Effects of Contact Pressure in Reflectance Photoplethysmography in an In Vitro Tissue-Vessel Phantom

With the continued development and rapid growth of wearable technologies, PPG has become increasingly common in everyday consumer devices such as smartphones and watches. There is, however, minimal knowledge on the effect of the contact pressure exerted by the sensor device on the PPG signal and how...

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Bibliographic Details
Published in:Sensors (Basel, Switzerland) Switzerland), 2021-12, Vol.21 (24), p.8421
Main Authors: May, James M, Mejía-Mejía, Elisa, Nomoni, Michelle, Budidha, Karthik, Choi, Changmok, Kyriacou, Panicos A
Format: Article
Language:English
Subjects:
artificial blood vessels
Artificial tissues
Blood pressure
Contact pressure
Heart Rate
Hypertension
Investigations
Laboratories
Light
Measurement techniques
Morphology
Nervous system
Oxygen Saturation
Phantoms, Imaging
Photoplethysmography
photoplethysmography (PPG)
Physiology
PPG features
Pressure effects
Reflectance
Sensors
Signal to noise ratio
Statistical analysis
tissue phantoms
Veins & arteries
Wearable computers
Wearable Electronic Devices
Wearable technology
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Summary:With the continued development and rapid growth of wearable technologies, PPG has become increasingly common in everyday consumer devices such as smartphones and watches. There is, however, minimal knowledge on the effect of the contact pressure exerted by the sensor device on the PPG signal and how it might affect its morphology and the parameters being calculated. This study explores a controlled in vitro study to investigate the effect of continually applied contact pressure on PPG signals (signal-to-noise ratio (SNR) and 17 morphological PPG features) from an artificial tissue-vessel phantom across a range of simulated blood pressure values. This experiment confirmed that for reflectance PPG signal measurements for a given anatomical model, there exists an optimum sensor contact pressure (between 35.1 mmHg and 48.1 mmHg). Statistical analysis shows that temporal morphological features are less affected by contact pressure, lending credit to the hypothesis that for some physiological parameters, such as heart rate and respiration rate, the contact pressure of the sensor is of little significance, whereas the amplitude and geometric features can show significant change, and care must be taken when using morphological analysis for parameters such as SpO2 and assessing autonomic responses.
ISSN:1424-8220
1424-8220
DOI:10.3390/s21248421