END-TIDAL CARBON-DIOXIDE DURING CARDIOPULMONARY-RESUSCITATION IN HUMANS PRESENTING MOSTLY WITH ASYSTOLE - A PREDICTOR OF OUTCOME

Objective: To determine whether continuous semiquantitative assessment of end-tidal CO2 could provide a highly sensitive predictor of return of spontaneous circulation during cardiopulmonary resuscitation (CPR) . Design: Prospective, clinical study, Setting: Prehospital CPR, Patie nts: One hundred twenty patients, during nontraumatic cardiac arrest. Interventions: End-tidal CO2 values were measured continuously after t racheal intubation, and were categorized as the initial value, and as minimal and maximal values during the first 20 mins. Measurements and Main Results: Presenting rhythm was asystole in 22 of the first 24 pat ients, Return of spontaneous circulation occurred in eight patients, I nitial, minimal, and maximal end tidal CO2 values were significantly ( p < .01) higher in these patients than in the patients without return of spontaneous circulation. Cutoff values providing a 100% sensitivity and the highest specificity in predicting return of spontaneous circu lation were found to be 10 torr for initial and maximal end tidal CO2 values, and 2 torr for the minimal end-tidal CO2 value, The number of patients required to reject (with a risk error of < .05) the hypothesi s of an actual sensitivity of less than or equal to 90% for an observe d sensitivity of 100% was found to be 95, In the second part of the st udy, this hypothesis was prospectively tested for initial and maximal end-tidal CO2 values in the subsequent 96 patients. Presenting cardiac rhythm was asystole in 87 patients. Return of spontaneous circulation was obtained in 30 patients. The cutoff value of 10 torr for maximal end tidal CO2 during the first 20 mins after tracheal intubation provi ded an observed sensitivity of 100% in predicting return of spontaneou s circulation with a specificity of 67%. This result allows rejection of the hypothesis of an actual sensitivity of less than or equal to 90 % (p = .042). By contrast, the observed sensitivity of initial end-tid al CO2 was only 87%. Conclusions: End-tidal CO2 represents a valuable tool for monitoring patients presenting with asystole during prehospit al CPR, Fluctuations in end tidal CO2 during CPR and the utility of en d-tidal CO2 in detecting return of spontaneous circulation justify its continuous measurement. In addition, a high sensitivity (>90%) in pre dicting return of spontaneous circulation is prospectively demonstrate d using the maximal end-tidal CO2 during the first 20 mins after trach eal intubation, with a cutoff value of 10 torr, Such a prognostic indi cator could be used for a more rational approach to prolonged CPR.