Sleep Medicine

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Obstructive Sleep Apnea (OSA)

Since Obstructive Sleep Apnea is a syndrome, this means several disorders may produce similar symptoms. Sleep apnea syndrome may include sleep apnea, sleep hypopnea, or abnormal upper airway resistance during sleep. 

The main difference of this disorder is the degree of airway blockage or obstruction. Obstructions may be complete or partial. With obstruction, oxygen levels often drop. The repeated events of pharyngeal collapse distinguish obstructive sleep apnea syndrome from other breathing disorders like asthma or tracheal stenosis, where obstruction is continuous. 

The breathing obstruction in Obstructive Sleep Apnea Syndrome occurs in the throat (pharynx) and other soft tissues of the upper airway. 

With sleep onset, there is loss of the wakefulness stimulus to upper airway muscles. This results in airway collapse, increased resistance to airflow, decreased breathing, and increased breathing effort

The mechanical stimulus to the airway resulting from obstruction causes a brief awakening from sleep. The brief awakening or arousal increases muscle tone, which opens the airway. Unfortunately, it also fragments sleep. 

With apneas and oxygen drops, marked fluctuations in blood pressure, cerebrospinal fluid pressure, and cardiac arrhythmias may occur.

Obstructive sleep apnea results from collapse and obstruction of the throat pharyngeal airway. It is accepted that this occurs due to both a structurally small upper airway and a loss of muscle tone

In all individuals, some degree of airway collapse occurs as muscle tone decreases. When combined with the structurally small upper airway in obstructive sleep apnea syndrome, the collapse obstructs the airway.

Airway closure varies also with changes in body and head position, sleep state, and muscular tone (relationship between the muscles and the nerves). Partial airway collapse produces increased resistance to breathing. Muscles working to overcome this blockage may then "suck" the airway closed. 

In most subjects, the narrowest airway cross-section area occurs behind the palate and uvula. This area is the most vulnerable to obstruction from loss of muscle tone during sleep. 

On physical exam a long and wide soft palate, a large edematous (swollen) uvula, large tonsils, and redundancy of pharyngeal walls may be found. Lower throat findings may include a large tongue and lingual tonsils. Other causes may or may not occur.

Diagnoses of sleep apnea syndrome requires both airway blockage and associated symptoms of disrupted sleep or medical complications.
© 2014 Medical College of Wisconsin
Page Updated 01/28/2014