NEW ASPECTS ON ATELECTASIS DURING ANAESTHESIA

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Abstract
Sixteen subjects were studied with regard to lung tissue changes during general anaesthesia. The transverse area and the structure of the lung tissue were studied by computerized tomography. No abnormalities were noted in the lung tissue before anaesthesia, but within five minutes after induction, all subjects had developed crest-shaped dependent changes of an increased density in both lungs. They correspond to 4 - 5 per cent of the total transverse area. The size of the densities could not be correlated to the age of the subjects, or time of the anaesthesia, and they were not affected by the inspiratory oxygen fraction. They could be rotated by turning the patient, and the application of a positive end-expiratory pressure eliminated or reduced the densities. It is suggested that the densities are atelectases, which develop by compression of lung tissue, and not by gas resorption.