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.
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.
Connections
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 (Open RN, Chippewa Valley Technical College (via LibreTexts), 2021); Nursing Skills, 4.4: 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 (British Thoracic Society, 2017).
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Representative model, for educational purposes only.