Normal chemoreceptor function in obesity before and after ileal bypass surgery to force weight reduction

Ventilatory responses to progressive isocapnic hypoxia and rebreathing of carbon dioxide in oxygen were determined in four obese women before and approximately 1 year after ileal bypass surgery to force weight reduction. None of the patients was hypoventilating and all had normal pulmonary function tests. The ventilatory responses to hypoxia were normal before surgery and were not effected by weight reduction. The ventilatory responses to hypercapnia did not change in slope but a shift of the carbon dioxide response line toward a lower arterial carbon dioxide tension occurred in two subjects after weight reduction. We conclude that obesity per se does not necessarily cause loss of hypoxic ventilatory drive.