ObjectiveThe objective of this study was to measure stroke volumes produced by precordial compression during cardiopulmonary resuscitation and to quantitate relationships of stroke volume to measurements of end-tidal carbon dioxide.DesignA prospective, observational animal study.SettingMedical research laboratory in a university-affiliated research and educational foundation.SubjectsDomestic pigs.InterventionsEighteen anesthetized male, domestic pigs weighing between 40 and 45 kg were investigated. Ventricular fibrillation was electrically induced and continued for intervals ranging from 4 to 10 mins. Precordial compression was maintained at 80 per minute together with mechanical ventilation after endotracheal intubation.Measurements and Main ResultsStroke volumes were measured with the aid of transesophageal echocardiographic imaging. End-tidal carbon dioxide was quantitated with conventional capnography. Baseline values of thermodilution cardiac output were highly correlated with echocardiographic measurements (r = .92). The stroke volume index produced by precordial compression averaged 0.45 mL/kg or approximately 37% of the average prearrest value of 1.22 mL/kg. The end-tidal carbon dioxide was highly predictive of stroke volume index (r = .88,p< .001) with a mean bias of 0.003 mL/kg.ConclusionsWe confirmed that precordial compression produces approximately one third of prearrest stroke volumes during cardiopulmonary resuscitation and demonstrated that end-tidal carbon dioxide was quantitatively predictive of stroke volume index estimated by transesophageal echocardiographic imaging.