Prescribing Oxygen

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PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

See also: Inhalers for COPD (including Inhaled Steroids) written for patients

Oxygen therapy is used to treat hypoxia. The concentration of oxygen required depends on the condition being treated. Inappropriate concentrations of oxygen may cause very serious problems for the patient - even death.

NB: this does NOT apply to Scotland and Northern Ireland. Please see further reading below. The method of prescribing home oxygen was changed in February 2006. Details of the changes are available in the EMIS home oxygen order forms (HOOF) wizard.  However, the main changes are[1]:
  • All oxygen therapy is to be supplied by designated contractors.
  • Hospital specialists can directly prescribe oxygen on dedicated HOOF forms and this is the same for both primary and secondary care.
  • Ambulatory oxygen therapy is now available on prescription - previously this was rarely funded by hospitals and had to be purchased privately or obtained through charities.

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There are now five types of home oxygen provision[2]

  • Long-term oxygen therapy (LTOT).
  • Ambulatory - new development with light portable cylinders lasting six hours.
  • Short-burst - via a cylinder.
  • Nocturnal oxygen therapy.
  • Palliative oxygen therapy.

Travel - usually portable cylinders. For holidays in the UK, the usual contractor will make reciprocal arrangements with another contractor to supply oxygen at the holiday destination.

Emergency oxygen - can be supplied within four hours. Enough for three days will be arranged prior to specialist assessment. Out of hours arrangements exist - but the emergency doctor may need to carry a supply of HOOFs to leave with the patient or fax to suppliers. A second HOOF will be required if the patient is to continue oxygen after the emergency period pending assessment.

High-concentration oxygen, up to 60%, is safe in conditions such as pneumonia, pulmonary thromboembolism and fibrosing alveolitis. Low-concentration oxygen (of 24-28%) is used in patients with chronic obstructive pulmonary disease (COPD) or other conditions causing underventilation and CO2 retention. 24-28% oxygen significantly increases haemoglobin saturation, without risking further underventilation and a rising pCO2, which can cause coma and death. Repeated blood gas measurements are required to assess the correct oxygen concentration.

Patients with a resting stable oxygen saturation of ≤92% should be referred for a blood gas assessment in order to assess eligibility for LTOT.

British Thoracic Society guideline

LTOT is indicated for the following conditions (see the guideline for further details of indications):

Chronic hypoxaemia
In patients with chronic hypoxaemia, LTOT should usually be prescribed after appropriate assessment, when the PaO2 is consistently at or below 7.3 kPa (55 mm Hg) when breathing air during a period of clinical stability. Clinical stability is defined as the absence of exacerbation of chronic lung disease for the previous five weeks. The level of PaCO2 (which may be normal or elevated) does not influence the need for LTOT prescription.

In addition, LTOT can be prescribed in chronic hypoxaemia patients when the clinically stable PaO2 is between 7.3kPa and 8kPa, together with the presence of one of the following:
  • Secondary polycythaemia.
  • Clinical and or echocardiographic evidence of pulmonary hypertension.
LTOT should not be prescribed in patients with chronic hypoxaemia with a PaO2 value above 8kPa.

Assessment for LTOT requires referral to a physician with a specialist interest in these disorders. LTOT will normally be used as an adjunct to non-invasive ventilation (NIV) or continuous positive airway pressure (CPAP).

Palliative use
Domiciliary oxygen therapy can be prescribed for palliation of dyspnoea in pulmonary malignancy and other causes of disabling dyspnoea due to terminal disease. One study, however, suggested that opiates are better in controlling dyspnoea in this situation and implied that it may only be effective if hypoxia is demonstrated[3]. This was supported by a large meta-analysis[4].

NIV should be the treatment of choice for patients with chest wall or neuromuscular disease causing type 2 respiratory failure. Additional LTOT may be required in case of hypoxaemia not corrected with NIV.

Nocturnal oxygen therapy (NOT) is not recommended in patients with COPD who have nocturnal hypoxaemia but who fail to meet the criteria for LTOT. Other causes of nocturnal desaturation in COPD should be considered, such as obesity hypoventilation, respiratory muscle weakness or obstructive sleep apnoea (OSA). Patients with OSA, obesity hypoventilation syndrome or overlap syndrome should not have NOT alone ordered. It can be considered in patients with evidence of established ventilatory failure, where it should be given with NIV support.

See also the separate Use of Oxygen Therapy in COPD article.

Smoking and home oxygen

Patients should be made aware of the dangers of continuing to smoke in the presence of home oxygen therapy[2].

Assessment is important because some breathless patients are not hypoxic and hypoxic (even cyanosed) patients are not always breathless. Detailed assessment involving structured exercise testing and blood gas measurements may be needed.

Oxygen cylinders[5]

Oxygen may be supplied under the NHS as oxygen cylinders. Oxygen flow can be adjusted using an oxygen flow meter with 'medium' (2 litres/minute) and 'high' (4 litres/minute) settings.

A concentrator is recommended if oxygen is required for more than eight hours a day (or 21 cylinders per month). Occasionally, if a higher concentration of oxygen is required, the output of two oxygen concentrators can be combined using a 'Y' connection.

A nasal cannula is usually preferred for long-term oxygen therapy from an oxygen concentrator. However, it may cause dermatitis and mucosal drying. Also the concentration of oxygen is not controlled and so nasal cannula may not be appropriate for acute respiratory failure.

When oxygen is given through a nasal cannula at a rate of 1-2 litres/minute, the inspiratory oxygen concentration is usually low; however, it varies with ventilation and can be high if the patient is hypoventilating.

Oxygen concentrators are more economical for patients who require oxygen for long periods and can be ordered on the NHS in England and Wales on a regional tendering basis (contact details are available in the British National Formulary). Arrangements for oxygen supply are different in Scotland and Northern Ireland:[5]

  • In Scotland, patients should be referred for assessment by a respiratory consultant. If the need for a concentrator is confirmed, the consultant will arrange for the provision of a concentrator through the Common Services Agency.
  • In Northern Ireland, oxygen concentrators and cylinders should be prescribed on form HS21. Oxygen concentrators are supplied by a local contractor.
  • In Scotland and Northern Ireland, prescriptions for oxygen cylinders and accessories can be dispensed by pharmacists contracted to provide domiciliary oxygen services.

The type of oxygen service (or combination of services) should be ordered on a HOOF (home oxygen order form). The amount of oxygen required (hours per day) and flow rate should be specified. Special needs or preferences should be specified on the HOOF.

Patients must provide consent for their details to be passed on to the supplier, the fire brigade and any other relevant organisations. The supplier will contact the patient to make arrangements for delivery, installation and maintenance of the equipment. The supplier will also train the patient to use the equipment.

The clinician should send the HOOF to the supplier who will continue to provide the service until a revised HOOF is received or until notified that the patient no longer requires the home oxygen service.

LTOT prolongs survival in COPD if given for at least 15 hours daily to include night time (arterial hypoxaemia is worse at night), to raise oxygen tension above 8 kPa.

Patients should undergo formal assessment for LTOT after a period of stability of at least eight weeks from their last acute exacerbation.

Most patients needing this will also be using LTOT. Housebound patients may benefit from occasional use (eg, up to an hour a day). More active patients on LTOT may benefit from ambulatory oxygen for longer, although few need it for longer than four hours daily. The same flow rate should be used as for LTOT. Further assessment is not essential unless the flow rate needs re-adjusting. The aim is to enable the patient to leave the home to improve quality of life, although expectations should be reasonable. One study of COPD patients found that although the use of ambulatory oxygen enhanced activities, the actual amount of physical activity did not increase[6]. The cost of ambulatory oxygen does not appear to be excessive compared to conventional oxygen cylinder use[7]. Patients not on LTOT but with exercise desaturation (a fall in SaO2 of 4% below 90%) may benefit from ambulatory oxygen to increase exercise capacity. This group needs detailed assessment with walking tests. Ambulatory oxygen should only be prescribed if there is evidence of exercise desaturation and improvement in exercise capacity.

Short-burst therapy (eg, for 10-20 minutes) is indicated to relieve dyspnoea in palliative care or episodic breathlessness, not relieved by other treatments in severe COPD, interstitial lung disease or heart failure. Review annually and repeat assessment in the event of clinical deterioration.

Education should cover diagnosis, use of ambulatory oxygen therapy, principles of treatment, maintenance of portable equipment, servicing arrangements and electricity reimbursement, use of nasal cannulae or masks, requirement for humidifier, contact telephone number and advice on travel. Further education is provided by the engineer at the time of delivery. A family member or carer should attend the education sessions.

NB: the patient should be made aware of the dangers of smoking and fire risk.

People should know that there are a few side-effects of oxygen therapy. These include a dry or bloody nose, skin irritation from the face mask or nasal prongs, tiredness and morning headaches. If these happen, they should be encouraged to let their clinician know, as they may be able to change the prescription to ease the patient's problems.

Used to measure SaO2, this can be a useful guide to spot exercise desaturation (a drop of at least 4% below 90%), to diagnose sleep apnoea and to monitor ambulatory oxygen flow rate (aim to maintain above 90% during exercise).

However, patients potentially requiring LTOT should not be assessed using pulse oximetry alone[2].

See the reference link for details of the BTS guideline for home oxygen for children.

Many children only need oxygen for a limited period. Assessment is different to that of adults, due to difficulty of arterial blood sampling and growth and neuro-developmental considerations. Specific equipment is required to allow for lower oxygen flows.

Almost all children receiving LTOT also require ambulatory oxygen therapy. Many children require LTOT overnight only (less than the 15 hours that forms part of the adult LTOT definition). Provision of oxygen may be necessary at school. All children require supervision from a parent/carer.

Further reading & references

  1. Wedzicha JA, Calverley PM; All change for home oxygen services in England and Wales. Thorax. 2006 Jan;61(1):7-9.
  2. BTS Guidelines for Home Oxygen Use in Adults; British Thoracic Society and BTS Home Oxygen Guideline Group (2015)
  3. Clemens KE, Quednau I, Klaschik E; Use of oxygen and opioids in the palliation of dyspnoea in hypoxic and non-hypoxic palliative care patients: a prospective study. Support Care Cancer. 2009 Apr;17(4):367-77. Epub 2008 Aug 22.
  4. Uronis HE, Currow DC, McCrory DC, et al; Oxygen for relief of dyspnoea in mildly- or non-hypoxaemic patients with cancer: a systematic review and meta-analysis. Br J Cancer. 2008 Jan 29;98(2):294-9. Epub 2008 Jan 8.
  5. British National Formulary; 69th Edition (Mar 2015) British Medical Association and Royal Pharmaceutical Society of Great Britain, London
  6. Sandland CJ, Morgan MD, Singh SJ; Patterns of domestic activity and ambulatory oxygen usage in COPD. Chest. 2008 Oct;134(4):753-60. Epub 2008 Jul 14.
  7. Mapel DW, Robinson SB, Lydick E; A comparison of health-care costs in patients with chronic obstructive pulmonary disease using lightweight portable oxygen systems versus traditional compressed-oxygen systems. Respir Care. 2008 Sep;53(9):1169-75.
  8. Why prescribe short-burst oxygen?; Drug and Therapeutics Bulletin, 2007 Sep;45(9):70-2.
  9. BTS guidelines for home oxygen in children; British Thoracic Society (April 2009)

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Gurvinder Rull
Current Version:
Peer Reviewer:
Prof Cathy Jackson
Document ID:
470 (v7)
Last Checked:
Next Review:

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