Lung ultrasound score to determine the effect of fraction inspired oxygen during alveolar recruitment on absorption atelectasis in laparoscopic surgery: a randomized controlled trial

Background: Although the intraoperative alveolar recruitment maneuver (RM) efficiently treats atelectasis, the effect of Fio(2) on atelectasis during RM is uncertain. We hypothesized that a high Fio(2) (1.0) during RM would lead to a higher degree of postoperative atelectasis without benefiting oxygenation when compared to low Fio(2) (0.4). Methods: In this randomized controlled trial, patients undergoing elective laparoscopic surgery in the Trendelenburg position were allocated to low- (Fio(2) 0.4,n = 44) and high-Fio(2) (Fio(2) 1.0,n = 46) groups. RM was performed 1-min post tracheal intubation and post changes in supine and Trendelenburg positions during surgery. We set the intraoperative Fio(2) at 0.4 for both groups and calculated the modified lung ultrasound score (LUSS) to assess lung aeration after anesthesia induction and at surgery completion. The primary outcome was modified LUSS at the end of the surgery. The secondary outcomes were the intra- and postoperative Pao(2) to Fio(2) ratio and postoperative pulmonary complications. Results: The modified LUSS before capnoperitoneum and RM (P = 0.747) were similar in both groups. However, the postoperative modified LUSS was significantly lower in the low Fio(2) group (median difference 5.0, 95% CI 3.0-7.0,P < 0.001). Postoperatively, substantial atelectasis was more common in the high-Fio(2) group (relative risk 1.77, 95% CI 1.27-2.47,P < 0.001). Intra- and postoperative Pao(2) to Fio(2) were similar with no postoperative pulmonary complications. Atelectasis occurred more frequently when RM was performed with high than with low Fio(2) ; oxygenation was not benefitted by a high-Fio(2.) Conclusions: In patients undergoing laparoscopic surgery in the Trendelenburg position, absorption atelectasis occurred more frequently with high rather than low Fio(2). No oxygenation benefit was observed in the high-Fio(2) group.