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Obstructive sleep apnea

Last updated: March 15, 2021

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Obstructive sleep apnea (OSA) is the most common breathing-related sleep disorder and is typically associated with obesity. It is characterized by obstruction of the upper airways due to the collapse of the pharyngeal muscles. OSA results in multiple episodes of interrupted breathing (apnea and hypopnea) during sleep, which leads to alveolar hypoventilation. Affected individuals generally suffer from severe daytime sleepiness and impaired cognitive function (e.g., deficits in attention and/or memory) as a result of sleep disruption. Their partners commonly describe observing restless sleep associated with irregular snoring, gasping, or choking episodes. Diagnosis is based on the assessment of risk factors and polysomnography. Many patients with OSA (> 50%) are affected by secondary hypertension. The cardiovascular consequences of secondary hypertension reduce life expectancy. However, these effects can be counteracted with weight loss and nightly continuous positive airway pressure (CPAP). Other important aspects of management include avoidance of precipitating factors (e.g., alcohol) and improvement of sleep hygiene.

  • Obstructive sleep apnea (OSA): breathing-related sleep disorder in which airflow significantly decreases or ceases because of upper airway obstruction (typically the oropharynx)
  • Apnea: respiratory arrests of ≥ 10 seconds
  • Hypopnea: reduction of airflow by ≥ 30% of pre-event baseline for ≥ 10 seconds in combination with reduction of blood oxygenation by ≥ 3% or EEG arousal



Epidemiological data refers to the US, unless otherwise specified.

Obesity is the most important risk factor for OSA.



  • Restless sleep with waking, gasping, or choking
  • Loud, irregular snoring with apneic episodes (third-party reports)
  • Excessive daytime sleepiness (e.g., patient falls asleep, microsleep during meetings or while watching TV)
  • Impaired cognitive function; (e.g., impaired concentration, memory loss)
  • Depression, decreased libido

General considerations

  • Initial assessment: standardized questionnaires and third-party reports; (interview sleeping partner regarding snoring and respiratory interruptions)
  • Laboratory tests are not usually considered useful in the diagnosis of OSA, but may help identify underlying conditions or physiological consequences of OSA.

Sleep studies

  • Polysomnography: first-line method; a test that records physiologic variables during sleep (including sleep stages, respiratory flow, respiratory pauses, and oxygen saturation); it may also help to identify the type of sleep disorder and associated conditions (e.g., seizures)
  • Home sleep apnea testing (less sensitive): ambulatory screening method based on the use of a device for monitoring cardiorespiratory parameters during the night.

Obstructive sleep apnea is a very frequent cause of secondary hypertension!


Central sleep apnea (CSA)

The 3 C’s of Central sleep apnea are Congestive heart failure, CNS trauma or toxicity, and Cheyne-Stokes breathing.

Obesity hypoventilation syndrome (Pickwickian syndrome)

  • Definition: : a breathing disorder that only affects morbidly obese individuals; ; frequently accompanied by OSA, it is characterized by diurnal hypercapnia
  • Etiology: obesity (BMI ≥ 30 kg/m2)
  • Risk factors: identical to those of obesity
  • Pathophysiology: obesity reduces inspiratory muscle strength and restricts respiratory excursions → alveolar hypoventilation, sleep-disordered breathing (e.g., OSA), and failure of ventilatory compensatory mechanisms → decreased PaO2 and increased PaCO2 during sleep (PaCO2 retention extends to the waking hours)
  • Clinical features
    • Same symptoms as those of OSA
    • Headaches and severe sleepiness
  • Diagnostic criteria
  • Treatment


The differential diagnoses listed here are not exhaustive.

Nocturnal positive pressure therapy via CPAP is the therapy of choice in symptomatic OSA. The success of therapy is highly dependent on patient adherence and regular monitoring with sleep studies!


We list the most important complications. The selection is not exhaustive.

  • The mortality rate is higher in patients with severe OSA who do not receive adequate treatment.
  • CPAP ventilation can significantly lower the risk of mortality in OSA.
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