Reflex control of the cutaneous circulation during passive body core heating in humans

1 Children's Hospital, Technical University of Munich, 80804 Munich, Germany; and 2 John B. Pierce Laboratory and Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut 06519 The impact of body core heating on the interaction between the cutaneous and central circulation during blood pressure challenges was examined in eight adults. Subjects were exposed to 10 to 90 mmHg lower body negative pressure (LBNP) in thermoneutral conditions and 10 to 60 mmHg LBNP during heat stress. We measured forearm vascular conductance (FVC; ml · min 1 · 100 ml 1 · mmHg 1 ) by plethysmography; cutaneous vascular conductance (CVC) by laser-Doppler techniques; and central venous pressure, arterial blood pressure, and cardiac output by impedance cardiography. Heat stress increased FVC from 5.7 ± 0.9 to 18.8 ± 1.3 conductance units (CU) and CVC from 0.21 ± 0.07 to 1.02 ± 0.20 CU. The FVC-CVP relationship was linear over the entire range of LBNP and was shifted upward during heat stress with a slope increase from 0.46 ± 0.10 to 1.57 ± 0.3 CU/mmHg CVP ( P