USMLE Guide: Sleep Apnea

Sleep apnea is a common sleep disorder characterized by interruptions in breathing during sleep. This guide aims to provide an overview of sleep apnea, including its definition, types, pathophysiology, clinical features, diagnosis, and management.

Definition

Sleep apnea is a sleep disorder characterized by recurrent episodes of partial or complete cessation of breathing during sleep, resulting in decreased oxygen levels and disrupted sleep patterns.

Types of Sleep Apnea

1. Obstructive Sleep Apnea (OSA): Most common form, caused by upper airway collapse or obstruction during sleep.
2. Central Sleep Apnea (CSA): Less common form, occurs due to failure of the brain to transmit appropriate signals to the muscles that control breathing.

Pathophysiology

• OSA: Airway collapse during sleep leads to decreased airflow, resulting in hypoxemia, hypercapnia, and sleep fragmentation.
• CSA: Dysfunction in the central respiratory centers impairs the drive to breathe, leading to pauses in breathing.

Clinical Features

1. Excessive Daytime Sleepiness (EDS)
2. Loud snoring
3. Witnessed apneas or gasping during sleep
4. Morning headaches
5. Nocturnal awakening with a choking sensation
6. Difficulty concentrating
7. Irritability and mood changes

Diagnosis

1. Polysomnography (PSG): Overnight sleep study to evaluate breathing patterns, brain activity, heart rate, and oxygen levels during sleep.
2. Home Sleep Apnea Testing (HSAT): A simplified version of PSG for patients with high pretest probability and no significant comorbidities.

Management

1. Lifestyle modifications:
   • Weight loss: Encourage weight reduction in overweight/obese individuals.
   • Avoidance of alcohol and sedatives: These substances worsen sleep apnea symptoms.
   • Sleep position: Encourage side sleeping rather than supine position.
2. Continuous Positive Airway Pressure (CPAP):
   • First-line treatment for moderate to severe OSA.
   • Delivers a constant flow of air through a mask to keep the airway open during sleep.
3. Oral Appliances:
   • Used for mild to moderate OSA or individuals who cannot tolerate CPAP.
   • Devices that reposition the lower jaw and tongue to maintain airway patency.
4. Surgery:
   • Considered in refractory cases or anatomical abnormalities.
   • Procedures include uvulopalatopharyngoplasty, genioglossus advancement, etc.

Remember, sleep apnea can have significant consequences if left untreated, including cardiovascular disease, hypertension, and increased risk of accidents. Early recognition and appropriate management are crucial for improving patient outcomes.

Note: This guide aims to provide a concise overview for USMLE preparation and may not encompass all aspects of sleep apnea management.