Factors Influencing Cardiopulmonary Exercise Testing in Obstructive Sleep Apnea Syndrome Patients

The exercise capacity of obstructive sleep apnea syndrome (OSAS) patients has been demonstrated to be impaired, but the factors responsible are still unclear. In addition, ventilatory efficiency during exercise has never been studied in OSAS. Hypertension (HT), commonly found in OSAS patients, could be a contributing factor to exercise capacity. The aim of the study is：1) to determine possible factors that could influence the exercise in OSAS patients, and 2) to compare the exercise capacity and ventilatory efficiency of patients with and without HT. Twenty-two male OSAS patients were submitted to cardiopulmonary exercise testing. Multiple linear regression analyses were used to find possible factors that could influence the exercise capacity and ventilatory efficiency of OSAS patients. Patients were divided into two groups according to the presence of HT, and cardiopulmonary exercise testing (CPET) results were compared between them. No factors emerged as predictors of oxygen consumption at peak exercise (VO2peak). The slope of increase of ventilation relative to carbon dioxide production (VE/VCO2-slope) was associated with body mass index (BMI) negatively and with apnea-hypopnea index (AHI) positively (p = 0.019 and p = 0.047, respectively). There were no differences in either VO2peak or anaerobic threshold (AT) between OSAS with and without HT, but the VE/VCO2-slope was higher in the HT group (p = 0.008). Our results suggest that the severity of sleep apnea can influence the ventilatory efficiency of OSAS patients along with BMI and HT.