[The role of ventilatory disturbances in the late postoperative hypoxaemia after upper abdominal surgery. A contribution to the risk of upper abdominal surgery in patients with respiratory damage (author's transl)].

The purpose of our investigations was to evaluate the influence of disturbed inspiratory gas distribution on postoperative hypoxemia in patients with abnormal lung function undergoing upper abdominal surgery. The lung function analyzer Hewlett-Packard 47402 A was used (Volume-time and flow-volume curves of forced expiration, single and multiple breath nitrogen washout tests with indices of ventilatory gas distribution). It was demonstrated that postoperative hypoxaemia in the undamaged lung is almost exclusively the result of augmented true right to left shunt. In patients with abnormal lung function the cause of postoperative hypoxaemia is, for the most part, an increase of disturbances of ventilatory gas distribution. These changes in the postoperative period can be explained by a reduction of FRC, that follows from changing of position (sitting-lying) and from pain. In patients with borderline lung function this reduction of FRC postoperatively may limit surgical treatment. The management of pain is of great importance in these patients. Continuous epidural anaesthesia certainly produces the best results in this respect.