Humphreys, Kenneth and Ward, Tomas E. and Markham, Charles (2007) Noncontact simultaneous dual wavelength photoplethysmography: a further step toward noncontact pulse oximetry. The Review of Scientific Instruments, 78 (4).

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Abstract

We present a camera-based device capable of capturing two photoplethysmographic (PPG) signals at two different wavelengths simultaneously, in a remote noncontact manner. The system comprises a complementary metal-oxide semiconductor camera and dual wavelength array of light emitting diodes (760 and 880 nm). By alternately illuminating a region of tissue with each wavelength of light, and detecting the backscattered photons with the camera at a rate of 16 frames/wavelength s, two multiplexed PPG wave forms are simultaneously captured. This process is the basis of pulse oximetry, and we describe how, with the inclusion of a calibration procedure, this system could be used as a noncontact pulse oximeter to measure arterial oxygen saturation (S(p)O(2)) remotely. Results from an experiment on ten subjects, exhibiting normal S(p)O(2) readings, that demonstrate the instrument's ability to capture signals from a range of subjects under realistic lighting and environmental conditions are presented. We compare the signals captured by the noncontact system to a conventional PPG signal captured concurrently from a finger, and show by means of a J. Bland and D. Altman [Lancet 327, 307 (1986); Statistician 32, 307 (1983)] test, the noncontact device to be comparable to a contact device as a monitor of heart rate. We highlight some considerations that should be made when using camera-based "integrative" sampling methods and demonstrate through simulation, the suitability of the captured PPG signals for application of existing pulse oximetry calibration procedures.

Item Type:	Article
Keywords:	dual wavelength photoplethysmography; noncontact pulse oximetry;
Academic Unit:	Faculty of Science and Engineering > Electronic Engineering
Item ID:	1354
Depositing User:	Dr Tomas Ward
Date Deposited:	12 May 2009 14:30
Journal or Publication Title:	The Review of Scientific Instruments
Publisher:	American Institute of Physics
Refereed:	Yes
URI:
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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