Thirteen patients with healthy hearts and lungs, and with a mean age of 68 years, who were scheduled for lower abdominal surgery during
isoflurane anaesthesia with muscular
paralysis, were investigated with arterial blood
gases, spirometry, pulmonary x-ray and computed tomography (CT) of the chest before and during anaesthesia, as well as during the first 4 postoperative days. Before anaesthesia, lung function and gas exchange were normal in all patients. Pulmonary x-ray and CT scans of the lungs were also normal. During anaesthesia, 6 of 13 patients developed
atelectasis (mean 1.0% of intrathoracic transverse area in all patients). Two hours postoperatively, 11 of 13 patients had
atelectasis and the mean atelectatic area was 1.8%. Pao2 was significantly reduced by 2.1 kPa to 9.8 kPa. On the first postoperative day, the mean
atelectasis was unaltered (1.8%). None of the
atelectasis found on CT scanning could be detected on standard pulmonary x-ray. Forced vital capacity (FVC) and forced expired volume in 1 s (FEV1) were significantly decreased to 2/3 of preoperative level. Pao2 was significantly reduced to less than 80% of the preoperative level (mean 9.4 kPa). There were significant correlations between the atelectatic area and the impairment in FVC, FEV1, and Pao2. Spirometry and blood
gases improved during the succeeding postoperative days, and
atelectasis decreased. No patient suffered from pulmonary complications, as judged from clinical criteria and pulmonary x-ray, in contrast to the findings of
atelectasis in 85% of the patients by computed tomography.