Oxygen Therapy
Oxygen therapy should be used with caution in COPD as if used incorrectly it can cause respiratory depression. The target oxygen saturation range which is measured using pulse oximetry (SpO2) should be 88-92% in COPD (compared to 94-98% normally). There is a risk of fire and explosion and patients should be warned of the danger of smoking while using it.
When is oxygen indicated in COPD?
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If the partial pressure of oxygen in arterial blood (PaO2) < 7.3kPa when stable or PaO2 > 7.3 and <8kPa when stable with either:
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Secondary polycythaemia
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Nocturnal hypoxaemia (oxygen saturation of arterial blood [SaO2] < 90% for 30% or more of the time)
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Peripheral oedema or pulmonary hypertension
Who should be assessed?
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All patients with very severe airflow obstruction (FEV1 < 30% predicted)
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Patients with cyanosis
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Patients with polycythaemia
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Patients with peripheral oedema
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Patients with a raised jugular venous pressure
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Patients with oxygen saturations ≤ 92% breathing air
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Consider if FEV1 30-49% predicted
There are three types of oxygen therapy used:
Long-term oxygen therapy (LTOT)
The benefits of LTOT are only seen if used for at least 15hours/day, with greater benefits seen if used for 20hours/day. Assessment for use should include arterial blood gases on two occasions with at least three weeks in between. The patient should have stable COPD and are receiving optimal medical management. The patient should then be reviewed annually including pulse oximetry.
Ambulatory oxygen therapy (AOT)
This is for patients already using LTOT who would like to use it outside their home. It should be considered in those who struggle while exercising due to oxygen levels dropping as it will improve exercise capacity and dyspnoea with oxygen. This should only be offered after an appropriate assessment of need and is not recommended if PaO2 > 7.3kPa.
The choice of equipment used depends on the hours of use and oxygen flow rate that is required. There is a choice between small light-weight cylinders, portable liquid oxygen systems and oxygen-conserving devices.
Short-burst oxygen therapy (SBOT)
Should be used for episodes of severe breathlessness that is not relieved by other medications. It should then only be continued if an improvement was seen following its use.
Cylinders are used to deliver SBOT.
Oxygen
Side-effects: Can be related to the delivery device (e.g. discomfort due to facemask). A lack of water vapour can cause a dry throat.
Cautions: In COPD a too high oxygen dose can cause respiratory acidosis, depressed consciousness and worsen tissue hypoxia.
Monitoring: The device and flow rate should be adjusted where necessary to keep the SpO2 within range. Arterial blood gas measurements should also be done due to the risk of serious side-effects (described above).
For more information on living with oxygen therapy see the following: https://www.blf.org.uk/support-for-you/oxygen/life-with-oxygen
Bibliography:
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https://www.nice.org.uk/guidance/CG101/chapter/1-Guidance#managing-stable-copd
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The Top 100 Drugs by A. Hitchings, D. Lonsdale, D. Burrage and E. Baker.
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CPPE - Chronic Obstructive Pulmonary Disease Book 1