Objective:We explored the feasibility of use of continuous positive airway pressure (CPAP) with 15-and 4-cmH 2 O for a randomized controlled trial with patients with pleural drainage.Methods: Ten patients with traumatic pleural effusion drained within 24 hr, with controlled pain received randomly CPAP with 0-, 4-, and 15-cmH 2 O. Computed tomography was used to assess the lung aeration. Patients reported the level of tolerability. Air leak was also observed as a parameter of safety. The levels of pressure were compared using the Friedman test followed by the Tukey test as post hoc. Results:The lung area under CPAP with 15 cmH 2 O (median = 3,913 mm 2 ; IQR = 3,416-4,390 mm 2 ) was greater than 4 (median = 3,495 mm 2 ; IQR = 3,075-3,954 mm 2 ) and 0 cmH 2 O (median = 3,382 mm 2 ; IQR = 2,962-3,658 mm 2 ; p < 0.001). There was no difference between lung areas under CPAP with 4 and 0 cmH 2 O. All levels of pressure were well tolerated by patients. No air leak was observed during the assessments.Conclusion: CPAP with 15 cmH 2 O is able to expand lungs of patients with pleural drainage. CPAP with 4 cmH 2 O seems not have therapeutic effect. In addition, CPAP with 15 cmH 2 O is well tolerated and safe in this population. KEYWORDScontinuous positive airway pressure, computerized tomography, pleural effusion, thoracic surgery