[Pulmonary hypertension]

Repetitive pulmonary artery pressure(PAP) elevation during apnea is commonly reported in patients with obstructive sleep apnea syndrome(OSAS). Hypoxic pulmonary vasoconstriction(HPV) plays an important role in this PAP elevation. In addition to the HPV, augmentation of intrathoracic negative pressure which occurs concomitantly with apnea and activation of sympathetic nervous system during REM sleep, influences pulmonary blood flow, resulting in the PAP elevation. Many previous study have been declared that the daytime pulmonary hypertension(PH), which is observed in significant populations of OSAS, is related to chronic airflow limitation and/or daytime hypoxemia. Furthermore, it had been suggested that the daytime PH in OSAS can be elicited, at least in parts, by vascular remodeling together with both nocturnal and daytime hypoxemia. Such pulmonary vascular remodeling may induce greater vascular sensitivity to sympathetic stimulation and modify HPV in OSAS with daytime PH.