Somers - Figure 14
Stages
FIG. 14: After seeing the microneurography results in wide awake patient with OSA in the previous Figure, the next question is to know what happens to these apneic patients when they are sleep. To better understand this, we had to first understand what happens in normal people during wakefulness and the transition to sleep. This Figure shows measurements of sympathetic nervous activity (SNA) and blood pressure (BP), from wakefulness to Stages 2, 3, and 4, and then rapid-eye movement (REM) sleep.[6]
As shown in this Figure, during non-REM (Stages 2–4) sleep sympathetic activity clearly decreases from the levels during wakefulness, and blood pressure and heart rate are lower. Then as the subject enters REM sleep there are marked increases in sympathetic nerve traffic, with intermittent surges in blood pressure.
So, during sleep in normal subjects there is a controlled structure change in sympathetic drive from deeper stages of non-REM sleep into the increased activity of REM sleep, and the question is: What happens in patients with OSA?
References
Somers VK, Dyken ME, Mark AL, Abboud FM. Sympathetic-nerve activity during sleep in normal subjects. N Engl J Med. 1993; 328:303–307.
