Non-rapid eye movement (NREM)
· N1: 5-10% of total sleep, slow rolling eye movements
· N2: 40-50% of total sleep, sleep spindles and K complexes on EEG
· N3: 25% of total sleep, deepest stage & can be difficult to awaken
· Release of growth hormone
· Restorative or “slow wave” sleep
· Decrease in heart rate, blood pressure, and cardiac output
Rapid eye movement (REM)
· Rapid fluttering or rolling of the eyes
· Loss of muscle tone (measured by EMG)
· Partial skeletal muscle paralysis
· Dreaming almost always occurs
· 25% of total sleep
· Decreased minute ventilation = hypoxemia & hypercarbia
· Pa02 decreases by 2-12 mmHg, PaC02 increases by 2-8 mmHg
· Both the hypercapnic and hypoxic drives are suppressed
· HR may increase, and cardiac arrhythmias are commonly seen
NREM and REM stages cycle back and forth every 60-90 minutes = 4-5 cycles
Evaluation of sleep disorders
Epworth Sleepiness Scale: 8-item questionnaire, assesses daytime sleepiness
Berlin Questionnaire: 10-item survey, assesses sleep apnea risk factors
STOP-BANG Assessment: 8-item questionnaire, assesses sleep apnea risk factors