Oxygen is one of the most commonly used treatments in hospital, and it is a drug: it should be prescribed with a target, given with the right device, monitored, and weaned. Too little causes hypoxia; too much can harm some patients, particularly those at risk of hypercapnic (COâ‚‚-retaining) respiratory failure. During COVID-19, many countries discovered how precious, and how scarce, medical oxygen is. WHO now treats access to medical oxygen as a global health priority.
Target saturations
- Most acutely ill adults: 94–98% (British Thoracic Society).
- Patients at risk of hypercapnic respiratory failure (e.g. some COPD, severe obesity, neuromuscular disease, chest wall deformities): 88–92%, unless blood gases show otherwise.
- WHO guidance for children: give oxygen if SpOâ‚‚ is below 90%, (below 94% with emergency signs), and aim to keep it at 90% or above (94% or above during resuscitation and emergency treatment). Follow your national paediatric protocol.
- Critical illness (cardiac arrest, shock, major trauma, anaphylaxis): high-concentration oxygen via a reservoir mask initially.
Delivery devices compared
| Device | Flow rate | Approximate oxygen delivered | Use for |
|---|---|---|---|
| Nasal cannula | 1–4 L/min (up to 6) | About 24–40% (variable) | Mild hypoxia; comfortable for eating and talking |
| Simple face mask | 5–10 L/min (never below 5) | About 40–60% (variable) | Moderate hypoxia |
| Venturi mask | Set by colour-coded valve | Fixed 24%, 28%, 31%, 35%, 40%, 60% | Patients needing precise oxygen, e.g. COPD with COâ‚‚ retention |
| Non-rebreather (reservoir) mask | 15 L/min | Up to about 60–90% | Critical illness, emergencies; short-term |
| High-flow nasal oxygen | Up to 60 L/min, heated and humidified | 21–100% (set) | Severe hypoxaemic respiratory failure, in monitored areas |
Why not run a simple face mask below 5 L/min? Low flow allows exhaled COâ‚‚ to build up inside the mask and be re-breathed. Make sure the reservoir bag on a non-rebreather is inflated before putting it on the patient.
Monitoring
- SpOâ‚‚, respiratory rate and effort, heart rate, conscious level, and NEWS2 (remember the 2 points for oxygen; see our NEWS2 guide).
- Record the device and flow rate every time you record SpOâ‚‚.
- A patient needing more and more oxygen is deteriorating, even if the saturation looks fine. Escalate.
- In COâ‚‚ retainers, watch for drowsiness, headache, flushed skin and a bounding pulse; check blood gases as requested.
Comfort and skin care
- Check ears, nose and cheeks for pressure damage from tubing and masks; pad as needed.
- Mouth care: oxygen dries the mouth.
- Humidification for high flows or prolonged use, or if secretions are thick.
- Change masks for nasal cannula at mealtimes if the patient can tolerate it safely.
Safety
- Fire risk: no smoking, candles or open flames near oxygen. Oil-based products (some lip balms, petroleum jelly) should not be used near the face with oxygen.
- Secure cylinders upright in holders; never leave them free-standing.
- Check there is enough oxygen in the cylinder before transferring a patient.
- Turn off oxygen when not in use.
- Use the right outlet: oxygen and medical air outlets can look similar. Check the label.
Oxygen in low-resource settings
Oxygen concentrators are common where piped oxygen and cylinders are unreliable; they usually deliver up to 5–10 L/min. Use them with nasal cannulae or prongs, especially for children with pneumonia. Pulse oximeters are essential to target oxygen wisely and save supplies. If oxygen is scarce, prioritise patients by need, and wean as soon as the patient is stable.
Weaning
Reduce oxygen step by step as the patient improves and saturations stay in the target range. Switch to a lower-flow device, then stop and monitor SpOâ‚‚ on air.
Related: ABG interpretation · Pneumonia care plan · Acute asthma
Based on the British Thoracic Society guideline for oxygen use in healthcare and emergency settings and WHO guidance on oxygen therapy for children. Educational content: follow your prescription and local policy.