Towards skin tissue oxygen monitoring: An investigation of optimal visible spectral range and minimal spectral resolution

Abstract

This paper investigated the minimum spectral resolution and optimal spectra range for optical monitoring of skin blood oxygen saturation (StO2). For this purpose, this study recruited fourteen Asian volunteers for demonstration work. The performed measurements included reflectance information collected from the recruits during at rest and after a pressure of 140 mmHg was applied on their upper right arm. The prediction of the required value was via analysis of data of the considered visible ranges of 500-660 nm, 520-645 nm, 520-600 nm, and 530-570 nm, with sampling resolutions of 1 nm, 2 nm, 5 nm, and 10 nm. The offline data analysis using Extended Modified Lambert Beer model revealed that the StO2 value predicted using spectral data in the range 530-570 nm showed considerable similarity with that obtained from 520-645 nm range at spectral resolutions of up to 5 nm. The mean and standard deviation of the differences in the values obtained from these spectral ranges in the case of 5 nm sampling is given by 7 ±8.6 % and 14 ±3.2 % for at rest and blood occlusion experiment, respectively. The higher variability in the value predicted for the latter experiment is likely due to insufficiency of the employed technique to extricate the distinctive features in hemoglobin spectra using the corresponding resolution. The findings of this study may be useful as a guide to facilitate in the design of multispectral imaging system for optical monitoring of one's StO2 with high speed.