Characteristics of Obstructive Sleep Apnea Syndrome Related Hypertension and the Effect of Continuous Positive Airway Pressure Treatment on Blood Pressure

Study Overview
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Brief Summary
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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.

Detailed Description
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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.

Official Title
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Huai'an First People's Hospital

Conditions
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Hypertension Secondary

Intervention / Treatment
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* Other: continuous positive airway pressure


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: BP≤180/110mmHg,but≥140/90mmHg without taking oral antihypertensive drugs. Exclusion criteria. (1) patients who had been hospitalized for cardiac or respiratory exacerbation<6wk prior to recruiting; (2) with autonomic nervous system diseases or endocrine disorders which might influence BP; (3) unwilling to participate in the study.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 70 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Group l<br>SBP index was less than 30% of AHI | Other: continuous positive airway pressure<br>* 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.<br>|
| Group 2<br>SBP index was less than 60% but more than 30% | Other: continuous positive airway pressure<br>* 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.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| awake systolic blood pressure(SBP)changes | as the mean systolic blood pressure measurements during a supine resting period of 1 0minute at awake state | 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 | 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 | 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 | change from Baseline Systolic Blood Pressure at 2 weeks | 
| AHI changes | the combined number of apnea and hypopnea episodes per hour of sleep | change from Baseline Systolic Blood Pressure at 2 weeks | 
| TST90 changes | percentage of sleep time with oxygen saturation < 90% | change from Baseline Systolic Blood Pressure at 2 weeks | 
| oxygen desaturation index（ODI） changes | oxygen desaturation index | 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 | 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. | 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 | one night | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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blood pressure fluctuation, hypertension, continuous positive airway pressure, intermittent hypixa, oxygen desaturation