Nursing care
Oxygen Therapy: the nurse's role, start to finish
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Oxygen therapy nursing management means matching the delivery device and flow rate to the patient's target saturation, then watching for both hypoxaemia and oxygen toxicity. A nasal cannula run above 6 L/min stops improving saturation and starts drying the mucosa, so the device and the rate are chosen together, not separately.
When it is done and why
Oxygen is ordered when a patient's SpO2 falls below their target range, typically 94-98% for most adults or 88-92% for patients with chronic CO2 retention, or when clinical signs of hypoxaemia appear before the number does: restlessness, tachypnoea, tachycardia, or a change in level of consciousness. The trigger is the patient, not the monitor alone.
Common indications include acute respiratory failure, COPD exacerbation, pneumonia, post-operative recovery, chest pain with suspected cardiac ischaemia, and carbon monoxide poisoning. Each of these carries a different target saturation and a different tolerance for delay, which is why the order should specify a target range rather than a flat instruction to 'apply oxygen'.
Preparing the patient
Check the order for device, flow rate, and target SpO2, and confirm it matches the patient's diagnosis. A COPD patient ordered 15 L/min via non-rebreather mask is a mismatch worth querying before you apply it, since chronic retainers can lose their hypoxic respiratory drive at high flows.
Assess baseline respiratory status: rate, depth, effort, skin colour, and a baseline SpO2 reading. Check the nares and skin behind the ears for existing breakdown if a cannula or mask has been used before, and explain to the patient what the device will feel like, particularly the dryness of nasal prongs and the claustrophobic feel of a tight-fitting mask.
The steps that matter for safety
Every delivery device has a flow rate range, and running outside it either fails to deliver the intended FiO2 or causes harm without benefit. A nasal cannula is built for 1-6 L/min; above that the airflow won't raise saturation meaningfully but it will dry and crust the nasal mucosa, causing nosebleeds and patient discomfort. Simple face masks need a minimum of 5 L/min to flush exhaled CO2 from the mask; below that the patient rebreathes their own carbon dioxide.
Match device to need: cannula for low-flow, stable patients; Venturi mask when a precise FiO2 matters, as in COPD; non-rebreather mask for high-flow acute hypoxaemia. No smoking, no naked flame, and no petroleum-based lip products near an oxygen source, since oxygen supports combustion even though it isn't itself flammable.
During the procedure — the nurse's role
Apply the device, set the flow rate to the ordered value, and confirm delivery by checking the flowmeter ball or dial rather than assuming the tubing is patent. Reassess SpO2 within minutes of starting or changing a device, and titrate within the prescribed range if a protocol allows it.
Watch the patient's response, not just the number: work of breathing, colour, and mentation should trend the same direction as the saturation. Reposition tubing over the ears and cheeks to avoid pressure injury, and keep the humidifier bottle filled and functioning for flows above 4 L/min or for any patient on oxygen longer than a few hours.
After: monitoring and complications
Continue pulse oximetry and periodic ABGs as ordered, especially in CO2 retainers where a rising PaCO2 with falling consciousness signals oxygen-induced hypoventilation rather than improvement. Watch for signs of oxygen toxicity with prolonged high FiO2: substernal chest pain, dry cough, and progressive dyspnoea, most relevant beyond 24 hours at FiO2 above 50-60%.
Check skin integrity at contact points at least every shift, and inspect nares for dryness or bleeding. Absorptive atelectasis is a risk with very high FiO2 delivered over time, so the lowest flow that meets the target saturation is always the goal, reassessed as the patient's condition changes rather than left running unchanged.
Documentation and teaching
Chart the device, flow rate, FiO2 where applicable, SpO2 before and after initiation, and the patient's respiratory assessment. Document any skin breakdown, adjustments made, and the rationale for titration so the next nurse can see the trend rather than a single reading.
Teach the patient why the flow rate is set where it is and why they shouldn't turn the dial up themselves if they feel breathless, since more oxygen isn't automatically better and can suppress drive to breathe in CO2 retainers. Cover fire safety at home if they're being discharged on oxygen, and confirm they can demonstrate correct cannula or mask application before leaving.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our respiratory practice questions are the closest set to what this page covers.
Common questions
What flow rate is too high for a nasal cannula?
Above 6 L/min a standard nasal cannula stops delivering a meaningfully higher FiO2 and instead dries and irritates the nasal mucosa. If a patient needs more oxygen than a cannula at 6 L/min provides, the correct response is to switch devices, such as to a Venturi or non-rebreather mask, not to keep increasing the cannula flow.
Why is a Venturi mask used instead of a simple face mask?
A Venturi mask delivers a precise, fixed FiO2 regardless of the patient's breathing pattern, using colour-coded adaptors. This matters most in COPD, where too much oxygen can blunt the hypoxic drive to breathe and a controlled, predictable FiO2 is safer than the variable delivery of a simple mask.
What is the target SpO2 for a patient with COPD?
Most guidelines set 88-92% for patients at risk of hypercapnic respiratory failure, compared with 94-98% for the general adult population. The lower target avoids over-oxygenation, which can suppress respiratory drive and raise PaCO2 in chronic retainers.
How do you recognise oxygen toxicity in a patient on high-flow oxygen?
Early signs are substernal chest pain, a dry non-productive cough, and progressive shortness of breath, typically after more than 24 hours at high FiO2. The nursing response is to notify the provider and use the lowest FiO2 that still meets the target saturation, since prevention through titration is the main defence.
Do you need a humidifier for all oxygen therapy?
Low flows through a nasal cannula, generally 4 L/min or less, don't usually need humidification for short-term use. Higher flows, longer duration of therapy, or any tracheostomy or artificial airway delivery should be humidified, since dry gas at volume rapidly dries and irritates the airway mucosa.