Continuous positive airway pressure by mask in patients after coronary surgery

Thirty patients who underwent coronary artery bypass grafting were randomized to receive 30% oxygen by mask either with an ambient airway pressure or with 7.4 mmHg (1 kPa) continuous positive airway pressure (CPAP) for 8 h after extubation. Arterial blood oxygen tension (PaO2) decreased remarkably in the control group after extubation (from 19.2 +/- 5.3 kPa to 12.4 +/- 2.7 kPa) but less in the CPAP group (from 16.4 +/- 3.3 kPa to 14.0 +/- 2.1 kPa). On the second postoperative morning PaO2 was equally low in both groups (control: 8.4 +/- 1.5 kPa, CPAP: 8.9 +/- 1.9 kPa). Atelectatic areas were seen with similar frequency in both groups, 17% (whole material) on the first and 50% on the second postoperative morning. Atelectasis was more common in patients with internal thoracic artery grafting and/or pleural drainage. In conclusion, CPAP therapy was well tolerated, and minimized the decrease in PaO2 after extubation, but could not prevent the poor oxygenation or the late development of atelectatic areas on the second postoperative day.