This is a UKMLA-centred article about prescribing and administering oxygen.

Introduction

Oxygen therapy plays a crucial role in the management of various medical conditions. It is one of the most commonly prescribed medications, therefore understanding the principles of prescribing and administering oxygen is essential to ensure optimal patient outcomes.

Prescribing Oxygen

Assessment: taking an ABCDE approach, measure the patient’s oxygen saturation (SpO2) using pulse oximetry. Assess the patient’s respiratory rate, signs of respiratory distress and overall clinical status. Going forwards, an arterial blood gas may be needed. 

If the patient is not breathing, call for help and commence resuscitation. This would involve inserting airway adjuncts and applying high-flow oxygen (15L/min) via a bag-valve-mask ventilation. If not controlled senior review is advised and consideration of non-invasive ventilation.

Target oxygen saturation: determine the saturation range based on the patient’s condition. Common targets include 94-98%, and a target of 88-92% on any patient at risk of CO2 retention. If a patient is in type 2 respiratory failure e.g. COPD patients, a target saturation range of 88-92% is normally used. Higher oxygen saturations in this population are associated with hypercapnia and acidosis leading to death.

Prescription: since oxygen is a drug, it must be prescribed on a drug chart. The prescriber would need to specify the target oxygen saturations, the indication for oxygen therapy, the delivery method and oxygen flow rate.

Documentation: document the rationale for oxygen therapy, prescribed flow rates, and the patient’s response in the medical records.

Types of Oxygen Delivery Devices

Nasal Cannula

Indication

• Provides a low concentration of oxygen. Suitable for patients with mild hypoxaemia.

Dose

• The maximum flow rate is 6l/min although do not exceed 4L/min due to nasal irritation.

Venturi Mask

Indication

• Allows precise control of oxygen concentration. Ideal for patients with specific oxygenation requirements e.g. in COPD patients who need to maintain specific saturations of 88-92%.

Dose

• BLUE = 2-4L/min 

• WHITE = 4-6L/min 

• YELLOW = 8-10L/min 

• RED = 10-12L/min 

• GREEN = 12-15L/min 60% O2

Simple Face Mask

Indication

• Delivers higher oxygen concentrations than nasal cannulas. Useful for patients requiring moderate oxygen supplementation.

Dose

• Delivers oxygen between 5-10L/min

Non-Rebreather Mask

Indication

• Provides the highest concentration of oxygen among masks. Used in emergencies for patients with severe hypoxaemia.

The reservoir bag is filled with oxygen which the patient inhales and a one-way valve prevents exhaled air from entering the reservoir bag.

Dose

• Delivers up to 15L/min

Monitoring

For a patient who has just been initiated on oxygen, it is advisable to monitor oxygen hourly until they stabilise.

Patient specific monitoring thereafter remains dependent on the National Early Warning Score (NEWS). A higher frequency of observations is needed if NEWS increases.

Weaning and Discontinuing Oxygen

Weaning down oxygen should only be commenced once the patient has been stabilised at their target oxygen saturations for 4-6 hours consecutively. If the patient is on a specific flow rate, consider gradually reducing the oxygen flow in small increments while closely monitoring the patient’s response. If the patient requires de-escalation by changing delivery method, this can be done by stepping down devices dependent on their maximum flow rates.

For example, if using a nasal cannulae, reduce the flow rate by 0.5-1L per minute every 15-30 minutes, assessing the patient’s oxygen saturation and respiratory status at each step.

Once the patient is stable on 1-2L/min via nasal cannulae, you can cease oxygen completely. Monitor the patient’s oxygen saturation for 10 minutes, if they remain within target saturations, measure their saturations at 1 hour and then re-assess.

Complications

While oxygen therapy is generally safe, caution should be taken with the subject of oxygen toxicity. Prolonged exposure to high concentrations of oxygen may lead to lung damage.

Additionally, awareness of dry or irritated mucous membranes and infection control is important, which can be tackled through following device specific flow rates and adhering to strict infection control practices.

Conclusion

Prescribing and administering oxygen is a fundamental aspect of patient care in various clinical settings. Healthcare professionals must tailor oxygen therapy to individual patient needs, closely monitor their response and be vigilant to possible complications.

References
 
1. https://bmjopenquality.bmj.com/content/7/4/e000371

2. https://healthandwillness.org/oxygen-deliverydevices-and-flow-rates/

3. https://rc.rcjournal.com/content/64/10/1293

4. https://bnf.nice.org.uk/treatment-summaries/oxygen/

Author – Mohona Sengupta 

Editor – James Mackintosh

Last updated 18/12/23