• Chao Liang, Yuechang Lv, Yu Shi, Jing Cang, and Changhong Miao.
• Department of Anesthesia, Zhongshan Hospital, Fudan University, Shanghai, China.
• BMC Anesthesiol. 2020 Jul 22; 20 (1): 180.

BackgroundThe 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.MethodsThis 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.ResultsAccording 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.ConclusionsIn patients undergoing VATS, the EC50 and EC95 of N2O in O2 for rapid lung collapse were 27.7 and 48.7%, respectively.Trial Registrationhttp://www.chictr.org/cn/ Identifier ChiCTR19 00021474 , registered on 22 February 2019.

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