Background: The impact of intraoperative ventilation on postoperative pulmonary complications is not defined. The authors aimed at determining the effectiveness of protective mechanical ventilation during open abdominal surgery on a modified Clinical Pulmonary Infection Score as primary outcome and postoperative pulmonary function. Methods: Prospective randomized, open-label, clinical trial performed in 56 patients scheduled to undergo elective open abdominal surgery lasting more than 2 h. Patients were assigned by envelopes to mechanical ventilation with tidal volume of 9 ml/kg ideal body weight and zero-positive endexpiratory pressure (standard ventilation strategy) or tidal volumes of 7 ml/kg ideal body weight, 10 cm H 2 O positive end-expiratory pressure, and recruitment maneuvers (protective ventilation strategy). Modified Clinical Pulmonary Infection Score, gas exchange, and pulmonary functional tests were measured preoperatively, as well as at days 1, 3, and 5 after surgery. Results: Patients ventilated protectively showed better pulmonary functional tests up to day 5, fewer alterations on chest x-ray up to day 3 and higher arterial oxygenation in air at days 1, 3, and 5 (mmHg; mean ± SD): 77.1 ± 13.0 versus 64.9 ± 11.3 (P = 0.0006), 80.5 ± 10.1 versus 69.7 ± 9.3 (P = 0.0002), and 82.1 ± 10.7 versus 78.5 ± 21.7 (P = 0.44) respectively. The modified Clinical Pulmonary Infection Score was lower in the protective ventilation strategy at days 1 and 3. The percentage of patients in hospital at day 28 after surgery was not different between groups (7 vs. 15% respectively, P = 0.42). Conclusion: A protective ventilation strategy during abdominal surgery lasting more than 2 h improved respiratory function and reduced the modified Clinical Pulmonary Infection Score without affecting length of hospital stay. What We Already Know about This Topic • The use of large tidal volumes during mechanical ventilation of the lungs can injure the lungs of critically ill patients What This Article Tells Us That Is New • A prospective, randomized, open-label trial of protective ventilation in 56 patients undergoing more than 2 h of open abdominal surgery showed that lower tidal volumes, positive end-expiratory pressure, and recruitment maneuvers led to significantly improved pulmonary function test results up to 5 days after surgery, fewer chest x-ray findings and improved Clinical Pulmonary Infection Scores ◆ This article is accompanied by an Editorial View. Please see: Vidal Melo MF, Eikermann M: Protect the lungs during abdominal surgery: It may change the postoperative outcome.