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long term oxygen therapy (LTOT)

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  • Long term Oxygen Therapy (LTOT) refers to the provision of oxygen therapy for continuous use at home for patients with chronic hypoxaemia (PaO2 at or below 7.3 kPa, (55mHg))
    • oxygen flow rate must be sufficient to raise the waking oxygen tension above 8 kPa, (60 mmHg)
    • LTOT is likely to be life long
    • LTOT is usually given for at least 15 hours daily, to include night time, in view of the presence of worsening arterial hypoxaemia during sleep
  • indications for LTOT
    • chronic hypoxaemia
      • long term oxygen therapy is indicated for the following conditions with chronic hypoxaemia:
        • chronic obstructive pulmonary disease
        • severe chronic asthma
        • interstitial lung disease
        • cystic fibrosis
        • bronchiectasis
        • pulmonary vascular disease
        • primary pulmonary hypertension
        • pulmonary malignancy
        • chronic heart failure

        • 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 mmHg), when breathing air during a period of clinical stability (defined as the absence of exacerbation of chronic lung disease for the previous five weeks)
          • level of PaCO2 (which may be normal or elevated) does not influence the need for LTOT prescription
          • also, LTOT can be prescribed in chronic hypoxaemia patients when the clinically stable PaO2 is between 7.3 kPa and 8 kPa, 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 patients with a PaO2 value above 8kPa
      • nocturnal hypoventilation
        • obesity Neuromuscular/spinal/chest wall disease*
        • obstructive sleep apnoea (with CPAP therapy)*
        • *assessment for LTOT requires referral to a physician with a specialist interest in these disorders. LTOT will normally be used as an adjunct to ventilatory support techniques (noninvasive 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
  • assessment for long term oxygen therapy in adults
    • patient will require referral to a service directed by a consultant physician with an interest in respiratory medicine for measurement of arterial blood gases and assessment for LTOT prescription


  • smoking and home oxygen
    • smoking cessation techniques should be continued prior to any home oxygen assessment and prescription. Patients should be made aware of the dangers of continuing to smoke in the presence of home oxygen therapy


  1. British Thoracic Society (January 2006). Report on Clinical Component for the Home Oxygen Service in England and Wales.


General Practice Notebook
General Practice Notebook
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