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The incidence of postoperative atelectasis in the dependent lung following thoracotomy: the value of added nitrogen.

SUMMARY Radiological evidence of postoperative atelectasis in the lower zone of the dependent contralateral right lung occurred in 50.8 per cent of patients who had undergone a left thoracotomy for repair of hiatus hernia between the years 1960–66. This condition was clinically asymptomatic and was not related to the age and sex of the patient, the presence of pre-operative chronic bronchitis or the presence of air under the right diaphragm. The substitution of a nitrogen-containing mixture for nitrous oxide in the inspired gases throughout the operation was associated with a highly significant reduction in the incidence of postoperative atelectasis in the dependent lung from 50.8 to 24.0 per cent, while postoperative hyperinflation with 100 per cent oxygen following the use of nitrous oxide during anaesthesia was without significant effect.