Somers - Figure 13
Awake
FIG. 13: This Figure shows recordings of sympathetic activity in a group of normal subjects on the left, and patients with newly diagnosed, never-treated OSA on the right.[5] There are several important factors here. The first is that the OSA patients have no cardiovascular or other comorbidities; in other words, apart from sleep apnea they are completely healthy. The second point is that all the subjects are wide-awake and breathing normally, so there is no hypoxemia. As a result, what the Figure illustrates is that in patients with sleep apnea, sympathetic activity is very high (seeing the height and the number of bursts as a measure of sympathetic nervous activity). In other words, in a sense each burst is a reflection of catecholamines being released into the neurovascular junction, causing vasoconstriction.
Thus it is clear from this Figure that even in healthy untreated patients with OSA who are normoxic and wide-awake, sympathetic nervous system activity during daytime is markedly increased.
References
Somers VK, Dyken ME, Clary MP, Abboud FM. Sympathetic neural mechanisms in obstructive sleep apnea. J Clin Invest. 1995;96:1897–1904.
