Laser speckle contrast imaging and laser Doppler flowmetry reproducibly assess reflex cutaneous vasoconstriction.

Abstract

Reproducibility of the reflex cutaneous vasoconstriction response is currently unknown. Our aim was to determine the test-retest reproducibility of laser speckle contrast imaging (LSCI) and varying sampling depths of laser Doppler flowmetry (LDF) in response to whole-body cooling. Over two studies, nine and fourteen healthy, young adults underwent a 40-min cooling bout over two separate experiments. Participants were cooled from 34.0°C to 30.5°C and held at a 30.5°C plateau for 10-min prior to rewarming. Throughout the cooling bout, changes in blood flow were measured as LSCI flux and LDF flux for Study 1 and LDF flux by three different LDF sampling depths in Study 2. Test-retest reproducibility and reliability were evaluated by the coefficient of variation (CV) and intraclass correlation coefficients (ICC), respectively. Vasoconstriction was presented as cutaneous vascular conductance (CVC=flux/mean arterial pressure) and expressed as a percent change from baseline (%ΔCVCBASELINE). For Study 1, test-retest reproducibility displayed good reproducibility for LSCI (CV: <9.0%) and good-to-moderate for LDF (CV: <17.0%) throughout the cooling bout and at plateau (LSCI CV: 1.0%; LDF CV: 1.9%). For Study 2, all Doppler depths displayed good reproducibility during the cooling bout (CV: <9.0%) and at plateau (CV: 0.9-2.0%). Only LSCI demonstrated reliability across both studies (ICC: 0.58-0.88). A reduced vasoconstriction response was measured with the shallowest penetration in the skin (LSCI: 26±0.9%ΔCVCBASELINE) compared to the Doppler with the deepest penetration (35±0.6%ΔCVCBASELINE, p<0.001). Although Dopplers better discriminate the reflex cutaneous vasoconstriction response, LSCI exhibits greater test-retest reproducibility and reliability, and thus may be more suitable for longitudinal assessments.