Obesity hypoventilation syndrome (OHS)

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. (1)

When to suspect OHS (2)

• 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 apnoea
      • 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

1. Masa JF, Pépin JL, Borel JC, Mokhlesi B, Murphy PB, Sánchez-Quiroga MA. Obesity hypoventilation syndrome. Eur Respir Rev. 2019;28(151):180097
2. NICE. Obstructive sleep apnoea/hypopnoea syndrome and obesity hypoventilation syndrome in over 16s. NICE guideline NG202. Published August 2021.