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Supine hypoxemia and erythrocytosis due to airway closure at low lung volumes

1973; Elsevier BV; Volume: 55; Issue: 1 Linguagem: Inglês

10.1016/0002-9343(73)90152-6

1555-7162

Paul Hamosh, Angelo M.T. Da Silva,

Thermoregulation and physiological responses

Two patients with polycythemia and supine hypoxemia are described. Lung function was within normal limits in both with the exception of an increased alveolar-arterial oxygen gradient, and one of them showed frequency dependence of dynamic lung compliance. Expiratory reserve volumes (ERV) were very low, and the “closing volume” significantly overlapped with the tidal volume with the patients in the supine position. The resulting ventilatory impairment caused shunting of venous blood in the lung which, in turn, led to arterial hypoxemia. Hypoxemia caused by this mechanism has been described in obese subjects with minimal lung disease. These two patients are only moderately overweight and have only minimal lung disease, probably involving the “small airways.” However, the erythrocytosis is entirely due to supine hypoxemia, and therefore airway closure during supine breathing is the primary cause of this clinical entity.