Respiratory and sleep medicine
Pulse oximetry and oxygen therapy
How oximeters work, where SpO2 misleads (carbon monoxide, methaemoglobin, skin pigmentation, poor perfusion), the saturation gap, TSANZ acute oxygen targets and devices, and who qualifies for home oxygen under the TSANZ 2024 guideline.
Tier 2Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- A pulse oximeter estimates arterial oxygen saturation (SpO2) from the ratio of red (660 nm) to infrared (940 nm) light absorbed by the pulsatile signal. Accuracy is about plus or minus 2 to 3% above 70% saturation and worse below that.
- SpO2 tells you nothing about ventilation. A patient on oxygen can have a normal SpO2 and a rising PaCO2.
- TSANZ 2022: target 92 to 96%, or 88 to 92% if at risk of hypercapnia. Too much oxygen harms too.
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Sources
- Barnett A et al. Thoracic Society of Australia and New Zealand position statement on acute oxygen use in adults: 'Swimming between the flags'. Respirology 2022;27:262-76AU/NZThoracic Society of Australia and New Zealand (Respirology), 2022
- McDonald CF et al. Thoracic Society of Australia and New Zealand clinical practice guideline on adult home oxygen therapy. Respirology 2024;29(9):765-84AU/NZThoracic Society of Australia and New Zealand (Respirology), 2024
- Ekström M et al. Long-term oxygen therapy for 24 or 15 hours per day in severe hypoxemia (REDOX). N Engl J Med 2024;391:977-88AU/NZNew England Journal of Medicine, 2024
- Holland AE et al. Ambulatory oxygen for treatment of exertional hypoxaemia in pulmonary fibrosis (PFOX). Lancet Respir Med 2026;14(4):317-26AU/NZThe Lancet Respiratory Medicine, 2026
- Sjoding MW et al. Racial bias in pulse oximetry measurement. N Engl J Med 2020;383:2477-8New England Journal of Medicine, 2020
- BTS Guideline for oxygen use in adults in healthcare and emergency settingsBritish Thoracic Society (Thorax), 2017 (target saturation update in development since 2023)
- Last updated
- 14 November 2026
What changed
- 14 November 2026 Turnstile bot check on sign-in and signed-out feedback