BACKGROUND: Patients undergoing pulmonary lobectomy carry a high risk of respiratory complications after surgery. The postoperative prophylactic treatment with helmet CPAP may prevent postoperative acute respiratory failure and improve the P-aO2/F-IO2. METHODS: We randomly allocated 50 subjects to receive continuous oxygen therapy (air-entrainment mask, F-IO2 0.4) or 2 cycles of helmet CPAP for 120 min, alternating with analog oxygen therapy for 4 hours. Blood gas values were collected at admission to ICU, after 1, 3, 7, 9, 24 hours, and then in the thoracic ward after 48 hours and one week after surgery. We investigated the incidence of postoperative complications, mortality, and length of hospital stay. RESULTS: At the end of the second helmet CPAP treatment, the subjects had a significantly higher P-aO2/F-IO2, compared with the control group (366 +/- 106 mm Hg vs 259 +/- 60 mm Hg, P = .004), but the improvement in oxygenation did not continue beyond 24 hours. The postoperative preventive helmet CPAP treatment was associated with a significantly shorter hospital stay, in comparison to standard treatment (7 +/- 4 d and 8 +/- 13 d, respectively, P = .042). The number of minor or major postoperative complications was similar between the 2 groups. No difference in ICU readmission or mortality was observed. CONCLUSIONS: The prophylactic use of helmet CPAP improved the P-aO2/F-IO2, but the oxygenation benefit was not lasting. In our study, helmet CPAP was a secure and well tolerated method in subjects who underwent pulmonary lobectomy. It might be safely applied whenever necessary.