Comparison of wearable and bedside laser Doppler flowmetry and fluorescence spectroscopy monitors

Abstract

The recent trend is to minimise many biophotonics technologies and implement them in the format of wearable electronics devices. This includes such technologies as laser Doppler flowmetry (LDF) and fluorescence spectroscopy (FS). Although the first generation of wearable devices equipped with LDF and FS channels have already undergone preliminary studies of microcirculation in patients of different age and health status, there are still no data comparing the principles of acquisition and processing of diagnostic data by these devices with similar parameters of standard bedside monitors, long established in clinical practice. The aim of this work was to evaluate the correlation between diagnostic parameters simultaneously registered by two devices: a newly developed wearable device and a standard bedside fiber-based technique.
Experimental studies were conducted with participation of 14 conditionally healthy volunteers. Two commercially produced devices were used in this study: newly developed wireless wearable LDF and FS monitor “LAZMA-W2” (Aston Medical Technology Ltd., UK; SPE “LAZMA” Ltd, Russia) and bedside monitor “LAZMA-D” (SPE “LAZMA” Ltd., Russia). During the research, the wearable monitor was attached to the subject's wrist and the bedside monitor fiber was placed a few centimeters away. Experimental studies were carried out with subjects in the sitting position with their hands placed on the table. LDF signals were recorded simultaneously by 2 devices for 20 minutes; at the end of each measurement, the value of the fluorescence intensity excited with 365 nm light was also recorded. In order to compare the reproducibility of LDF data, a functional test, brachial artery occlusion for 3 minutes, was used in this study.
The Pearson correlation coefficient was calculated to compare the parameters recorded by the devices. The results of the study revealed a high correlation between the fluorescence registration of the compared devices (r = 0.81, p < 0.05). Since the LDF channels of devices used in this study operate at different wavelengths and have different probing depth and diagnostic volume, our study focused more on comparing the dynamic changes in microcirculation during the occlusion test. The blood flow reserve (BFR, %) parameter, calculated as the increment of microcirculation during reactive postocclusive hyperemia, was found to be highly correlated (r = 0.70, p < 0.05) when measured by two devices.
This work represents the first stage of testing new wearable monitors for laser Doppler flowmetry and fluorescence spectroscopy. In this work, we have shown that the compared bedside and wearable monitors exhibit a high correlation of recorded data. Additional studies to analyze the inter-day reproducibility of both baseline signals and various functional tests are required. It is also necessary to take into account the inter-site variability of the LDF signal and conduct experiments in different areas of interest.
VD kindly acknowledges personal support from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 839888. YL acknowledges support from the research project No. 20-08-01153 (Russian Foundation for Basic Research). AD acknowledges support from the research project No. 19-29-14194 (Russian Foundation for Basic Research).

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Elena Zharkikh
Research & Development Center of Biomedical Photonics, Orel State University, Orel
Russian Federation

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