Obstructive sleep apnea and its therapy

1. Big picture

Obstructive sleep apnea (OSA) is a sleep-related breathing disorder caused by repeated collapse of the upper airway during sleep. The patient tries to breathe, but airflow stops or decreases because the pharyngeal airway is obstructed.

The key exam sentence:

Obstructive sleep apnea causes repeated nocturnal apneas/hypopneas, intermittent hypoxemia, arousals, fragmented sleep, excessive daytime sleepiness, and increased cardiovascular risk.

The most important exam trap:

Snoring alone is not enough for OSA. OSA requires obstructive apneas/hypopneas with oxygen desaturation, arousals, daytime symptoms, or associated cardiovascular/metabolic risk.

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2. Definition

Obstructive sleep apnea syndrome (OSAS) is characterized by repeated episodes of complete or partial upper airway obstruction during sleep.

This causes:

• reduced or absent airflow;
• continued respiratory effort;
• oxygen desaturation;
• increased carbon dioxide;
• arousal from sleep;
• sleep fragmentation;
• daytime symptoms.

Important terms:

• Apnea = complete cessation of airflow.
• Hypopnea = partial reduction of airflow with desaturation and/or arousal.
• AHI = apnea-hypopnea index = number of apneas and hypopneas per hour of sleep.

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3. Classification of sleep-related breathing disorders

Sleep-related breathing disorders include:

1. Obstructive sleep apnea disorders
2. Central sleep apnea syndromes
3. Sleep-related hypoventilation disorders
4. Sleep-related hypoxemia disorders

The exam-relevant distinction:

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4. Pathophysiology