The states of NREM (non-rapid eye movement) and REM (rapid eye movement) each perform a different function, and both are crucial to overall daytime effectiveness. Going to sleep is like descending a stairway. As brain activity slows, we transition into NREM sleep until we reach deep sleep. When in deep sleep, pulse and respiratory slows, blood
pressure drops, muscles relax, and growth hormone is released to facilitate physical healing, enhanced pain control, and physical rejuvenation.
About every hour and a half we come out of deep sleep into REM sleep, an active state of sleep.
REM sleep is crucial since our breathing, blood pressure, pulse rate, and blood flow to the brain all increase during this phase. During REM sleep, our peripheral muscles are atonic.
REM presents a challenge to sustain breathing, oxygenation, and cardiac stability in patients at risk for sleep apnea. Clinical functions all become more difficult to sustain because apneic events are longer during REM, oxygen desaturation is lower, and more cardiac arrhythmias are noted during REM sleep.
Since the longest REM period occurs in the early morning hours between 4:00 – 6:00 AM the best sleep and biggest problems for sleep apnea sufferers come at this time.