Objective: To investigate the development of pulmonary hypertension in obstructive sleep apnea syndrome (OSAS) patients and to analyze the correlated factors.
Methods: Pulmonary arterial pressure was monitored by right cardiac catheterization in 15 OSAS patients, and simultaneously polysomnography was performed. Blood gas analysis and lung function were also measured.
Results: Pulmonary arterial pressure at awake state was correlated positively to mean maximal pulmonary pressure during sleep, body mass index (BMI) and hemoglobin (Hb), but negatively to PaO2, the percent predicted forced vital capacity (FVC% pred). Compared with OSAS patients without pulmonary hypertension, the BMI, PaCO2, and Hb of OSAS patients with pulmonary hypertension increased significantly, while FVC% pred and PaO2 decreased. Stepwise linear regression indicated that pulmonary arterial pressure at awake state was closely correlated with mean maximal pressure during sleep (beta = 0.35, standard error 0.10, R(2) = 0.89, P = 0.006) and PaCO2 (beta = 0.72, standard error 0.27, R(2) = 0.94, P = 0.022), and mean maximal pulmonary arterial pressure during sleep was closely correlated to PaCO2, BMI, PaO2 and the ratio of arterial pressure and oxygen concentration during rapid eye movement sleep (RDeltaPAP/DeltaSpO2). The regression equation was y' = -152.70 + 1.92 PaCO2 + 1.37 BMI + 0.67 PaO2 + 16.29 RDeltaPAP/DeltaSpO2.
Conclusion: Pulmonary arterial pressure increasing in OSAS patients is induced mainly by hypercapnia and hypoxia at day time, and related to forced ventilation capacity, BMI and the ratio of pulmonary arterial pressure and oxygen concentration variation during rapid eye movement sleep. There was no obvious relation between pulmonary arterial pressure and apnea index.