Many physiological processes like temperature, BMR, respiration rate changes in sleep wake transitions. As sleep has been categorized in to two types as REM sleep and NREM sleep, various studies have shown that during REM/dreaming sleep the level of carbon dioxide increases, as from an evolutionary point of view REM sleep has evolved to wash off the extra level of carbon dioxide during the sleep. Locus coeruleus, which is a wake promoting nucleus responds to the hypercapnic condition and I wonder how the signalling goes on?
REM sleep, or paradoxical sleep, is a sleep state during which the body experiences increased hypotonia.It is during this sleep phase that most children exhibit obstructive sleep apnea, accompanied or not with desaturations. The monitoring of the end tidal CO2 allows us to se that in some cases, the ETCO2 increases too, during that phase of sleep, if the obstructive sleep apnea syndrome is accompanied by hypoventilation. But REM sleep is also the sleep state with the lowest arousal threshold, meaning that waking up from this state is "easier". This is important, as the relative hypotonia of this sleep state facilitates hypercapnia: the "easy" arousals allow the individual suffering from obstructive sleep apnea (or any other cause of hypoventilation) to "respond" rapidly to a potential obnoxous stimuli by moving or by waking up, thus explaining the disturbed sleep of those patients suffering from OSAS.
This is an interesting question. I'm not sure it is that clear that CO2 levels increase during paradoxical sleep. Do you know publications reporting that? Also, it would be important to know whether there is a progressive increase in CO2 levels across PS episodes. It could indeed play a role in the ending of the state. One possiblity is that serotoninergic neurons could play a role in this case since they are CO2 sensor involved in awakening induced by hypercapnia (Buchanan and Richerson, 2010).
C02 can rise during REM sleep. The set point for the hypercapnic ventilatory response is higher in REM sleep, and the slope if the HVR is lower in REM. Dangerous for those with gas exchange problems (e.g., COPD). Classic paper is 1982 by Douglas PMID: 7149440. Also with the intercostals offline in REM, there can be restriction.
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