Attenuation of hypoxic ventilatory response after recovery from chronic hypoxaemia in a case of pulmonary A-V fistula.

We studied respiratory chemosensitivity in a patient with pulmonary arterio-venous (AV) fistulae before and after surgical removal of the lesions. The patient had had moderate hypoxaemia with hyperventilation before the operation. When first studied, 21 days following surgery, both hypoxic and hypercapnic ventilatory responses were found to be lower than they were preoperatively. During the next 1-2 months, hypoxic ventilatory response continued to fall significantly to a steady value, whereas hypercapnic response showed no further fall. There has been no previous report of such a phenomenon in humans after recovery from chronic hypoxaemia.