2 , in accordance with an exemplary embodiment of the present invention; 
         FIGS. 5A through 5C  illustrate various exemplary embodiments of an external gas port used with the gas control units of  FIGS. 1 and 2 , the external gas port comprising pilot and main outlets, in accordance with an exemplary embodiment of the present invention; 
         FIG. 6  illustrates an exemplary simplified block diagram of the exemplary embodiment of the gas sparing circuit of  FIG. 1  or  FIG. 2 , in accordance with an exemplary embodiment of the present invention; 
         FIG. 7A  illustrates a graph of exemplary pressures at various points in the exemplary simplified block diagram illustrated in  FIG. 6 , in accordance with an exemplary embodiment of the present invention; 
         FIG. 7B  illustrates a graph of exemplary gas flow through the primary branch and the pilot control branch in the gas sparing circuit of  FIG. 1  or  FIG. 2 , in accordance with an exemplary embodiment of the present invention; 
         FIGS. 8A and 8B  illustrate exemplary operation of an exemplary embodiment of a pilot control switch used to selectively occlude the pilot control branches of  FIGS. 1 and 2 , in accordance with an exemplary embodiment of the present invention; 
         FIGS. 8C through 8E  illustrate various views of an exemplary alternative embodiment of a disposable breathing circuit, in accordance with an exemplary embodiment of the present invention; 
         FIG. 9  illustrates an exemplary embodiment of a gas sparing circuit comprising a timer control for main-flow on-time control, in accordance with an exemplary embodiment of the present invention; 
         FIG. 10  illustrates another exemplary embodiment of a gas sparing circuit comprising a timer control for main-flow on-time and off-time control, in accordance with an exemplary embodiment of the present invention; 
         FIGS. 11A and 11B  illustrate exemplary views of an exemplary embodiment of a timer-based trigger used to selectively occlude the pilot control branches of  FIGS. 1 and 2 , the timer-based trigger providing main-flow on-time control, in accordance with an exemplary embodiment of the present invention; 
         FIG. 12  illustrates an exemplary embodiment of a mask connection for use with a gas sparing circuit, the mask connection comprising a spontaneous breath valve, in accordance with an exemplary embodiment of the present invention; 
         FIG. 12A  illustrates an exemplary alternative embodiment of the spontaneous breath valve of  FIG. 12 , in accordance with an exemplary embodiment of the present invention; 
         FIGS. 12B and 12C  respectively illustrate side cross-sectional and top views of the exemplary embodiment of the mask connection of  FIG. 12  connected to the exemplary alternative embodiment of the disposable breathing circuit of  FIG. 8C , in accordance with an exemplary embodiment of the present invention; 
         FIG. 13  illustrates an exemplary embodiment of a hand piece for controlling operation of a gas sparing circuit, the hand piece comprising a pilot control switch, in accordance with an exemplary embodiment of the present invention; 
         FIG. 13A  illustrates an exemplary embodiment of the pilot control switch of  FIG. 13 , in accordance with an exemplary embodiment of the present invention; 
         FIG. 14  illustrates an exemplary embodiment of a system incorporating the hand piece of  FIG. 13 , in accordance with an exemplary embodiment of the present invention; 
         FIG. 15  illustrates an exemplary embodiment of an endotracheal hand piece for control operation of a gas sparing circuit, in accordance with an exemplary embodiment of the present invention; 
         FIGS. 16A and 16B  illustrate exemplary alternative embodiments of masks with integrated hand pieces for control operation of a gas sparing circuit, in accordance with an exemplary embodiment of the present invention; 
         FIG. 17  illustrates an exemplary embodiment of a mask with a CPAP port for use with a system providing resuscitation and CPAP air delivery, in accordance with an exemplary embodiment of the present invention; 
         FIG. 18  illustrates another view of the exemplary embodiment of the hand piece of  FIG. 13  showing the pilot control switch attached to the mask, in accordance with an exemplary embodiment of the present invention; 
         FIG. 19  illustrates an exemplary alternative embodiment of a hand piece for controlling operation of a gas sparing circuit, in accordance with an exemplary embodiment of the present invention; 
         FIGS. 20A through 20C  illustrate various views of another alternative embodiment of a hand piece for controlling operation of a gas sparing circuit, in accordance with an exemplary embodiment of the present invention; 
         FIG. 21  illustrates a view of an exemplary housing for the gas control unit of  FIG. 2 , in accordance with an exemplary embodiment of the present invention; 
         FIGS. 22A through 22C  illustrate various views of another exemplary embodiment of a mask with a CPAP port for use with a system providing resuscitation and CPAP air delivery, in accordance with an exemplary embodiment of the present invention; 
         FIGS. 23A through 23F  illustrate various views of various components of a combination of the mask of  FIGS. 22A through 22C  connected to the mask connection of  FIG. 12 , which is connected to the exemplary alternative embodiment of the disposable breathing circuit of  FIG. 8C , in accordance with an exemplary embodiment of the present invention; 
         FIG. 24  illustrates an exemplary block diagram of an exemplary embodiment of a system for delivering gas to a patient using electrical solenoid and electrical switch control of a pilot control branch, in accordance with an exemplary embodiment of the present invention; 
         FIG. 25  illustrates an exemplary block diagram of an exemplary embodiment of a system for delivering gas to a patient using electrical switch control of a gas sparing valve, in accordance with an exemplary embodiment of the present invention; 
         FIG. 26A  illustrates an exemplary block diagram of an exemplary embodiment of a gas sparing using selectable manual pilot line control and electrical timer control of a gas sparing valve, in accordance with an exemplary embodiment of the present invention; 
         FIG. 26B  illustrates an exemplary block diagram of an exemplary embodiment of a gas sparing circuit of using selectable manual pilot line control of a gas sparing valve and electrical timer control of the gas sparing valve contained in an external, removable module, in accordance with an exemplary embodiment of the present invention; 
         FIG. 27  illustrates an exemplary block diagram of an exemplary embodiment of a gas sparing circuit using selectable manual pilot line control of a gas sparing valve and pneumatic timer control of the gas sparing valve, in accordance with an exemplary embodiment of the present invention; 
         FIG. 28  illustrates an exemplary block diagram of an exemplary embodiment of a gas sparing circuit using a timer control for main-flow on-time and off-time control implemented with two on-time timers, in accordance with an exemplary embodiment of the present invention; 
         FIG. 29  illustrates an exemplary block diagram of an exemplary embodiment of a gas sparing circuit using selectable manual pilot line control of a gas sparing valve and pneumatic timer for main-flow on-time and off-time control utilizing two on-time timers, in accordance with an exemplary embodiment of the present invention; 
         FIG. 30  illustrates an exemplary block diagram of an exemplary embodiment of a gas sparing circuit comprising a pressure surge damping element to eliminate pressure surges when a gas sparing valve is opened, in accordance with an exemplary embodiment of the present invention; 
         FIG. 30A  illustrates an exemplary embodiment of the pressure surge dampening element of  FIG. 30 , in accordance with an exemplary embodiment of the present invention; 
         FIG. 31A  illustrates a graph of exemplary gas pressure through the primary branch in the exemplary embodiment of the gas sparing circuit illustrated in  FIG. 3 , in accordance with an exemplary embodiment of the present invention; 
         FIG. 31B  illustrates a graph of exemplary gas pressure through the primary branch in the exemplary embodiment of the gas sparing illustrated in  FIG. 30 , in accordance with an exemplary embodiment of the present invention; and 
         FIG. 32  illustrates an exemplary embodiment of an endotracheal hand piece for control operation of a gas sparing circuit including a CPAP port for CPAP functionality, in accordance with an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Conventional pneumatic flow circuits or devices do not allow for resuscitation gas flow to be controlled pneumatically. Although it is possible to put a spring-actuated flow control valve near an outlet point of a conventional pneumatic flow circuit, this placement of the flow control valve would make the pneumatic flow circuit complicated and bulky. Further, because the portion of the pneumatic flow circuit connected to the patient may be disposable, placement of the flow control valve on the disposable portion would result in a possibly unacceptable increase in cost of the disposable portion. Further, locating the flow control valve in the disposable portion may not allow for a pop off and peak inspiratory pressure (PIP) pressure control valve arrangement with a gauge remotely located within the pneumatic flow circuit. If located after the flow control valve in the disposable portion, such components would make the disposable portion bulky and expensive. Locating such pressure control valve arrangement at the patient site may increase the size and cost of the disposable portion. 
     Conventional manual and pneumatic devices suffer from numerous disadvantages, such as continuous large gas flows, no flow control, and no pressure control. In addition, some devices waste significant amounts of compressed gases, thereby causing compressed gas tanks to have very limited life. Furthermore, conventional pneumatic devices do not offer the option of delivering fixed, user set flow rates in a continuous positive airway pressure (CPAP) mode through a combined resuscitation and CPAP unitary breathing circuit and mask assembly. 
     An exemplary embodiment of the present invention provides a gas sparing circuit that minimizes the continuous large gas flows from conventional pneumatic devices while allowing for user activation of the large gas flows required for resuscitation. In addition, the gas sparing circuit allows for precise pressure and volume control to the patient currently not available in conventional resuscitation devices. 
     Referring now to  FIG. 1 , there is illustrated a block diagram of a system, generally designated as  100 , for delivering gas to a patient, in accordance with an exemplary embodiment of the present invention. The system comprises a gas control unit  110 , a disposable breathing circuit  120 , and a patient mask  130 . The disposable breathing circuit  120  operates in a resuscitation mode to deliver resuscitating gas to a patient (not illustrated) via a patient mask  130  worn by the patient. A first end  121  of the disposable breathing circuit  120  is coupled to the gas control unit  110 , and a second end  122  of the disposable breathing circuit  120  is coupled to a connection port  131  of the patient mask  130  to deliver gas to the patient during inhalation. The mask  130  interfaces with the patient via a patient-mask interface  132 . A pilot control switch  125  is disposed near the end  122  of the disposable breathing circuit  120  for selective control of main gas delivery flow to the patient. In one exemplary embodiment, the gas comprises air. In another exemplary embodiment, the gas comprises an oxygen mixture. Although not illustrated, it is to be understood that, in an exemplary embodiment, the mask  130  may include one or more exhaust ports to allow for exhalation by the patient. 
     The basic principle of operation for the system  100  is to utilize a pneumatic pilot controlled valve in the gas control unit  110 . As discussed below with respect to  FIG. 3 , the pneumatic pilot controlled valve is coupled to a high pressure, low flow small diameter pilot control circuit that is controlled by a user, such as a medical practitioner, to control a high pressure, high flow main gas circuit to provide on-demand high flow to the patient when needed and to only allow a small trickle pilot flow when there is no main gas demand. This control conserves gas supply by closing the main gas circuit when not demanded. Demanded gas flows at a rate of 35 to 50 liters/minute. A trickle flow of 1-3 liters/minute flows through the pilot control circuit when there is no main gas demand or need for gas by the patient. In an exemplary embodiment, pilot gas flows through the pilot control circuit at not more than 2 liters per minute. 
     Accordingly, the gas control unit  110  comprises a gas inlet  111  and a gas port  112  comprising a pilot control port  116  and a main gas port  117 . (As used herein, the terms “port,” “outlet,” and “outlet port” may be used interchangeably herein as context permits. The same holds true for the terms “port,” “inlet,” and “inlet port” and the terms “primary gas,” “main gas,” and “patient gas.”) The gas inlet  111  is coupled to a gas source (supply), such as a wall source, compressed gas line, or a canister of compressed breathing gas. The pilot control port  116  is coupled to a pilot control line, and the main gas outlet  117  is coupled to a high pressure, high flow main gas line. The gas control unit  110  includes a flow rate control selection means  115  to allow the user to select a desired flow rate in the main gas line. An example of selection means  115  is a flow control valve. The gas control unit  110  further comprises a flow meter  113  to display the current flow rate of the gas through the inlet  111  and a pressure gauge  114  to display the current gas pressure in the main gas outlet  117  being delivered to the patient. The gas control unit  110  also comprises a pop off maximum pressure relief valve  118  and a peak inspiratory pressure (PIP) relief valve  119 . Although the gas control unit  110  is configured for receiving gas from an external gas source via the inlet  111 , other exemplary embodiments are contemplated. For example, it is contemplated that the gas control unit  110  may comprise an internal gas source, such as an internal tank, for storing primary gas, or internal gas pump. 
     The maximum pressure relief valve  118  allows the user to set the maximum pressure that can build up in the gas control unit  110  and the disposable breathing circuit  120  before safely venting to atmosphere. It ensures that pressure in the system  100  does not exceed this maximum pressure. Thus, the valve  118  protects the patient from the high main gas source outlet pressure, typically 50 psi. 
     The peak inspiratory pressure (PIP) valve  119  allows the user to set the peak inspiratory pressure the patient will be exposed to. Thus, the PIP valve  119  protects the patient from gas delivery pressures above PIP pressure. In the event that gas pressure at the main gas outlet  117  is above PIP, the PIP valve  119  opens to maintain the pressure at the outlet  117  at the PIP setting to ensure that the pressure of the gas delivered to the mask  130  is safe for the patient&#39;s lungs. The valve  118  acts as a safety valve in the event that the PIP valve  119  fails to properly operate. 
     Referring now to  FIG. 3 , there is illustrated a block diagram of a gas sparing circuit  300  comprising the gas control unit  110 , the disposable breathing circuit  120 , and the patient mask  130 , in accordance with an exemplary embodiment of the present invention. The gas sparing circuit  300  uses all of the components illustrated in  FIG. 1  and additional components, as illustrated in  FIG. 3 . 
     The gas control unit  110  comprises a primary branch  310  comprising portions or lines  310 A- 310 E and a secondary branch  320 . The secondary branch is a pilot control branch  320  comprising portions or lines  320 A- 320 D. The primary branch  310 , specifically the portion  310 A of the primary branch  310 , is coupled to the gas inlet  111  via an inlet portion or line  305 . The flow meter  113  and the flow rate control  115 , which may be separate components or a unitary device, as illustrated in  FIG. 3 , are disposed within the inlet portion  305 . The flow meter  113  displays the flow rate of supply gas through the gas inlet  111 , and the flow rate control  115  allows a user or operator to modify this flow rate. In an exemplary embodiment, the portions  305 ,  310 A-E, and  320 A-D are respective tubes. As used herein, a user or operator may be the patient receiving gas or may be a person, such as a medical practitioner, who operates a gas control unit for benefit of a patient. 
     The portion  310 A couples the primary branch  310  to the inlet portion  305  and is coupled to a primary flow inlet  331  of a pilot activated gas sparing valve  330  (also referred to herein as “pilot valve  330 ” or “pneumatic control valve  330 ”). The gas sparing valve  330  additionally comprises a primary flow outlet  332  and a pilot control input  333 . The gas sparing valve  330  is normally closed, i.e., when the pressure at the pilot control input  333  is below a threshold pressure required to active the gas sparing valve  330 , the gas sparing valve  330  is closed, and no primary gas flows from the primary flow inlet  331  to the primary flow outlet  332 . 
     As described in more detail below, the pilot activated gas sparing valve  330  is controlled by the pilot control branch  320  to cause primary gas to flow through the primary flow outlet  332  of the valve  330 . Such outputted gas flows through a portion  310 B of the primary branch  310 , through the pop off pressure relief valve  118 , through a portion  310 C of the primary branch  310 , through the PIP pressure relief valve  119 , and through portions  310 D- 310 E of the primary branch  310  to the main gas outlet  117 . 
     The pilot control branch  320 , specifically the portion  320 A of the pilot control branch  320 , is coupled to the gas inlet  111  via the inlet portion  305 . The portion  320 A connects through a check valve  340  to a portion  320 B. The portion  320 B is connected to a portion  320 C via an element  341  for pilot flow reduction. In an exemplary embodiment, the valve  341  is an orifice flow control element. In another exemplary embodiment, the valve  341  is a needle valve. The portion  320 C is connected to the pilot control port  116 . 
     The pilot control branch  320  is coupled to the control input  333  via a portion  320 D of the pilot control branch  320 , which portion  320 D is tapped into the portion  320 C. As is discussed in further detail below, the pilot control branch  320  controls the gas sparing valve  330  via the pilot control input  333 . 
     Additional details regarding the disposable breathing circuit  120  are illustrated in  FIG. 3  and are now described. The disposable breathing circuit  120  comprises a main gas line  355  (also referred to herein as a “primary gas line  355 ”) comprising a first end  121  and a second end  122 . The first end  121  of the main gas line  355  is coupled to the main gas outlet  117  for delivering source gas to the patient. The disposable breathing circuit  120  further comprises a pilot control line  365  comprising a first end  121  and a second end  123 . The first end  121  of the pilot control line  365  is coupled to the pilot control port  116 . The pilot control line  365  traverses the disposable breathing circuit  120  from the first end  121  to the pilot air flow control switch  125  at the second end  123 . Located at the end  123  of the pilot control line  365  at the switch  125  is a vent port  351 , which vents the end  123  of the pilot control line  365  to atmosphere. It is to be understood that the end  123  of the pilot control line  365  and, therefore, the pilot air flow control switch  125  may be disposed at any place along the disposable breathing circuit  120 . In an exemplary embodiment, the end  123  of the pilot control line  365  and, therefore, the pilot air flow control switch  125  are disposed near the end  122  of the disposable breathing circuit  120  for convenience of use by the user activating the device for the patient wearing the mask  130 . 
     As also illustrated in  FIG. 3 , the second end  122  of the disposable breathing circuit  120  is coupled to the mask  130  via a mask connection  370 . In an exemplary embodiment, the mask connection  370  comprises a non-rebreathing element  371  which comprises a flow in/vent out configuration  372 , which may include one or more exhaust ports to allow for exhalation by the patient. In an exemplary alternative embodiment, the one or more exhaust ports may be included in the mask  130  itself. 
     The pilot activated gas sparing valve  330  is controlled by the pressure in the portion  320 D at the pilot control input  333  of the gas sparing valve  330 . When the pressure at the pilot control input  333  reaches a threshold pressure, the valve  330  actuates and opens, thereby allowing full primary gas flow. When the pressure at the pilot control input  333  decreases below the threshold activating pressure, the valve  330  deactivates and closes, thereby stopping full primary gas flow. 
     The primary branch  310  and the main gas line  355  together form a main gas circuit  350  for delivering gas to a patient. The pilot control branch  320  and the pilot control line  365  together form a pilot control circuit  360  for controlling the delivery of gas in the main gas circuit  350 . By using a main gas circuit  350  and a pilot control circuit  360  coupled to the same inlet  111 , the same inlet gas flow is used to charge the main gas circuit  350  and the pilot control circuit  360 . It is to be understood that description herein of occluding, un-occluding, charging, and venting the pilot control circuit  360  may be referred to as occluding, un-occluding, charging, and venting portions of the pilot control circuit  360 , such as the pilot control branch  320  or the pilot control line, and vice versa. 
       FIGS. 5A through 5C  illustrate alternative exemplary embodiments of the gas port  112 , in accordance with an exemplary embodiment of the present invention. In a first exemplary embodiment illustrated in  FIG. 5A , the pilot control port  116  is separate from the main gas port  117 . In a second exemplary embodiment illustrated in  FIG. 5B , the pilot control port  116  is disposed within the main gas port  117  to provide a unitary port  112 . In a third exemplary embodiment illustrated in  FIG. 5C , the pilot control port  116  is disposed adjacent to and in contact with the main gas port  117  to provide a unitary port  112 . In such embodiment, the unitary port  112  has a lopsided figure-8 cross section. 
     Referring now to  FIG. 6 , there is illustrated an exemplary block diagram of a system, generally designated as  600 , which is a simplified version of the gas sparing circuit  300 , in accordance with an exemplary embodiment of the present invention. The block diagram  600  shows the gas sparing circuit  300  in terms of pressures. Further, the block diagram  600  in conjunction with  FIG. 7A  shows how a charged pilot control circuit  360  aids in system response. System response is plotted in  FIG. 7A , which is described below. 
     In an exemplary embodiment, the pilot valve  330  requires a minimum threshold pressure P C  to actuate and open the valve  330 . It is to be understood that in any system, for a given circuit size, e.g., the size of the pilot control circuit  360 , there will be a time value, t, for the full pressure in the system to build, i.e., for the gas sparing circuit  300  to activate, when the system is acted upon or, in the case herein, when the pilot control line  365  (pilot control circuit  360 ) is occluded. 
     The time t is affected by the total dead volume in the circuit  360 . Thus minimizing the dead volume by controlling the interior diameter of the tubing in the circuit  360 , the pliancy in the tubing material, and the length to the occluding part, e.g., the length from the flow reduction element  341  to the pilot air flow control switch  125 , assists in reducing the time t. To reduce the time t to activation even further, a pilot control circuit  360  that not only utilizes the lowest dead volume available but also maintains a pressure as high as possible in the pilot control circuit  360 , i.e., as close to the activation pressure of the valve  330  as possible, allows for almost immediate activation of the valve  330 , thereby reducing the activation time t. Allowing a constant, albeit small, flow in the pilot control circuit  360  allows the gas sparing circuit  300  to maintain a pressure in the pilot control circuit  360  that is very close to the pressure P C . Should the pilot control circuit  360  have no initial flow, the time required to equalize to the system inlet pressure, once flow is initiated and the circuit  360  occluded, would be significantly greater than the subject pilot control circuit  360  with constant flow. 
     Because there is a desire to minimize vented or lost gas in the main gas circuit  350 , the flow rate in the pilot control circuit  360  is desirably minimized. Thus, the gas control unit  110 , desirably includes a flow reduction element  341  which causes a small drop in pressure in the pilot control branch  320  to just below the threshold pressure P C  of the valve  330  and which limits the flow rate in the pilot control circuit  360  when not occluded. A properly sized flow reduction element  341  in the pilot branch  320  provides both pressure drop and flow rate control when the pilot control circuit  360  is un-occluded and the gas in the pilot control circuit  360  is allowed to flow. When the pilot control circuit  360  is occluded and no flow occurs, i.e., when the pilot air flow control switch  125  occludes the vent port  351 , there will be no pressure drop across the flow reduction element  341 , and the pressure in the pilot control circuit  360  will rise quickly, because of the minimized circuit dead volume. The pressure in the pilot control circuit  360  equalizes with the pressure at the inlet  111  to actuate the valve  330 . 
     In  FIG. 6 : 
       P 1 =System inlet pressure  (1)
 
       P 2 =Pressure just after the flow reduction element 341 at the pilot control input 333 of the gas sparing valve 330  (2)
 
       P 3 =Pressure in the pilot control line 365 proximal to the vent port 351 and at the end 122 of the main gas line 355  (3)
 
       P C =Pressure at the input 333 required to actuate the valve 330  (4)
 
     For the simplified system  600  of  FIG. 6 , the following relationships hold true when the vent port  351  is open: 
       P 2 &lt;P 1   (5)
 
       P 2 &gt;P 3 ,  (6)
 
       P 2 &lt;P C ≦P 1   (7)
 
     By selecting the flow reduction element  341  and by reducing dead volume and pliancy (expandability of components) in the pilot control circuit  360 , the pressure P 2  can be held very close to P C , such that upon occlusion of the pilot circuit, P 2  quickly rises to the level of P 1 , which is greater than P C , and actuates the valve  330 . 
     Pilot control is accomplished by occluding and venting the pilot control circuit  360 , more specifically the control line  365 .  FIG. 3  illustrates that the gas sparing circuit  300  comprises a pilot air flow control switch  125 . It is to be understood that the gas sparing circuit  300  is not limited to the element  125  being a switch. Any device to temporarily occlude the pilot control line  365  to actuate and open the gas sparing valve  330  is contemplated. The pilot control switch  125  operates in a normally open condition which holds the gas sparing valve  330  closed so that no gas flow occurs through the main gas branch  310  and the main gas line  355 . 
     Illustrated in  FIG. 7A  is a graph of the pressures, P 1 , P 2 , and P 3  in the system  600 , plotted over time as the pilot control circuit  360  is un-occluded, then is occluded, and then re-un-occluded. Illustrated in  FIG. 7B  is a graph of the main gas flow, designated as V 1 , in the main gas line  355  and the pilot gas flow, designated as V 2 , in the pilot control line  365 , in accordance with an exemplary embodiment of the present invention. These graphs are now described with reference to occluding and un-occluding the pilot control line  365 . 
     As illustrated, when the system  600  is in its initial state in which the pilot control circuit  360  is not occluded, the system inlet pressure P 1  remains relatively constant at a pressure P A , the pressure in the line  305 ; pressure P 2  remains relatively constant at a pressure P B , the residual, pre-charged pressure in (the original was better) the pilot control circuit  360 ; and pressure P 3  is constant at a pressure P atm , atmospheric pressure, because the vent port  351  is open to atmosphere. Main gas flow V 1  is at 0 because the gas sparing valve  330  is closed. Pilot gas flow V 2  in the pilot control line  365  is at V P , the un-occluded flow rate. 
     Pressure P 2  remains relatively constant at a pressure P B  because the element  341  provides for a constant pressure drop from pressure P A . As noted above, pressure P C , which is illustrated in  FIG. 6 , is a constant, as it is the predetermined pressure required to actuate the valve  330 . P C  can be adjusted by altering the internal valve actuation spring and/or diaphragm in the valve  330 . 
     Pressures P 2  and P 3  respond to occlusion and then un-occlusion in the pilot control circuit  360  (pilot control line  365 ). At time t 1 , the pilot control circuit  360  is occluded, and pressure P 2  increases as the gas in the pilot control line  365  is no longer vented at the vent port  351 . Pilot gas flow V 2  quickly reduces to zero because the pilot control line  365  is occluded. Pressure P 2  increases until equal to P C  at time t 2 , at which time the valve  330  is actuated and opens to allow the primary gas to flow through the main gas circuit  350  at the full inlet pressure P 1 . The pilot gas flow V 1  begins to quickly increase from 0 to V M , the un-occluded flow rate, at t 2 +Δt, where Δt is a small elapsed time after t 2 . The pressure P 2  continues to increase until it reaches the inlet pressure P 1  (P A ) at time t 3 , at which time the pressure drop across the valve  330  is 0 psi. P 2  remains at P 1  (P A ) and V 1  remains at V m  while the pilot control circuit  360  is occluded. 
     At time t 4 , the pilot control circuit  360  is un-occluded and begins to vent. The pilot gas flow V 2  quickly increases to V P . The pressure P 2  begins to decrease and continues to do so through time t 5 , until it reaches P C  at which time the valve  330  deactivates and closes, and the flow V 1  precipitously decreases to 0. The pressure P 2  continues to decrease until it settles back at its initial pressure P B  at time t 6 . When vented, the pressure P 2  drops enough to allow the main valve  330  to close but does not drop to atmospheric pressure P atm  due to the residual constant flow in the pilot control circuit  360  and the length of the pilot control circuit  360 . 
     Also illustrated in  FIG. 7A  is a plot of pressure P 3  at the vent port  351  and at the end  122  of the main gas line  355 . The plot of P 3  is also approximately similar to the pressure after the flow reduction element  341  if the pilot control circuit  360  were held at atmospheric pressure. For purposes of the following discussion, the pressure P 2  just after the flow reduction element  341  in the pilot control circuit  360  when held at atmospheric pressure is designated as P 2 ′. 
     The plot of P 3  is now described with the understanding that P 3  is approximately the same as P 2 ′. Pressure P 3  is initially at atmospheric pressure, P atm . At time 1, the pilot control circuit  360  is occluded, and pressure P 3  increases as the gas in the pilot control line  365  is no longer vented at the vent port  351 . Pressure P 3  increases until equal to the threshold pressure P C  at time t 7 , The pressure P 3  continues to increase until it reaches P 1  (P A ) at time t 8 . P 3  remains at P 1  (P A ) while the pilot control circuit  360  is occluded. At time, t 4 , the pilot control circuit  360  is un-occluded and begins to vent, and the pressure P 3  begins to decrease and continues to do so through time t 5  when the valve  330  deactivates and closes. The pressure P 3  continues to decrease until it settles back at its initial pressure P atm . 
       FIGS. 7A and 7B  show that a pilot control circuit  360  which maintains a residual pressure P B  higher than atmospheric pressure P atm , will actuate the valve  330  and start the flow V 1  of main gas in the main gas circuit  350  more quickly than a system maintained at P atm . The actuation time for the valve  330  for the system  300 ,  600  having a residual pressure P B  in the pilot control circuit  360  higher than atmospheric pressure P atm , is t 2 −t 1 . The time for V 1  to go from 0 to V M  is t 2 +Δt−t 1 . The actuation time for the valve  330  if the system  300 ,  600  were to have a residual pressure P atm  in the pilot control circuit  360  at the valve  330  would be t 8 −t 1 . Exemplary values for t 2 +Δt−t 1  and t 8 −t 1  are 250 ms and 1250 ms, respectively. An exemplary value for Δt is 25 ms. By maintaining the pilot control circuit  360  with pressure P 2  at a residual pressure P B  rather than at P atm  and by minimizing flow volume (dead volume) in the pilot control circuit  360 , the time t 2 −t 1  for pressure charging in the pilot control circuit  360  and for actuation of the valve  330  is minimized. 
     As discussed above, the pilot control branch  360  desirably causes quick response of the valve  330  to provide almost instantaneous flow to the patient after activation by the user. The pilot control circuit  360  also desirably uses minimal gas flow to actuate the valve  330  circuit and vent minimal gas to the environment when not activated. Conventional gas delivery circuits allow constant full, high-volume flow to the environment even when such gas is not being using by a patient. Such waste is not acceptable and is costly. The gas control unit  110  greatly reduces such waste. 
     In an exemplary embodiment, the reduced flow and quick response in the pilot control circuit  360  is accomplished by use of a small flow orifice in the element  341  to restrict and lower flow rate and volume in the pilot control circuit  360 . Further, small bore tubing with minimal wall pliancy is used in the portions  320 A-D of the pilot control branch  320  and in the pilot control line  365  to allow for a minimal flow area (cross section) and a minimal dead volume to provide for quick actuation of the gas sparing valve  330  when desired. 
     In addition, allowing a continuous small positive flow in the pilot control circuit  360  at all times minimizes the response time even further since, when occluded while having an initial positive flow, the pilot control circuit  360  is already almost fully charged with gas, as shown in  FIG. 7A , and, thus, the internal flow V 2 +in the pilot control circuit  360  will be almost immediately directed into the gas sparing valve  330  upon occlusion, thereby building enough back pressure, quickly, to activate the gas sparing valve  330 . In an exemplary embodiment, under such conditions, patient flow V 1  to a patient wearing the mask  130  is initiated in fewer than 500 milliseconds. In another exemplary embodiment, patient flow V 1  is initiated in about 250 milliseconds or less. 
     As shown in  FIGS. 7A and 7B , by maintaining the pilot control circuit  360  fully charged or nearly fully charged, response time is reduced compared to conventional systems. Should the pilot control circuit  360  be evacuated with no positive pressure or flow, the circuit  360  would be at atmospheric pressure P atm  and would require time to fill and fully charge once flow was applied and the circuit  360  occluded. This charge time significantly delays system activation and renders use of the system  100  not desirable. Since the gas sparing valve  330  requires a minimum threshold pressure P C  to activate, the closer the pilot control circuit  360  is maintained to this minimum threshold pressure P C , the quicker activation of the valve  330  occurs when the pilot circuit  330  is occluded and the full pilot pressure P A  reached. 
     Separate gas sources for the main gas circuit  350  and the pilot control circuit  360  are not practical in a modular portable system with minimal complexity. Thus, the system  300  is designed so that the pilot control gas, the gas within the pilot control circuit  360 , is sourced from the same place as the system gas (also referred to herein as the “primary gas” or “patient gas”), the gas within the main gas circuit  350  (also referred to herein as the “primary gas circuit  350 ”). 
     Because the system  300  uses a common gas source for both the primary and pilot gas flow, means to stop the loss of pilot gas flow and pressure upon activating the gas sparing valve  330 , until desired by the operator, is desirably implemented. Should no means be provided to maintain the required pressure in the pilot control circuit  360  to hold the main valve  330  open, the main valve  330  may begin to oscillate between an open and closed position as the pressure P 2  in the pilot control branch  320  fluctuates down and then up as the main valve  330  opens and then closes, respectively. This may result in gas flow in the main gas line  355  oscillating between flow and no flow in a manner not desired by the operator. 
     To reduce or eliminate oscillation of the valve  330 , the system  300  comprises a check valve  340 , which is designed to eliminate backflow in the pilot branch  320  if there is a shift in the pressure differential across the element  341  when the gas sparing valve  330  opens, this shift in pressure differential would reverse the flow direction of gas in the pilot branch  320 . The check valve  340  is used to lock and maintain pressure in the pilot branch  320  once a pressure level has been established assuming no gas is then allowed to escape from the opposite end of the branch  320 , i.e., via the vent port  351 . Thus, by placing a check valve in the pilot control circuit  360  before the flow reduction element  341 , when the outlet switch/valve  125  is occluded by the operator and the pilot control circuit  360  is pressurized, any drop in pressure on the inlet side of the check valve  340 , which may occur upon the main valve  330  opening, will not cause a pressure drop in the pilot control circuit  360 . Thus, the main valve  330  remains open and does not oscillate between open and closed. Without the check valve  340 , any undesired (uncontrolled) loss of pressure in the main gas circuit  350  might cause the main valve  330  to close prematurely in an uncontrolled manner or to oscillate between open and closed due to pressure fluctuations in the pilot control circuit  360 . Both premature closing of the main valve  330  and uncontrolled oscillation of the main valve  330  between open and closed are undesirable. 
     Referring now to  FIGS. 8A and 8B  together, there is illustrated operation of an exemplary embodiment of the pilot air flow control switch  125  disposed within a handle  800 , in accordance with an exemplary embodiment of the present invention.  FIG. 8A  illustrates the switch  125  in an open position A.  FIG. 8B  illustrates the switch  125  in a closed position B. As illustrated in  FIGS. 8A and 8B , the handle  800  is connected to a second end  122  of an exemplary embodiment of the disposable breathing circuit  120 , generally designated as  120 ′ in  FIGS. 8A and 8B . The handle  800  may be permanently or removably attached to the disposable breathing circuit  120 .  FIG. 8C  illustrates various views of an exemplary embodiment of the disposable breathing circuit  120 ′, in accordance with an exemplary embodiment of the present invention. 
     The disposable breathing circuit  120 ′ illustrated in  FIGS. 8A-8C  differs from the disposable breathing circuit  120  because the disposable breathing circuit  120 ′ does not include the switch  125  or the vent  351 . Instead, those components are disposed within the handle  800  illustrated in  FIGS. 8A and 8B . Thus, the main gas line  355  extends through the disposable breathing circuit  120 ′ from the first end  121  to the second end  122 , which second end  122  is connected to a first end  821  of the handle  800 . The pilot gas line  365  extends through the disposable breathing circuit  120 ′ from near the first end  121  to near the second end  122 , as seen best in  FIG. 8C . 
     In the embodiment of the handle  800  illustrated in  FIGS. 8A and 8B , the pilot air flow control switch  125  is a pliant membrane  810  disposed over a pilot control orifice  820 . The switch  125  and specifically the pliant membrane  810 , when in position A, does not occlude the pilot control orifice  820  and when in position B, does occlude the orifice  820 . In an alternative embodiment, a rigid flow switch could replace the pliant member  810  and perform the same function. 
     The handle  800  allows the user to hold the mask  130  against the patient&#39;s mouth and nose. The handle  800  comprises a bend  830  and an end  822  to which the mask  130  is attached. At the second end  123  of the pilot control line  365 , the pilot control line  365  comprises a bend  825 , which connects the pilot control line  365  to a riser or port  835  which opens to atmosphere at the pilot control orifice  820 . 
     As illustrated in  FIG. 8A , when the pilot air flow control switch  125  is in the open position A, pilot gas  840  flows through the pilot control line  365 , around the bend  825 , up the riser or port  835 , and through the pilot control orifice  820 . The pilot gas  840  then passes through an exhaust port  845  and is exhausted through the vent port  351 . Because pilot gas  840  is vented through the vent port  351 , the gas sparing valve  330  is deactivated and does not allow main gas  850  to flow through the main gas line  355 . 
     As illustrated in  FIG. 8B , when the pilot air flow control switch  125  is in the closed position B, i.e., when the pliant member  810  is depressed, the pilot control orifice  820  is occluded by the membrane  810 , and pilot gas  840  is not vented through the vent port  351 . The lack of pilot gas flow is labeled as  840 ′ in  FIG. 8B . Because there is no pilot gas flow  840 ′, the gas sparing valve  300  is actuated and main gas  850  flows through the main gas line  355 , out the second end  822  of the handle  800 , and through the mask  130 . Upon release of the pliant member  810 , the pilot gas  840  vents, de-actuating and closing the gas sparing valve  330  and stopping flow of the main gas  850  to the patient mask  130 . 
       FIGS. 8A-8C  illustrate that the pilot control line  365  is extended through the breathing circuit  120 ′ to the end  122  (or near to the end  122 ) of the breathing circuit  120 , and the handle  830  is attached to the end of the breathing circuit  120 . It is to be understood that in an exemplary embodiment, the breathing circuit  120  may be modified so that the handle  830  is disposed at the end  122  of the breathing circuit  120 . 
     Referring now to  FIG. 2 , there is illustrated a block diagram of an alternative system, generally designated as  200 , for delivering gas to a patient via an alternative embodiment of the patient mask  130 , generally designated in  FIG. 2  as  130 ′, in accordance with an exemplary embodiment of the present invention. The system  200  comprises all of the elements of the system  100 , except for the patient mask  130 , but additionally includes functionality for a second gas delivery mode, as described below, namely in a continuous positive airway pressure (CPAP) gas delivery mode where a continuous low pressure, low flow-rate gas is required after resuscitation. 
     The system  200  comprises a gas control unit  210 , rather than the gas control unit  110 . The gas control unit  210  comprises the elements  111 - 119 , though used in the system  200  capable of a CPAP gas delivery mode, as is now described. Accordingly, the gas control unit  210  additionally comprises a CPAP flow rate control  212  to allow the user to select a desired CPAP flow rate and a mode-selection switch  214  for selection between the CPAP mode and the gas-sparing resuscitation mode of the system  100 . 
     The mask  130 ′ used with the system  200  differs from the mask  130  used with the system  100 . The mask  130 ′ incorporates a CPAP exhalation port  216 , which allows the user of the mask  130 ′ to exhale when the system  200  is operating in the CPAP gas delivery mode. The mask  130 ′ is described in more detail below with respect to  FIG. 17 . 
     An exemplary view of the external of the gas control unit  210  is illustrated in  FIG. 21 , in accordance with an exemplary embodiment of the present invention. The various components of the gas control unit  210  illustrated in  FIG. 2  and described above are mounted to an enclosure  2100  of the gas control unit  210 . Attached to the enclosure  2100  is a handle  2110  for carrying the gas control unit  210 . 
     Referring now to  FIG. 4 , there is illustrated a block diagram of a gas sparing circuit  400  comprising the gas control unit  210 , an embodiment of the disposable breathing circuit  120 , generally designated in  FIG. 4  as  120 ′, and an alternative embodiment of the patient mask  130 ′, generally designated in  FIG. 4  as  130 ″, in accordance with an exemplary embodiment of the present invention. The gas sparing circuit  400  uses all of the components illustrated in  FIG. 2  and additional components, as illustrated in  FIG. 4 . The gas sparing circuit  400  incorporates the primary branch  310  and the pilot control branch  320  of the gas sparing circuit  300  in the resuscitation side  410  of the gas sparing circuit  400 . The gas control unit  210  additionally comprises a CPAP circuit or branch  430  in a CPAP side  420  of the gas sparing circuit  400 . The CPAP circuit or branch  430  comprises portions or lines  430 A- 430 B. The CPAP circuit or branch  430  is a continuous flow circuit when in use as there is no gas sparing control on this side. 
     The resuscitation side  410  comprises the primary branch  310  and the pilot control branch  320  of the gas sparing circuit  300 , which branches operate similarly in the gas sparing circuit  400  to those in the gas sparing circuit  300 . The primary branch  310  and the pilot control branch  320 , however, are modified slightly for use in the gas sparing circuit. First, the portions  310 A and  320 A are not directly connected to the flow meter  113  with flow control  115  via the inlet line  305 , as they are in the gas sparing circuit  300 . Instead, the inlet line  305  is directly connected to the mode-selection switch  214 . Second, the portion  310   e  of the primary branch  310  in the gas sparing circuit  400 , while still directly connected to the main air port  117 , is also connected to the portion  430 B of the CPAP branch  430 . Third, the primary branch  310  may include a check valve  440 A in the portion  310 B or a check valve  440 B in the portion  310 D to further restrict back flow into the resuscitation side  410  when the gas sparing circuit  400  is operating in CPAP mode. 
     The CPAP branch  430  comprises the portion  430 A, which couples the mode-selection switch  214  to the CPAP flow control valve  212  as needed. The portion  430 B couples the CPAP flow control valve  212  to the portion  310 E of the primary branch  310 . The mode-selection switch  214  is coupled to the flow meter  113  and flow control  115  via a portion  440 . The mode-selection switch  214  allows the operator to select for CPAP continuous air delivery (CPAP mode) through the primary gas line  355  via the CPAP branch  430  or to select for pilot-controlled primary gas delivery (resuscitation mode) through the primary gas line  355  via the resuscitation side  410 , and the flow control valve  212  allows the operator to select the rate of gas flow in the CPAP branch  430 . 
     In an exemplary embodiment, the portion  430 B includes a pressure relief valve  435 A and/or a check valve  435 B. The pressure relief valve  435 A provides venting for overpressure in the CPAP branch  430 , and the check valve  435 B prevents backflow in the CPAP branch  430 . In another exemplary embodiment, CPAP Branch portion  430 B could be connected to Main branch portion  310 B allowing the pressure relief valve  118  to be disposed downstream downstream of the connection with the portion  430 B. In such embodiment, the pressure relief valve  118  provides venting for overpressure in either the CPAP branch  430  or the primary branch  310 . 
     Separate flow control valves in the CPAP branch  430  and the main gas branch  310  are contemplated. These valves are, respectively, the flow control valves  212  and  115 . In an exemplary alternative embodiment, the flow control valve  212  is removed, and the flow control valve  115  is used to regulate the rate of gas flow in the main gas branch  310  and the CPAP branch  430 . In another exemplary alternative embodiment, the flow control valve  115  is disposed in the portion  310 A downstream of the mode-selection switch  214  to control flow in the primary branch  310 , and the flow control valve  212  is disposed in the CPAP branch  430  to control CPAP flow. In yet another exemplary alternative embodiment, check valves  440 A and/or  440 B are contemplated to stop backflow in the primary branch  310 . The check valves  435 B,  440 A, and  440 B also prevent cross flow between the CPAP branch  430  and the primary branch  310 . 
     The mask  130 ″ differs from the mask  130 ′ because the mask  130 ′ includes the switch  125  and the vent  351 , respectively designated as  125 ′ and  351 ′ in  FIG. 4 . It is to be understood that the mask  130 ″ incorporates the CPAP exhalation port  216  used in the mask  130 ′. This port is open when in CPAP mode but is closed when in resuscitation mode. In an exemplary alternative embodiment, the disposable breathing circuit  120  and the mask  130 ′ are used with the gas sparing circuit  400 . In another exemplary alternative embodiment, the handle  800  may be attached to the disposable breathing circuit  120 ′ and the mask  130 ′ if used with the gas sparing circuit  400  or may be incorporated into the mask  130 ″ if used with the gas sparing circuit  400 . 
     Referring now to  FIG. 9 , there is illustrated an exemplary alternative embodiment of the gas sparing circuit  300 , generally designated in  FIG. 9  as  900 , in accordance with an exemplary embodiment of the present invention. The gas sparing circuit  900  uses all of the components illustrated in  FIG. 3 , modified as described below, and additional components, as illustrated in  FIG. 9 . The gas sparing circuit  900  incorporates the main gas branch  310  and the pilot control branch  320 , as modified as a pilot control branch  320 ′. In another exemplary embodiment, a CPAP branch, such as the CPAP branch  430  of  FIG. 4 , could also be added to the gas sparing circuit  900  to add CPAP functionality. 
     The pilot control branch  320 ′ comprises the elements of the pilot control branch  320  of the pilot control branch  320  and additionally a pneumatic timer control  910  configured to control the on-time of the main gas sparing valve  330 . The portion  310 D of the pilot control branch  320  is replaced by portions  320 D′ and  920 A and  920 B. If used to control the on-time of the main gas sparing valve  330 , the pneumatic timer control  910  is a normally open valve. 
     The portion  320 D′ couples an output  992  the pneumatic timer control  910  to the control side  333  of the gas sparing valve  330 . The portion  920 A couples the portion  320 C to an input  911  of the pneumatic timer control  910 . The portion  920 B couples the portion  320 C to a timer unit  993 . 
     Operation of the gas sparing circuit  900 , with on-time control, is now described. Operation begins with the pilot control circuit  360  in an un-occluded state, the gas sparing valve  330  closed, and pilot gas at pressure PB is applied to the control side  333  of the gas sparing valve  330  through the pneumatic timer control  910 , which is in an open state. Upon closure or occlusion of the pilot control line  365 , the gas sparing valve  330  opens, as described above with respect to  FIGS. 3, 6, and 7 , and pressure at the timer unit  993  increases. When the pressure at the time unit  993  reaches a threshold pressure, a counter within the timer unit  993  starts and counts until it reaches an activation time. After the activation time of the timer  993  is reached, the timer  993  cycles and closes a valve in the pneumatic timer  910  and vents the pilot connection  320 D′ of the gas sparing valve  330  via a vent  994 , thereby causing the gas sparing value  330  to close and main flow through the main gas line  355  to stop. The cycle may repeat after the pilot control line  365  is vented, which causes the timer unit  993  to reset. In this modality, the provision of primary gas through the gas sparing valve  330  for each breath is triggered by the user occluding the pilot control line  365 . Thus, re-occlusion of the pilot control line  365  starts each resuscitation breath. Also, in this modality, the user could deliver inhalation breaths in succession without allowing for complete exhalation, if desired, since any venting of the pilot line would reset the timer valve  993  and allow the cycle to restart very quickly. Exhalation is accomplished as described herein, such as via exhaust ports in the mask  130  or  130 ′ or via exhaust ports in a hand piece to which the mask  130  or  130 ′ is connected, such as the exhaust ports  1226  in the hand piece  1200  described below. 
     In this way, the gas sparing circuit  900  controls the amount of time gas is provided via the main gas line  355  and thereby controls the inhalation time of the patient using the gas sparing circuit  900 . The activation time can be adjusted from fractions of a second to several seconds as desired by the user. The user may set the activation (breath) time of the timer unit  993  to be between 0.5 to 3 seconds. Desirable breath time is approximately 1.0 to 1.5 second for inhalation breath flow followed by 1.0 to 3.0 seconds of vent or exhalation time. 
     Should the user desire automatic continuous control of the inhalation time followed by automatic control of the exhalation time, two pneumatic timers could be used in an exemplary embodiment of the gas sparing circuit  900 , generally designated as  1000  in  FIG. 10 , in accordance with an exemplary embodiment of the present invention. The gas sparing circuit  1000  uses all of the components illustrated in  FIG. 3 , modified as described below, and additional components, as illustrated in  FIG. 10 . The gas sparing circuit  1000  incorporates the primary branch  310  and the pilot control branch  320 ′, as modified as a pilot control branch  320 ″. In another exemplary embodiment, a CPAP branch, such as the CPAP branch  430  of  FIG. 4 , could also be added to the gas sparing circuit  1000  to add CPAP functionality. 
     The pilot control branch  320 ″ comprises the elements of the pilot control branch  320 ′ of the gas sparing circuit  900  and additionally two pneumatic timer controls  1010  and  1020 . In this configuration, the first timer control  1010  controls the on (inhalation) time (the time during which the gas sparing valve  330  is open) and the second timer control  1020  controls the off (exhalation) time (the time during which the gas sparing valve  330  is closed). 
     In the pilot control branch  320 ″, the element  341  is coupled to an inlet  1011  of the first timer  1010  via a portion  1030 A. An outlet  1012  of the first timer control  1010  is coupled to an inlet  1021  of the second timer control  1020  via portion  1030 D. An outlet  1022  of the second timer control  1020  is coupled to a timer  1013  of the first timer control  1010  via a portion  1030 B. 
     The control side  333  of the gas sparing valve  330  is coupled to the outlet  1012  and the inlet  1021  via a portion  1030 E which also connects to the outlet port  112 . The portion  1030 E is also coupled to a timer  1023  of the first timer control  1020  via a portion  1030 F. 
     Operation of the gas sparing circuit  1000  is now described. Operation begins with the pilot control circuit  360  in an un-occluded state, the gas sparing valve  330  closed, and pilot gas at pressure P B  is applied to the control side  333  of the gas sparing valve  330  through the pneumatic timer control  1010 , which is in an open state. The pneumatic timer control  1020  is in a closed state, and the line  1030 B has been vented. Upon closure or occlusion of the pilot control line  365 , the gas sparing valve  330  opens, as described above with respect to  FIGS. 3, 6 , and  7 , and primary gas is provided to the patient via the primary circuit  350 . At the same time, pressure at the timer unit  1023  increases. When (almost instantaneously) the pressure at the timer unit  1023  reaches a threshold pressure, a valve within the pneumatic timer control  1020  closes and a counter within the timer unit  1023  starts. When the counter within the timer unit  1023  reaches an activation time, the timer  1023  cycles a valve in the pneumatic timer control  1020  to an open state and vents the pilot circuit  360 . 
     Because the valve in the pneumatic timer control  1020  is opened, pilot gas is allowed to pass from the inlet  1021  to the outlet  1022  and to the timer  1013  of the pneumatic timer control  1010  via the line  1030 B. Pressure at the timer unit  1013  increases. When (almost instantaneously) the pressure at the timer unit  1013  reaches a threshold pressure, a valve within the pneumatic timer control  1010  closes, thereby shutting down flow of the pilot gas from the inlet  1011  to the outlet  1012  of the pneumatic timer control  1010 . Because the pneumatic timer control  1020  is in an open state and is venting the pilot circuit  360 , the gas sparing valve  330  closes. This stops the flow of gas to the patient and allows exhalation to occur. This discontinuation of pilot flow also resets timer  1020 . 
     A counter within the timer unit  1013  starts and counts until it reaches an activation time. After the activation time of the timer  1013  is reached, the timer  1013  cycles the valve in the pneumatic timer  1010  to an open state to restart the flow of pilot gas from the inlet  1011  to the outlet  1012 , which applies pilot gas to the pneumatic timer control  1020  to close the valve therein. At the same time, the gas sparing valve  330  opens, and primary gas is again provided to the patient via the primary circuit  350 . Once the exhalation cycle is started, i.e. when the valve in the pneumatic timer  1010  closes, the user cannot deliver another inhalation breath until the exhalation cycle is fully completed. This ensures a full exhalation cycle is completed. 
     Operation of the gas sparing circuit  1000  cycles through the above-described process as long at the pilot air flow control switch  125  is closed. When the user releases the switch  125 , the cycle stops. Additionally a mechanical or electrical latch or closure device can be added to the gas sparing circuit  1000 , at the pilot control switch  125 , that would allow for mechanical latching (closure) of the switch  125  in the closed position thus allowing for continued ventilation of the patient where the user would not have to hold the switch  125  in the closed position with his or her hand. This latch could be switched in and out to hold the pilot control switch  125  in the closed position or allow it to be in the open position for manual, finger-based activation. 
     In this configuration, once the pilot control line  365  is occluded, the system  1000  automatically cycles between inhalation (gas sparing valve  330  open to provide gas in the main gas line  355 ), and exhalation (gas sparing valve  330  closed). The user may set the ventilation breath time by setting the activation time of the timer unit  1023  to be between 0.5 to 3 seconds. Desirable breath time is approximately 1.0 to 1.5 second for inhalation breath flow. The user may set the exhalation time by setting the activation time of the timer unit  1013 . Desirable exhalation time is approximately 1.0 to 3.0 seconds for exhalation breath flow. 
     Although  FIGS. 9 and 10  illustrate using pneumatic time controls, other embodiments using electro-pneumatic controls or timer-based triggers are contemplated. In a gas-sparing circuit incorporating a timer-based trigger, the user activates the trigger to occlude the pilot control line  365  and activate the gas sparing valve  330 . Then, within the trigger, a mechanical, electrical, or pneumatic-mechanical switch cycles over the desired time period and opens the pilot control line  365  to atmosphere, thereby closing the gas sparing valve  330 , stopping primary airflow. 
     Referring now to  FIG. 11A , there is illustrated a side cross-sectional view of an exemplary embodiment of a pneumatic-mechanical timer-based trigger  125 ′ and to  FIG. 11B , there is illustrated a top view revealing internal details of the trigger  125 ′, in accordance with an exemplary embodiment of the present invention. The trigger  125 ′ may be substituted into the gas sparing circuits  300  and  400  to replace the trigger  125 . 
     The trigger  125 ′ comprises a housing  1101  in which a trigger handle  1102  is slidably disposed. The trigger handle  1102  is connected to a guide rod  1107  which passes through slots  1103  and  1104  in the housing. The guide rode  1107  may slide from one end of the slots  1103  and  1104  to the other as the trigger handle  1102  slides within the housing  1101 . The trigger handle  1102  is coupled to a plunger which terminates in a soft diaphragm  1106 . Disposed on the plunger between the trigger handle  1102  and the diaphragm  1106  is a spring  1114 . 
     The pilot control line  365  pierces a first end  1121  of the housing  1101  and terminates within an interior space  1120  of the housing  1101  formed between the housing  1101  and the diaphragm  1106 . The interior space  1120  vents to the outside of the housing  1101  via vents  1111 . Disposed at a second end  1131  of the housing  1101  is a plunger  1130 , which is attached to the trigger handle  1102 . The housing  1101  forms an interior space  1140  between the plunger  1130  and the second end  1131  of the housing  1101 . The interior space  1140  vents to the outside of the housing  1101  via a one-way diaphragm valve  1112 . Also disposed in the housing  1101  at the second end  1131  is a vent valve  1113 , which is used to set vent time. 
     Disposed on the housing of the housing  1101  is a timer adjuster nut  1108  for adjusting the timer. Disposed around the housing  1101  between the nut  1108  and the trigger handle  1102  is a spring  1110 . A stop  1109  provides a stop for lateral movement of the trigger handle  1102 . 
     Operation of the trigger  125 ′ is now described. The user pulls the trigger  125 ′ toward the first end  1121 , thereby pushing the soft diaphragm  1106  against the end of the pilot control line  365  and compressing the spring  1114  between the diaphragm  1106  and the trigger handle  1102 . The spring  1114  provides for tactile feeling in the trigger  125 ′. Once the pilot control line  365  is occluded, the gas sparing valve  330  opens allowing primary flow. 
     When the trigger handle  1102  is pulled, in addition to advancing the soft diaphragm  1106 , the trigger handle  1102  pulls the plunger  1130  away from the second end of the housing  1101 . As the trigger handle  1102  and plunger  1130  advance, the chamber fills  1140  with air via the one way diaphragm valve  1112 . When the trigger handle  1102  is released either by the user or by design via an automatically disengaging trigger activator, the spring  1110  applies force on the trigger handle  1102  to move the plunger  1130  back to its initial position. Since the chamber  1140  is now filled with air, the pressure in the chamber  1140  resists movement of the plunger  1130 . Air from the chamber  1140  vents with movement of the plunger  1130 . The adjustable vent valve  1113  allows the rate of the venting of the chamber  1140  to be controlled. 
     As the air in the chamber  1140  vents through the vent valve  1113 , the plunger  1105  moves toward its original position and the pressure of the spring  1114  on the soft diaphragm  1106  begins to reduce. When the plunger  1105  has travelled a sufficient distance, the force of the spring  1114  on the diaphragm  1106  will be low enough such that the pressure in the pilot control line  365 , which is 50 psi, will create enough force on the rear surface of the soft diaphragm  1106  to force the diaphragm  1106  open. The pilot control line  365  vents through the chamber  1120  and the vents  1111  to the outside of the housing  1101 . As the pressure in the pilot control line  365  reduces past pressure PC, the gas sparing valve  330  closes and air flow in the main gas line  355  stops. The spring  1110  pushes the trigger handle  1102  laterally until the trigger handle  1102  comes into contact with the stop  1109 , at which time the plunger  1130  stops moving. 
     Thus, a timer circuit is created by the timer-based trigger  125 ′. The time duration of air flow through the main gas line  355  is controlled by the return travel distance of the trigger handle  1102  and the speed of the plunger  1130 . Adjustment of the nut  1108  adjusts travel of the trigger handle  1102  to allow adjustment of the timer circuit of the timer-based trigger  125 ′. Further, the vent time of the chamber  1140  is adjustable by the vent valve  1113  to further provide for adjustment of the timer circuit of the timer-based trigger  125 ′. 
     A patient using the CPAP system  200  may attempt to breathe in an amount of air that is larger than baseline air flow provided by the CPAP side  420  of the system  200 . Under these conditions, a means is desirably provided to allow for this larger air quantity to enter the system  200 . 
     In conventional CPAP systems, the masks have special valves that allow for this larger air quantity. Although use of a special mask is possible in the CPAP system  200 , it is not optimal. In addition, if spontaneous breathing were to occur during normal resuscitation where a CPAP mask in a conventional CPAP system cannot be used, the patient would not be able to draw in the extra air desired. 
     In conventional bag and mask systems, a valve within the rear of the bag system allows for air flow should the patient begin to breathe. However, these devices cannot provide CPAP functionality, and they have no flow and pressure controls. In the system  200  or  400  described above, because such systems are closed or could be very remote from the patient, a valve in the system that would allow for spontaneous breathing would be ineffective because the breathing circuit  120  would be too long to allow for minimal flow restriction. Thus, in order to minimize the restriction to a spontaneous breath with the system  200  or  400 , it is desirable to provide a spontaneous breath valve system as close to the patient as possible. However, this valve desirably remains closed during resuscitation and CPAP positive air flow and only opens when an air flow, larger than the resuscitation or CPAP flow, is demanded by the patient via inhalation breath volume. 
     Referring now to  FIG. 12 , there is illustrated an exemplary embodiment of the mask connection  370 , generally designated as  1200  in  FIG. 12 , in use with a valve system  1250  to accommodate a patient&#39;s ability to draw in extra air if desired, in accordance with an exemplary embodiment of the present invention. The mask connection  1200  comprises a housing  1210 , a rotating outlet port  1220 , and the valve system  1250 . The housing  1210  comprises, at a first end  1212 , a gas inlet  1211 , which is connected to the second end  122  of the disposable breathing circuit  120 , and, at a second end  1220 , an outlet  1222 , which is connected to the mask  130 . In an exemplary embodiment, the housing  1210  is a two-piece housing comprising a first portion  1210 A and a second portion  1210 B. The valve system  1250  allows the same mask  130  (illustrated in  FIGS. 3-4 ) to be used for either respiration or CPAP and allows for spontaneous breathing along with the traditional non-rebreathing function. 
     The valve system  1250  comprises a unidirectional valve  1260  and a two-way valve diaphragm  1270  comprising a duck bill valve  1272 , and a diaphragm  1275  connected to the duck bill valve  1272 . In the exemplary embodiment illustrated in  FIG. 12 , the duck bill valve  1272  and the diaphragm  1275  are a flexible unitary structure. It is to be understood that other embodiments in which the duck bill valve  1272  is separate from the diaphragm  1275  are contemplated. 
     The unidirectional valve  1260  is in a normally closed state in which it seals breath ports  1265  in the housing  1210 . Disposed inside of the housing  1210  around the unidirectional valve  1260  is a seal ring  1264 , which is configured to provide a seal against the two-way valve diaphragm  1270  during patient exhalation. A view of an alternative embodiment of the unidirectional valve  1260  is illustrated in  FIG. 12A . 
     The rotating outlet port  1220  is rotatably attached to the housing  1210 . The outlet port  1220  is configured to rotate relative to the housing  1210  to provide for patient comfort during use. A portion of the rotation outlet port  1220  adjacent to the two-way valve diaphragm  1270  is a seal rim  1224  which is configured to seal against the two-way valve diaphragm  1270  during patient inhalation. 
     Disposed in the housing adjacent the rotating outlet port  1220  are exhaust ports  1226  and an exhaust seal  1228  for allowing one-way operation of the exhaust ports  1226 . In an exemplary embodiment, the exhaust ports  1226  and the exhaust seal  1228  are disposed in the second portion  1210 B of the housing  1210 . 
     Operation of the mask connection  1200  is now described. In the mask connection  1200 , when air flows into the inlet  1211  in the resuscitation or CPAP mode, it flows through the two-way inlet valve diaphragm  1270 , via the duck bill valve  1272 , which opens under positive inhalation air flow, to the outlet  1222 . This air also forces the diaphragm  1275  of this valve diaphragm  1270  against the seal rim  1224 . 
     Air flows to the mask  130  during gas delivery or when the patient inhales. During patient exhalation, the Duck bill portion  1272  of the two-way valve diaphragm  1270  closes and the exhaled air forces the diaphragm portion  1275  off the seal  1224  and against the seal rim  1264 . The outlet  1222  is thereby sealed from the interior space  1211  of the housing  1210 . So sealed, the outlet  1222  directs the patient&#39;s exhaled air in from the outlet  1222  around the seal rim  1224  and through the exhaust ports  1226  and past the exhaust seal  1228 . The exhaust seal  1228  is a one-way exhaust seal that serves as a backup for the diaphragm seal ring  1224  during inhalation to ensure that no air can reverse flow into the exhaust ports  1228 . 
     The unidirectional valve  1260  allows for the patient to breathe spontaneously. Should the patient spontaneously breathe or inhale a volume that is higher than that being delivered at the inlet  1211  of the mask connection  1200 , the spontaneous breath valve  1260  opens and allows additional air to flow to the patient through the spontaneous breath ports  1265 . This valve  1260  only stay opens if the volume demanded at the output  1222  is higher than the volume at the inlet  1211 , i.e., a negative pressure at the inlet  1212  is developed. As soon as the volume demanded at the output  1222  drops below the volume provided at the inlet  1212 , the valve  1260  closes and seals the spontaneous breath ports  1265 . Thus, the spontaneous breath valve  1265  remains closed during all gas inlet  1212  function unless the patient creates an excess demand. Because the valve system  1250  is proximal to the patient, minimal restriction to airflow is created. This restriction is designed to be no more than 5cmH 2 O in negative pressure. Thus, a single valve assembly  1250  breathing circuit can be used for both direct resuscitation and for CPAP wherein spontaneous breathing could occur. 
     Illustrated in  FIG. 12B  are exemplary side and top views of the mask connection  1200  attached the second end  122  of the disposable breathing circuit  120 ′, in accordance with an exemplary embodiment of the present invention. The pilot control line  365  is shown unconnected at the first and second ends  121  and  122 . It is to be understood that the pilot control line  365  at the first end  121  of the disposable breathing circuit  120 ′ may be connected to the pilot control port  116  of the system  100 , and the second end  122  of the disposable breathing circuit  120 ′ may be connected to a pilot connection point on a mask or mask connection, as described herein.  FIG. 12B  illustrates a closer cross-sectional view of the first end  121  of the disposable breathing circuit  120 ′. 
     Referring now to  FIG. 13 , there is illustrated a hand piece, generally designated as  1300 , in accordance with an exemplary embodiment of the present invention. The hand piece  1300  may be used in cooperation with a conventional mask or the mask of  FIG. 17  described below. 
     The hand piece  1300  comprises a flexible frame  1310  which is configured to fit over a conventional resuscitation mask. The hand piece includes a hole  1320  through which the connection port of the conventional mask passes. Positioned at a first end  1301  of the hand piece  1300  is a pilot control switch  1340  coupled to a vent  1344  for venting a pilot circuit, such as the pilot circuit  360 . The switch  1340  and vent  1344  function similarly to the switch  125  and vent  315  illustrated in  FIGS. 8A and 8B . A flexible elastomeric switch cap  1342  is placed over the switch  1340  for operating the switch  1340 . 
     The switch  1340  is coupled to a pilot control line extension tube  1330  at a first end  1331  of the tube  1330 . Coupled to a second end  1332  of the tube  1330  is a connector  1335  for connecting the tube  1330  to other portions of the pilot control circuit  360 . 
     A system  1400  in which the hand piece  1300  may be used is illustrated in  FIG. 14 , in accordance with an exemplary embodiment of the present invention. The system  1400  comprises the disposable breathing circuit  120 ′, an adapter  1401  connected to the end  122  of the disposable breathing circuit  120 ′, an optional capnometer  1410  coupled to the adapter  1401 , and mask connection  1200  coupled to the capnometer  1410 . The mask  130  is connected to the mask connection  1200  via the connection port  131 . 
     The adapter  1401  comprises a positive end-expiratory pressure (PEEP) control  1402  for regulating PEEP through the adapter  1401 . The adapter  1401  further comprises a pilot control line  1404  that outputs via an output connection  1406  connected to the luer  1335  and a main gas line  1408  that is connected to the main gas line  355  of the disposable breathing circuit  120 ′. 
     As illustrated in  FIG. 14 , the hand piece  1300  is configured to fit over the mask  130 . The hole  1320  of the hand piece  1300  is sized to accommodate the connection port  131  of the mask  130 . Activation of air flow through the mask  130  is achieved by depressing the elastomeric switch cap  1342  which actuates the switch  1340  to occlude the pilot control circuit  360 , which in the embodiment illustrated in  FIG. 14  includes the pilot control line  365 , the pilot control line  1404  and the pilot control line extension tube  1330 . The gas sparing valve  330  is thereby opened. 
     An enlarged view of the pilot control switch  1340  is shown in  FIG. 13A , in accordance with an exemplary embodiment of the present invention. The switch  1340  is constructed similarly to the switch  125  illustrated in  FIGS. 8A and 8B  and operates similarly. 
     As seen in  FIG. 13A , the switch  1340  is formed by the elastomeric membrane  1342  which is attached to the frame  1310  of the hand piece  1300  over a chamber  1348 . The end  1331  of pilot control line  1330  is disposed within the frame  1310  and opens to the chamber  1348  at an opening  1349 . A seal ridge  1346  is disposed around the opening  1349  of the pilot control line  1330 . 
     When the elastomeric membrane  1342  is in the state shown in  FIG. 13A , i.e., when it is in a non-depressed state, pilot gas passes through the pilot control line  1330 , out the opening  1349 , through the air chamber  1348 , and out the vent port  1344 . Under this condition, the gas sparing valve  330  is not activated and there is no flow in the primary gas circuit  305 . When the elastomeric switch element  1342  is depressed against the seal ridge  1346 , the pilot gas air flows out the vent  1344  is occluded, thereby activating the gas sparing valve  330  and allowing primary gas to flow through the primary gas circuit  350  until the elastomeric switch element  1342  is released. 
     In addition to the hand piece  1300  described above, a simple hand piece that could be used without a mask, and used with other resuscitation apparatus such as an endotracheal tube, is contemplated. Illustrated in  FIG. 15  is an endotracheal tube hand piece (also referred to herein as “endotracheal tube adapter”)  1500 , in accordance with an exemplary embodiment of the present invention. The endotracheal hand piece  1500  is configured to be used with the disposable breathing circuit  120 ′. The disposable breathing circuit  120 ′ differs from the disposable breathing circuit  120  in that the disposable breathing circuit  120 ′ does not include the pilot control switch  125  or the vent  351 . Instead, the pilot control line  365  extends through the entire length of the disposable breathing circuit  120 ′ to the second end  122 . The end  122  of the disposable breathing circuit  120 ′ comprises an outlet  1510  of the pilot control line  365  and an outlet  1520  of the main gas line  355 . 
     The endotracheal hand piece  1500  comprises a first end  1501  comprising an inlet port  1530  and an inlet port  1540 . The port  1540  is configured to receive the outlet port  1510  of the pilot control line  365 . The port  1540  is coupled to the pilot control switch  1340  and the vent  1344 . The port  1530  is configured to receive the outlet port  1520  of the main gas line  355 . The port  1530  communicates with an endotracheal tube connection  1550  at a second end  1502  of the endotracheal hand piece  1500 . The switch  1340  is operated as described above to control the main gas line  355 . When operated, the switch  1340  actuates the gas sparing valve  330  to provide primary gas through the main gas line  355 , to the port  1530 , and to an endotracheal tube  1560  connected to the connection  1550 . 
     Alternative exemplary embodiments of the hand piece  1300  are illustrated in  FIGS. 16A and 16B , in accordance with an exemplary embodiment of the present invention. Illustrated in  FIG. 16A  is a hand piece  1600 A, which is, generally, a combination of the hand piece  1300  and the mask connection  1200 , in accordance with an exemplary embodiment of the present invention. The hand piece  1600 A comprises a handle  1610 , a body portion  1630 , and a mask  1640 . The mask  1640  may be rotatably connected to the body portion  1630 . The body portion  1630  is connected to the handle  1610  by a pliant section  1620 , which allows for the handle  1610  to bend relative to the body portion  1630 . 
     The disposable breathing circuit  120 ′ is connected to the hand piece  1600 A via a rotatable coupling  1640 . The rotatable coupling  1640  allows for the position of the disposable breathing circuit  120 ′ to be positioned for patient comfort when the mask is installed on the patient. Activation of the gas sparing system is by way of the elastomeric element  1340 . It is to be understood that the hand piece  1600 A may be used in any of the systems for delivering gas to a patient and gas sparing circuits described herein. 
     Illustrated in  FIG. 16B  is a hand piece  1600 B, which is also, generally, a combination of the hand piece  1300  and the mask connection  1200 , in accordance with an exemplary embodiment of the present invention. The hand piece  1600 B comprises all of the elements of the hand piece  1600 A, with a few modifications. The hand piece  1600 B comprises an L-shaped handle  1610 ′ rather than the mostly vertical handle  1610  of the hand piece  1600 A. In one embodiment, the disposable breathing circuit  120 ′ may be connected to the rotating body portion  1630  of the hand piece  1600 B. In another embodiment, an end  1611  of the handle  1610 ′ is configured to receive the end  122  of the disposable breathing circuit  120 ′. 
     Referring now to  FIG. 17 , there is illustrated an exemplary embodiment of the patient mask  130 ′, in accordance with an exemplary embodiment of the present invention. The patient mask  130 ′ is used with a gas sparing circuit, such as the gas sparing circuit  400  of the gas delivery system  400 , in which both resuscitation and CPAP gas delivery modes are desired. The mask  130 ′ comprises the CPAP port  216  described above with respect to  FIG. 2 .  FIG. 17  illustrates the CPAP port  216  in further detail. 
     The CPAP port  216  comprises a vent port  1700  comprising valve housing  1702  integrated with the mask  130 ′. The valve housing  1702  is capped by a removable cap  1704 , which is tethered to the housing  1702  by a lanyard  1708 . Disposed within the valve housing  1702  is a one-way valve  1706 . When the mask  130 ′ is used with the system  200 , and the system  200  is operating in resuscitation mode, the cap  1704  is placed over the port  1700  to not allow resuscitation gas to bypass the patient and exit the mask  130 ′. When operating in CPAP mode, the cap  1704  is removed to allow exhalation breath. 
     In the case that the mask  130 ′ is used with the mask connection  1200 , exhalation through the ports  1226  is not possible as the diaphragm  1275  is in the open position in the CPAP mode. Thus, a second exhalation port is provided via the exhalation port in the mask in  FIG. 17 . Thus, the vent port  1700  allows for an exhalation breath along with inlet gas flow exhaust for pressure relief within the mask  130 ′ during CPAP mode so that the pressure within the mask  130 ′ during use is maintained at a controlled level. 
       FIG. 18  illustrates another embodiment of a system, generally designated as  1800 , comprising the disposable breathing circuit  120 ′, the mask connection  1200 , the mask  130 , and the hand piece  1300 , in accordance with an exemplary embodiment of the present invention. The connector  1335  of the hand piece  1300  is connected to the second end  122  of the pilot control line  365  of the disposable breathing circuit  120 ′. The first end  1212  of the mask connection  1200  is connected to the second end  122  of the main gas line  355  of the disposable breathing circuit  120 ′, and the second end  1222  of the mask connection  1200  is connected to the connection port  131  of the patient mask  130 . Activation of air flow through the mask  130  is achieved by depressing the elastomeric switch cap  1342  (Should this be  1340 ) which actuates the switch  1340  to occlude the pilot control circuit  360 , which in the embodiment illustrated in  FIG. 18  includes the pilot control line  365  and the pilot control line extension tube  1330 . The gas sparing valve  330  is thereby opened. Although  FIG. 18  illustrates using the mask  130  in the system  1800 , it is to be understood that the mask  130 ′ may be also used. 
       FIG. 19  illustrates an exemplary alternative embodiment of the hand piece of  FIG. 13 , generally designated as  1900  in  FIG. 19 , in accordance with an exemplary embodiment of the present invention. The hand piece  1900  includes all of the components of the hand piece  1300 , but the frame  1310  is modified as a frame  1310 ′ having a smaller profile. 
       FIGS. 20A-20C  illustrate various views of yet another alternative embodiment of the hand piece of  FIG. 13 , generally designated as  2000  in  FIGS. 20A-C , in accordance with an exemplary embodiment of the present invention. The hand piece  2000  includes all of the components of the hand piece  1300 , but the frame  1310  is modified as a frame  1310 ″ having a smaller profile. 
     Referring now to  FIGS. 22A through 22C , there are illustrated, respectively, front, side, and perspective views of an alternative embodiment of the patient mask  130 ′, generally designated in  FIGS. 22A-22C  as  130 ″, in accordance with an exemplary embodiment of the present invention. The patient mask  130 ″ is similar to the patient mask  130 ′, particularly in that it includes the CPAP vent port  1700 . The patient mask  130 ″ differs, however, in that it further includes the pilot control switch  1340 , which is disposed on the patient mask  130 ″ in the embodiment illustrated, rather than on a hand piece.  FIGS. 23A through 23F  illustrate various views of various components of a combination of the patient mask  130 ″ connected to the mask connection  1200 , which is connected to the disposable breathing circuit  120 ′, in accordance with an exemplary embodiment of the present invention. 
     Referring now to  FIG. 24 , there is illustrated an exemplary alternative embodiment of the gas sparing circuit  300 , generally designated in  FIG. 24  as  2400 , in accordance with an exemplary embodiment of the present invention. In this gas sparing circuit  2400 , the manual pneumatic pilot control line  365  of the breathing circuit  120  or  120 ′ is replaced by an electrical switch-activated pilot control line  2465 , and the mechanical pilot control switch  125  is replaced by an electric switch  2425 , as shown in  FIG. 24 . The electrical switch  2425  is placed under a pliant cap  1340  on the mask  130 ″. The gas sparing circuit  2400  uses all the components illustrated in  FIG. 3 , modified as described below, and additional components as illustrated in  FIG. 24 . For example, the gas sparing circuit  2400  incorporates the main gas branch  310  and the pilot control branch  320 , as modified to include an electrical pilot control branch  2420  and an electrical pilot control line  2465 . In another exemplary embodiment, a CPAP branch, such as the CPAP branch  430  of  FIG. 4 , could also be added to the gas sparing circuit  2400  to add CPAP functionality. 
     The electrical pilot control branch  2420  of the gas sparing circuit  2400  is an electronic control circuit which comprises an electric solenoid valve  2410  configured to control the gas flow to the main gas sparing valve  330 . The electrically controlled solenoid  2410  is a normally open valve that allows pilot gas to vent to the atmosphere through a vent port  2414 . The pilot input  320 C is coupled to the valve  2410  at an inlet  2411 . The outlet  2412  of the valve  2410  is coupled to the portion  320 D of the pilot control branch  320 . 
     The valve  2410  operation is controlled electrically through the pilot control circuit  360 , specifically the electrical pilot control branch  2420 , the electrical pilot control line  2465 , and the switch  2425 . The electrical pilot control branch  2420  comprises wires  2422  and an optional timer circuit  2423 , and the electrical pilot control line  2465  is formed from wires. The optional timer circuit  2423  functions to control the on time and off time of the valve  2410  and, therefore, the on and off time of the gas sparing valve  330 , thereby providing for continued cycling of the gas sparing valve  330  when activated. The pilot control line  2465  replaces the pilot control line  365  of  FIG. 3 . The pilot control line  2465  couples to the connector  112  at a connection (input)  2416 , thereby creating a complete electrical circuit with the electrical pilot control branch  2420 . 
     Operation of the gas sparing circuit  2400 , with electronic solenoid control, is now described. Operation begins with the solenoid valve  2410  in the normally closed state which allows pilot branch  1420  to be in the occluded state. In this condition the pilot gas does not flow past the solenoid valve  2410  into the pilot control line  320 D. The gas sparing valve  330  remains closed as the pilot line  320 D on the gas sparing valve control side is vented to atmosphere, P atm . Upon closure of electrical switch  2425 , by depression of the pliant switch cap  1340  on the mask  130 ″, an electrical signal is sent through the wires  2465  and  2422 , and the solenoid valve  2410  is activated. Pilot gas flow is directed into pilot line  320 D. Pilot gas at pressure PB is applied to the control side  333  of the gas sparing valve  330 , and the valve  330  opens allowing gas to flow into the main gas side  310 , as described above with respect to  FIGS. 3, 6, and 7 . The solenoid valve  2410  remains activated, and main gas continues to flow until the switch  2425  is released and the signal to the solenoid valve  2410  is deactivated. Upon deactivation of the solenoid valve  2410 , the pilot gas in the circuit  2460  is occluded, and pilot gas in the line  320 D is vented to atmosphere through the vent port  2414 . Pressure in the control side  333  of the gas sparing valve  330  drops to P atm , and the gas sparing valve  330  closes, thereby stopping main gas flow through the circuit  310 . This operation can is repeated manually for each desired breath by depressing the pliant mask switch cap  1340 . 
     In an alternative exemplary embodiment of the gas sparing circuit  2400 , there is an optional timer circuit  2423  that will allow for cycling of the electrically controlled solenoid valve  2410  for the auto breath function with settable on and off times for resuscitation. In this configuration and any of the timer configurations described herein, the mask switch  2425  could have a hold-closed latch to allow for the auto breath function to continue after latching the switch closed so the user does not have to hold the switch in place. 
     It is to be understood that the gas sparing circuit  2400  may be modified as described herein to provide for CPAP functionality as shown in  FIG. 4  and/or to include an internal gas supply. 
       FIG. 25  illustrates a block diagram for yet another exemplary embodiment of a gas sparing circuit, generally designated as  2500 , in accordance with an exemplary embodiment of the present invention. The gas sparing valve  2530  in this embodiment is an electrically activated solenoid valve  2530  which is controlled through a mask switch, such as the mask switch  2425 . In this embodiment, in addition to the external gas inlet  111 , there may be an internal air generation-supply module  2510 , which can create the desired gas pressure and flow on demand to an outlet  2503 . A selector valve  2520  is used to select the appropriate gas source from the inlet  111  or the internal air generation-supply module  2510 . 
     Operation of the electrically controlled main gas solenoid valve  2530  is controlled electrically through the electrical pilot control circuit  2460 . The solenoid valve  2530  is connected through the wires  2422  of the electrical pilot control branch  2420  to an external electrical pilot control line, e.g., the electrical pilot control line  2465 , and to a switch, e.g., the switch  2425 . In an exemplary alternative embodiment, the electrical pilot control branch include the optional timer circuit  2423  that functions to control the on time and off time of the valve  2530  and, therefore, the on and off time of the main gas flow to the patient. 
     Operation of the gas circuit  2500 , with electronic solenoid control, is now described. Operation begins with the solenoid valve  2530  in the normally closed state which does not allow main gas flow through the main gas circuit  350 . Upon closure of the electrical switch  2425  by depression of the pliant switch cap  1340  in the mask  130 ″, an electrical signal is sent through the wires  2465  and  2422 , and the solenoid valve  2530  is activated. Main gas flow is directed through the main gas branch  310 . The solenoid valve  2530  remains activated and main gas continues to flow until the switch  2425  is released, at which time the signal to the solenoid valve  2530  is deactivated. Upon deactivation of the solenoid valve  2530 , main gas flow stops. This operation can is repeated manually for each desired breath by depressing the pliant mask switch cap  1340 . 
     In addition there is an optional timer circuit  2423  that will allow for cycling of the electrically controlled solenoid valve  2530  for the auto breath function with settable on and off times for resuscitation. In this configuration and any of the timer configurations described herein, the mask switch  2425  could have a hold closed latch to allow for the auto breath function to continue after latching the switch closed so the user does not have to hold the switch in place. 
     It is to be understood that the gas sparing circuit  2500  may be modified as described herein to provide for CPAP functionality as shown in  FIG. 4  and/or to include an internal gas supply  2510 , i.e., the internal supply  2510  is optional. Also, it is contemplated that the gas sparing circuit  2500  can be applied directly to either the internal gas supply  2510  or an external gas supply via the inlet  111  to provide a time controlled breath pulse through the outlet  2503  to the main gas side  310  and thus to the patient through the port  117 . 
       FIG. 26A  illustrates and describes a block diagram for still another exemplary embodiment of a gas sparing circuit, generally designated as  2600 , in accordance with an exemplary embodiment of the present invention. This gas sparing circuit  2600  includes both pneumatic manual pilot control functionality and automatic electronic-based auto breath control that is activated by way of a pneumatic valve/switch actuator  2603  disposed in the gas line portion  320 C. The pneumatic valve/switch actuator  2603  includes a toggle  2603 A for toggling between manual and automatic positions. When the pneumatic valve/switch actuator  2603  is switched to the automatic position, the gas sparing circuit  2600  cycles electro-pneumatically in an automatic manner until the switch  2603  is set back to the manual position or gas pressure is removed from the pilot line. This gas sparing circuit  2600  includes both the manual pilot control functionality of  FIG. 3  (the manual pneumatic pilot control line  365  and the mechanical pilot air flow control switch  125 ) and the electrical switch-activated pilot control of  FIG. 24  (the solenoid valve  2410  and electrical pilot control branch  2420  with the electronic timer circuit  2423 ) for auto breath capability. The solenoid valve  2410  is disposed in the portion  320 D connected to the control side  333  of the gas sparing valve  330 . 
     Operation of the gas circuit  2600 , with manual pilot control and electrical switch-activated pilot control for auto breath capability, is now described. Operation of the gas sparing circuit  2600  is identical in operation to  FIG. 3  when the pneumatic valve/switch actuator  2603  is in the manual gas control position for utilization of the pilot control circuit  320 , specifically the pilot control line  365  and flow control switch  125 . In this configuration the electronically controlled solenoid valve  2410  is in a normally open configuration when no control signal is provided and pilot gas can pass through the solenoid valve  2410  freely. 
     When the pneumatic valve/switch actuator  2603 A is set in the manual position, pilot gas flows through the pilot control line  320 C. When the pilot control line  365  is occluded by use of the flow control switch  125 , the pilot circuit  320 C becomes occluded, thereby allowing pilot gas to flow through the solenoid valve  2410  and the control line  320 D. Pilot gas at pressure PB is applied to the control side  333  of the gas sparing valve  330 , and the valve  330  opens, thereby allowing gas to flow into the main gas branch  310 , as described above with respect to  FIGS. 3, 6, and 7 . Releasing the mask switch  125  causes the pressure to drop in the pilot line  320 D and at control side  333  of the gas sparing valve  330 , and the valve  330  closes, thereby stopping gas flow into the main gas branch  310 , as described above with respect to  FIGS. 3, 6 , and  7 . 
     When the pneumatic valve/switch actuator  2603  is set in the auto breath position, a toggle  2613 A electrically connected to the electronic timer circuit  2423  is closed, and the electronic time circuit  2423  is energized. Additionally, gas is directed to the pilot line  320 D and the control side  333  of the gas sparing valve  330 , which opens to allow gas flow through the main gas side  310 . At this time, the electronic timer circuit  2423  begins to cycle the electronic solenoid valve  2410  between the normally open position, which allows pilot gas flow through its outlet  2412  to the gas sparing valve  330 , and the closed position, in which the solenoid  2410  stops pilot flow to the outlet  2412  and to the gas sparing valve  300  at the control side  333 . In the closed position of the electronic solenoid  2410 , flow is closed at inlet  2411 , but flow is then opened at the vent  2414 , which allows the pilot control line  320 D to vent and the pressure at the control side  333  to drop to P atm , thereby closing the gas sparing valve  330  and stopping flow in the main gas side  310 . The electronic timer  2423  cycles the solenoid valve  2410  between the closed and open state creating a controlled auto breath function that can be user adjusted for on time and off time. This operation continues until the valve/switch actuator  2603  is set back to the manual position by way of the toggle  2603 A. 
     It is to be understood that the gas sparing circuit  2400  may be modified as described herein to provide for CPAP functionality as shown in  FIG. 4  and/or to include an internal gas supply, as shown in  FIG. 25 . 
     Now turning to  FIG. 26B , there is illustrated a block diagram for yet another exemplary embodiment of a gas sparing circuit  2600 ′, in accordance with an exemplary embodiment of the present invention. This gas sparing circuit  2600 ′ includes both the manual pilot control functionality of  FIGS. 3 and 4  (the gas sparing circuit  400 ) and the electrical switch-activated pilot control of  FIG. 24  (the electrically controlled solenoid pilot valve  2410 ) for auto breath capability with the exception that the electrical switch-activated pilot control valve  2410  is located in a removable accessory enclosure  2650  external to the gas sparing circuit  400  and is attached to the pilot control port  116  at outlet  112 . An electrical switch  2655  in the accessory enclosure  2650  activates the electronic pilot circuit control. 
     The gas sparing circuit  2600 ′ incorporates a gas sparing configuration identical to the gas sparing circuit  400  shown in  FIG. 4  and includes the resuscitation side  410  and the CPAP side  420 . In addition to including the gas sparing circuit  400 , the gas sparing circuit  2600 ′ further includes the removable auto breath control module  2650  connected to the outlet port  116  of the gas sparing circuit  400 . The removable auto breath control module  2650  includes its own pilot control port  116 ′. When not installed, the breathing circuit  120  or  120 ′ can be attached to the gas port  112  (described above with respect to  FIG. 4 ). When the auto breath control module  2650  is attached to the pilot control port  116 , the pilot control line  365  of the breathing circuit  120  or  120 ′ can still be connected to the pilot control port  116 ′ for manual operation. 
     The auto breath control module  2650  includes an inlet line  2651 , which connects to the pilot control port  116 , and an outlet line  2652 , which connects to a pilot outlet port  116 ′. An electronic solenoid valve  2410  is connected between the inlet and outlet lines  2651  and  2652 . Specifically, an inlet  2411  of the electronic solenoid valve  2410  is connected to the inlet port  2651 , and an outlet  2412  of the electronic solenoid valve  2410  is connected to the outlet port  2652 . A timer circuit  2433  is connected to the electronic solenoid valve  2410  through wires  2424  and to a control switch  2655  via wires  2654 . The pilot control line  365  of circuit  120  connects to outlet port  116 ′ of the auto breath control module and provides for manual control. 
     Operation of the gas circuit  2600 ′ of  FIG. 26B , with manual pilot control and electrical switch-activated pilot control for auto breath capability, is now described. The external auto breath module  2650  is attached to the gas control circuit  410  through the inlet line  2651  of the auto breath control module  2650  which is connected to the pilot port  116  of the main gas circuit  410 . The output line  2652  is provided from the auto breath control module  2650  for connection to the pilot control line  365  of breathing circuit  120 . For operation of gas circuit  2600 ′, the main gas line  355  of breathing circuit  120  is connected to outlet port  117 , as described with respect to  FIGS. 3 and 4 . The pilot control line  365  of breathing circuit  120  is connected to the outlet port  116 ′ of the auto breath control module  2650 . 
     When the auto breath control module control switch  2655  is in the Off position the electronic solenoid valve  2410  is in the normally open position allowing pilot gas to flow unrestricted through the solenoid valve  2410 . Then operation of the gas sparing circuit  2600 ′ is identical in operation to that described in  FIGS. 3 and 4  with manual control of the main gas line  320  provided through activation of the pilot control switch  125 . 
     If auto breath functionality is desired, the control switch  2655  on the auto breath control module  2650  is switched to the On position. The timer circuit  2423  is energized and then cycles the solenoid valve  2410  from the normally open position to the normally closed position. The pilot line  320 C is then occluded at solenoid input  2651  and pilot gas flow is directed into the pilot control line  320 D. Pilot gas at pressure P B  is applied to the control side  333  of the gas sparing valve  330 , and the valve  330  opens allowing gas to flow into the main gas side  310 , as described above with respect to  FIGS. 3, 6, and 7 . The solenoid valve  2410  remains activated, and main gas continues to flow until the timer  2423  cycles the solenoid valve  2410  to the normally open position, at which time the solenoid valve  2410  vents the pilot line  320 C through the solenoid valve to the pilot control line  365  and out vent port  351  on the mask switch  125 . At this time pressure in the control side  333  of the gas sparing valve  330  drops to P atm , and the gas sparing valve  330  closes, thereby stopping main gas flow through the circuit  310 . The electronic timer  2423  cycles the solenoid valve  2410  between the closed and open state to create a controlled auto breath function that can be user adjusted for on time and off time. This operation continues until the control switch  2655  is set back to the Off position. 
     It is to be understood that an alternate embodiment for the external electronic auto breath control module  2650  would be to utilize pneumatic timers such as those illustrated in  FIG. 10 ,  FIG. 27 , and  FIGS. 28 and 29 , and a pneumatic valve/switch as necessary but in a configuration where the pneumatic timers would be located within an external removable module, as described in  FIG. 26B . In another exemplary embodiment, CPAP branch portion  430 B could be connected to main branch portion  310 B allowing the pressure relief valve  118  to be disposed downstream of the connection with the portion  430 B. In such embodiment, the pressure relief valve  118  provides venting for overpressure in either the CPAP branch  430  or the primary branch  310 . Furthermore, it is to be understood that the gas sparing circuit  2400 ′ may be modified to include an internal gas supply. 
       FIG. 27  illustrates still another exemplary embodiment of a gas sparing circuit, generally designated as  2700 , in accordance with an exemplary embodiment of the present invention. This gas sparing circuit  2700  includes both pneumatic manual pilot control functionality through the attached circuit and automatic pneumatic timer based auto breath control set with a switch on the gas control unit instead of having to hold the manual pilot line occluded. Once switched to automatic, the gas sparing circuit  2700  cycles pneumatically until the switch is set back to manual or gas pressure removed from the pilot line. This gas sparing circuit  2700  includes both the manual pilot control functionality of  FIG. 3  (the manual pneumatic pilot control line  365  and the pilot air flow control switch  125 ) and the pneumatic timer pilot control of  FIG. 10  for auto breath capability. 
     Operation of the gas sparing circuit  2700 , with manual pilot control and pneumatic timer activated pilot control for auto breath capability, is now described. Operation of the gas sparing circuit  2700  is identical in operation to the gas sparing circuit  300  in  FIG. 3  when the pneumatic valve/switch actuator  2702  is in the manual control position for utilization of the pilot circuit portion  320 C in conjunction with pilot control line  365  and flow control switch  125 . In this configuration, when the pneumatic valve/switch actuator  2702  is set in the manual position the pneumatic timers  1010  and  1020  are not active and pilot flow bypasses the timers and is directed to pilot control line  320 C. When the pilot control line  365  is occluded by use of flow control switch  125 , pilot circuit  320 C is also occluded allowing pilot gas to flow through line  2701 B and into pilot line  320 D. Pilot gas at pressure PB is applied to the control side  333  of the gas sparing valve  330  and the valve opens allowing gas to flow into the main gas side  310  as described above with respect to  FIGS. 3, 6, and 7 . Releasing mask switch  125  causes the pressure to drop in pilot line  320 D and at control side  333  of the gas sparing valve and the valve closes stopping gas flow into the main gas side  310  as described above with respect to  FIGS. 3, 6, and 7 . When the pneumatic valve/switch actuator  2702  is set in the auto breath position, the pneumatic timer circuit is activated and auto breath operation occurs in an automatic manner. When the pneumatic valve/switch actuator  2702  is set in the auto breath position pilot gas is directed to the pneumatic timer through line  1030 A and operation occurs in the same manner as described with respect to gas sparing circuit  1000  in  FIG. 10 . At this time the pneumatic timers  1010  and  1020  begin to cycle the pilot gas flow on and off based on used selected time settings, to the gas sparing valve  330 . In the first part of the timer cycle pilot gas is directed from the timer circuit through line  1030 E to pilot line  320 D and at control side  333  of the gas sparing valve  330  and the valve opens to allow gas flow through main gas side  310 . In the second part of the timer cycle pilot gas flow is stopped to the gas sparing valve  300  at control side  333  which allows the pilot control line  320 D to vent and the pressure at control side  333  to drop to Patm, closing the gas sparing valve  330  and stopping flow in the main gas side  310 . The pneumatic timers  1010  and  1020  cycles the gas sparing valve  330  between the closed and open state creating a controlled auto breath function that can be user adjusted for on time and off time. This operation continues until the pneumatic valve/switch actuator  2702  is set back to the manual position or gas pressure is removed from the pilot line. 
     It is to be understood that the gas sparing circuit  2700  may be modified as described herein to provide for CPAP functionality as shown in  FIG. 4  and/or to include an internal gas supply. 
       FIG. 28  illustrates a block diagram for a further exemplary embodiment of a gas sparing circuit  2800 , in accordance with an exemplary embodiment of the present invention. This gas sparing circuit is similar to the gas sparing circuit  1000  illustrated in  FIG. 10 . As described herein, the gas sparing circuit  1000  uses an on-timer  1020  and an off-timer  1030  to control the auto breath circuit  1000 . The gas sparing circuit in  FIG. 28  uses two on-timers  2820 ,  2830 , and a 4-way spool valve  2810  to effectively make one on-timer (the on-timer  2830 ) and an off-timer (the other on-timer  2820 ), without having to use a real off-timer, to control the pneumatically timing circuit  2800 . The result is a gas sparing circuit that has the same control of inhalation and exhalation breath as the circuit  1000 . In this gas sparing circuit  2800 , as in the gas sparing circuit  1000 , auto breath operation is activated through occlusion of the pilot line  365  at switch  125 . Auto breath function stops when the pilot line  365  is un-occluded at mask switch  125 . 
     It is to be understood that the gas sparing circuit  2800  may be modified as described herein to provide for CPAP functionality as shown in  FIG. 4  and/or to include an internal gas supply. 
       FIG. 29  illustrates and describes a block diagram for another exemplary embodiment of a gas sparing circuit  2900 , in accordance with an exemplary embodiment of the present invention. This gas sparing circuit is similar to the gas sparing circuit  2700  in  FIG. 27  but uses two on-timers  2820  and  2830  and a 4-way spool valve  2810  to effectively make one on-timer (the on-timer  2830 ) and one off-time (the off-timer  2620 ), without having to have a real off-timer, to control the pneumatically timing circuit  2900 . As with gas sparing circuit  2700  in  FIG. 27 , the function of the gas sparing circuit is activated by pneumatic valve/switch  2702  so that manual pilot control is still possible with this gas sparing circuit but the circuit can be switched into automatic auto breath mode without having to hold the external pilot line  365  occluded. 
     It is to be understood that the gas sparing circuit  2700  may be modified as described herein to provide for CPAP functionality as shown in  FIG. 4  and/or to include an internal gas supply. 
     An exemplary feature which may be added to any of the exemplary embodiments of the gas sparing circuits described herein. In any of the gas sparing circuits having manual pilot control lines  365 , a latch can be added to the switch  125  or  1340  or  2425  to allow the switch to be held closed without the need for the user to apply constant pressure to the switch  125  or  1340  or  2425 . This latch may be desirably used for auto breath modes to allow the user to not have to hold the switch  125  or  1340  or  2425  down continuously. 
     Now referring to  FIG. 30 , there is illustrated an exemplary embodiment of a gas sparing circuit  3000  which functions similarly to the gas sparing circuit  300  of  FIG. 3 , but further includes a pressure surge damper configuration, in accordance with an exemplary embodiment of the present invention. The pressure surge damper configuration comprises a series of damping elements comprising reducing elements  3020 , reduced tube ID sections  3040 , and expansion elements  3030  in exemplary positions to dampen gas pressure surges that may occur in the main gas line  310 B when the gas sparing valve  330  opens. It is to be understood that this pressure surge damper configuration may be added to any of the exemplary gas sparing circuits described herein. 
     Operation of the pressure surge damper configuration using reducing elements  3020 , reduced ID elements  3040 , and expansion elements  3030  is now described. Referring to  FIG. 30 , as the gas sparing valve  330  opens pressurized gas quickly flows into the main gas line  310 B. This instant release of pressurized gas flow can create a pressure wave front in the main gas line  310 C,  310 D and  310 E that may be slightly higher than the steady state pressure after the gas sparing valve  330  has been opened for a period of time. It may therefore be beneficial to dampen this pressure surge using a pressure surge damper system containing damping elements  3020 ,  3030  and  3040  as illustrated. As the gas pressure front moves along main gas line  310 B it encounters the reducer element  3020  in the main gas line. The gas pressure enters the reducer  3020  where the flow path ID is decreased abruptly creating a velocity increase in the gas flow and a turbulence effect. The gas flow then traverses through a reduced ID flow element  3040  and then enters an expansion element  3030  where the flow path ID is increased abruptly creating a velocity decrease and a second turbulent effect which combines to reduce the pressure wave an incremental amount. Additional elements located at  3020 ′,  3030 ′ and  3040 ′ and at  3020 ″,  3030 ″ and  3040 ″ are added to further dampen the pressure surge to the desired level. By combining a series of these elements in series, or if desired in parallel, the pressure wave front can be either partially suppressed or fully suppressed as desired. As the initial pressure surge damper elements  3020 ,  3030 , and  3040  act to dampen the pressure wave front, the main gas with a reduced pressure wave progresses through main gas line  310 C′ to line  310 D and then to damping elements  3020 ′,  3030 ′ and  3040 ′ where the pressure wave front is reduced further. The main gas then progresses through main line  310 D′ with even further reduction in the amplitude of the pressure wave front to main line  310 E. The gas then interacts with the damping element  3020 ″,  3030 ″ and  3040 ″ where again the pressure wave front is further reduced to the point where it is totally eliminated and the main gas, without the pressure wave front, then progresses to the reaming main gas lines  310 E′ and into the breathing circuit  120  at outlet  117 . When the gas sparing valve  330  is closed, and the gas flow in the main gas line  310 B ceases. The pressure surge damper configuration is then ready for the next pressure wave. 
     In an exemplary alternative embodiment, a pressure surge damper  3010  may be used in place of or in addition to the dampening elements illustrated in  FIG. 30  and described above.  FIG. 30A  illustrates an exemplary embodiment of the damper  3010 , in accordance with an exemplary embodiment of the present invention. The pressure surge damper contains a base  3027 , with inlet port  3021 , a pliant damper diaphragm  3023 , a spring  3024 , a vent control valve  3025  with vent port  3026 , and a cap  3028 . The diaphragm  3023 , cap  3028 , and base  3027  interact to create a sealed damper chamber  3022 . This pressure damper is shown in the unpressurized state. 
     Operation of the pressure surge damper  3010  is now described. Referring to  FIGS. 30 and 30A , as the gas sparing valve  330  opens pressurized gas quickly flows into main gas line  310 B. This instant release of pressurized gas flow can create a pressure wave front in the main gas line  310 C,  310 D and  310 E that may be slightly higher than the steady state pressure after the gas sparing valve has been opened for a period of time. It may therefore be beneficial to dampen this pressure surge using a pressure surge damper  3010  as illustrated. As the gas pressure front moves along main gas line  310 B it encounters the pressure surge damper  3010  at a 90 degree bend in the main gas line. The gas pressure enters the inlet port  3021  of the pressure surge damper and encounters the pliant damper diaphragm  3023 . The gas pressure fills the sealed damper chamber  3022  and forces the damper diaphragm to expand and move against the spring  3024 . The air trapped behind the pliant diaphragm is compressed and in a controlled manner exits through the vent port  3026 . The vent control valve  3025  controls the rate at which the air can be vented from the space behind the pliant diaphragm and thus the rate at which the pliant diaphragm can expand and move against the spring. The pliant diaphragm  3023  in combination with the spring  3024  and the vent control valve  3025  act together to create a controlled damping effect on the main gas entering the inlet port. As the pressure surge damper  3010  acts to dampen the pressure wave, the pliant diaphragm  3023  reaches its full equilibrium travel and the main gas without the pressure wave then progresses to the reaming main gas lines  310 C,  310 D,  310 E and into the breathing circuit  120 . When the gas sparing valve  330  is closed, and the gas flow in the main gas line  310 B ceases, the pliant diaphragm  3023  returns to its original unpressurized condition by reaction force of the spring  3024 . The pressure surge damper is then ready for the next pressure wave. 
       FIGS. 31A and 31B  illustrate the damping effect of the pressure surge damper  3010  in the gas sparing circuit  3000 .  FIG. 31A  illustrates the pressure in the main gas line after the time T 1  that the gas sparing valve  330  opens without the pressure surge damper. The pressure in the main gas line  310  increase quickly to P 2  which is the surge pressure and is above the steady state pressure P 1 . The pressure then drops at time T 2  to the steady state pressure P 1 .  FIG. 31B  illustrates the pressure in the main gas line after the time T 1  that the gas sparing valve  330  opens with the pressure surge damper. The pressure in the main gas line  310  is damped and slowly increases to P 1 , the steady state pressure at time T 2 . The pressure wave in the main gas line  310  is suppressed and no pressure spike occurs at the breathing circuit  120 . 
       FIG. 32  illustrates an exemplary alternative embodiment of the endotracheal (ET) hand piece  1500  of  FIG. 15 , generally designated as  1500 ′ in  FIG. 32 , in accordance with an exemplary embodiment of the present invention. The ET hand piece  1500 ′ includes several similarities with the ET hand piece  1500 . For example, the inlet port  1530  of the ET hand piece  1500 ′ is configured to be connected to the rotating outlet port  1220  of the mask connection  1200 , and the outlet port  1550  of the ET hand piece  1500 ′ is configured to be connected to the endotracheal tube  1560 . Furthermore, the ET hand piece  1500 ′ includes the pilot control switch  1340 ′, as does the ET hand piece  1500 , but further includes a CPAP vent port  1700 ′ containing the CPAP valve  1706 ′ and port cap  1704 ′ as described in  FIGS. 22 and 23 , which the ET hand piece  1500  does not contain. When used in conjunction with the gas sparing circuit  400  of  FIG. 4  set to CPAP mode, the port cap  1704 ′ is removed from the valve housing  1702 ′ and CPAP functionality is possible. 
     It is to be understood that the ET hand piece  1500 ′ may be modified as described herein to include electrical wires such as those illustrated in  FIG. 24 , element  2465 , and an electrical switch similar to switch  2425  in  FIG. 24  to allow functionality with the gas sparing circuit  2400  shown in  FIG. 24 . 
     Because the various embodiments of the gas sparing systems, devices, and circuits described herein provide for control of main (primary) gas, large continuous gas flows are minimized, and gas is conserved. In addition, the gas sparing systems, devices, and circuits described herein allow for precise pressure and volume control. Several examples of patient interfaces, such as the masks  130 ,  130 ′,  130 ″, and  130 ′″ and ET hand pieces  1500  and  1500 ′, are described herein for delivering the gas to a patient. It is to be understood that the patient interfaces are not limited to these examples. 
     These and other advantages of the present invention will be apparent to those skilled in the art from the foregoing specification. For example, it is contemplated that the gas sparing valve  330  and the pilot control line  365  may be replaced, respectively, by an electronically controlled valve and a switch coupled to the valve via a conductor for selective control of the valve. Further, the pneumatic timer controls may be replaced by electrical timer controls. Accordingly, it is to be recognized by those skilled in the art that changes or modifications may be made to the above-described embodiments without departing from the broad inventive concepts of the invention. It is to be understood that this invention is not limited to the particular embodiments described herein, but is intended to include all changes and modifications that are within the scope and spirit of the invention.