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This Guidelines summary consists of selected sections of the British Thoracic Society (BTS) guideline for oxygen use in adults in healthcare and emergency settings. Please refer to the full guideline for the complete set of recommendations.

Which patients need oxygen therapy?

  • Critical illness requiring high levels of supplemental oxygen:
    • cardiac arrest or resuscitation
    • shock, sepsis, major trauma, drowning, anaphylaxis, major pulmonary haemorrhage, status epilepticus
    • major head injury
    • carbon monoxide poisoning
  • Serious illnesses requiring moderate levels of supplemental oxygen if the patient is hypoxaemic:
    • acute hypoxaemia
    • acute asthma, pneumonia, and lung cancer
    • deterioration of lung fibrosis or other interstitial lung disease
    • pneumothorax
    • pleural effusions
    • pulmonary embolism
    • acute heart failure
    • severe anaemia
    • postoperative breathlessness
  • Conditions for which patients should be monitored closely but oxygen therapy is not required unless the patient is hypoxaemic:
    • myocardial infarction and acute coronary syndromes
    • stroke
    • hyperventilation or dysfunctional breathing
    • most poisonings and drug overdoses (see full guideline for carbon monoxide poisoning)
    • poisoning with paraquat or bleomycin
    • metabolic and renal disorders
    • acute and subacute neurological and muscular conditions producing muscle weakness
    • pregnancy and obstetric emergencies 
  • Chronic obstructive pulmonary disease (COPD) and other conditions requiring controlled or low-dose oxygen therapy:
    • COPD and other conditions causing fixed airflow obstruction (for example, bronchiectasis)
    • exacerbation of cystic fibrosis
    • neuromuscular disease, neurological condition and chest wall deformity
    • morbid obesity.

Target oxygen prescription

  • Oxygen should be prescribed to achieve a target saturation of 94–98% for most acutely ill patients, or 88–92% or patient-specific target range for those at risk of hypercapnic respiratory failure.

Clinical and laboratory assessment of hypoxaemia and hypercapnia

  • Fully trained clinicians should assess all acutely ill patients by measuring respiratory rate, pulse rate, blood pressure, and temperature, and assessing circulating blood volume and anaemia. Expert assistance from specialists in intensive care or from other disciplines should be sought at an early stage if patients are thought to have major life-threatening illnesses, and clinicians should be prepared to call for assistance when necessary, including a call for a 999 ambulance in prehospital care or a call for the resuscitation team or intensive care unit outreach team in hospital care
  • Oxygen saturation, ‘the fifth vital sign’, should be checked by trained staff using pulse oximetry in all breathless and acutely ill patients (supplemented by blood gases when necessary), and the inspired oxygen device and flow rate should be recorded on the observation chart with the oximetry result.

Clinical assessment by first responder(s) (GP, nurse, or ambulance staff)

  • Clinical assessment of a breathless patient starts with ‘ABC’ (Airway, Breathing, Circulation)
  • A brief history should be taken from the patient or other informant
  • Initial assessment should include pulse and respiratory rate in all cases
  • Pulse oximetry should always be measured in patients with breathlessness or suspected hypoxaemia
  • Disease-specific measurements should also be recorded (for example, peak expiratory flow in asthma, blood pressure in cardiac disease).

Practical aspects of oxygen use in prehospital and hospital care and use of oxygen alert cards

  • Emergency oxygen should be available in primary care medical centres, preferably using oxygen cylinders with integral high-flow regulators. Alternatively, oxygen cylinders fitted with high-flow regulators (delivering up to 15 l/min) must be used to allow use with reservoir masks
  • Healthcare organisations should take measures to eliminate the risk of oxygen tubing being connected to the incorrect wall oxygen outlet or to outlets that deliver compressed air or other gases instead of oxygen. Air flow meters should be removed from the wall sockets or covered with a designated air outlet cover when not in use. Special care should be taken if twin oxygen outlets are in use.

Assessment and immediate oxygen therapy

  • Chronically hypoxaemic patients with a clinical exacerbation associated with a 3% or greater fall in oxygen saturation on their usual oxygen therapy should usually be assessed in hospital with blood gas estimations. An arterial oxygen tension (PaO2) of less than 7 kPa equates to an arterial oxygen saturation measured by pulse oximetry (SpO2) below ∼85%
  • The initial oxygen therapy to be used in the various clinical situations is given in tables 1–4 of the full guideline
  • If there is a clear history of asthma or heart failure or other treatable illness, appropriate treatment should be instituted in accordance with guidelines or standard management plans for each disease
  • The oxygen saturation should be monitored continuously until the patient is stable or arrives at hospital for a full assessment. The oxygen concentration should be adjusted upwards or downwards to maintain the target saturation range
  • In most emergency situations, oxygen is given to patients immediately without a formal prescription or drug order. The lack of a prescription should never preclude oxygen being given when needed in an emergency situation. However, a subsequent written record must be made of what oxygen therapy has been given to every patient (in a similar manner to the recording of all other emergency treatment)
  • GPs or first responders visiting a patient’s home should carry a portable pulse oximeter to assess hypoxaemia and guide use of oxygen if available, and should call emergency services if hypoxaemia or other serious illness is suspected
  • Those attending patients as an emergency in rural or remote areas should consider carrying a portable oxygen cylinder as part of their emergency equipment. 

Oxygen alert cards for patients with hypercapnic respiratory failure

  • Patients with COPD (and other at-risk conditions) who have had an episode of hypercapnic respiratory failure should be issued with an oxygen alert card and with a 24% or 28% Venturi mask. They should be instructed to show the card to the ambulance crew and emergency department staff in the event of an exacerbation
  • Oxygen alert cards with agreed content can be obtained via the BTS website 
  • The content of the alert card should be specified by the physician in charge of the patient’s care, based on previous blood gas results
  • The primary care team and ambulance service should also be informed by the hospital COPD team that the patient has had an episode of hypercapnic respiratory failure and carries an oxygen alert card. The home address and ideal oxygen concentration or target saturation ranges of these patients can be flagged in the ambulance control systems and information disseminated to ambulance crews when required
  • When possible, out-of-hours services providing emergency primary care services should be informed by the hospital COPD team or by the primary care team that the patient has had an episode of hypercapnic respiratory failure and carries an oxygen alert card. Use of oxygen in these patients will be guided by the instructions on the alert card or by a patient-specific protocol which can be shared by hospital teams, the ambulance service, and the primary care team.

Choice of devices in prehospital care

  • It is recommended that the following delivery devices should be available in prehospital settings where oxygen is administered:
    • high-concentration reservoir mask (non-rebreathe mask) for high-concentration oxygen therapy
    • nasal cannulae (preferably) or a simple face mask for medium-concentration oxygen therapy
    • 28% Venturi mask for patients with definite or likely COPD (patients who have an oxygen alert card may have their own 24% or 28% Venturi mask)
    • tracheostomy masks for patients with tracheostomy or previous laryngectomy.

Oxygen carriage in private vehicles, primary care settings, and patients’ homes

Oxygen carriage in private cars (Health and Safety Executive guidance)

  • When travelling by car, patients have the freedom to carry their own portable oxygen cylinder. Some GPs in rural areas also carry oxygen in their cars. However, it is advised that certain safety precautions should be followed:
    • patients are allowed to carry oxygen cylinders for their own use without putting any labels or signs on their vehicle. This includes public transport, such as buses or taxis. It is an offence to display a hazard diamond if oxygen is not being transported in a vehicle, so it is preferable not to use a hazard triangle on a private vehicle
    • the cylinder should be secure within the car, and cannot move during transport or in the event of an accident
    • patients should inform their car insurance company if oxygen is carried in the car.

Medical centres and primary care practices

  • The majority of medical centres and practices should have a supply of oxygen for emergency use. Generally, cylinders with integral high-flow regulators should be ordered. Otherwise, the cylinder must be fitted with a high-flow regulator capable of delivering a flow of up to 15 l/min in order to deliver medium-concentration and high-concentration oxygen therapy. A recommended list of oxygen delivery devices for use in prehospital care is given above
  • Emergency oxygen should be available in primary care medical centres, preferably using oxygen cylinders with integral high-flow regulators. Alternatively, oxygen cylinders fitted with high-flow regulators (delivering up to 15 l/min) must be used to allow use with reservoir masks.

Emergency use of oxygen in the patient’s home

  • In patients’ homes, oxygen is usually provided for long-term therapy with an oxygen concentrator and an ambulatory supply with lightweight cylinders (or a portable liquid oxygen system). Long-term oxygen therapy is covered in other guidelines
  • In some circumstances, there may be a supply of cylinders for short-term/short-burst therapy or palliative use. The existing home oxygen supply may be used by a patient or GP in an emergency situation before the arrival of an ambulance, using the patient’s existing interface
  • If a GP is attending a patient at home with oxygen, ideally the use of oxygen should be guided by pulse oximetry
  • The existence of any oxygen alert card should be asked for so that the emergency services attending can be aware of the target saturation and oxygen supply titrated accordingly
  • The patient/carers should be made aware of the following health and safety recommendations:
    • all cylinders should be stored on a cylinder trolley or suitably secured so they cannot be knocked over
    • there should be no trailing oxygen tubing
    • a green warning triangle for ‘compressed gas’ should be displayed by the front door (warns emergency services in the event of a fire)
    • the minimum number of cylinders should be stored in the house
    • there should be no smoking in the vicinity of oxygen cylinders
    • cylinders must be checked regularly for obvious signs of leakage
    • cylinders must be kept out of direct sunlight
    • oxygen must not be used near a naked flame or source of heat.


Full guideline:

O’Driscoll B, Howard L, Earis J, et al. BTS guideline for oxygen use in adults in healthcare and emergency settings. Thorax 2017; 72: i1–i90. Available at: brit-thoracic.org.uk/quality-improvement/guidelines/emergency-oxygen

Published date: June 2017 (reviewed December 2019).

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