Individualized positive end-expiratory pressure (PEEP) guided by dynamic compliance improves oxygenation and reduces postoperative atelectasis in nonobese patients. We hypothesized that dynamic compliance–guided PEEP could also reduce postoperative atelectasis in patients undergoing bariatric surgery.


Patients scheduled to undergo laparoscopic bariatric surgery were eligible. Dynamic compliance–guided PEEP titration was conducted in all patients using a downward approach. A recruitment maneuver (PEEP from 10 to 25 cm H2O at 5–cm H2O step every 30 s, with 15–cm H2O driving pressure) was conducted both before and after the titration. Patients were then randomized (1:1) to undergo surgery under dynamic compliance–guided PEEP (PEEP with highest dynamic compliance plus 2 cm H2O) or PEEP of 8 cm H2O. The primary outcome was postoperative atelectasis, as assessed with computed tomography at 60 to 90 min after extubation, and expressed as percentage to total lung tissue volume. Secondary outcomes included Pao2/inspiratory oxygen fraction (Fio2) and postoperative pulmonary complications.


Forty patients (mean ± SD; 28 ± 7 yr of age; 25 females; average body mass index, 41.0 ± 4.7 kg/m2) were enrolled. Median PEEP with highest dynamic compliance during titration was 15 cm H2O (interquartile range, 13 to 17; range, 8 to 19) in the entire sample of 40 patients. The primary outcome of postoperative atelectasis (available in 19 patients in each group) was 13.1 ± 5.3% and 9.5 ± 4.3% in the PEEP of 8 cm H2O and dynamic compliance–guided PEEP groups, respectively (intergroup difference, 3.7%; 95% CI, 0.5 to 6.8%; P = 0.025). Pao2/Fio2 at 1 h after pneumoperitoneum was higher in the dynamic compliance–guided PEEP group (397 vs. 337 mmHg; group difference, 60; 95% CI, 9 to 111; P = 0.017) but did not differ between the two groups 30 min after extubation (359 vs. 375 mmHg; group difference, –17; 95% CI, –53 to 21; P = 0.183). The incidence of postoperative pulmonary complications was 4 of 20 in both groups.


Postoperative atelectasis was lower in patients undergoing laparoscopic bariatric surgery under dynamic compliance–guided PEEP versus PEEP of 8 cm H2O. Postoperative Pao2/Fio2 did not differ between the two groups.

Editor’s Perspective
What We Already Know about This Topic
  • Atelectasis is common after bariatric surgery and may predispose the patient to postoperative pulmonary complications.
  • Optimal methods for reducing atelectasis using varying levels of positive end-expiratory pressure (PEEP) or recruitment maneuvers are controversial.
What This Article Tells Us That Is New
  • The authors randomized patients undergoing bariatric surgery to undergo surgery with an optimal dynamic compliance–determined level of PEEP or a fixed PEEP level of 8 cm H2O (following a standardized recruitment maneuver). Computed tomography was performed in the early postoperative period to quantitate the degree of atelectasis (primary outcome). Secondary outcomes included Pao2/inspiratory oxygen fraction ratio and postoperative pulmonary complications.
  • The median PEEP level determined by optimal dynamic compliance was nearly double that of the control group (15 cm H2O).
  • The primary outcome was significantly reduced, although no significant differences were noted in postoperative secondary outcomes.