摘要Objective To evaluate the frequency, the change of sleep structure ,pulmonary function and respiratory muscle functions of overlap syndrome: a serious respiratory disease of sleep apnea syndrome (SAS) with chronic obstructive pulmonary diseases (COPD), for the further study of clinical and experimental characteristics.Methods 44 consecutive, unselected SAS patients (39 males and 5 females) were analyzed. All received continuous and overnight polysomonography monitoring with HMS-5500 polysomnography system (Respironics Inc USA) in our sleep laboratory. A thorough and detailed collection of case history, physical examination, blood gas analysis and pulmonary functions, as well as respiratory muscle functions and right ventricular functions were taken before the polysomnographic examination.Results A chronic obstructive spirographic pattern, defined by a FEV1/VC ratio (60%,was observed in 16 of 44 SAS patients (36.3%, the overlap group). The overlap patients were older (62.6±12.5 vs 54.7±11.4 years) than the simple SAS patients. The number of heavy smokers in overlap group was more than that in simple SAS group (600±210 vs 550±127 cigarette-year). There were signi-ficant difference in FEV1.0% (58.70±4.76 vs 86.42±7.50%, P<0.01), maximal expiration pressure (MEP,198.54±21.76 vs 129.3±31.9 cm H2O, P<0.01), maximal inspiration pressure (MIP, 72.75±11.4 vs 111.3±33.6 cm H2O, P<0.01) and minimal nocturnal oxyhemoglobin saturation (63.7±14.7 vs 74.8±11.4%, P<0.01) between two groups. And the total recording time (513±45.8 vs 521±48.6 min, P>0.05), however, showed no significant difference between two groups, while the percentage of total sleep time/total recorded time (73.4±9.6 vs 87.6±8.8%, P<0.01), rapid eye movement sleep time/total sleep time (6.0±4.3 vs 8.9±5.8%, P<0.01) in the overlap group were significantly decreased, and apnea plus hypopnea index (AHI) were significantly higher (54.6±20.3 vs 39.9±16.8, P<0.05) in the overlap group. Also, the incidence rate of right heart failure measured by cardiac ultrasonography was higher in the overlap group than in the simple SAS group. No differences were found in body mass index (BMI) and daytime arterial blood gas analysis between overlap group and simple SAS group.Conlusion Sleep apnea plus hypopnea index, as well as nocturnal hypoxemia, were more obviours in overlap syndrome than in the simple SAS patients. Also pulmonary function and respiratory muscle function were more significantly impaired, indicating a higher risk of developing pulmonary hypertension, cor pulmonale and respiratory failure in overlap syndrome.