Reference — Oxygen Therapy
Oxygen Device Flow Ranges & FiO₂
The flow rates and approximate FiO₂ for the oxygen devices you reach for every shift — from nasal cannula to non-rebreather to HFNC — plus the low-flow versus high-flow distinction that explains why some devices hold a steady FiO₂ and others don’t.
Written by Apex Respiratory Editorial Team
Educational use only. This material supports respiratory therapy education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional protocols, or physician orders. Always follow facility policies and current provider orders, and verify calculations independently before clinical use.
Overview
The FiO₂ values below are approximations. For every low-flow device, the actual inspired oxygen fraction depends on the patient’s tidal volume, respiratory rate, and inspiratory flow demand — a fast, deep breather entrains more room air and dilutes the delivered oxygen. High-flow devices sidestep this by meeting or exceeding the patient’s inspiratory demand, so the set FiO₂ is what the patient actually receives. Titrate to the SpO₂ target, not to a number on a flowmeter.
Device Flow & FiO₂ Reference
| Device | Flow Rate | Approx FiO₂ | Type | Key Notes |
|---|---|---|---|---|
| Nasal cannula | 1 – 6 L/min | 24 – 44% (~+4%/L) | Low-flow, variable | Comfortable and well tolerated; humidify above 4 L/min to prevent mucosal drying. |
| Simple mask | 5 – 10 L/min | 35 – 50% | Low-flow, variable | Run a minimum of 5 L/min to flush exhaled CO₂ from the mask reservoir. |
| Venturi mask | 2 – 15 L/min (per adapter) | Precise 24 / 28 / 31 / 35 / 40 / 50% | High-flow, fixed | Air-entrainment jet delivers a set FiO₂ regardless of breathing pattern — ideal for COPD. |
| Partial rebreather | 10 – 15 L/min | 60 – 80% | Low-flow, variable | Keep the reservoir bag inflated throughout the breath; titrate flow so it never fully collapses. |
| Non-rebreather | 10 – 15 L/min | 60 – 90% with good seal | Low-flow, variable | Emergency high FiO₂; one-way valves prevent rebreathing. Verify mask seal and reservoir fill. |
| High-flow nasal cannula (HFNC) | Up to 60 L/min | 21 – 100% | High-flow | Heated and humidified; provides a mild PEEP effect and anatomical dead-space washout. |
| Tracheostomy collar | 8 – 10 L/min | Variable | Humidified | Delivers humidified gas to the bypassed upper airway; pair with a heated humidifier or nebulizer. |
Low-Flow vs High-Flow
Low-flow devices deliver less gas than the patient’s peak inspiratory demand, so room air is entrained on every breath and the delivered FiO₂ rises and falls with the breathing pattern. Nasal cannula, simple mask, and rebreather masks are all low-flow.
High-flow devices meet or exceed the patient’s inspiratory demand, so no room air is entrained and the FiO₂ stays consistent regardless of how the patient breathes. The Venturi mask achieves this with a fixed air-entrainment jet; HFNC achieves it with high heated, humidified flow.
Clinical Notes
- Know your SpO₂ target before you titrate. A general acutely ill adult target is 92 – 96%. For patients at risk of hypercapnic respiratory failure — most notably COPD — the target narrows to 88 – 92% to avoid oxygen-induced hypercapnia (worsened V/Q matching plus the Haldane effect).
- Humidify above 4 L/min on nasal cannula. Dry medical gas at higher flows desiccates the nasal mucosa, causing discomfort, bleeding, and thickened secretions. Add bubble or heated humidification once flow exceeds 4 L/min.
- Match the device to the goal, not the panic. A non-rebreather is for genuine high-FiO₂ emergencies; a Venturi mask is the right choice when a precise, stable FiO₂ matters more than a high one. Escalating to HFNC adds humidified flow, a mild PEEP effect, and dead-space washout that a non-rebreather cannot provide.
Related Resources
Sources
- Kacmarek RM, Stoller JK, Heuer AJ. Egan's Fundamentals of Respiratory Care. 12th ed. Elsevier; 2021. Medical gas therapy.
- American Association for Respiratory Care. AARC Clinical Practice Guideline: Oxygen therapy for adults in the acute care facility — 2002 revision & update. Respir Care. 2002;47(6):717-720.