Study On BP Variation In OSAHS Patients With Phlegm-Dampness Constitution

Background:Obstructive sleep apnea-hypopnea syndrome (OSAHS) and systemic hypertension (HT) are common conditions seeing in obese population. From a TCM prospective, patients with phlegm-dampness constitution is more likely to suffer from OSAHS or hypertension. Both conditions are associated with significant morbidity and mortality. Transient elevation of systemic blood pressure (BP) occurs with each episode of apnea, which suggests a causal relationship between sleep apnea and sustained systemic hypertension. Despite the fact that the association between OSA and HT has been documented, and the reported prevalence of HT in those with OSA is high, Our understanding of the implications of obesity, OSAHS, HT and the circadian variation of BP is still not clear enough. The characteristics of the circadian variation of BP, especially nocturnal BP changes in OSAS, have not been well investigated.Objective:This study was designed to evaluate the correlations among BMI, AHI, night-time SaO2min, average nocturnal SaO2, HT and 24h-ABP patterns, aiming to assess 1)the role of AHI in OSAHS and BP variation; 2)whether the severity of apneas/hypopneas or nocturnal SaO2 relates more closely to the circadian variation of blood pressure.Method:Patients with chief complaints of snoring were initially evaluated by a TCM Constitution Scale. All subjects included in this study are those who have been categorized with Phlegm-dampness constitution. They were advised to take a whole night PSG and 24-h ambulatory blood pressure (24h-ABP). All data were collected in subjects who met the inclusion criteria. The 24h-ABP patterns in OSAS patients were classified into three types:dipping circadian BP throughout the 24-h period with nocturnal BP fall, non-dipping circadian BP, that is without nocturnal BP fall or even BP elevation from onset of sleep to early morning during a 24-h period. Data analysis was performed using SPSS for windows. Demographic, clinical, and BP characteristics were compared in all subjects. Results:A total of 51 participants (48.8±13.3yr) were enrolled in the study. There were 14 (27.5%) women. The 24-hour systolic and diastolic BP values showed the average values were 137±16 and 85±11mmHg, respectively.Hypertension during the daytime (BP≥140/90mmHg) and night time (BP≥125/75mmHg) was observed in 24(47.1%) and 31(60.7%) of the participants, respectively.There was a significant positive association between body mass index(BMI) and AHI, average SaO2 and SaO2min in sleep(p<0.01), as well as positive relation between BMI and 24-hour BP, daytime BP, and nighttime DBP (p<0.05). Statistic results suggest that individuals with moderate to severe SDB showed significantly more BP variation. There was statistically significant association between AHI and 24-hour average BP, daytime SBP, nighttime DBP and SBP (p<0.01), and also relation between AHI and SBP (p<0.05). AHI was significantly correlated with increased nighttime BP. Statistically association is also seen between SaO2min and 24-hour average DBP and nighttime DBP.Conclusion:The prevalence of obesity is likely to increase the risks of both OSAHS and HT. Daytime hypertension is frequently associated with obstructive sleep apnea syndrome. The severity of OSAHS is an important factor in nocturnal elevation of BP, hence affecting the circadian variation of BP. Noninvasive 24h-ABP monitoring is an important procedure for understanding the clinical features of OSAS patients with or without hypertension.