Effect of recruitment manoeuvres under lung ultrasound-guidance and positive end-expiratory pressure on postoperative atelectasis and hypoxemia in major open upper abdominal surgery: A randomized controlled trial

Background: Postoperative pulmonary complications (PPCs) especially atelectasis and hypoxemia are common during abdominal surgery. Studies on the effect of either recruitment manoeuvres (RMs) or positive end-expiratory pressure (PEEP) on PPCs are controversial. The objective of this study is to evaluate the effect of perioperative lung ultrasound (LUS)-guided RMs combined with PEEP on the reduction of postoperative atelectasis and hypoxemia in major open upper abdominal surgery.Methods: In this randomized controlled trial, 122 adult patients undergoing major open upper abdominal surgery were allocated into three groups: control (C) group (n = 42); PEEP (P) group (n = 40); RMs combined with PEEP (RP) group (n = 40). All patients were scheduled for general anaesthesia using the lung-protective ventilation (LPV) strategy. The levels of PEEP in the three groups were 0 cmH2O, 5 cmH2O and 5 cmH2O. LUS examination was carried out at 3 predetermined time points in each group: 5 min after intubation (T1), at the end of surgery (T2) and 15 min after extubation (T3). Patients with atelectasis on the sonogram in the RP group received LUS-guided RMs at point T2. LUS scores were used to estimate the severity of aeration loss. The P/ F ratio (PaO2/FiO2) at 15min after extubation was used to assess the incidence of postoperative hypoxemia. Primary outcomes were the incidences of postoperative atelectasis and hypoxemia (PaO2/FiO2 < 300 mmHg). The secondary outcome was the distribution of LUS scores in each lung area.Results: From July 2021 to December 2021, 122 consecutive patients were enrolled. No typical atelectasis was observed 5 min after intubation. The incidence of atelectasis was 52.4%, 50.0% and 42.5% in the C group, P group and RP group at the end of surgery, respectively. The rate of atelectasis in the C group, P group and RP group (after RMs) was 52.4%, 50.0% and 17.5%, respectively, 15 min after extubation (P < 0.01). The frequency of postoperative hypoxemia was 27.5%, 15.0% and 5.0% in the C group, P group and RP group, respectively (P < 0.017). The increased LUS scores mainly occurred in the superoposterior and inferoposterior quadrants at the