Sleep Characteristics And Blood Level Of ET-1 And NO In Patients With OSAHS And Their Links With BP

Background: Epidemiological and clinical studies in recent years confirmed that OSAHS is an independent risk factor for hypertension, but the underlying pathogenic mechanism remains unclear. Moreover, the pathophysiologic mechanism in OSAHS patients with hypertension has not been claritied. Studies indicate the pathophysiologic changes , which may be related to OSAHS-associated hypertension, included repetitive episodic hypoxia, frequently microarousal and sleep architecture disturb because of repeated sleep apnea episodes. But it is disputed that which pathophysiologic change mainly contribute to the correlation between OSAHS and hypertension. Meanwhile, study results about the pathogenetic mechanism disagree each other. It is reported that vascular endothelial dysfunction, which may provoke the disequilibrium between endothelium derived relaxing factor and endothelium derived relaxing factor, might be important reason contributed to hypertension. And OSAHS is characterized of recurrent apnea episodes which may result in vascular endothelial dysfunction. So we study the sleep characteristics and blood level of ET-1 and NO in patients with OSAHS and their link with BP.Objective: To study the sleep characteristics in OSAHS patients with hypertension and explore the relation between these characteristics and blood pressure. To evaluate the changes of serum nitric oxide and plasma endothelin-1 in patients with OSAHS and explore the relation between these changes and various sleep disordered breathing events. To explore the role of serum nitric oxide and plasma endothelin-1 in the correlation between OSAHS and hypertension.Methods: Polysomnography(PSG) was performed in 104 patients with OSAHS and in 30 healthy controls(group III). It was analyzed the relation between various sleep disordered breathing events and blood pressure in patients with OSAHS. According to complicating hypertension or not, OSAHS patients were divided into two groups, OSAHS with hypertension group(57 patients, group I) and OSAHS without hypertension group(47 patients, group II). The PSG results were compared among three groups. After excluded the patients who were taking medicine and complicated with the severity infect and the heart and lung disease, we selected 17 OSAHS patients with hypertension diagnosed for the first time(group A) from group I . Matched age, gender and body mass index(BMI), 16 OSAHS patients without hypertension were randomly selected from group II as simple OSAHS group(group B). 23 healthy controls were randomly selected as group C. Blood samples from 56 patients were taken in the morning, plasma ET-1 and serum NO, which can evaluate the function of vascular endothelium, were measured by radioimmunoassay and nitrate reductase, respectively.Results:1. Study of sleep characteristic in patients with OSAHS1) Compared with healthy controls, OSAHS patients with hypertension showed older, more obesity, sleepiness obviously, more frequently sleep apnea and hypoxia and microarousal. Their sleep architecture also more disturbed, displayed the increase of superficial sleep and the decrease of slow wave sleep and rapid eye movement sleep. But, compared with OSAHS without hypertension group, hypoxia index and microarousal index increased and degree of sleepiness, sleep architecture, the lowest oxygen desaturation and OLT90% did not change significantly in OSAHS with hypertension group.2) Changes in systolic blood pressure and diastolic blood pressure level in OSAHS patients(group I+11) were correlated statistically with changes in BMI,apnea-hypopnea index(AHI), hypoxia index and microarousal index, respectively. Furthermore, stepwise regression analysis showed that microarousal index was most contributed to change of systolic blood pressure and hypoxia index was most contributed to change of diastolic blood pressure in patients with OSAHS. 2. Study of blood level of ET-1 and NO in patients with OSAHS l)Matched age, gender and BMI, plasma ET-1 level in group C, group B and group A increased progressively, serum NO level did not change significantly and NO/ET-1 decreased progressively.2) Changes in plasma ET-1 level in OSAHS patients(group A+B) were correlated statistically with changes in AHI, hypoxia index and OLT90 % , respectively. Furthermore, stepwise regression analysis showed that hypoxia index was most contributed to change of plasma ET-1 level in patients with OSAHS.3) Changes in plasma ET-1 level in patients with OSAHS were positively correlated with changes in diastolic blood pressure, but not with changes in systolic blood pressure.4) Changes in serum NO level in OSAHS patients(group A+B) were not correlated statistically with changes in AHI, hypoxia index, OLT90%, microarousal index, diastolic blood pressure and systolic blood pressure, respectively.Conclusions1) The degree of sleep disordered breathing is more serious in OSAHS patients with hypertension. The degree of AHI were correlated statistically with changes in systolic blood pressure, diastolic blood pressure in OSAHS patients. It indicated that more sleep disordered breathing, more tendency developing hypertension in patients with OSAHS.2) The frequency degree of arousal response and hypoxia, which are among the pathogenesis caused by sleep apnea, play important role in the OSAHS- associated hypertension. The frequncy degree of hypoxia is more associated with the elevation of diastolic blood pressure in patients with OSAHS, while the frequncy degree of arousal...