Epinephrine-Iontophoresis Attenuates Changes in Skin Blood Flow and Abolishes Cutaneous Contamination of NIR-DCS Estimations of Muscle Perfusion by Miles F Bartlett

Near-infrared diffuse correlation spectroscopy (NIR-DCS) is an optical imaging technique for measuring relative changes in skeletal muscle microvascular perfusion (i.e., fold-change above baseline) during reactive hyperemia testing and exercise and is reported as a blood flow index (BFI). Although it is generally accepted that changes in BFI are primarily driven by changes in muscle perfusion, it is well-known that large, hyperthermia-induced changes in cutaneous blood flow can uncouple this…

Am J Physiol Regul Integr Comp Physiol. 2023 Jan 24. doi: 10.1152/ajpregu.00242.2022. Online ahead of print.

ABSTRACT

Near-infrared diffuse correlation spectroscopy (NIR-DCS) is an optical imaging technique for measuring relative changes in skeletal muscle microvascular perfusion (i.e., fold-change above baseline) during reactive hyperemia testing and exercise and is reported as a blood flow index (BFI). Although it is generally accepted that changes in BFI are primarily driven by changes in muscle perfusion, it is well-known that large, hyperthermia-induced changes in cutaneous blood flow can uncouple this relationship. What remains unknown, is how much of an impact that changes in cutaneous perfusion have on NIR-DCS BFI and estimates of skeletal muscle perfusion under thermoneutral conditions, where changes in cutaneous blood flow are assumed to be relatively low. We therefore used epinephrine-iontophoresis to pharmacologically block changes in cutaneous perfusion throughout a battery of experimental procedures. The data show that: (1) epinephrine-iontophoresis attenuates changes in cutaneous perfusion for up to 4-hours post-treatment, even in the face of significant neural- and local-stimuli, (2) under thermoneutral conditions, cutaneous perfusion does not significantly impact NIR-DCS BFI during reactive hyperemia testing or moderate-intensity exercise, and (3) during passive whole-body heat stress, when cutaneous vasodilation is pronounced, epinephrine-iontophoresis preserves NIR-DCS measures of skeletal muscle BFI during moderate-intensity exercise. Collectively, these data suggest that cutaneous perfusion is unlikely to have a major impact on NIR-DCS estimates of skeletal muscle BFI under thermoneutral conditions, but that epinephrine-iontophoresis can be used to abolish cutaneous contamination of the NIR-DCS BFI signal during studies where skin blood flow may be elevated but skeletal muscle perfusion is of specific interest.

PMID:36693173 | DOI:10.1152/ajpregu.00242.2022

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