Effect of sigh in lateral position on postoperative atelectasis in adults assessed by lung ultrasound: a randomized, controlled trial

BACKGROUND: Postoperative atelectasis occurs in 90% of patients receiving general anesthesia. Recruitment maneuvers (RMs) are not always effective and frequently associated with barotrauma and hemodynamic instability. It is reported that many natural physiological behaviors interrupted under general anesthesia could prevent atelectasis and restore lung aeration. This study aimed to find out whether a combined physiological recruitment maneuver (CPRM), sigh in lateral position, could reduce postoperative atelectasis using lung ultrasound (LUS). METHODS: We conducted a prospective, randomized, controlled trial in adults with open abdominal surgery under general anesthesia lasting for 2 h or longer. Subjects were randomly allocated to either control group (C-group) or CPRM-group and received volume-controlled ventilation with the same ventilator settings. Patients in CPRM group was ventilated in sequential lateral position, with the addition of periodic sighs to recruit the lung. LUS scores, dynamic compliance (Cdyn), the partial pressure of arterial oxygen (PaO(2)) and fraction of inspired oxygen (FiO(2)) ratio (PaO(2)/FiO(2)), and other explanatory variables were acquired from each patient before and after recruitment. RESULTS: Seventy patients were included in the analysis. Before recruitment, there was no significant difference in LUS scores, Cdyn and PaO(2)/FiO(2) between CPRM-group and C-group. After recruitment, LUS scores in CPRM-group decreased significantly compared with C-group (6.00 [5.00, 7.00] vs. 8.00 [7.00, 9.00], p = 4.463e-11 < 0.05), while PaO(2)/FiO(2) and Cdyn in CPRM-group increased significantly compared with C-group respectively (377.92 (93.73) vs. 309.19 (92.98), p = 0.008 < 0.05, and 52.00 [47.00, 60.00] vs. 47.70 [41.00, 59.50], p = 6.325e-07 < 0.05). No hemodynamic instability, detectable barotrauma or position-related complications were encountered. CONCLUSIONS: Sigh in lateral position can effectively reduce postoperative atelectasis even without causing severe side effects. Further large-scale studies are necessary to evaluate it’s long-term effects on pulmonary complications and hospital length of stay. TRIAL REGISTRATION: ChiCTR1900024379. Registered 8 July 2019, SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12871-022-01748-9.