Device Comparison
| Device | Flow rate | Approx. FiO2 |
|---|---|---|
| Nasal cannula | 1-6 L/min | 24-44% |
| Simple face mask | 5-10 L/min | 40-60% |
| Venturi mask | Variable | 24-60% (fixed, precise) |
| Non-rebreather mask | 10-15 L/min | 60-95% |
| High-flow nasal cannula (HFNC) | Up to 60 L/min | Up to ~100%, titratable |
| Bag-valve mask | 15 L/min | Up to 100% |
Nasal Cannula
Simple and well-tolerated, but FiO2 is imprecise and varies with the patient's breathing pattern. Good for mild hypoxemia or stable patients.
Masks
The Venturi mask delivers a fixed, precise FiO2 regardless of breathing pattern — useful when controlled oxygen is important (e.g. COPD patients at risk of CO2 retention). The non-rebreather mask delivers high FiO2 via a reservoir bag with one-way valves, used for significant hypoxemia.
HFNC Basics
High-flow nasal cannula delivers heated, humidified oxygen at high flow rates, providing a small amount of positive pressure and washing out dead-space CO2. It's increasingly used as a step between standard oxygen and non-invasive ventilation in conditions like acute hypoxemic respiratory failure.
When to Escalate
Persistent hypoxemia despite an appropriate device, increasing work of breathing, or a rising respiratory rate are signs to escalate — to a higher-FiO2 device, HFNC, non-invasive ventilation, or intubation, depending on the clinical picture and trajectory.