Synopsis
Prescribe oxygen as a titrated treatment with an explicit saturation target, appropriate device and reassessment plan, including safe management of patients at risk of hypercapnic respiratory failure.
- Oxygen treats hypoxaemia, not breathlessness. Prescribe a target saturation, device/flow and monitoring plan rather than a fixed dose with no endpoint.
- For most acutely ill adults, target SpO2 94–98%. For known COPD or another risk of hypercapnic respiratory failure, target 88–92% pending blood gases.
- Risk factors for hypercapnia include prior hypercapnic failure, severe COPD, morbid obesity, neuromuscular disease, chest-wall deformity, cystic fibrosis and fixed airflow obstruction in bronchiectasis.
Key red flags
Cardiac arrest, shock, major trauma, sepsis with critical illness or severe hypoxaemia needs immediate oxygen and airway assessment before precise titration.
Investigation priorities
Titrate oxygen and trend response.
Management branches
Acutely ill adult without known risk of hypercapnic respiratory failure.
- Prescribe SpO2 94–98% and select the lowest-intensity device expected to achieve it.
- If critically ill or SpO2 is below about 85%, start reservoir mask 15 L/min while assessing airway/breathing and obtaining senior help; titrate down once stable.
Key medicines
Medical oxygen—reservoir mask15 L/min initially in critical illness, severe hypoxaemia or carbon monoxide poisoning; ensure the reservoir bag remains inflated and titrate to the prescribed target when the exception no longer applies.
Medical oxygen—Venturi maskChoose the labelled concentration, commonly 24% or 28% for hypercapnia risk, and set at least the flow printed on that manufacturer's valve; increase flow if inspiratory demand collapses the mask flow.