Diagnostic tests for obesity hypoventilation syndrome (OHS)
Diagnostic tests for obesity hypoventilation syndrome (OHS)
Diagnosing OHS and assessing ventilatory failure
- consider measuring serum venous bicarbonate as a preliminary test if the pre-test probability of OHS is low. If bicarbonate levels are below 27 mmol/litre, OHS is unlikely.
- measure arterial or arterialised capillary blood gases when the person with suspected OHS is awake, to diagnose OHS and assess the extent of chronic ventilatory failure
- do not delay treatment for acute ventilatory failure to carry out further investigations for OHS
Diagnosing the presence of OSAHS (obstructive sleep apnoea/hypopnoea syndrome) or nocturnal hypoventilation in people with OHS
- offer respiratory polygraphy, either in hospital or at home, to determine the presence of OSAHS in people with suspected OHS
- consider adding transcutaneous CO2 monitoring during sleep to respiratory polygraphy in people with suspected OHS to determine the extent of nocturnal hypoventilation and provide additional information to guide treatment
- do not use oximetry alone to determine the presence of OSAHS in people with OHS
Reference
- NICE. Obstructive sleep apnoea/hypopnoea syndrome and obesity hypoventilation syndrome in over 16s. NICE guideline NG202. Published August 2021.
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