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

Overview

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.

Methods: Between March 2016 and December 2016,the investigators initially recruited 450 individuals reporting severe habitual snoring. Primal evaluations including office blood pressure, Epworth Sleepiness Scale Score(ESS), antihypertensive medicine demographic and anthropometric data. Then overnight polysomnography were performed. Of them,100 were severe OSA (AHI\>30 episode/h) with hypertension, who were agreed to stop taking antihypertensive medicine. The investigators calculated the time to stop based on the half-life of patients taking oral drugs and last time administration time. The subject who withdrawal time was less than three days was enrolled in this study. These patients were hospitalized and close monitoring of blood pressure, for blood pressure three times greater than 180/110mmHg or appearing dizziness, headache and other clinical syndrome, the investigators will give a timely clinical intervention and get rid of this study. The control group consisted of 100 subjects just with severe OSA whose blood pressure is normal. The investigators recorded nocturnal blood pressure, oximetry, beat-to-beat BPV, AHI, BP event was calculated. Screening of 40 newly diagnosed patients with hypertension and subjects with poor blood pressure control, the investigators would give one-night continuous positive airway pressure(CPAP) to compare the AHI, the mean nocturnal systolic blood pressure and diastolic blood pressure, the number of blood events before and after short-term CPAP therapy, to compare the AHI, the mean nocturnal systolic blood pressure and diastolic blood pressure, the number of blood events before and after short-term CPAP therapy.