Driving control of a reciprocating cpr apparatus

Abstract

A method of controlling the amount of compressed gas used for driving a reciprocating apparatus for cardio-pulmonary resuscitation (CPR) comprising a valve means for controlling the provision of driving gas comprises operation of the valve means during the compression phase to stop provision of driving gas, which operation is separated in time from the venting of the driving gas from the apparatus at the end of the compression phase. Also disclosed are; a CPR apparatus operated by the method; a method of compression depth sensing.

1 . A method of sensing the Compression Depth and/or a compression depth in a reciprocating apparatus for cardio-pulmonary resuscitation (CPR) driven by a compressed gas and comprising a reciprocating part and a non-reciprocating part, the method comprising arranging a sensor mounted on the non-reciprocating part capable of sensing a signal emanating from the reciprocating part at a selected position thereof, transmitting the signal to a microprocessor unit that records its arrival time. 
   
   
       2 . The method of  claim 1 , wherein the sensor is one for contactless sensing. 
   
   
       3 . The method of  claim 1 , comprising sweeping one or several magnetic or radiation sensors mounted at the non-reciprocating part with a magnetic field or radiation, respectively, emanating from a corresponding field or radiation source mounted at or deflected or reflected by the reciprocating part, thereby giving rise to an electric signal in a swept sensor. 
   
   
       4 . The method of  claim 3 , wherein the radiation source is one emitting UV, visible or IR radiation. 
   
   
       5 . The method of  claim 2 , wherein the sensor is an ultrasound sensor. 
   
   
       6 . The method of  claim 1 , wherein the sensor is a contact sensor. 
   
   
       7 . The method of  claim 6 , wherein the Compression Depth of the apparatus is kept constant by physical means, and wherein the contact sensor is activated at the moment when the reciprocating part reaches the Compression Depth. 
   
   
       8 . A method of controlling the amount of compressed gas used for driving a reciprocating apparatus for cardio-pulmonary resuscitation (CPR) comprising a valve means for controlling the provision of driving gas to a reciprocating part of the apparatus and for venting of the used driving gas from the apparatus, comprising
 (a) operating the valve means at the start of a compression/decompression cycle to provide driving gas;   (b) operating the valve means during the compression phase to stop the provision of driving gas;   (c) operating the valve means at the end of the compression phase to vent the driving gas from the apparatus.   
   
   
       9 . The method of  claim 8 , wherein step (b) is initiated at a point in time when the pressure of the provided driving gas is from 30 percent to 70 percent of the pressure of the driving gas. 
   
   
       10 . The method of  claim 9 , wherein the pressure of provided driving gas is from 40 percent to 60 percent of the pressure of the driving gas. 
   
   
       11 . The method of  claim 8 , wherein the pressure of provided driving gas is about 50 percent of the pressure of the driving gas. 
   
   
       12 . The method of  claim 8 , wherein step (b) is initiated at a point in time when from 25 percent to 40 percent of the compression phase has passed. 
   
   
       13 . The method of  claim 8 , wherein step (b) is initiated at a point in time before the moment at which the reciprocating part has reached the Compression Depth. 
   
   
       14 . The method of  claim 13 , wherein initiation is from 0 to 50 milliseconds prior, in particular from 10 to 30 milliseconds prior, most preferred about 10 to 20 milliseconds prior to the moment at which the Compression Depth is reached. 
   
   
       15 . The method of  claim 13 , wherein the moment at which the reciprocating part reaches the Compression Depth or the moment of initiation has been determined in a preceding compression/decompression cycle. 
   
   
       16 . The method of  claim 13 , wherein the moment at which the reciprocating part reaches the Compression Depth or the moment of initiation is determined by means of sensor mounted at a non-reciprocating part of the apparatus sensing radiation reflected from a reciprocating part of the apparatus or a magnetic field moving with a reciprocating part of the apparatus. 
   
   
       17 . The method of  claim 8 , wherein the valve means comprises a solenoid valve. 
   
   
       18 . The method of  claim 8 , wherein the control is confined to a steady-state CPR phase starting from one to five minutes, preferably from one to two minutes after the onset of administration of chest compressions. 
   
   
       19 . The method of  claim 8 , wherein the pressure of the driving gas is from 2.5 to 4 bar, preferably about 3 bar. 
   
   
       20 . The method of  claim 8 , wherein the valve means is operated by means of a microprocessor. 
   
   
       21 . A reciprocating apparatus for cardiopulmonary resuscitation (CPR) driven by a compressed gas, comprising a housing, a piston displaceable in the housing defining an upper chamber and a lower chamber, a valve controlling the supply of driving gas to the upper chamber during a reciprocating cycle, wherein the closure of the valve is controlled by a microprocessor based on the time at which the piston reached a selected position, in particular its lower extreme position, in an earlier cycle stored in a memory of the microprocessor. 
   
   
       22 . The apparatus of  claim 21 , comprising a means for sensing the position of the piston coupled to the microprocessor. 
   
   
       23 . The apparatus of  claim 22 , wherein the sensing means is for contactless sensing. 
   
   
       24 . The apparatus of  claim 23 , wherein the sensing means comprises a radiation source and a radiation detector. 
   
   
       25 . The apparatus of  claim 23 , wherein the sensing means comprises a permanent magnet and a Hall-effect switch. 
   
   
       26 . The apparatus of  claim 23 , wherein the sensing means comprises an ultrasound source and an ultrasound detector. 
   
   
       27 . The apparatus of  claim 22 , wherein the stroke of the piston is mechanically limited and wherein the sensing means is for sensing by contact. 
   
   
       28 . The apparatus of  claim 21 , wherein the memory of the microprocessor comprises a program instructing the microprocessor to control the valve so as to shut it from 0 to 50 milliseconds prior, in particular from 10 to 30 milliseconds prior, most preferred about 10 to 20 milliseconds prior to the time at which the lower extreme position had been reached in an earlier cycle. 
   
   
       29 . The apparatus of  claim 21 , comprising a manometer for sensing the gas pressure in the upper chamber, wherein the memory of the microprocessor comprises a program instructing the microprocessor to control the valve so as to shut it when the gas pressure in the upper chamber is from 30 percent to 70 percent of the pressure of the driving gas before its provision to the upper chamber, more preferred from 40 to 60 percent, most preferred about 50 percent. 
   
   
       30 . The apparatus of  claim 21 , wherein the valve is a solenoid valve. 
   
   
       31 . The apparatus of  claim 21 , wherein the gas used for driving of the piston is a breathing gas, which is vented to a means for supplying breathing gas to the lungs of the patient. 
   
   
       32 . The apparatus of  claim 31 , wherein the means for supplying breathing gas is selected from breathing mask and intubation device.