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 (N ₂ O) in oxygen (O ₂ ) for rapid lung collapse remains unclear. Accordingly, this prospective trial aimed to determine the 50% effective concentration (EC ₅₀ ) and 95% effective concentration (EC ₉₅ ) of N ₂ O in O ₂ 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% N ₂ O in O ₂ , and the subsequent N ₂ O fraction in O ₂ 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 EC ₅₀ and EC ₉₅ of N ₂ O in O ₂ for rapid lung collapse were analyzed using a probit test.
Results: According to the up-and-down method, the N ₂ O fraction in O ₂ at which all patients exhibited successful lung collapse was 50%. The EC ₅₀ and EC ₉₅ of N ₂ O in O ₂ 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 EC ₅₀ and EC ₉₅ of N ₂ O in O ₂ 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.