Airway Obstruction, Obesity And C02 Ventilatory Responsiveness In The Sleep Apnea Syndrome

Abstract

In 32 patients with sleep apnea syndrome (SAS), pulmonary function, blood gases and the ventilatory response to C02 (C02 VR) were studied before and 6 months after uvulopalatopharyngoplasty. Nine of the SAS patients had airway obstruction (AO-SAS), defined as FEVj 0 < 72 % of the predicted value. They had a significantly higher PaC02, lower Pa02 and a lower C02 VR than the remaining SAS patients. Preoperatively 4 SAS patients were hypercapnic (PaC02 >5.8 kPa) and compared with the normocapnic ones they were more obese; in 3 of them FEV1.0 was < 72%. The hypercapnic SAS patients had a significantly lower C02 VR. The C02 VR was significantly correlated to AO and the degree of oxygen desaturation during sleep, but not to the number of episodes of apnea and hypopnea nor their length. The VR to C02 did not predict the postoperative outcome. Postoperatively 2 hypercapnic obese AO-SAS patients showed a large decrease in episodes of apnea and hypopnea and an increase in C02 VR, and became normocapnic. Other patients showed no consistent changes in C02 VR postoperatively. © 1992, Informa UK Ltd. All rights reserved.