Reproducibility of Whole‐Body Cooling Response Using Laser Doppler Flowmetry

Abstract

Laser Doppler Flowmetry (LDF) has been used as a non‐invasive tool to measure cutaneous microvascular function. While previous studies have assessed reproducibility with perturbations that increase skin blood flow, it is unclear as to the reproducibility of the whole body cooling response. We hypothesized that the reflex vasoconstriction response to whole‐body cooling would be reproducible. Eight healthy, young adults participated in two cooling bouts, each separated by 48 hours to one 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 min period. The final Tsk was maintained for an additional ten minutes. Mean Tsk was calculated as the unweighted average temperature of the calf, thigh, abdomen, upper chest, back, and upper arm. LDF flux was measured at the ventral forearm and cutaneous vascular conductance (CVC) was calculated at each 0.5°C reduction in skin temperature, CVC = flux/MAP and expressed as percent changes from baseline (%ΔCVC). The coefficient of variation (CV) for each 0.5°C reduction in skin temperature were determined (33.5°C = 44.3, 33.0°C = 27.9). The data indicate poor reproducibility at the onset of cooling. Reproducibility steadily improved with lower skin temperature ranging from moderate at 32.5°C to 30.5°C to good at the cooling plateau. The data suggest that skin blood flow measurements collected at colder skin temperatures are reproducible and may be used as a longitudinal indicator of microvasculature function.Support or Funding InformationThis study received funding from the Wilderness Medical Society Hackett‐Auerbach Grant, supported by the Academy of Wilderness Medicine(r).