The relationship of carbon dioxide excretion during cardiopulmonary resuscitation to regional blood flow and survival

Abstract Currently, there are no practical means of prospectively determining cardiopulmonary resuscitation (CPR) adequacy in the field. Airway CO 2 excretion can be noninvasively and stably measured under changing environmental conditions. We investigated the relationship between the volume of airway CO 2 excreted (CO2EX) during CPR to regional blood flow (RBF) and survival. A total of 21 dogs were randomly divided into four CO2EX groups ( 6–7 and >7 ml CO 2 /min per kg), anesthetized, instrumented and ventilated with an in-line infrared airway CO 2 sensor. Anesthesia was reduced and baseline measurements made. Ventricular fibrillation (VF) was initiated and resuscitation withheld for 3 min, followed by 17 min of CPR. Compression force alone was adjusted to maintain predetermined CO2EX. Animals were resuscitated, monitored for 2 h and observed for an additional 22 h. RBF was determind at baseline, 16 min post-VF and 60 min post-resuscitation. Mean CO2EX during CPR was significantly higher in survivors than nonsurvivors. The probability of survival increased as CO2EX increased. The highest CO2EX group had the highest rate of survival (86%), but did not always have significantly higher cardiac output (CO), myocardial or cerebral blood flows (MBF, CBF) than the lowest CO2EX group with a 0% survival rate. These data suggest survival is tracked better by CO2EX than by CO, MBF or CBF. Therefore, CO2EX appears to provide a practical reliable noninvasive method of determining CPR efficacy in the field.