Reperfusion protection in resuscitation

Abstract

An apparatus and method for resuscitating a patient suffering from cardiac arrest or another condition in which normal circulation has been interrupted. A ventilator is used for delivering a gas mixture to the patient. The ventilator is configured to adjust the partial pressure of CO2 to one or more partial pressures high enough to slow expiration of CO2 from the patient's lungs and thereby maintain a reduced pH in the patient's tissues for a period of time following return of spontaneous circulation.

1 . Resuscitation apparatus for resuscitating a patient suffering from cardiac arrest or another condition in which normal circulation has been interrupted, the apparatus comprising: 
 a ventilator for delivering a gas mixture to the patient,    wherein the ventilator includes apparatus configured to adjust the partial pressure of CO 2  to one or more partial pressures high enough to slow expiration of CO 2  from the patient's lungs and thereby maintain a reduced pH in the patient's tissues for a period of time following return of spontaneous circulation.    
   
   
       2 . The apparatus of  claim 1  wherein the partial pressure of CO 2  is adjusted to be higher than ambient CO 2  partial pressure during the period of time.  
   
   
       3 . The apparatus of  claim 1  wherein adjustment of the partial pressure of CO 2  includes adding CO 2  to the gas inspired by the patient.  
   
   
       4 . The apparatus of  claim 1  further comprising a sensor and associated processing for measuring a physiological status of the patient, wherein the partial pressure of CO 2  is adjusted at least in part in response to the output of the sensor.  
   
   
       5 . The apparatus of  claim 4  wherein the sensor and associated processing are configured to detect return of spontaneous circulation, and wherein the partial pressure of CO 2  is changed in response to detection of return of spontaneous circulation.  
   
   
       6 . The apparatus of  claim 1  wherein the period of time is greater than 30 seconds.  
   
   
       7 . The apparatus of  claim 6  wherein the period of time is greater than 3 minutes.  
   
   
       8 . The apparatus of  claim 5  wherein the sensor comprises a CO 2  sensor.  
   
   
       9 . The apparatus of  claim 1  wherein adjustment of the partial pressure of CO 2  has the effect of maintaining the pH of the patient's tissues below 7.0 for the period of time following return of spontaneous circulation.  
   
   
       10 . The apparatus of  claim 9  wherein the pH of the patient's tissues is maintained below 6.8.  
   
   
       11 . The apparatus of  claim 10  wherein the pH of the patient's tissues is maintained below 6.5.  
   
   
       12 . The apparatus of  claim 1  further comprising a defibrillator.  
   
   
       13 . The apparatus of  claim 1  further comprising a chest compressor.  
   
   
       14 . The apparatus of  claim 1  further comprising an infuser.  
   
   
       15 . The apparatus of  claim 1  further comprising a sensor and associated processing for determining the pH of the patient's tissue, wherein the partial pressure of CO 2  is adjusted at least in part in response to the pH of the patient's tissue.  
   
   
       16 . The apparatus of  claim 15  wherein the partial pressure of CO 2  is adjusted to maintain tissue pH below  6 . 8  for a period of time following return of spontaneous circulation.  
   
   
       17 . The apparatus of  claim 1  wherein the partial pressure of CO 2  is gradually lowered over at least a portion of the period of time so as to gradually raise the pH of the patient's tissues.  
   
   
       18 . The apparatus of  claim 1  further comprising processing using a mathematical model of the relationship between CO 2  retention in the patient and the pH of the patient's tissues.  
   
   
       19 . The apparatus of  claim 18  wherein the mathematical model comprises processing using the Henderson-Hasselbalch equations.  
   
   
       20 . The apparatus of  claim 1  further comprising apparatus and processing for measuring the inspired volume and expired volume of CO 2  in the ventilation cycle, and using the inspired and expired volumes to adjust the partial pressure of CO 2 .  
   
   
       21 . The apparatus of  claim 1  further comprising apparatus and processing for monitoring an E t CO 2  level, and wherein the partial pressure of CO 2  is adjusted to maintain the E t CO 2  level above a level found in the arrest victim prior to the arrest.  
   
   
       22 . The apparatus of  claim 21  wherein the adjustment of the partial pressure of CO 2  is accomplished by adjusting the partial pressure between a lower level in a first cycle and a higher level in a second cycle, wherein in the first cycle the partial pressure of CO 2  is lower than a previously measured E t CO 2  level, and wherein in the second cycle the partial pressure of CO 2  is higher than the previously measured E t CO 2  level, and wherein the lower and higher levels are adjusted to maintain E t CO 2  at a desired level.  
   
   
       23 . The apparatus of  claim 13  wherein the ventilator and chest compressor are controlled so that a ratio of chest compression rate to ventilation rate is less than 15:2 during at least a portion of the period of time following return of spontaneous circulation.  
   
   
       24 . The apparatus of  claim 23  wherein the ratio is less than 5:1.  
   
   
       25 . The apparatus of  claim 24  wherein the ratio is about 6:2.  
   
   
       26 . The apparatus of  claim 1  further comprising a fluid infusion device.  
   
   
       27 . The apparatus of  claim 26  wherein the fluid infusion device is configured to infuse fluids containing metabolic substances during reperfusion.  
   
   
       28 . The apparatus of  claim 27  wherein the metabolic substances comprise amino acids.  
   
   
       29 . The apparatus of  claim 28  wherein the amino acids comprise aspartate, dihydroxyacetone phosphate or glutamate.  
   
   
       30 . The apparatus of  claim 1  further comprising a defibrillator, compressor, and infuser.  
   
   
       31 . The apparatus of  claim 30  wherein the defibrillator, compressor, ventilator, and infuserare separate devices and are linked by a communications link.  
   
   
       32 . The apparatus of  claim 31  wherein an additional computing device is used to synchronize all of the separate devices.  
   
   
       33 . The apparatus of  claim 1  wherein there are both negative and positive pressures available from the ventilator.  
   
   
       34 . The apparatus of  claim 1  wherein the ventilator is configured to elevate oxygen levels to greater than 40%.  
   
   
       35 . The apparatus of  claim 1  wherein the period of time begins prior to the return of spontaneous circulation.  
   
   
       36 . The apparatus of  claim 35  wherein the period of time begins immediately prior to the return of spontaneous circulation.  
   
   
       37 . A method of resuscitating a patient suffering from cardiac arrest or another condition in which normal circulation has been interrupted, the method comprising: 
 applying a ventilator to the patient;    delivering a gas mixture to the patient using the ventilator,    wherein the ventilator is configured to adjust the partial pressure of CO 2  to one or more partial pressures high enough to slow expiration of CO2 from the patient's lungs and thereby maintain a reduced pH in the patient's tissues for a period of time following return of spontaneous circulation.    
   
   
       38 . The method of  claim 37  wherein the partial pressure of CO 2  is adjusted to be higher than ambient CO 2  partial pressure during the period of time.  
   
   
       39 . The method of  claim 37  wherein adjustment of the partial pressure of CO 2  includes adding CO 2  to the gas inspired by the patient.  
   
   
       40 . The method of  claim 37  further comprising providing a sensor and associated processing for measuring a physiological status of the patient, wherein the partial pressure of CO 2  is adjusted at least in part in response to the output of the sensor.  
   
   
       41 . The method of  claim 40  wherein the sensor and associated processing are configured to detect return of spontaneous circulation, and wherein the partial pressure of CO 2  is changed in response to detection of return of spontaneous circulation.  
   
   
       42 . The method of  claim 37  wherein adjustment of the partial pressure of CO 2  has the effect of maintaining the pH of the patient's tissues below 7.0 for the period of time following return of spontaneous circulation.  
   
   
       43 . The method of  claim 37  further comprising using a sensor and associated processing for determining the pH of the patient's tissue, and adjusting the partial pressure of CO 2  at least in part in response to the pH of the patient's tissue.  
   
   
       44 . The method of  claim 37  wherein the period of time begins prior to the return of spontaneous circulation.