Defining the severity of obstructive sleep apnoea in adults

severity of obstructive sleep apnoea

Apnoeas or hypopnoeas measured during polysomnography (PSG) are often combined as the apnoea/hypopnoea index (AHI), which is the total number of apnoeas and hypopnoeas per hour of sleep (1).

• although it is unclear whether AHI is the best measure of the severity of OSA, it is the most widely used
  
  
• the severity of OSA can be categorized as:
  
  
  • mild - >5-14 events per hour
    
    
  • moderate - 15-29 events per hour
    
    
  • severe - >30 events per hour
    
    
• due to the non-linear correlation of the AHI with symptoms, the results of testing must be interpreted with the history (1,2)

In settings where PSG is not available, the number of peripheral oxyhaemoglobin desaturations >4% h−1 (oxygen desaturation index, ODI) may be used to assess OSA.

• an ODI of ≥5 is considered significant (2)

Reference:

• (1) Greenstone M, Hack M. Obstructive sleep apnoea. BMJ. 2014;348:g3745
• (2) Martinez G, Faber P. Obstructive sleep apnoea. Contin Educ Anaesth Crit Care Pain (2011) 11 (1): 5-8