Hypercapnia alters sleep state pattern

Mild hypercapnia in the adult animal does not affect sleep pattern but more severe hypercapnia in the fetus increases the duration of REM sleep. Adult male rats were exposed daily for 2-3 h sessions at random to 6, 7, and 8% CO2 or room air. Breathing CO2 caused a 60% increase in sleep onset latency, a 28% decrease in sleep duration, but no change in percent time spent in REM. However, the duration of REM sleep episodes increased by 30%. Thus, in both fetal and adult animals severe hypercapnia appears to have a similar effect on sleep pattern.