Effect of one-lung ventilation on end-tidal carbon dioxide during cardiopulmonary resuscitation in a pig model of cardiac arrest

Unrecognized endobronchial intubation frequently occurs after emergency intubation. However, no study has evaluated the effect of one-lung ventilation on end-tidal carbon dioxide (ETCO(2)) during cardiopulmonary resuscitation (CPR). We compared the hemodynamic parameters, blood gases, and ETCO(2) during one-lung ventilation with those during conventional two-lung ventilation in a pig model of CPR, to determine the effect of the former on ETCO(2). A randomized crossover study was conducted in 12 pigs intubated with double-lumen endobronchial tube to achieve lung separation. During CPR, the animals underwent three 5-min ventilation trials based on a randomized crossover design: left-lung, right-lung, or two-lung ventilation. Arterial blood gases were measured at the end of each ventilation trial. Ventilation was provided using the same tidal volume throughout the ventilation trials. Comparison using generalized linear mixed model revealed no significant group effects with respect to aortic pressure, coronary perfusion pressure, and carotid blood flow; however, significant group effect in terms of ETCO(2) was found (P < 0.001). In the post hoc analyses, ETCO(2) was lower during the right-lung ventilation than during the two-lung (P = 0.006) or left-lung ventilation (P < 0.001). However, no difference in ETCO(2) was detected between the left-lung and two-lung ventilations. The partial pressure of arterial carbon dioxide (PaCO(2)), partial pressure of arterial oxygen (PaO(2)), and oxygen saturation (SaO(2)) differed among the three types of ventilation (P = 0.003, P = 0.001, and P = 0.001, respectively). The post hoc analyses revealed a higher PaCO(2), lower PaO(2), and lower SaO(2) during right-lung ventilation than during two-lung or left-lung ventilation. However, the levels of these blood gases did not differ between the left-lung and two-lung ventilations. In a pig model of CPR, ETCO(2) was significantly lower during right-lung ventilation than during two-lung ventilation. However, interestingly, ETCO(2) during left-lung ventilation was comparable to that during two-lung ventilation.