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obstructive sleep apnoea - hypopnoea syndrome (OSAHS)

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Sleep apnoea is a disorder of breathing during sleep where there is a cessation of airflow lasting at least 10 seconds and is often associated with oxygen desaturation (1).

According to the revised International Classification of Sleep Disorders, apnoea can be divided into three types (2)

  • obstructive sleep apnea
    • occurs due to upper airway obstruction, but movement of the chest wall (rib cage and abdomen) persists
    • the most common disorder of breathing during sleep
    • the patient is woken - not necessarily to full awareness - by airway obstruction
    • it is prominent during REM sleep (when muscle tone is at its lowest).
    • patients with this condition may wake from 3 to 400 times a night.
  • central sleep apnoea  
    • is less common than obstructive apnoea
    • there is loss of both inspiratory air flow and the drive to breathe
    • seen in
      • most commonly, accompanying Cheyne–Stokes breathing
      • infants with an immature respiratory control system
      • adult patients with cerebrovascular or neuromuscular disease (3)
  • mixed
    • contains components of both obstructive and central sleep apnoea (1)

Obstructive sleep apnoea syndrome (OSAS) or obstructive sleep apnoea/hypopnoea syndrome (OSAHS) is a condition with repetitive apnoeas and symptoms of sleep fragmentation, most commonly excessive daytime sleepiness. Majority of the patients have a combination of complete obstruction (apnoea) and partial obstruction (hypopnoea) (1,3).

The American Academy of Sleep Medicine definition of obstructive sleep apnoea syndrome is as follows:

  • combination of at least five obstructive breathing episodes per hour during sleep (apnoea, hypopnoea and respiratory effort related arousals events) and at least one of the following criteria:
    • excessive daytime sleepiness that is not better explained by other factors
    • two or more of the following symptoms that are not better explained by other factors:
      • choking or gasping during sleep
      • recurrent awakenings from sleep
      • unrefreshing sleep
      • daytime fatigue
      • impaired concentration (4)



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