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 CO, (CO, VR) were studied before and 6 months after uvulopalatopharyngoplasty. Nine of the SAS patients had airway obstruction (AO-SAS), defined as FEV1.o I 72 % of the predicted value. They had a significantly higher PaCO,, lower PaO, and a lower CO, VR than the remaining SAS patients. Preoperatively 4 SAS patients were hypercapnic (PaCO, >5.8 Wa) and compared with the normocapnic ones they were more obese; in 3 of them FEV,.o was I72%. The hypercapnic SAS patients had a significantly lower CO, VR. The CO, VR was significantly correlated to A0 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 CO, 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 CO, VR, and became normocapnic. Other patients showed no consistent changes in CO, VR postoperatively.