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Emergency oxygen: guidance and best practice for respiratory patients


Oxygen is a treatment for hypoxaemia, not breathlessness. There is no evidence it can reduce the sensation of breathlessness in patients who are not hypoxaemic.[1]

Although principally lifesaving, in certain circumstances it can be lethal if prescribed and/or administered incorrectly.[2] This article takes a closer look at the guidance and best practice for emergency oxygen.

Administering oxygen

The administration of emergency oxygen is an essential element of appropriate management for a wide range of clinical conditions. However, oxygen is a medicine and requires prescribing in all but the immediate management of critical illness.[3]

Failure to administer oxygen appropriately can be harmful.[2] The safe implementation of oxygen therapy with appropriate monitoring is an integral component of the healthcare professional’s role.

Oxygen is often given by medical, nursing and other healthcare professionals in community and hospital settings. As with any medication, indications and potential contraindications exist and complications may occur.

In acute emergencies high flow oxygen can save lives by preventing severe hypoxaemia.[4] However, excessive oxygen can cause harm in some situations, especially to some vulnerable patients.[5]

Audits of oxygen use and oxygen prescription have also shown consistently poor performance in many countries, with clinicians encountering adverse incidents due to underuse and overuse of oxygen.[5]

Prescribing oxygen therapy

 All nurses, midwives, medical and other healthcare professionals involved in prescribing or administering oxygen should be instructed on the safe use of oxygen therapy.

Oxygen should be prescribed to achieve a target saturation of 94-98% for most acutely unwell patients, or 88-92% or patient-specific target range for those at risk of hypercapnic respiratory failure.[1] The below points are vital in oxygen prescribing:

  • Oxygen should be recorded on the ‘prescription chart’ or ‘drug kardex’ alongside drugs in the ‘prescription-only’ category such as antibiotics.[5]
  • In most emergency situations, an oxygen prescription is not needed, and oxygen should be administered to the patient immediately – with this prescribed and documented later in the patient’s record.[1]
  • Once the target saturation is identified and prescribed, the choice of device – for example, nasal cannula or Venturi mask – and flow rate help to maintain the prescribed oxygen saturation in the target range.[1]
  • The patient’s oxygen saturation and oxygen delivery system should be recorded on the observation chart alongside other physiological variables.[1]
  • Oxygen therapy should be increased if the saturation is below the desired range or decreased if the saturation is above the desired range, and eventually discontinued as the patient recovers. [1]
  • Any sudden fall in oxygen saturation – greater or equal to 3% – should lead to a prompt clinical assessment of the patient.[1]

Oxygen concentrations in critical care patients

All critically ill patients are recommended to have highest feasible oxygen – a reservoir mask at 15 L/min – whilst awaiting immediate medical review. This advice also applies to patients with critical illness who have risk factors for hypercapnia pending the results of blood gas measurements and expert assessment.[1]

 There should be a written record of the oxygen therapy that every patient has had, as well as all other emergency treatment.[1]

Patients with COPD and other risk factors for hypercapnia who develop critical illness should have the same initial target saturations as other critically ill patients, pending the results of blood gas results. After these, patients may need controlled oxygen therapy or supported ventilation if there is severe hypoxaemia and/or hypercapnia with respiratory acidosis.[1]

When nebulised therapy is administered to patients at risk of hypercapnic respiratory failure it should be driven by compressed air.[1] If necessary, supplementary oxygen should be given concurrently by nasal cannula to maintain an oxygen saturation of 88-92%.[1] For asthma patients, nebulisers should be driven by piped oxygen or from an oxygen cylinder fitted with a high flow regulator capable of delivering a flow rate of >6 L/min.[1]

Some patients may need humidification. This can be the case with patients who have a tracheostomy or those who have difficulty in clearing airway secretions.[1]

In the risk of confusing oxygen and medical compressed air, a nebuliser compressor must be used. As per the National Patient Safety Alert, all airflow meters have been removed from clinical areas to prevent misconnection to medical air when oxygen therapy is required.[6]


In conclusion, oxygen therapy must be prescribed using oxygen saturation ranges, signed for by the nurse administering it. It needs constant monitoring to ensure its safe and effective use. Healthcare professionals need to be aware of the choice and benefits of the various delivery devices on initiation, as well as for ongoing management.

Any advice given and opinions expressed in this article are those of the author and do not reflect the view of Chiesi Limited (Chiesi).  All content in this article is for informational and educational purposes only.  Although Chiesi strives to always provide accurate information, it is not responsible for and does not verify for accuracy any of the information contained within.

[1] O’Driscoll BR, Howard LS, Earis J et al. British Thoracic Society Guideline for oxygen use in adults in healthcare and emergency settings. BMJ Open Respiratory Research. 2017;4: e000170

[2] Tees, Esk and Wear Valleys NHS Foundation Trust. Oxygen & other medical gases – administration, prescribing, storage and safety. Available at: https://www.tewv.nhs.uk/content/uploads/2021/12/Oxygen-and-other-medical-gases-Administration-Prescribing-Storage-Safety.pdf

[3] Kane B, Decalmer S, O’Driscoll BR. Emergency oxygen therapy: from guideline to implementation. Breathe. 2013; 9(4): 246-253

[4] Vincent JL. High-flow oxygen cannula: a very effective method to correct severe hypoxemia. J Thorac Dis. 2015;7(8):E207-E208

[5] BTS. Guideline for oxygen use in adults in healthcare and emergency settings. Available at: https://www.brit-thoracic.org.uk/document-library/guidelines/emergency-oxygen/bts-guideline-for-oxygen-use-in-adults-in-healthcare-and-emergency-settings/

[6] NHS England. Eliminating the risk of inadvertent connection to medical air via a flowmeter. Available at: https://www.england.nhs.uk/2021/06/eliminating-the-risk-of-inadvertent-connection-to-medical-air-via-a-flowmeter/

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UK-RES-2300735 June 2023