Regional Cutaneous Vasodilator Responses to Rapid Local Heating in Young Women and Men
Authors: McGarr Gregory W. , Saci Samah , Muia Caroline M. , Gemae Mohamed R. , Schmidt Madison D. , Fujii Naoto , Kenny Glen P. 
Published: April 2020

The cutaneous vasodilator response to rapid, non‐painful, local skin heating is commonly used to test microvascular reactivity in health and disease states. The response is characterized by a transient initial vasodilatory peak that is primarily mediated by cutaneous sensory nerves, followed by a sustained plateau phase that is mainly nitric oxide dependent. While this test is most often performed on the forearm due to ease of administration, examining how local neurovascular (initial peak) and endothelium‐dependent (sustained plateau) vasodilator function varies across the body may provide important knowledge underlying regional differences in cutaneous perfusion. Thus, the purpose of this study was to characterize regional cutaneous vasodilator responses to rapid local skin heating in young adults and to determine if sex modulates these responses. In twenty‐nine (14 women) young adults, cutaneous red blood cell flux (AU, arbitrary units) was measured via laser‐Doppler flowmetry on the anterior calf, anterior thigh, abdomen, dorsal forearm, arm, and chest. Participants rested in the supine position for 30 min with skin sites in all regions controlled at 33°C. Following a 10 min baseline period all sites were rapidly heated to 42°C (1°C×20−s) with local heaters and maintained until a stable plateau was achieved (20–30 min). Sites were then heated to 44°C (20–30 min) to achieve maximum vasodilation. Blood pressure was measured manually every 10 min throughout. Cutaneous vasodilator responses were presented as cutaneous vascular conductance (CVC, AU×mmHg−1), normalized to maximum local heating (%CVCmax). Statistical significance was set at P<0.05 and all comparisons are presented as mean differences (95%CI) relative to the forearm. Baseline, initial peak, and plateau responses represent the combined group (n=29) since there were no sex differences across body regions (all P>0.05). At baseline, only responses at the chest (+5.0[2.2,7.8]%CVCmax), thigh (+4.8[1.9,7.6]%CVCmax), and calf (+4.8[1.4,8.2]%CVCmax) differed from the forearm (all P<0.05). For the initial peak, only the arm (+6.5[0.5,12.5]%CVCmax) and abdomen (−10.0[−17.2,−2.8]%CVCmax) differed from the forearm (both P<0.05). During the sustained plateau phase only the abdomen (−13.7[−19.4,−7.9]%CVCmax) and thigh (−6.0[−9.5,−2.4]CVCmax) differed from the forearm (both P<0.05). During maximum local heating, there was a significant sex by region interaction for absolute CVC (P<0.05). No regional differences in maximum responses were found for women, while for men maximum responses were greater at the thigh (−1.3[−2.1,−0.4] AU×mmHg−1) and calf (−1.3[−2.1,−0.5] AU×mmHg−1) relative to the forearm (both P<0.05). Our findings demonstrate that neurovascular (initial peak) and endothelium‐dependent (sustained plateau) cutaneous vasodilator responses to rapid local heating across the body are similar to the forearm, except for the abdomen, which was attenuated. Further, sex does not modulate these responses in young adults.Support or Funding InformationFunding support: Natural Sciences and Engineering Research Council of Canada (held by Dr. Kenny).