Volumetric capnography and return of spontaneous circulation in an experimental model of pediatric asphyxial cardiac arrest

A secondary analysis of a randomized study was performed to study the relationship between volumetric capnography (VCAP) and arterial CO(2) partial pressure (PCO(2)) during cardiopulmonary resuscitation (CPR) and to analyze the ability of these parameters to predict the return of spontaneous circulation (ROSC) in a pediatric animal model of asphyxial cardiac arrest (CA). Asphyxial CA was induced by sedation, muscle relaxation and extubation. CPR was started 2 min after CA occurred. Airway management was performed with early endotracheal intubation or bag-mask ventilation, according to randomization group. CPR was continued until ROSC or 24 min of resuscitation. End-tidal carbon dioxide (EtCO(2)), CO(2) production (VCO(2)), and EtCO(2)/VCO(2)/kg ratio were continuously recorded. Seventy-nine piglets were included, 26 (32.9%) of whom achieved ROSC. EtCO(2) was the best predictor of ROSC (AUC 0.72, p < 0.01 and optimal cutoff point of 21.6 mmHg). No statistical differences were obtained regarding VCO(2), VCO(2)/kg and EtCO(2)/VCO(2)/kg ratios. VCO(2) and VCO(2)/kg showed an inverse correlation with PCO(2), with a higher correlation coefficient as resuscitation progressed. EtCO(2) also had an inverse correlation with PCO(2) from minute 18 to 24 of resuscitation. Our findings suggest that EtCO(2) is the best VCAP-derived parameter for predicting ROSC. EtCO(2) and VCO(2) showed an inverse correlation with PCO(2). Therefore, these parameters are not adequate to measure ventilation during CPR.