Changes in expired end-tidal carbon dioxide during cardiopulmonary resuscitation in dogs: A prognostic guide for resuscitation efforts

Expired end-tidal carbon dioxide (Pco₂) measurements made during cardiopulmonary resuscitation have correlated with cardiac output and coronary perfusion pressure when wide ranges of blood flow are included. The utility of such measurements for predicting resuscitation outcome during the low flow state associated with closed chest cardiopulmonary resuscitation remains uncertain. Expired end-tidal Pco₂ and coronary perfusion pressures were measured in 15 mongrel dogs undergoing 15 min of closed chest cardiopulmonary resuscitation after a 3 min period of untreated ventricular fibrillation. In six successfully resuscitated dogs, the mean expired end-tidal Pco₂ was significantly higher than that in nine nonresuscitated dogs only after 14 min of cardiopulmonary resuscitation (6.2 ± 1.2 versus 3.4 ± 0.8 mm Hg; p < 0.05). No differences in expired end-tidal Pco₂ values were found at 2, 7 or 12 min of cardiopulmonary resuscitation. A significant decline in end-tidal Pco₂ levels during the resuscitation effort was seen in the nonresuscitated group (from 6.3 ± 0.8 to 3.4 ± 0.8 mm Hg; p < 0.05); the successfully resuscitated group had constant Pco₂ levels throughout the 15 min of cardiac arrest (from 6.8 ± 1.1 to 6.2 ± 1.2 mm Hg). Changes in expired PC02 levels during cardiopulmonary resuscitation may be a useful noninvasive predictor of successful resuscitation and survival from cardiac arrest.