Oxygen desaturations and sleep fragmentations are frequently seen during sleep in OSA. These events provoke heightened sympathetic activity and may impair vascular function. We investigated flow and nitroglycerin-mediated (FMD and NMD, respectively) vascular dilation in middle-aged (<65) and elderly (> 65) patients with moderate to severe OSA.
We recorded polysomnograms from 18 male subjects (mean age = 55 +10.99]) with symptomatic OSA and measured FMD and NMD in brachial artery using high-resolution vascular ultrasound with a 10-MHz linear-array transducer. The right brachial artery diameter (BAD) was measured at baseline, and then a pneumatic tourniquet was placed around the forearm and inflated to a pressure of 200 mm Hg for 5 minutes. BAD measurements were repeated at 15 seconds, then at every minute for 5 minutes following cuff deflation and following administration of 0.4 mg of sublingual NTG. The FMD was expressed as a percentage change of diameter after reactive hyperemia relative to the baseline scan. Likewise, the NMD was expressed as a percentage change of diameter after NTG administration relative to the baseline scan.
Mean [SD] ESS was 14 , mean [SD] AI and AHI were 30 and 50  respectively, and lowest and mean O2 saturations were 75% [22%] and 93%[3%] respectively. Brachial artery diameter (mm) at baseline, 1 minute post hyperemia, and 3 minutes post NTG were 0.45 [0.09], 0.48 [0.06], and 0.49 [0.05] mm. Baseline and post NTG diameters were significantly different (p < 0.01). The FMD and NMD were 1% [2%] and 11% [3%], respectively (p< 0.001). Our study did not have enough power to detect any difference in FMD and NMD in elderly versus middle-aged adults.
Endothelial dependent vascular function is impaired in subjects with moderate to severe OSA. Further studies will evaluate the effect of therapeutic intervention to determine if this is a reversible alteration in vascular function.
Restoration of endothelial dependent vascular function may be useful in evaluation obstructive sleep apnea treatment.
Hossein Sharafkhaneh, None.