Pulmonary atelectasis and other respiratory complications after cardiopulmonary bypass and investigation of aetiological factors.

Radiological evidence of pulmonary complications and possible aetiological factors were investigated in 50 consecutive patients after heart operations with cardiopulmonary bypass. Atelectasis was the most frequent pulmonary complication except for small pleural effusions, with an incidence of 64 per cent. Several types of atelectasis frequently co-existed, with a predominance of the less extensive plate and subsegmental forms. The incidence of atelectasis was the same on each side and the site of atelectasis was basal in three quarters of the patients. Preoperative clinical and catheter data were unrelated to the incidence of atelectasis. There was a significant positive correlation between a short cardiopulmonary bypass time and plate atelectasis, between a large fluid load after bypass and segmental atelectasis, between re-operation for bleeding and subsegmental atelectasis and between post-operative gastric dilation and atelectasis. The type of operation, the use of the intra-aortic balloon and the length of postoperative respiratory ventilation were unrelated to the incidence of atelectasis. The mechanism of development of atelectasis is discussed.