The authors would like to acknowledge David A. Miller for his contributions that remain unchanged from the first edition.
CHARACTERISTICS OF BREATHING AND SLEEP
I. Tidal volume and respiratory rate decline as a person becomes more deeply asleep. Skeletal muscle tone decreases progressively in deeper stages of sleep, with frank atony occurring during rapid eye movement (REM) sleep.
II. Peak airway resistance tends to be highest from 2 am to 6 am and lowest from 2 pm to 6 pm.
III. Cough and shortness of breath may be aggravated during the normal sleeping period at night.
IV. Normal pauses in respiration are infrequent and brief, lasting 5 to 10 seconds. These pauses are central in origin and are not associated with physical obstruction of the oropharynx or hypopharynx.
OBSTRUCTIVE SLEEP APNEA (OSA)
I. Etiology
A. Obstruction of the upper airway caused by collapse of the soft tissues (muscle, fat) during sleep
B. Obstruction causes arousals and awakenings from sleep, and effective sleep time is reduced.
III. Clinical manifestations
A. The classic manifestation of significant OSA is excessive daytime sleepiness (EDS).
B. Snoring is commonly heard, although severe sleep apnea may be accompanied by quiet snoring.
C. Severe daytime sleepiness interferes with normal daytime functioning.
1. Additional attempts to “catch up” on sleep fail.
2. Driving a vehicle or operating heavy machinery may become dangerous.
D. Hypoxemia during the apneic and hypopneic episodes may lead to adverse health consequences, including the following:
1. Myocardial ischemia, infarction, arrhythmias, and congestive heart failure
2. Cerebral ischemia and stroke
3. Sudden death
4. Cardiorespiratory arrest after surgery or administration of sedatives, hypnotics, and opioids
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