Combination Of Nitrous Oxide And The Modified Inflation-Deflation Method For Identifying The Intersegmental Plane In Segmentectomy: A Randomized Controlled Trial

Background During thoracoscopic segmentectomy, accurately and rapidly identifying the intersegmental plane (ISP) is of great importance. This study aimed to investigate the effect and safety of a nitrous oxide (N2O)/oxygen (O-2) inspired mixture on the appearance time of the ISP (T-ISP) via the modified inflation-deflation method.Methods A total of 65 participants who underwent segmentectomy were randomized into three groups: 75% N2O (n = 24), 50% N2O (n = 23) or 0% N2O (n = 18). The 75% N2O group received a gas mixture of N2O/O-2 (Fio(2) = 0.25), the 50% N2O group received N2O/O-2 (Fio(2) = 0.5), and the 0% N2O group received 100% oxygen during lung expansion. The appearance time of satisfactory and ideal planes was recorded. Furthermore, arterial blood gas at breathing room air, one-lung ventilation (OLV) before lung expansion, 5 and 15 min after lung expansion were also recorded.Results T-ISP was significantly shorter in the 75% N2O group (320.2 +/- 65.9 s) compared with that of the 50% N2O group (552.4 +/- 88.9 s, p < 0.001) and the 0% N2O group (968.3 +/- 85.5 s, p < 0.001), while the 50% N2O group was shorter than that of the 0% N2O group (p < 0.001). Arterial oxygenation was significantly improved in the 0% N2O group only after lung expansion, before which there were no differences in mean PaO2 values among groups.Conclusions The use of N2O in the inspired gas mixture during lung expansion is an applicable strategy to rapidly identify the ISP via the modified inflation-deflation method without any adverse effect on OLV related arterial oxygenation during segmentectomy.