Influence of inspired nitrogen concentration during anaesthesia for coronary artery bypass grafting on postoperative atelectasis.

Pulmonary collapse is a common problem after coronary artery bypass graft surgery (CABG). If absorption atelectasis during anaesthesia is an important mechanism in the genesis of pulmonary collapse after CABG, the addition of nitrogen to the inspired gas during anaesthesia should reduce the amount of postoperative collapse. We studied 30 patients who were allocated randomly and prospectively to receive either 100% oxygen or an oxygen-air mixture as the inspired gas during anaesthesia for CABG. Lung volumes, PaO2, and an x-ray atelectasis score were measured before and after surgery to assess the degree of atelectasis. There were no significant differences between the two treatment groups in any of these measurements.