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Novel Noninvasive Assessment of Microvascular Structure and Function in Humans

Smith, Kurt J.1,2; Argarini, Raden1,3; Carter, Howard H.1; Quirk, Bryden C.4,5; Haynes, Andrew1; Naylor, Louise H.1; McKirdy, Hamish1; Kirk, Rodney W.4,5; McLaughlin, Robert A.4,5,6; Green, Daniel J.1

Medicine & Science in Sports & Exercise: January 24, 2019 - Volume Publish Ahead of Print - Issue - p
doi: 10.1249/MSS.0000000000001898
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Introduction Optical coherence tomography (OCT) is a novel high-resolution imaging technique capable of visualising in vivo structures at a resolution of ~10 μm. We have developed specialised OCT-based approaches that quantify diameter, speed and flow rate in human cutaneous microvessels. In this study we hypothesized that OCT-based microvascular assessments would possess comparable levels of reliability when compared to those derived using conventional laser Doppler flowmetry (LDF).

Methods Speckle decorrelation images (OCT) and red blood cell flux (LDF) measures were collected from adjacent forearm skin locations on two days (48 hours apart), at baseline and following a 30-minute rapid local heating protocol (30C–44C) in 8 healthy young individuals. OCT post-processing quantified cutaneous microvascular diameter, speed, flow rate and density (vessel recruitment) within a region of interest and data were compared between days.

Results Forearm skin LDF (13±4 to 182±31 AU, p<0.05), and OCT-derived diameter (41.8±6.6 vs 64.5±6.9μm), speed (68.4±9.5 vs 89.0±7.3μm.s-1), flow rate (145.0±60.6 vs 485±132pL.s-1) and density (9.9±4.9 vs 45.4±5.9%) increased in response to local heating. The average OCT-derived microvascular flow response (pL.s-1) to heating (234% increase) was lower (p<0.05) than the LDF derived change (AU) (1360% increase). Pearson correlation was significant for between-day local heating responses in terms of OCT flow (r=0.93, p<0.01), but not LDF (P=0.49). Bland-Altman analysis revealed that between-day baseline OCT derived flow rates were less variable than LDF-derived flux.

Conclusions Our findings indicate that OCT, which directly visualizes human microvessels, not only allows microvascular quantification of diameter, speed, flow rate and vessel recruitment, but also provides outputs that are highly reproducible. OCT is a promising novel approach that enables comprehensive assessment of cutaneous microvascular structure and function in humans.

1Cardiovascular Research Group, School of Human Sciences (Exercise and Sport Science), The University of Western Australia, Perth, Australia;

2School of Kinesiology, Faculty of Health and Behavioural Science, Lakehead University, Thunderbay, Ontario, Canada;

3Airlangga University, Department of Physiology, Faculty of Medicine, Indonesia;

4Australian Research Council Centre of Excellence for Nanoscale Biophotonics, Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, Australia;

5Institute for Photonics and Advanced Sensing, University of Adelaide, Adelaide, Australia;

6School of Electrical, Electronic and Computer Engineering, The University of Western Australia, Perth, Australia

Corresponding Author: Winthrop Professor Daniel J. Green. danny.green@uwa.edu.au. +61 8 6488 2361. School of Human Sciences (Exercise and Sport Science) M408, 35 Stirling Highway, Nedlands, 6000, The University of Western Australia

Authors contributed equally to this work (Kurt J. Smith and Raden Argarini)

Source of Funding: This work was supported by The Australian Research Council (DP160104175, CE140100003) and a Premier's Research and Industry Fund grant provided by the South Australian Government Department for Industry and Skills. Disclosures: R. McLaughlin, B. Quirk and R. Kirk are co-founders and Directors of Miniprobes Pty Ltd, a company that develops novel optical imaging systems. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation, and statement that results of the present study do not constitute endorsement by ACSM.

Accepted for publication: 3 January 2019.

© 2019 American College of Sports Medicine