Objective To compare the effect of continuous positive airway pressure (CPAP)and bilevel positive airway pressure(BiPAP)on the cardiac structure and function of patients with obstructive sleep apnea and hypopnea syndrome(OSAHS).Methods 100 patients with OSAHS were selected as the research subjects.The patients were randomly divided into two groups by digital table method,CPAP group had 50 cases,adopted the CPAP ventilation mode,BiPAP group had 50 cases,adopted the BiPAP ventilation mode.The heart rate,blood pressure, blood brain natriuretic peptide(BNP),nitric oxide(NO),endothelin -1 protease,matrix metalloprotein 9(MMP -9), C -reactive protein (CRP) and polysomnography (PSG) related indicators,cardiac structure and function and endothelial function changes before and after treatment were observed in the two groups,compared the clinical effect of the two modes.Results Before treatment,in both groups,there were no statistical differences in blood pressure,heart rate,BNP,NO,endothelin -1,MMP -9,CRP,PSG related indicators,cardiac structure and function,endothelial function.After six months of noninvasive ventilator treatment,results of the heart rate,systolic pressure,diastolic blood pressure,blood oxygen saturation,oxygen partial pressure,the BNP,endothelin -1,NO,MMP -9,CRP,body mass index,the Epworth sleepiness scale(ESS),Apnea hypoventilation index(AHI),oxygen and lowest at night,aortic di-ameter(AO),left ventricular inner diameter (LA),right ventricular(RV)inside diameter,left ventricular ejection fraction(LVEF),pulmonary artery systolic pressure(PASP)of the CPAP group were (79.83 ±11.47)times/min, (114.06 ±11.45)mmHg,(72.44 ±7.38)mmHg,(97.6 ±1.45)%,(93.17 ±1.86)mmHg,(110.78 ±38.32)ng/L, (17.58 ±2.07)ng/L,(8.55 ±0.55)μmol/L,(372.73 ±189.00)μg/L,(3.34 ±2.29)mg/L,(23.87 ±1.59), (0.98 ±0.70),(0.65 ±0.30),(94.04 ±1.62)%,(31.52 ±2.17 )mm,(31.19 ±1.09 )mm,(20.86 ± 1.69)mm,(61.13 ±5.02)%,(20.74 ±5.49)mmHg.which of the BiPAP group were (80.96 ±8.56)times/min, (114.58 ±9.34)mmHg,(71.67 ±8.57)mmHg,(96.96 ±1.43)%,(94.52 ±1.66)mmHg,(87.63 ±28.33)ng/L, (17.76 ±2.20)ng/L,(8.54 ±0.52)μmol/L,(359.63 ±268.95)μg/L,(4.96 ±2.00)mg/L,(24.15 ±1.65), (0.85 ±0.75 ),(0.58 ±0.19 ),(94.50 ±1.18)%,(31.73 ±1.57 )mm,(31.97 ±1.12)mm,(21.58 ± 2.43)mm,(62.24 ±5.79)%,(21.45 ±3.76)mmHg.In the oxygen partial pressure,the BNP,MMP -9,CRP,ESS score,AHI,LA,LVEF and other indicators,BiPAP mode were better than CPAP mode(t =2.13,4.32,2.13,4.32, 1.39,4.93,2.58,4.36,all P <0.05 ).Conclusion BiPAP mode and CPAP mode can improve cardiovascular function in patients with OSAHS,improve the symptoms of low ventilation,reduce obesity,but in terms of reducing cardiac load,improve blood vessel function,BiPAP mode is better than CPAP.