In any seriously injured or critically ill patient, start high-flow oxygen 10-15 L/min through a face mask with reservoir bag (non-rebreather) if you have one, or the best mask available. Titrate later; in the first minutes of resuscitation, hypoxia kills and oxygen does not.
| Device | Flow | Approximate FiO2 |
|---|---|---|
| Nasal prongs | 1-4 L/min | 24-36% |
| Simple face mask | 5-8 L/min | 40-60% |
| Mask with reservoir bag | 10-15 L/min | 60-90% |
| Bag-valve-mask with reservoir | 15 L/min | up to 90%+ when ventilating |
Practical points for facilities running on cylinders:
- Check cylinder pressure at every shift change; know how long your cylinder lasts at 15 L/min (a full large cylinder empties in a few hours).
- If supply is limited, prioritise the sickest patient and wean using SpO2 (target 94-98%; 88-92% in known chronic lung disease).
- A concentrator (max ~5-10 L/min) can feed nasal prongs and simple masks but cannot drive a reservoir mask properly on its own.