In-ear SpO2: a tool for wearable, unobtrusive monitoring of core blood oxygen saturation
File(s)
Published version
OA Location
Author(s)
Davies, Harry J
Williams, Ian
Peters, Nicholas S
Mandic, Danilo P
Type
Journal Article
Abstract
The non-invasive estimation of blood oxygen saturation (SpO2) by pulse oximetry is of vital importance clinically, from the detection of sleep apnea to the recent ambulatory monitoring of hypoxemia in the delayed post-infective phase of COVID-19. In this proof of concept study, we set out to establish the feasibility of SpO2 measurement from the ear canal as a convenient site for long term monitoring, and perform a comprehensive comparison with the right index finger-the conventional clinical measurement site. During resting blood oxygen saturation estimation, we found a root mean square difference of 1.47% between the two measurement sites, with a mean difference of 0.23% higher SpO2 in the right ear canal. Using breath holds, we observe the known phenomena of time delay between central circulation and peripheral circulation with a mean delay between the ear and finger of 12.4 s across all subjects. Furthermore, we document the lower photoplethysmogram amplitude from the ear canal and suggest ways to mitigate this issue. In conjunction with the well-known robustness to temperature induced vasoconstriction, this makes conclusive evidence for in-ear SpO2 monitoring being both convenient and superior to conventional finger measurement for continuous non-intrusive monitoring in both clinical and everyday-life settings.
Date Issued
2020-08-28
Date Acceptance
2020-08-24
Citation
Sensors (Basel, Switzerland), 2020, 20 (17)
ISSN
1424-8220
Publisher
MDPI AG
Journal / Book Title
Sensors (Basel, Switzerland)
Volume
20
Issue
17
Copyright Statement
©2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC BY) license (http://creativecommons.org/licenses/by/4.0/).
article distributed under the terms and conditions of the Creative Commons Attribution
(CC BY) license (http://creativecommons.org/licenses/by/4.0/).
License URL
Sponsor
Imperial College Healthcare NHS Trust- BRC Funding
Royal Brompton & Harefield NHS Foundation Trust
Imperial College Healthcare NHS Trust- BRC Funding
Imperial Health Charity
British Heart Foundation
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/32872310
PII: s20174879
Grant Number
RDB02 79560
na 79560
RDB02
161744
RE/18/4/34215
Subjects
SpO2
covid-19
hearables
hypoxia
sleep apnea
wearable health
Publication Status
Published
Coverage Spatial
Switzerland
Article Number
ARTN 4879