title: Expired carbon dioxide: a noninvasive monitor of cardiopulmonary resuscitation.
abstract: End-tidal CO2 concentration (ETCO2) may serve as a simple noninvasive measurement of the blood flow generated by precordial compression during cardiopulmonary resuscitation (CPR). In a mechanically ventilated porcine preparation of ventricular fibrillation, onset of fibrillation was associated with a rapid decrease in ETCO2 from 4.0 +/- 0.2% to less than 0.7 +/- 0.2%. With precordial compression, it increased to 1.9 +/- 0.3%. Animals that were successfully defibrillated after 12 min of CPR demonstrated an immediate increase in ETCO2. The ETCO2 increased from 1.9 +/- 0.3% to 4.9 +/- 0.3% over an interval of between 30 and 60 sec. These changes in ETCO2 were closely related to proportionally similar decreases and increases in cardiac output (CO), and a close correlation between ETCO2 and CO was demonstrated (r = .92). A similar highly significant correlation between ETCO2 and CO was also demonstrated during open-chest cardiac massage (r = .95). ETCO2 therefore serves as a noninvasive measure of pulmonary blood flow and therefore CO. In 17 successfully resuscitated animals. ETCO2 during precordial compression averaged 1.7 +/- 0.2%, whereas it was only 0.5 +/- 0.1% in five animals in whom resuscitation procedures were unsuccessful (p less than .001). Accordingly, ETCO2 prognosticates outcome during CPR and immediately identifies restoration of spontaneous circulation.
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000032:analysis*; D002302:Cardiac Output; D008991:Monitoring, Physiologic / Q000379:methods*; D011659:Pulmonary Gas Exchange; D012151:Resuscitation; D013552:Swine; D013556:Swine, Miniature; D014693:Ventricular Fibrillation / Q000503:physiopathology*
chemical_list: D002245:Carbon Dioxide