Sleep

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