Differential Effects of Intraoperative Positive End-expiratory Pressure (PEEP) on Respiratory Outcome in Major Abdominal Surgery Versus Craniotomy

Objectives: In this study, we examined whether (1) positive end-expiratory pressure (PEEP) has a protective effect on the risk of major postoperative respiratory complications in a cohort of patients undergoing major abdominal surgeries and craniotomies, and (2) the effect of PEEP is differed by surgery type. Background: Protective mechanical ventilation with lower tidal volumes and PEEP reduces compounded postoperative complications after abdominal surgery. However, data regarding the use of intraoperative PEEP is conflicting. Methods: In this observational study, we included 5915 major abdominal surgery patients and 5063 craniotomy patients. Analysis was performed using multivariable logistic regression. The primary outcome was a composite of major postoperative respiratory complications (respiratory failure, reintubation, pulmonary edema, and pneumonia) within 3 days of surgery. Results: Within the entire study population (major abdominal surgeries and craniotomies), we found an association between application of PEEP ≥5cmH 2 O and a decreased risk of postoperative respiratory complications compared with PEEP <5cmH 2 O. Application of PEEP >5cmH 2 O was associated with a significant lower odds of respiratory complications in patients undergoing major abdominal surgery (odds ratio 0.53, 95% confidence interval 0.39 - 0.72), effects that translated to deceased hospital length of stay [median hospital length of stay: 6 days (4-9 days), incidence rate ratios for each additional day: 0.91 (0.84 - 0.98)], whereas PEEP >5cmH 2 O was not significantly associated with reduced odds of respiratory complications or hospital length of stay in patients undergoing craniotomy. Conclusions: The protective effects of PEEP are procedure specific with meaningful effects observed in patients undergoing major abdominal surgery. Our data suggest that default mechanical ventilator settings should include PEEP of 5-10cmH 2 O during major abdominal surgery.