Abstract:
An extended term resuscitation system includes a plurality of inflatable cuffs adapted to extend around separate portions of the anatomy of a patient (i.e. the chest, abdomen and legs) for enhancing the circulation when inflated/deflated periodically. A primary low-pressure-high-volume air compressor is in fluid communication with each of the cuffs through individual air handlers. The air handlers are formed with an inflation and a deflation diaphragm valve which, under the control of an electronic timer and a pneumatic circuit, connect the respective cuff to the output of the compressor for inflation or to the atmosphere for deflation. A secondary air compressor provides air under suitable pressure to the pneumatic circuit for the control of the diaphragm valves. As an option the operator may change the cyclical rate and cuff pressure. A ventilator provides oxygen to the patient in selected volumes or on demand.

Description:
FIELD OF THE INVENTION 
     This invention relates to an apparatus or system for providing cardiac and/or pulmonary resuscitation and more particularly to such a system that is automated and capable of enhancing a patient&#39;s circulation and ventilation for an extended period. 
     BACKGROUND OF THE INVENTION 
     State of the art methods and apparatus for providing external cardiac resuscitation are discussed to some extent in U.S. Pat. No. 5,806,512 (“&#39;512 patent”). The &#39;512 patent teaches the use of inflatable cuffs surrounding a patient&#39;s chest, abdomen and legs which are periodically inflated and deflated to force blood from the extremities to and through the heart with the chest and abdomen functioning in an out-of-phase relationship. Ventilation via a patient mask is also disclosed in the patent. 
     More recently a portable resuscitation/ventilation system using inflatable chest, abdominal and leg cuffs and a ventilator coupled to self-contained cylinders of compressed gas is described in international publication WO 2010/151278 A1 (“&#39;278 pub.”) and disclosed on the web site AutoCPR.net. Solenoid operated valves, controlled by an electronic timer, connect the cuffs alternately to the compressed gas cylinders and to the ambient or atmosphere to inflate and deflate the cuffs in a timed sequence. For example, the chest and abdominal cuffs are operated in an out-of-phase sequence at a 30 cycles per minute rate, i.e., one second on (inflation) and one second off (deflation). The leg cuffs can be inflated and deflated at the same or a different rate. For example, the leg cuffs can be inflated continuously or inflated/deflated every fifth cycle of the chest cuff with the inflation period exceeding the deflation period. The portable gas supply is designed to provide adequate time to achieve the return of spontaneous circulation (ROSC) and patient transport to a hospital emergency department. A face mask and a tank of breathable gas provide ventilation for the patient. The resuscitator/ventilator of the &#39;278 pub. is small enough to fit into a suitcase easily handled by a paramedic or other first responder. While it is believed to be cutting edge for its intended purpose, the use of compressed gas cylinders limits its operating time. 
     Recent clinical studies have demonstrated that the continued support of a patient&#39;s circulation (such as uninterrupted chest compression) after ROSC significantly improves the survival rate of patients after leaving the hospital. See, for example, the Journal of Emergency Medicine, 1008, Feb. 12, 2009 by M. Riscon, et al; the European Resuscitation Council Guideline for Resuscitation 2005 by A J Hadley, et al; Critical Care 2005, 9:287-290 by M H Weil and Shijie Sun; and Burst Stimulation Improves Hemodynamics during resuscitation etc. in Circulation: 2009, 2:57-62 by G. Walcott et al. 
     There is a need for a system/apparatus which will not only aid in achieving a patient&#39;s ROSC but in addition continue to support the patient&#39;s circulatory system over an adequate time period after ROSC to improve the out of hospital survival rates for patients suffering cardiac arrest or other serious heart problems. 
     SUMMARY OF THE INVENTION 
     A patient resuscitation system, in accordance with the present invention, includes a plurality of inflatable cuffs adapted to extend around separate portions of a patient&#39;s anatomy (e.g, chest, abdomen and legs) for increasing the patient&#39;s blood flow when periodically inflated/deflated (1) to achieve ROSC and subsequently (2) to continue the support of his/her circulatory system. A timer, such as the timer disclosed in the &#39;278 pub., sets the inflation/deflation periods. Air for the inflation steps is provided by a primary low-pressure-high-volume-air-compressor connected to a volume chamber (i.e. to smooth out pressure fluctuations). A pneumatic circuit, including a pressurized gas source, such as a secondary compressor, provides a separate pneumatic control signal associated with each cuff bracketing each inflation period set by the timer. An air handler is individually connected between each cuff, the volume chamber and the atmosphere (or ambient) and responsive to the pneumatic control signals for inflating/deflating each cuff in accordance with the inflation/deflation periods set by the timer. 
     Each air handle preferably includes an inflation and a deflation diaphragm valve with the valves being located between the cuff, the volume chamber and the atmosphere, respectively. Preferably each diaphragm valve is normally open connecting the cuff to the volume chamber and to the atmosphere with each valve being arranged to close in response to the receipt of a control signal and open in the absence of a control signal. Accordingly, each cuff will be connected to the volume chamber for inflation purposes in the absence of a control signal being applied to the inflation diaphragm valve and in the presence of a control signal being applied to the deflation diaphragm valve closing off the cuff from the atmosphere and visa versa. Alternatively the diaphragm valves connecting the cuffs to the volume chamber can be closed independently of the operation of the timer. 
     In a preferred embodiment the inflation diaphragm valve, in the form of an air module, connects the associated cuff to the volume chamber when open and the deflation valve, in the form of an air relay, connects the associated cuff to the atmosphere when open. 
     Preferably there is a chest, abdominal, and two leg cuffs. The pneumatic circuit includes a control valve for each air handler. The control valves for the chest and abdominal cuffs have (1) an auto position (responsive to the timer) in which the control signals are directed to the inflation and deflation diaphragm valves alternately to inflate and deflate the chest and abdominal cuffs in an out-of-phase relationship and (2) an off position in which the pneumatic control signals are continuously (when present) applied to the inflation diaphragm valves to close the same. At the same time the deflation diaphragm valves are opened by the absence of the next control signal, resulting in a deflation mode for the cuffs in the off mode. 
     The control valve for the leg cuffs has an auto position in which the cuffs are alternately inflated and deflated in accordance with the dictates of the timer, an on position in which the cuffs are continuously inflated, and an off position in which the cuffs are continuously deflated. 
     Preferably the diaphragm valves are mounted in a common manifold block with the block providing fluid communication between each pair of (inflation and deflation) valves and the associated cuff. 
     A manually adjustable pressure/cycle rate valve may be coupled to the volume chamber and the timer for allowing the operator to select different cyclical rates (e.g. 30 or 20 cycles per minute) and different pressures (e.g. 150 or 100 mm Hg.) in the volume chamber. A ventilator, like the one disclosed in the &#39;278 pub., may be included in the apparatus. 
     The face mask and cuffs may be disposable to comply with applicable health standards. The content of the &#39;278 pub. (now U.S. Pat. No. 8,277,399) are incorporated in their entirety herein, by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an apparatus/system in accordance with this invention, showing an individual air handler connecting each cuff (extending around a separate portion of a patient&#39;s anatomy) to the volume chamber and to the atmosphere. This figure also depicts a ventilator and a face mask. 
         FIG. 2  is a cross sectional view of an air handler comprising an air module (forming the inflation diaphragm valve) and an air relay (forming the deflation diaphragm valve) mounted to a common manifold block with both valves open, allowing air flow to and from an associated cuff; 
         FIGS. 3 and 4  represent the same view as  FIG. 2  showing the valves arranged to inflate and deflate the cuff, respectively. 
         FIGS. 5   a  and  5   b  are bottom and perspective views of the air module (inflation diaphragm valve), respectively. 
         FIGS. 6   a  and  6   b  are front and perspective views of the air relay (deflation diaphragm valve), respectively. 
         FIG. 7  is a pneumatic circuit diagram illustrating one method of operating the air handlers to inflate and deflate the several cuffs, i.e, with the chest and abdominal cuffs being inflated/deflated alternately. 
         FIGS. 8   a ,  8   b  and  8   c  are cross sectional views of one of the ball valves of  FIG. 7  showing possible valve positions to (1) allow the operation of the solenoids, in response to the timer, to control the inflation/deflation of the cuffs, (2) apply the control signal continuously to inflation diaphragm valve to close the same and (3) with respect to leg cuffs to isolate the inflation diaphragm valve from the control signals, respectively. 
         FIGS. 9   a  and  9   b  are a cross sectional and end view of an exhaust valve, respectively. 
         FIGS. 10   a  and  10   b  are a cross sectional and end view of a back flow valve, respectively. 
         FIGS. 11   a ,  11   b  and  11   c  are perspective, front and cross sectional views of the selector valve of  FIG. 7  for controlling the cyclical rate and cuff pressure. 
         FIGS. 12   a  and  12   b  are an end view and a cross sectional view, respectively, of the pressure compensated discharge valve which controls the pressure in the volume chamber. 
         FIG. 13  is a electrical schematic circuit diagram of a modification of the circuit shown in FIG. 4B of the &#39;278 pub. to accommodate two cyclical rates for inflation/deflation. 
         FIG. 14   a  is a graph illustrating the control of gas pressure to the ventilator and cuffs in an exemplary mode.  FIG. 14   b  illustrates operation of the solenoid valves to provide the gas pressure control illustrated in  FIG. 14   a.    
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Overview of the System Operating in an Exemplary Mode 
     Referring now to  FIG. 1  a patient  11 , shown in reclining position, is fitted with a chest cuff  10 , abdominal cuff  12  and leg cuffs  14 . A primary low-pressure-high-volume-compressor  16  supplies air to a volume chamber  16   a  (for smoothing out pressure fluctuations resulting from the periodic inflation of the cuffs). The volume chamber is connected to air handlers  18  (chest) and  20  (abdomen) via lines  16   b  and to air handlers  22  (legs) via line  16   c  and back flow valve  64 , to be described. A suitable compressor may be obtained from the Parker Hannifin Corporation under part no. 737-23-01. An adjustable flow restrictor  16   d  connected between the compressor and the volume chamber (in line  16   e ) controls the flow rate to the volume chamber to say about 150 l/min. A pressure compensated relief valve (to be described) controls the volume chamber pressure, e.g., 2-3 psi. The individual air handlers are mounted in a common manifold block  23  to supply air, under the moderate volume chamber pressure, to the several cuffs through lines  10   a ,  12   a , and  14   a  (via quick disconnect couplings  10   b ,  12   b  and  14   b ), as shown. A source of pneumatic control signals, such as a secondary air compressor  26 , supplies a moderate control signal pressure, e.g. 15 psi., to a solenoid/pneumatic circuit  28  described in connection with  FIG. 7 . The circuit  28  responds to control signals routed through solenoid valves (hereinafter sometimes simply referred to as “solenoids”), under the control of a timer  24  (such as the solenoids and timer disclosed in FIG. 4B of the &#39;278 pub.), to actuate the air handlers in accordance with the dictates of the timer. A ventilator  30  provides breathable gas, such as oxygen, to the patient  11  through a conventional face mask  30   a  and quick disconnect coupling  30   b ′ in the manner disclosed in the &#39;278 pub. 
     In an automated exemplary mode, the chest and abdominal cuffs are continuously inflated and deflated in an out of phase relationship in one second intervals, that is, one second inflated and one seconded deflated, while the leg cuffs are inflated and deflated in 10 second and 2 second intervals, respectively. See  FIG. 14  for a graphic depiction of this exemplary mode of operation. A cyclical rate/pressure switch (to be described) allows an operator, to set the rate and volume chamber pressure. For example, the rates may be set at 30 cycles/minute and the volume chamber pressure at 150 mmHg for resuscitation purposes and at 20 cycles/minute with the pressure at 100 mmHg for circulation support. The solenoid/pneumatic circuit  28  incorporates manually operated ball valves allowing an operator to override the timer and close the inflation diaphragm valves of the air handlers for all of the cuffs and, if desired, continuously apply a control signal to the leg cuffs&#39; deflation diaphragm valve while isolating the control signal from the leg cuffs&#39; inflation diaphragm valve, leaving the left cuffs continuously inflated. 
     Discussion of the Air Handlers 
     All of the air handlers are identical with the chest cuff air handler  18  which is shown in a cross sectional view in  FIGS. 2-4 . The air handler  18  comprises an air module  32 , in the form of an inflation diaphragm valve, and an air relay  34 , in the form of a deflation diaphragm valve, mounted on a common manifold block  23 . The air modules for the abdomen and legs cuffs are identified by the reference numerals  36  and  40 , respectively, in  FIGS. 1 &amp; 7 , while the air relays for the abdomen and leg cuffs are identified by the reference numerals  38  and  42 , respectively, in those figures. 
     Referring again to  FIGS. 2-4 , the air module  32 , having an outer body  32   a  and an inner tubular member  32   b , is secured within a bore  23   a  in the block  23 . The tubular member  32   b  terminates at its distal end  32   c  within the longitudinal bore  23   a  of the block and at its proximal end  32   d  a short distance from the inner surface of an end cap  32   e , as shown. The longitudinal bore  23   a  terminates in the quick disconnect coupling  10   b  for transferring air to and from the chest cuff. A flexible diaphragm  32   f , mounted within the body  32   a , is normally spaced from the proximal end  32   d  of the tubular member as is shown in  FIG. 2 . A tubular inlet  32   g  of the inflation diaphragm valve or air module is arranged to be connected to the volume chamber  16   a  via the hose connection  16   b  ( FIG. 1 ). A control signal inlet nipple  32   h  is arranged to conduct pneumatic control signals, emanating from the secondary compressor, to a chamber  32   i , to force the diaphragm  32   f  against the proximal end  32   d  of the member  32   b  and close the air module or inflation diaphragm valve, as will be discussed in more detail. 
     The air relay  34  (deflation diaphragm valve), mounted to the block  23  as shown, includes a tubular member  34   a  extending (at its distal or inlet end  34   b ) from a lateral bore  23   b  in the manifold block (which terminates at outlet  23   c  in the common longitudinal bore  23   a ) to a proximal end  34   c . The proximal end is normally spaced a short distance from a flexible diaphragm  34   d  with an annular volume  34   e , surrounding the tube  34   a , which opens to the atmosphere or ambient via an outlet orifice  34   f  to exhaust the chest cuff when the diaphragm valve is open. A nipple  34   g  is arranged to conduct (pressurized) control signals to a chamber  34   h  which closes the deflation diaphragm valve. 
     The air handler  18  is shown in its normal state in  FIG. 2  (with both diaphragm valves open in the absence of the application of control signals) so that air is free to flow between the cuff, the volume chamber and the atmosphere. 
       FIG. 3  shows the same air handler with the diaphragm valves of the air module and air relay open and closed, respectively, inflating the chest cuff.  FIG. 4  shows the air handler with the diaphragm valves of the air module and the air relay closed and open, respectively deflating the cuff. 
     See  FIGS. 5   a ,  5   b ,  6   a  and  6   b  for front and perspective views of the air modules and air relays, respectively. 
     Discussion of the Pneumatic/Solenoid Circuitry and Accessory Components 
     Referring now to  FIG. 7  which represents the pneumatic/solenoid circuit  28  and ventilator  30  depicted in  FIG. 1 . The ventilator, chest, abdomen and leg solenoids are given reference numerals  44 ,  46 ,  48  and  50  and correspond to solenoids 140-1, 140-2, 140-3 and 140-4 in FIG. 1A of the &#39;278 pub., respectively. The secondary compressor  26  supplies a constant pressurized (say 15 psi) control signal on line  26   a . The solenoid ports  46   a ,  48   a  and  50   a  are open to the atmosphere and serve the purpose of evacuating lines connected thereto by the solenoids. 
     The Pneutronics Division of Parker Hannifin Corporation offers such solenoids under the X-valve designation. 
     The pneumatic circuit includes manually adjustable ball valves  52 ,  54  and  56  with solenoid receptive ports S for accommodating automatic operation of the system in cooperation with air module interrelated ports A. Closure ports C provide closure of the air modules in cooperation with the control signal ports A, as will be explained. Ball valve  56  includes an additional function of allowing the continuous inflation of the leg cuffs by preventing control signals from reaching the air module  40 . An exhaust diaphragm valve  43 , when closed due to the absence of a control signal applied to nipple  43   g , allows the control signal passing through the restrictor  26   j  to close the air relay  42  allowing the cuffs to inflate. Air bleed orifice  41   a  also plays a part in controlling the operation of exhaust valve  43  by exhausting the pressure present at nipple  43   g  when the associated control signal is absent. 
     As discussed above, in an exemplary mode, the chest and abdomen cuffs are inflated and deflated alternately. As a result, when the chest cuff solenoid  46  is actuated to connect the pneumatic line  26   b  to the pressurized line  26   a , the abdomen solenoid  48  is inactivated disconnecting the line  26   c  from the control signal source, i.e. line  26   a . The control signal applied to nipple  38   g  of air relay  38  closes off the abdomen cuff from the atmosphere while the abdomen cuff is connected to the volume chamber  16   a  as a result of the absence of a control signal being applied to the nipple  36   h  of the abdomen air module  36 , thereby allowing the abdomen cuff to inflate. At the same time the control signal on line  26   b  is routed through ports S and A of the three-way valve  52  to the nipple  32   h  of the chest air module via line  26   e . The presence of the control signal closes off the chest cuff from the volume chamber, while the air relay  34  is open due to the absence of a control being applied to nipple  34   g , connecting the chest cuff to the atmosphere. 
     When the abdomen solenoid is activated the control signal is applied to the chest air relay  34  (via nipple  34   g ) and to abdomen air module  36  (via line  26   f  and nipple  36   h ) disconnecting the abdomen cuff from the volume chamber and the chest cuff from the atmosphere. The absence of a control signal being applied to the air relay  38  and the air module  32  results in inflating the chest cuff and deflating the abdomen cuff. 
     The ball valves  52  and  54  can be rotated to connect the A ports to the C ports for closing the chest and abdominal air modules by connecting line  26   a  to the nipples  32   h  and  36   h , thereby overriding the operation of the respective solenoid valves. In response to the absence of the next control signal the air relays  34  and  38  will open to connect the associated cuffs to the atmosphere resulting in the deflation of the cuffs. 
     Since the leg cuff(s)&#39; air handler operates independently, several accessories, namely exhaust valve  43 , bleed orifice  41   a  and flow restrictor  26   j  are needed for its control. The exhaust valve  43  has its input nipple  43   g  connected in parallel with the input nipple to the leg cuff(s)&#39; air module as shown. As a result when solenoid  50  is activated (as shown) a control signal is applied to the input nipples  40   h  and  43   g  of the air module  40  and exhaust valve  43 , respectively, via ports S and A in the ball valve  56  to close the air module and open the exhaust valve. At the same time the control signal pressure at the input nipple  42   g  of air relay  42  is exhausted to the atmosphere through exhaust valve  43  allowing this relay to open. Restrictor  26   i  serves the function of allowing the exhaust valve, when open, to drop the pressure at the nipple  42   g  thereby removing the control signal to that relay and allowing it to open, deflating the cuffs The restrictor  26   i  aids in the accomplishment of this function by restricting the flow through line  26   a.    
     When the solenoid  50  is inactivated (or open) the control signal disappears from the air module  40  and the exhaust valve  43 . This action connects the air module to the volume chamber, closes the exhaust valve  43  and applies the control signal (say 15 psi), via restrictor  26   j , to the air relay  42 . This control signal closes the air relay  42  and disconnects the leg cuff(s) from the atmosphere, allowing the cuff(s) to inflate. 
     Cross-sectional views of the ball valves  52 ,  54  and  56  are shown in  FIGS. 8   a - 8   c  with the ports S, A and C.  FIG. 8   c , illustrates the configuration of valve  56  in a position to disconnect the leg cuff(s)&#39; air module  40  and the exhaust valve  43  from the source of control signals. This action allows the bleed orifice  41   a  to bleed off any residual pressure existing at the inlet nipples  40   h  and  43   g  (1) causing the air module to open connecting the cuff to the volume chamber and (2) closing the exhaust valve  43 . At the same time the pressurized control signal flowing through restrictor  26   j  closes the air relay  42  disconnecting the cuff from the atmosphere. As a result the cuff(s) are continuously inflated as long as the valve  56  is set in this position as discussed above. Suitable ball valves may be acquired from the Hy-Lok Corporation under its 112 series designation. 
     Referring now to  FIGS. 9   a  and  9   b , the exhaust valve  43  is in the form of a poppet valve having an inlet  43   f  (arranged to be connected to the nipple  42   g ,  FIG. 7 ), an axially moveable shaft  43   a  biased into a closed position (via spring  43   b ) so that O ring  43   c  seats against valve seat  43   d . Outlet  43   h  is open to the atmosphere. A flexible diaphragm  43   e  is spaced between the proximal end  43   a ′ of the shaft  43   a  and a control signal receptive cavity  43   g ′ in fluid communication with the control signal nipple  43   g . Pressure of the control signal in the cavity  43   g ′ forces the diaphragm against the proximal end of the shaft  43   a  and opens the valve connecting the inlet  43   f  to the outlet  43   h  i.e. the atmosphere. 
     The backflow or check valve  64 , illustrated in  FIGS. 10   a  and  10   b , includes a housing  64   a  in which are mounted a valve plate  64   b , having a plurality of central openings  64   c , and a valve stem  64   d  with a deformable head  64   e . An inlet  64   f  is arranged to be connected to the volume chamber  16   a  while the outlet  64   g  is arranged to be connected to the inlet  32   g  of the air module  40  via line  16   c . See  FIGS. 1&amp;7 . The operation of such a simple backflow valve is simple and will be well understood by those skilled in the art. Its purpose is to isolate the leg cuff(s) from the volume chamber while the chest and abdominal cuffs are being inflated and thereby eliminate pressure fluctuations in the cuffs which might otherwise occur. 
     Discussion of the Selector Switch for Setting the Cyclical Rate and Volume Chamber Pressure 
     Referring now to  FIGS. 7 ,  11   a - 11   c  and  12   a - 12   b , the rotary selector switch  60  performs two separate functions, namely providing one of two cyclical rates e.g. 30 cycles per minute (“cpm”) or 20 cpm and one of two volume chamber (cuff) pressures e.g. 150 mm or 100 mm of Hg. The switch has a first rotor assembly  60   a  with a shaft  60   b  and a pneumatic inlet  60   c . The shaft  60   b  when rotated, via manual actuated knob  60   d  ( FIG. 11   a ), connects the inlet  60   c  to one of two relief valves  60   e  and  60   f  ( FIG. 7 ), via pneumatic outlet nipples  60   k  and  60   l , respectively. The relief valves may be set, for example, at 150 and 100 mmHg, respectively. The inlet  60   c  is connected to the dome  62   f  (via inlet  62   e ) of a compensated relief valve  62  ( FIG. 12   b ) secured to the volume chamber  16   a  ( FIG. 1 ) through an inlet  62   a  and a fitting  63  ( FIG. 7 ). Referring again to  FIG. 12   b , the poppet  62   b  carries a diaphragm  62   c  positioned between the atmosphere (via outlet  62   d ) and the inlet  62   a . The pressure in the volume chamber cannot exceed the pressure in line  63 , as will be apparent to those skilled in the art. 
     Referring again to  FIG. 11   c  the rotary switch  60  includes a second rotor assembly  60   g  carrying a magnet  60   h  which, when placed in close proximity to a Hall  1 C sensor  60   i , sends a digital signal, via output  60   j , to the timer to change the cyclical rate as will be explained with respect to a modification of the timer shown in  FIG. 13 . 
     Discussion of the Modification of the &#39;278 Pub. Timer 
     A modification of the timer disclosed in FIG. 4B of the &#39;278 pub., necessary to respond to the digital signal from the rate selector  60  ( FIG. 8   b ), is illustrated in  FIG. 13 . The time base 140-A (oscillator components C2, R18) of FIG. 4B (&#39;278 pub.) is deleted and replaced by (1) a crystal oscillator/divide by 256 (reference No.  65  in  FIG. 13 , herein) and (2) a dual J-K divide by 2 or 3 (reference  66  in  FIG. 13 ). The particular divider ratio activated is determined by the digital signal received on input  66   a  from the output on line  60   i  of the rate selector switch  60 . The divider  67  comprises the oscillator/divider U 1  from the &#39;278 pub. Dividers U 5 A and U 5 B constitute the dual J-K dividers. 
     Discussion of the Ventilator Components 
     Referring again to  FIG. 7 , the ventilator is of the same type as described in the &#39;278 pub. with a regulated oxygen supply  30   b  connected to a regulator  30   c  and a tidal volume control unit  30   d . The output of the regulator  30   c  is connected to the mask  30   a  through the tidal volume control unit  30   d  and solenoid valve  44 . The timer integrates the ventilation cycle with the abdomen compression cycles so as to operate without interruption. The ventilation cycle is timed to synchronize during abdominal compressions to prevent gastric insufflations and to deliver the correct tidal volume of oxygen during each compression of the abdomen. The tidal volume control unit includes a five position rotary switch (labeled  30   e ) within the control unit  30   d  which may be calibrated to deliver 400 ml, 600 ml, 800 ml and 1000 ml of breathable gas such as oxygen. A fifth position is the demand mode for use when the patient is breathing spontaneously. A gage  30   f  measures the pressure. In a preferred mode the oxygen is delivered for one second during every second cycle of the abdomen cuff inflation, followed by three seconds off. 
     CONCLUSION 
     There has been disclosed a simple and versatile system or apparatus for not only aiding a patient undergoing cardiac arrest to achieve the return of spontaneous circulation but to continue supporting the patient&#39;s circulation to improve his/her chances of long term survival after ROSC has been achieved. The diaphragm valves and air compressors are highly reliable and efficient, requiring little maintenance. It is to be noted that the various air pressures discussed above are by way of example only. Obviously the volume chamber pressure has to be adequate to properly inflate the cuffs; by the same token the control signal pressure must be sufficiently greater than the volume chamber pressure to insure closure of the diaphragm valves in the configuration as shown. While the apparatus is illustrated as operating in an automated mode with a higher cuff pressure and cyclical rate to achieve ROSC and with a lower pressure and cyclical rate subsequently, the invention is not so limited. 
     It is also to be noted that while the air modules and air relays are shown as being normally open and closed in response to the application of a control signal, one or both may be configured to be normally closed and opened in response to the control signal. As an example, the air relays may have a configuration similar to the exhaust valve  43  so that in the absence of a control signal the cuffs will be inflated and in response to a control signal the cuffs will be deflated. The system may be mounted on a wheeled cart for portability in a hospital or used in a paramedic&#39;s truck with compressors operating off of the truck&#39;s electrical system. While those skilled in the art may discover modifications or even improvements to the disclosed apparatus it is believed that such modifications will not involve a departure from the scope and spirit of our invention as defined in the appended claims.