The effect of varying LED intensity on pulse oximeter accuracy
Abstract
Most pulse oximeters automatically alter the intensity of their light-emitting diodes (LEDs) according to the absorption of the finger, toe or earlobe to which they are attached. This paper investigates the effect of changing LED intensity on pulse oximeter accuracy. Our results show that the peak wavelength of a red LED typically increases by 8 nm as its intensity is increased ten-fold. To determine whether this shift introduces a significant error, a simple theoretical model based on the Beer-Lambert law is used. The model predicts that a 10:1 change in LED intensity results in a 2.5% error at 50% arterial oxygen saturation (SpO2). At high saturations (SpO2 greater than or equal to 85%) the model predicts little loss of accuracy and thus any effect due to changes in LED intensity will be apparent only at low saturations.
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In low saturation conditions, a 10:1 variation in LED intensity can lead to an error of 2.5%.
“Another study to determine the effect of varying LED intensity on pulse oximeter accuracy showed that in low saturation conditions, a 10:1 variation in LED intensity can lead to an error of 2.5% [103].”
From Skin pigmentation influence on pulse oximetry accuracy: a systematic review and bibliometric analysis (2022) · cites this paper as [103]
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- Authors
- De Kock, J. P., Reynolds, K. J., Tarassenko, L., & Moyles, J. T. B.
- Affiliations
- John Radcliffe Hospital (GB)
- University of Oxford (GB)
- Milton Keynes Hospital (GB)
- Venue
- Journal of Medical Engineering & Technology
- Publisher
- Informa UK Limited
- Published
- 1991-01
- Volume
- 15
- Issue
- 3
- Pages
- 111-115
- ISSN
- 0309-1902 (ISSN-L)
- 1464-522X
- OpenAlex
- W2093531986
- Cited by
- 16
- References
- 10
- Citations by year
- 2026: 1 · 2025: 2 · 2023: 2 · 2022: 1 · 2018: 1 · 2012: 1
- FWCI
- 1.28
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Journal of Medical Engineering & Technology (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Physical Sciences › Engineering › Biomedical Engineering › Non-Invasive Vital Sign Monitoring
- Health Sciences › Medicine › Radiology, Nuclear Medicine and Imaging › Optical Imaging and Spectroscopy Techniques
- Physical Sciences › Chemical Engineering › Bioengineering › Analytical Chemistry and Sensors
- Keywords
- pulse oximetry, oxygen saturation measurement, red LED, peak wavelength shift, Beer-Lambert law, measurement error, arterial oxygen saturation
- MeSH terms
- Equipment Design, Hemoglobins, Humans, Hydrogen-Ion Concentration, Models, Theoretical, Oximetry, Oxygen, Predictive Value of Tests, Reference Values
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