[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Nursing](https://durgical.com/en/nursing/) › [Procedures](https://durgical.com/en/nursing/areas/procedures/) › Oxygen therapy: devices, flows and safety

# Oxygen therapy: devices, flows and safety

- Procedure

Oxygen is a medicine: give it with the ordered device and flow, toward a target saturation, and away from flames and sparks.

Updated Nov 5, 2026

## Key points

- Target saturation: 94 to 98 % for most; 88 to 92 % if at risk of CO2 retention (for example, COPD), per the BTS.
- Nasal cannula: 1 to 6 L/min, FiO2 about 24 to 44 % (roughly 4 % per litre).
- Simple mask: 6 to 10 L/min (35 to 50 %); never below 6 L/min, because the patient rebreathes CO2.
- Non-rebreather mask with reservoir: 10 to 15 L/min (60 to 80 %), with the bag inflated before it goes on.
- Safety: no smoking or flames nearby, no devices that spark, cylinders secured and away from heat.

On this page

- The basics Key points
- What it is
- Indications
- Equipment
- Step by step (and why)
- Oxygen devices: flow and approximate FiO2 (adult)
- Next step: when to call for help

- Clinical Complications

- Safety Contraindications and precautions

- Study Test yourself

- Connections Connections

## What it is

Oxygen therapy adds oxygen when a patient cannot oxygenate their tissues well. Each device delivers an approximate fraction of inspired oxygen (FiO2) depending on the flow in litres per minute. Oxygen is treated as a medicine: it needs an order, it is titrated toward a target saturation and it is not changed without consultation. The British Thoracic Society guideline (2017) proposes a target saturation of 94 to 98 % for most acutely ill patients and 88 to 92 % for those at risk of hypercapnic respiratory failure, such as many patients with COPD. Oxygen does not burn, but it makes everything burn more fiercely.

## Indications

- Hypoxaemia: saturation below the patient's target.
- Breathlessness or increased work of breathing with desaturation from the patient's baseline.
- Severe acute situations (arrest, shock, major trauma), where high flow is started and then titrated.
- Prescribed long-term home oxygen, for example in COPD.

## Contraindications and precautions

- It is a medicine: do not start or change the flow without an order or protocol; consult the doctor or respiratory therapist.
- In patients at risk of CO2 retention, too much oxygen also harms: titrate to the target, not to the maximum.
- Fire: no smoking or candles; avoid electric razors, hair dryers and synthetic fabrics that spark; electrical equipment in good repair.
- Cylinders upright, secured or in their holder, away from heat sources and never on the patient's bed.
- Check the skin of the nose and ears: cannulas and straps cause pressure injuries.

## Equipment

- An oxygen source (wall outlet, cylinder or concentrator) and a flowmeter.
- Nasal cannula, simple mask, reservoir mask or Venturi mask, per the order.
- A humidifier when indicated, so mucous membranes do not dry out.
- A pulse oximeter.
- A bag-valve-mask available on the unit.

## Step by step (and why)

- Check the order: device, flow or FiO2 and target saturation — oxygen is a medicine with a dose and a goal.
- Assess breathing, saturation, colour and consciousness before starting — it is the baseline to judge the response.
- Remove sources of sparks or flames and explain the safety rules — oxygen feeds any fire.
- Connect the flowmeter to the oxygen outlet, not the air outlet, and add a humidifier if indicated — it avoids giving air instead of oxygen.
- Fit the device and set the flow within its range (for example, a simple mask at least 6 L/min) — out of range it does not deliver as expected.
- With a reservoir mask, inflate the bag before fitting it and check it does not empty — an empty bag supplies no oxygen.
- Pad the ears and nose and watch the skin under the straps — constant pressure causes injuries.
- Reassess saturation and work of breathing and titrate per the order toward the target — neither too little nor too much.
- Record device, flow, saturation and response — it shows the trend and the need to escalate.

## Oxygen devices: flow and approximate FiO2 (adult)

| Device | Flow | Approximate FiO2 | Note |
| --- | --- | --- | --- |
| Nasal cannula | 1 to 6 L/min | 24 to 44 % | For stable patients with a low need |
| Simple mask | 6 to 10 L/min | 35 to 50 % | Never below 6 L/min |
| Non-rebreather mask with reservoir | 10 to 15 L/min | 60 to 80 % | Inflate the bag before fitting |
| Venturi mask | As stated on the adaptor | 24 to 60 % (fixed) | When a precise FiO2 is needed, as in COPD |
| High-flow nasal cannula | Up to 60 L/min | Up to 100 % | Heated and humidified; critically ill, monitored patient |

## Complications

- Worsening CO2 retention in at-risk patients who receive more oxygen than they need.
- Pressure injuries on the ears, nose and face.
- Dry mucous membranes with high flows without humidification.
- Burns and fires from smoking or sparks near oxygen.
- Hypoxaemia from a disconnection, an empty cylinder or a cannula out of the nostrils.

## Next step: when to call for help

- Report if saturation does not reach the target with the ordered device, or if the patient needs more and more oxygen.
- Report at once new drowsiness, confusion, cyanosis or respiratory exhaustion.
- In patients at risk of CO2 retention, report if saturation is above the target or their level of consciousness changes.
- Before a transfer, check the level of the portable cylinder.

## Test yourself

Think of the answer, then tap the question to see it.

## What target saturation does the BTS recommend for a patient at risk of CO2 retention?

Between 88 and 92 %. For most acutely ill patients without that risk, the target is 94 to 98 %.

## Why should a simple mask never run below 6 L/min?

Because at low flows the patient rebreathes the CO2 they exhale into the mask.

## What approximate FiO2 does a nasal cannula deliver?

Between 24 and 44 %, at flows of 1 to 6 L/min; each litre adds roughly 4 % to the FiO2.

## What fire-safety measures does oxygen require?

No smoking or flames nearby, no devices or fabrics that spark, electrical equipment in good repair, and cylinders secured and away from heat.

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## Connections

## Related 3

- [Pulse oximetry at the bedside: placement and pitfalls](https://durgical.com/en/nursing/pulse-oximetry-at-the-bedside-placement-and-pitfalls/)
- [Airway suctioning: oral, nasal and artificial airways](https://durgical.com/en/nursing/airway-suctioning-oral-nasal-and-artificial-airways/)
- [Recognising deterioration and calling the rapid response team](https://durgical.com/en/nursing/recognising-deterioration-and-calling-the-rapid-response-team/)

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Educational content for students; it does not replace your institution's protocols, supervised clinical training or a prescriber's order. Dose-calculation examples use made-up numbers: they are educational, not a clinical order.

Sources: [Nursing Skills, 4.3: Oxygenation Equipment](https://med.libretexts.org/Courses/University_of_South_Carolina_Upstate/Nursing_Skills_(OpenRN)/04%3A_Oxygen_Therapy/4.03%3A_Oxygenation_Equipment) (Open RN, Chippewa Valley Technical College (via LibreTexts), 2021); [Nursing Skills, 4.4: Nursing Process Related to Oxygen Therapy](https://med.libretexts.org/Courses/University_of_South_Carolina_Upstate/Nursing_Skills_(OpenRN)/04%3A_Oxygen_Therapy/4.04%3A_Nursing_Process_Related_to_Oxygen_Therapy) (Open RN, Chippewa Valley Technical College (via LibreTexts), 2021); [BTS Guideline for oxygen use in adults in healthcare and emergency settings](https://www.brit-thoracic.org.uk/quality-improvement/guidelines/emergency-oxygen/) (British Thoracic Society, 2017).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/nursing/oxygen-therapy-devices-flows-and-safety/