Synopsis
Distinguish chronic hypoxaemia from hypoventilation, prescribe home oxygen only after formal assessment, and coordinate safe long-term ventilatory support with specialist follow-up.
- Oxygen treats hypoxaemia; ventilation treats inadequate carbon dioxide clearance. A patient can need one, both or neither, and pulse oximetry alone cannot distinguish them.
- Refer stable COPD patients for LTOT assessment when resting saturation is persistently 92% or less, but prescribe from specialist blood-gas assessment rather than oximetry alone.
- NICE supports LTOT in stable COPD with PaO2 below 7.3 kPa, or 7.3 to 8 kPa with qualifying complications such as pulmonary hypertension, oedema or secondary polycythaemia.
Key red flags
Morning headache, hypersomnolence, orthopnoea, disturbed sleep, weak cough, recurrent chest infections or raised bicarbonate and PaCO2 suggests hypoventilation needing specialist sleep and ventilatory assessment.
Investigation priorities
Screen for referral to formal home-oxygen assessment.
Management branches
Resting hypoxaemia persists after recovery and optimal treatment of the underlying disease.
- Ensure clinical stability, optimise lung and cardiac disease, address tobacco dependence and obtain repeated resting oximetry before specialist referral.
- The home oxygen service obtains serial stable blood gases, checks NICE eligibility and titrates the flow while monitoring PaCO2 and pH.
Key medicines
Long-term oxygen therapyUse the specialist-titrated flow for at least fifteen hours daily in eligible stable COPD, with separate rest, sleep and exertion instructions where prescribed.
Specialist-prescribed ambulatory oxygenUse only the assessed portable device and flow during the specified activity, for the duration demonstrated to provide practical benefit.