Obstructive sleep apnea syndrome (OSAS) causes nocturnal chronic intermittent hypoxia (CIH) that contributes to the development of hypertension. CIH profiles, including the its length, speed and intensity were widely different in individuals. Until recently, the influence of OSAS-related IH profiles on hypertension development has not been fully explored. The present study aimed to investigate the effects of different CIH properties on blood pressure (BP) and short-term blood pressure variability (BPV) in severe OSAS patients. Continuous positive airway pressure (CPAP) prevents the airway collapse, avoids the occurrence of intermittent hypoxemia and arousal, is the preferred treatment for OSAS and has been widely used in clinical. In theory, CPAP maintains upper airway patency and preserves ventilation, thereby inhibits the chain reaction over activation of the sympathetic nervous system and blood pressure regulating mechanism, thus CPAP treatment have adequate scientific basis to cause a substantial reduction arterial blood pressure, but controlled studies showed either no effect or only a minor decrease in arterial blood pressure by 1.4 and 2.5 mmHg respectively.The current, which type of combination of hypertension OSA patients can obtain the best antihypertensive benefit from CPAP therapy is still under debate.
Nocturnal BP was continuously monitored via measurement of pulse transmit time (PTT). The value of apnea-related systolic BP elevation (△BP) was used to reflect short-term BPV. Beat-to-beat RR interval data were incorporated in polysomnography for heart rate variability analysis. LF/HF band ratio was compared between two groups which used to reflect sympatho-vagal balance. The length of the desaturation event was measured to the nearest 0.5 second (△t). The fall in SpO2 during apnea was calculated as the gap from start of the desaturation to the nadir of the desaturation. The rate of fall in SpO2 was counted as the change in the percentage of SpO2 per second (△SpO2 /△t) and expressed as oxygen desaturation rate (ODR), which reflected the speed and efficacy of oxygen desaturation during an apnea event. One hundred and two severe OSAS subjects were divided into two groups according to the their median ODR: faster ODR and slower ODR. In addtion,patient were categorized into three groups: Group l: systolic blood pressure index was less than 30% of AHI; Group 2: systolic blood pressure index was less than 60% but more than 30%; Group 3: systolic blood pressure index is more than 60% of AHI. The investigator would compare the effect of CPAP treatment on awake and sleep BP level at the first night and 2 weeks therapy among three groups. Moreover, whether or not the sympathetic-parasympathetic nerve balance and the renin-angiotensin-aldosterone system are different in three groups would also be evaluated. The main purpose of study is to confirm the OSA with hypertension and OSA secondary hypertension are two different concepts. Basis for the clinical treatment, the former, CPAP might have no effect or only a minor decrease in arterial blood pressure, while the latter CPAP treatment might achieve significant antihypertensive effect.
Study Type
OBSERVATIONAL
Enrollment
78
Continuous positive airway pressure (CPAP) prevents the airway collapse, avoids the occurrence of intermittent hypoxemia and arousal, is the preferred treatment for OSAS and has been widely used in clinical. The investigator would compare the effect of CPAP treatment on awake and sleep BP level at the first night and 2 weeks therapy among three groups. Moreover, whether or not the sympathetic-parasympathetic nerve balance and the renin-angiotensin-aldosterone system are different in three groups would also be evaluated.
Department Of Respiratory Medicine,Huai'an First People's Hospital,Nanjing Medical University
Huai'an, Jiangsu, China
awake systolic blood pressure(SBP)changes
as the mean systolic blood pressure measurements during a supine resting period of 1 0minute at awake state
Time frame: change from Baseline Systolic Blood Pressure at 2 weeks
sleep systolic blood pressure(SBP)changes
as the average of systolic blood pressure values during sleep
Time frame: change from Baseline Systolic Blood Pressure at 2 weeks
sympathetic-parasympathetic nerve balance changes
Studies using spectral analysis of R-R intervals have reported that the power spectrum contains both low-frequency(LF,0.04-0.15 Hz)and high-frequency peaks(HF,0.15-0.5Hz),HF power reflects parasympathetic activity,whereas LF power primarily reflects sympathetic activity with a parasympathetic component.The LF-to-HF ratio(LF/HF)is commonly regarded as an index of sympathovagal balance
Time frame: change from Baseline Systolic Blood Pressure at 2 weeks
renin-angiotensin-aldosterone systemchanges
as the levels of plasma angiotension ⅰ( Ang I) and angiotension ⅱ( Ang ⅱ) before and after CPAP treatment
Time frame: change from Baseline Systolic Blood Pressure at 2 weeks
AHI changes
the combined number of apnea and hypopnea episodes per hour of sleep
Time frame: change from Baseline Systolic Blood Pressure at 2 weeks
TST90 changes
percentage of sleep time with oxygen saturation \< 90%
Time frame: change from Baseline Systolic Blood Pressure at 2 weeks
oxygen desaturation index（ODI） changes
oxygen desaturation index
Time frame: change from Baseline Systolic Blood Pressure at 2 weeks
event-related systolic blood pressure elevation (△SBP) changes
as the gap between the peak value of postapneic SBP and lowest SBP during a obstructive respiratory event
Time frame: change from Baseline Systolic Blood Pressure at 2 weeks
systolic blood pressure(SBP)index
as the number of △SBP\>10mmHg per hour of sleep time.
Time frame: change from Baseline Systolic Blood Pressure at 2 weeks
Desaturation rate
The rate of fall in SpO2 was counted as the change in the percentage of SpO2 per second during apnea
Time frame: one night
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