The fraction of nitrous oxide in oxygen for facilitating lung collapse during one-lung ventilation with double lumen tube.

BACKGROUND The ideal fraction of nitrous oxide (N2O) in oxygen (O2) for rapid lung collapse remains unclear. Accordingly, this prospective trial aimed to determine the 50% effective concentration (EC50) and 95% effective concentration (EC95) of N2O in O2 for rapid lung collapse. METHODS This study included 38 consecutive patients undergoing video-assisted thoracoscopic surgery (VATS). The lung collapse score (LCS) of each patient during one-lung ventilation was evaluated by the same surgeon. The first patient received 30% N2O in O2, and the subsequent N2O fraction in O2 was determined by the LCS of the previous patient using the Dixon up-and-down method. The testing interval was set at 10%, and the lowest concentration was 10% (10, 20, 30, 40%, or 50%). The EC50 and EC95 of N2O in O2 for rapid lung collapse were analyzed using a probit test. RESULTS According to the up-and-down method, the N2O fraction in O2 at which all patients exhibited successful lung collapse was 50%. The EC50 and EC95 of N2O in O2 for rapid lung collapse were 27.7% (95% confidence interval 19.9-35.7%) and 48.7% (95% confidence interval 39.0-96.3%), respectively. CONCLUSIONS In patients undergoing VATS, the EC50 and EC95 of N2O in O2 for rapid lung collapse were 27.7 and 48.7%, respectively. TRIAL REGISTRATION http://www.chictr.org/cn/ Identifier ChiCTR19 00021474 , registered on 22 February 2019.