obesity hypoventilation syndrome (OHS)

Last edited 09/2021 and last reviewed 07/2022

Obesity hypoventilation syndrome (OHS)

• is defined as the combination of obesity (body mass index [BMI] of 30 kg/m2 or more), raised arterial or arterialised capillary carbon dioxide (CO2) level when awake, and breathing abnormalities during sleep, which may consist of obstructive apnoeas and hypopnoeas, or hypoventilation, or a combination of both. OHS is a specific formInitial assessment for OHS

When to suspect OHS

• take a sleep history and assess people for OHS if they have a BMI of 30 kg/m2 or more with:
  • features of obstructive sleep apnoea/hypopnoea syndrome of chronic ventilatory failure
    • take a sleep history and assess people for OSAHS if they have 2 or more of the following features:
      • snoring
      • witnessed apnoeas
      • unrefreshing sleep
      • waking headaches
      • unexplained excessive sleepiness, tiredness or fatigue
      • nocturia (waking from sleep to urinate)
      • choking during sleep
      • sleep fragmentation or insomnia
      • cognitive dysfunction or memory impairment
  • features of nocturnal hypoventilation such as:
    • waking headaches
    • peripheral oedema
    • hypoxaemia (arterial oxygen saturation less than 94% on air)
    • unexplained polycythaemia

Assessment scales for suspected OSAHS

• when assessing people with suspected OSAHS:
  • use the Epworth Sleepiness Scale in the preliminary assessment of sleepiness
  • consider using the STOP-Bang Questionnaire as well as the Epworth Sleepiness Scale
  • do not use the Epworth Sleepiness Scale alone to determine if referral is needed, because not all people with OSAHS have excessive sleepiness

Reference:

• NICE (August 2021). Obstructive sleep apnoea/hypopnoea syndrome and obesity hypoventilation syndrome in over 16s