Motion artefact reduction for reflection-mode photoplethysmography

Butler, Matthew J. (2018) Motion artefact reduction for reflection-mode photoplethysmography. PhD thesis, University of Nottingham.

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Photoplethysmography (PPG) is a technique that uses light to measure the local changes in blood-volume in subjects (predominantly humans). Multiple useful statistics can be gained from such a measurement; heart-rate and it's variability, blood-oxygen saturation and even an estimation of blood pressure, to name but a few. Compared to other measurement techniques, photoplethysmography is favourable as it is both non-invasive, since nothing physical penetrates the subjects skin, and safe, as the subject is galvanically isolated from the test equipment (additional benefits also exist).

Motion artefacts (errors in the measured signal caused by physical movement) are the largest source of error when photoplethysmographic measurements are made, and with the majority of applications involving some form of movement, a motion-tolerant PPG extraction technique would allow for more precise recordings/research/diagnosis etc. This thesis presents the development of an improved photoplethysmography technique that has increased resilience to motion.

The developed technique uses multiple PPG measurements at different locations to reconstruct a single PPG signal. It is shown that despite the signals being taken in close proximity to each other (less than 3 cm separation between the farthest elements), the variation in the signals gives sufficient redundancy to extract the uncorrupted PPG to a much higher accuracy using Independent Component Analysis, achieving in the worst case, a 78% reduction in the calculated artefact presence (using quality calculating functions, also presented).

As the vast majority of existing PPG systems use a single sensing element, it is hypothesised that such systems cannot be used to accurately and continuously detect the PPG for most motion types and severities. A working prototype of the developed system is demonstrated and directly compared to a single-channel system, showing its effectiveness.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Hayes-Gill, Barrie
Crowe, John
Keywords: Photoplethysmography; Motion; Artefact; Heartrate
Subjects: R Medicine > R Medicine (General) > R855 Medical technology. Biomedical engineering. Electronics
Faculties/Schools: UK Campuses > Faculty of Engineering
Item ID: 52390
Depositing User: Butler, Matthew
Date Deposited: 13 Jul 2018 04:41
Last Modified: 08 May 2020 08:18

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