The Study of Correlation between Diurnal Blood Pressure with Nocturnal Oxygen Desaturation and Nitrite Production in Subjects with Obstructive Sleep Apnea (OSA)

Abstract

Background: Endothelial dysfunction is often present in subjects with obstructive sleep apnea (OSA) on walking up. Although the intermittent hypoxia has been suggested as a main cause of endothelial dysfunction in these subjects, the precise mechanism of this event is still unclear. The aim of this study was to demonstrate the correlation between the level of hypoxia during sleep with arterial blood pressure and plasma concentration of nitrite. Methods: Non-smoker subjects were included in a cross-sectional study. They underwent systolic and diastolic blood pressure (SBP and DBP) measured at bed before sleep and on walking up, overnight polysomnography (PSG), and measurement of nitrite in plasma from peripheral blood at walking up. Results: Sixty-five subjects with mean age of 58 ± 12 years were included in this study. The male-female ratio was 0.9 and BMI was 23.3 ± 3.4 kg/m2. The mean of systolic BP and diastolic BP post-PSG of subjects with SpO2<93% was significantly higher than subjects with SpO2 ≥ 93% (P<0.05 and P<0.01; respectively). The mean SpO2 and nadir SpO2 of subjects with SpO2<93% were significantly lower than subjects with SpO2 ≥ 93% (90 ± 4% vs. 94 ± 2% and 73 ± 9% vs. 88 ± 8%; P<0.05 and P<0.01; respectively). The level of apnea-hypopnea index in subjects with SpO2<93% was significantly higher than that in subjects with SpO2 ≥ 93% (P<0.01). The concentration of NO2- in peripheral blood of subjects with SpO2<93% was significantly lower than that in subjects with SpO2 ≥ 93% (P<0.01). There were the significant correlations between nadir SpO2 and NO2- with SBP and DBP on walking up. Conclusion: Endothelial dysfunction is a crucial event in subjects with OSA, especially for whom with obstructive sleep apnea. This event might be linked to the diurnal increase of peripheral blood pressure. The concentration of NO2- in plasma measuring on walking up might be a relevant marker of endothelial dysfunction during sleep.