The effect of varying LED intensity on pulse oximeter accuracy

J. P. De Kock, K. J. Reynolds, L. Tarassenko, J. T.B. Moyles

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)


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 ≥ 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.

Original languageEnglish
Pages (from-to)111-115
Number of pages5
JournalJournal of Medical Engineering and Technology
Issue number3
Publication statusPublished - 1 Jan 1991
Externally publishedYes


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