Loading Calculator...
Please wait a moment
Please wait a moment
Estimate fraction of inspired oxygen (FiO2) based on delivery device and flow rate
Typical range: 1-6 L/min
NC 2L: ~29% | 4L: ~37% | 6L: ~45%
Simple Mask: 40-60% (5-10 L/min)
NRB: 85-95% (10-15 L/min)
| Device | Flow Rate | FiO2 Range | Accuracy |
|---|---|---|---|
| Room Air | N/A | 21% | Exact |
| Nasal Cannula | 1-6 L/min | 24-45% | Variable (±5-10%) |
| Simple Face Mask | 5-10 L/min | 40-60% | Variable (±10%) |
| Venturi Mask | Varies by valve | 24-50% | Precise (±2%) |
| Non-Rebreather | 10-15 L/min | 85-95% | Variable |
| HFNC | 20-60 L/min | 21-100% | Precise (±3%) |
| Mechanical Ventilation | Set on ventilator | 21-100% | Exact |
Best for: Stable patients, chronic conditions, long-term use. Comfortable and allows eating/talking.
Best for: COPD, precise FiO2 control needed. Most accurate non-invasive method.
Best for: Acute severe hypoxemia, trauma, MI. High FiO2 delivery quickly.
Best for: Respiratory failure, pre-intubation, post-extubation. Heated, humidified, precise.
Low-flow devices (NC, simple mask) deliver variable FiO2 because oxygen mixes with room air. Actual FiO2 depends on respiratory rate and tidal volume.
Simple face masks require minimum 5 L/min to prevent CO2 rebreathing. Never run simple masks below this flow rate.
Non-rebreather reservoir must remain at least 2/3 full during inspiration. If bag collapses, increase flow rate.
Flows >4 L/min should be humidified to prevent mucosal drying. HFNC always includes heated humidification.
FiO2 (Fraction of Inspired Oxygen) is the percentage of oxygen in the air being inhaled. Room air has an FiO2 of 21% (0.21). Medical oxygen therapy increases this to improve oxygenation in patients with respiratory compromise.
Nasal cannula delivers oxygen that mixes with room air in the nasopharynx. The actual FiO2 varies based on respiratory rate, tidal volume, and mouth breathing. The "4% rule" is a practical estimate but not exact.
Use Venturi masks for patients requiring precise FiO2 control, particularly COPD patients at risk of CO2 retention. Venturi masks provide consistent FiO2 regardless of breathing pattern, unlike variable-performance devices.
Standard nasal cannula should not exceed 6 L/min due to discomfort, mucosal drying, and limited additional benefit. For higher flow rates, use high-flow nasal cannula (HFNC), which can deliver 20-60 L/min with humidification.
HFNC provides heated humidification, precise FiO2 control, washout of nasopharyngeal dead space, and mild PEEP effect. It's more comfortable than non-rebreather masks and allows eating/talking. Often used as bridge to avoid intubation.
Consider severity of hypoxemia, need for precise FiO2, patient comfort, ability to eat/talk, and duration of therapy. Start with lowest FiO2 needed to maintain SpO2 88-92% (or target range). Escalate devices as needed for refractory hypoxemia.
This FiO2 conversion calculator provides estimates for educational purposes only. Actual delivered FiO2 varies based on patient factors and clinical conditions. All oxygen therapy must be prescribed and monitored by qualified healthcare professionals. This tool should not replace clinical judgment or proper oxygen titration based on patient response.