Capnography for monitoring response to care after out-of-hospital cardiac arrest

Objective: To analyze the usefulness of capnography to monitor patients after out-of-hospital cardiorespiratory arrest, in terms of the ability of capnography to confirm tracheal intubation and the ability of capnometry to promptly detect return of spontaneous circulation and predict patient recovery. Methods: Preliminary description of the first 30 cases in a prospective study of out-of-hospital cardiorespiratory arrest in elderly non-trauma patients attended by the 7 ambulance units of the SUMMA 112 emergency service in Madrid, Spain, in 2008. Clinical, evolutive and capnographic data were recorded. Results: Seventy percent of the 30 patients were men. The mean (SD) age was 64.5 (16.3) years. A capnogram was observed after the first intubation attempt in 28 cases. In the remaining 2 cases, the absence of a capnogram indicated esophageal intubation; correct intubation was accomplished and confirmed on the second try (positive and negative predictive values, 100%). However, no differences were observed between end-tidal carbon dioxide partial pressure (PETCO(2)) in the absence or presence of a capnogram with the first and second attempts at intubation. Eight patients recovered. In 5 of them (62.5%), a significant increase in PETCO(2) was observed before the change in the electrocardiographic signal and before detection of a carotid pulse (P<.05). Finally, PETCO(2) values after cardiopulmonary resuscitation (CPR) were significantly higher in the patients who recovered (33.5 [12.7] mm Hg) than in those who died (15.3 [11.1] mm Hg) (P<.01). After 20 minutes of CPR, PETCO(2) was more than 20 mm Hg in all patients who recovered. Conclusions: Capnography monitoring in responding to out-of-hospital cardiorespiratory arrest is useful for confirming correct placement of the endotracheal tube, as indicated by the presence of a capnogram. Capnometry offers the first sign of return of spontaneous circulation in some cases and can be used to predict the success of prolonged CPR. [Emergencias 2010;22:345-348]