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

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 (%ΔCVC_BASELINE).

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%ΔCVC_BASELINE) compared to the Doppler with the deepest penetration (35 ± 0.6%ΔCVC_BASELINE, 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.