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Obstructive Sleep Apnoea (OSA) and Obesity Hypoventilation Syndrome

NICE guideline [NG202] Obstructive sleep apnoea/hypopnoea syndrome and obesity hypoventilation syndrome in over 16s. Published: Aug 2021.

Obstructive Sleep Apnoea (OSA)

Note that NICE now name OSA obstructive sleep apnoea / hypopnoea syndrome (OSAHS)

  • Overweight / obesity
  • Treatment resistant hypertension
  • Type II diabetes
  • Atrial fibrillation
  • Stroke or TIA
  • Acromegaly
  • Down syndrome
  • Chronic heart failure

NICE recommends to suspect OOSAHS if there are ≥2 of the following:
  • Snoring
  • Witnessed apnoeas
  • Unrefreshing sleep
  • Waking headaches
  • Unexplained excessive sleepiness, tiredness or fatigue
  • Nocturia 
  • Choking during sleep
  • Sleep fragmentation or insomnia
  • Cognitive dysfunction or memory impairment

Use the Epworth Sleepiness Scale to asess sleepiness.

Note that not all patients with OSAHS have excessive sleepiness

Perform a sleep study with:
  • 1st line: home respiratory polygraphy
  • 2nd line: home oximetry (may be inaccurate)
  • 3rd line: hospital respiratory polygraphy

Gold standard: polysomnography (only considered if respiratory poylgraphy results are normal but symptoms continue)

The AHIApnoea-Hypopnoea index index is a key metric used to diagnose and determine the severity of OSAHS:
  • <5: normal
  • 5-15: mild
  • 15-30: moderate
  • >30: severe
 
 

Note that polygraphy and polysomnography are NOT the same. Polygraphy can be done at home or at hospital, but polysmnography can only be done at hospital.

They also differ in the recorded parameters:

  • Polygraphy: airflow, breathing effort, SpO2, heart rate, snoring
  • Polysomnography: also EEG, eye movement, EMG, ECG, limb movement in addition to those polygraphy records

Polysomnography allows the identification of other sleeping disorders and determine sleep stages

  • No treatment is needed
  • Advise on lifestyle changes
    • Weight loss
    • Regular physical activity
    • Advise on sleep hygiene
    • Smoking cessation
    • Limit alcohol consumption

  • 1st line: offer CPAPContinuous positive airway pressure
    • Consider heated humidification for those with upper airway side effects (e.g. nasal and mouth dryness, CPAP-induced rhinitis)
  • 2nd line: mandibular advancement splint
    • ​​​​​​​Only if >18 y/o and has optimal dental and periodontal health
  • ​​​​​​​3rd line: consider positional modifier (device that encourages the person to not sleep on their back)
​​​​​​​
Consider tonsillectomy in those with:
  • Large obstructive tonsils, and
  • BMI <35 kg/m2

1st line (all patients):
  • CPAPContinuous positive airway pressure, and
  • Advise on lifestyle changes
    • Weight loss
    • Regular physical activity
    • Advise on sleep hygiene
    • Smoking cessation
    • Limit alcohol consumption

2nd line:
  • Mandibular advancement splint - o​​​​​nly if >18 y/o and has optimal dental and periodontal health

​​​​​​​3rd line:
  • Consider positional modifier (device that encourages the person to not sleep on their back)
  • Note that it is unlikely to be effective in severe OSAHS

Consider tonsillectomy in those with:
  • Large obstructive tonsils, and
  • BMI <35 kg/m2

Obesity Hypoventilation Syndrome (OHS)

1st line (screening) test: serum venous bicarbonate
  • ≥27 mmol/L (high): possible OHS but requires further testing
  • <27 mmol/L (normal): OHS is unlikely

Confirmatory test: ABG while awake
  • Chronic hypercapnia (↑ PaCO2) is diagnostic (indicating daytime hypercapnia)

Offer respiratory polygraphy (hospital / home) to determine the presence of OSAHS in those with suspected OHS.

Although this is not in NICE guideline, but a general requirement for OHS to be diagnosed:
  • Daytime hypercapnia, and
  • Obesity, and
  • Exclude of other hypoventilation causes (e.g. COPD, neuromuscular causes)

Advise on lifestyle changes
  • Weight loss
  • Regular physical activity
  • Advise on sleep hygiene
  • Smoking cessation
  • Limit alcohol consumption

OHS with no acute ventilatory failure:
  • 1st line: CPAPContinuous positive airway pressure
  • 2nd line: non-invasive ventilation
  • 3rd line: consider adding supplemental oxygen therapy onto CPAPContinuous positive airway pressure or non-invasive ventilation

OHS with acute ventilatory failure → non-invasive ventilation

References

Author: Stella Panou
Reviewer:
Last edited: 30/07/25