Continuous Monitoring Nocturnal Beat-to-beat Blood Pressure Fluctuation in OSA With or Without Hypertension

Emerging evidence suggests that there is a causal link between obstructive sleep apnea(OSA) and hypertension. Patient with this syndrome exhibit several characteristics: high prevalence, frequent non-dipper status, diastolic and nocturnal predominance, which are related to clinical and subclinical organ damage in heart and brain. However, the influence of OSA on nocturnal hypertension development has not yet been clarified. Blood pressure variability (BPV) plays a role in vascular damage, independent of blood pressure. Apnea overloads the autonomic cardiovascular control system and may influence BPV,which is classified by different time interval, including beat-to-beat, hour-to-hour day-to-night changes or long-term, for example days, weeks, months, seasons, and even years. All BPV abnormalities are associated with an increased incidence of cardiovascular events and mortality. The investigators pre-experiment estimate BPV by ambulatory blood pressure monitoring (ABPM), which unable to capture the BP fluctuation accurately during the apnea event. The small studies exam beat-to-beat BP and OSA，and the investigators can't couple the events with blood fluctuation, also incapable calculate the correlation of them. This study is aimed to use pulse transmit time(PTT) based blood pressure measurement which can be useful for continuous monitoring of blood pressure to monitor nocturnal beat-to-beat blood pressure fluctuation in OSA with or without hypertension, investigating the degree of relevance between hypoxia, AHI, nocturnal hypertension development and BPV. Besides that the investigators also evaluate the effect of continuous positive airway pressure(CPAP) on blood pressure and nocturnal beat-to-beat BPV.