High positive end-expiratory pressure (PEEP) is commonly used to improve pulmonary ventilation in infants with injured lungs. However, its intraoperative application in infants with healthy lungs remains controversial. This study aimed to evaluate the effect of high PEEP on perioperative pulmonary outcomes (PPCs) in this population.

Neonates and small infants aged 0–6 months undergoing surgery were randomly assigned to receive mechanical ventilation with a conventional PEEP of 5 cmH ₂ O or a high PEEP of 8 cmH ₂ O. Lung ultrasound (LUS) score was measured at four time points: T1, after intubation; T2, at the end of surgery; T3, 30 min after extubation; and T4, 24 h postoperatively. The primary outcome was the LUS score at four time points. The secondary outcome was the incidence of PPCs within the first 7 postoperative days.

A total of 1056 ultrasonographic images were obtained from 44 subjects. During surgery, the driving pressure at PEEP 5 cmH ₂ O was significantly higher than PEEP 8 cmH ₂ O (12.4 [1.7]  vs.  10.8 [1.9] cmH ₂ O;  p  = 0.010). At the end of surgery, the total LUS score was significantly higher in the PEEP 5 cm H ₂ O group compared to the PEEP 8 cmH ₂ O group (14.5 [5.1] vs. 11.4 [4.4]; p  = 0.039). However, no significant difference between groups was observed at T3 or T4. The incidence of PPCs during the first 7 postoperative days remained low in both groups.

Although high PEEP is more effective than conventional PEEP in reducing intraoperative atelectasis, it does not appear to provide any postoperative benefits. The advantages of intraoperative high PEEP may not extend beyond the duration of surgery in neonates and infants with healthy lungs.

Chinese Clinical Trial Register (ChiCTR2300069230), date of registration: March 10, 2023.