Question: What level of noninvasive positive airway pressure is able to expand the lungs of people with pleural drainage? Design: Cross-sectional, experimental and randomized study. Participants: Four consecutive people with pleural effusion drained within 24 hours, with controlled pain and without contraindications to use of noninvasive positive pressure. Intervention: Each person will be randomly subjected to three levels of noninvasive positive airway pressure: 0 (zero), 4 and 15 cmH2O for evaluation via chest computed tomography. Outcome measures: Lung area.

Inclusion Criteria:

• age over 18 years
• presence of pleural drainage after traumatic hemothorax
• thoracic drainage within 24 hours
• controlled pain (below 3 points in the visual numeric scale, varying from zero to ten)

Exclusion Criteria:

• contraindication for use of noninvasive positive pressure in the airways, such as reduced level of consciousness (drowsiness, agitation or confusion), use of vasoactive drugs, complex arrhythmias, upper airway obstruction or trauma in the face, esophagus or upper airway, ineffective cough, inability to swallow, distended abdomen, nausea, vomiting, upper gastrointestinal bleeding
• previous application of any sort of lung expansion technique after thoracic drainage.