Laser Speckle Contrast Imaging and Laser Doppler Flowmetry Exhibit Test‐Retest Reproducibility During the Reflex Cutaneous Vasoconstriction Response

Abstract

Laser Doppler Flowmetry (LDF) has been extensively used to measure the cutaneous vasoconstriction response to whole-body cold exposure. Laser speckle contrast imaging (LSCI) provides a full-field microvascular measurement and may be a more reproducible method of assessment. However, reproducibility using either technique to assess reflex vasoconstriction has not been determined. We hypothesized that LSCI will have greater test-retest reproducibility than LDF when measuring the skin blood flow response during whole-body cooling. Nine healthy young adults participated in two cooling bouts, each separated by 48 hours to 1 week. Participants donned a whole-body suit and were cooled from a baseline skin temperature (Tsk) of 34°C to 30.5°C over a 30-minute period. Tsk of 30.5°C was maintained for an additional 10-min prior to rewarming. LDF flux and LSCI flux were measured on the dominant and non-dominant ventral forearm, respectively. Cutaneous vascular conductance (CVC) was calculated as CVC = flux/MAP at each 0.5°C reduction in Tsk and at the end of the plateau period and expressed as percent change from baseline (%ΔCVCBASELINE). Reproducibility was assessed using coefficient of variation (CV) for inter-day and intra-day analysis between visits and methods, respectively. The vasoconstriction response reached a plateau of 26±0.9% for LSCI and 32±1.0% for LDF (p<0.001). 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%). Intra-day analysis showed similar reproducibility for visit 1 (CV=14.5%) compared to visit 2 (CV=14.3%) at plateau. Although both methods provide a reproducible assessment, these data indicate that LSCI has greater test-retest reproducibility compared to LDF. This suggests that LSCI may be a preferable method for longitudinal assessment of the reflex cutaneous vasoconstriction response.