title: Reflex control of the cutaneous circulation during passive body core heating in humans.
abstract: 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 < 0.05). Resting CVP was lower during heat stress (6.3 +/- 0.6 vs. 7.7 +/- 0.6 mmHg; P < 0. 05) but fell to similar levels during LBNP as in normothermic conditions. Data analysis indicates an increased capacity, but not sensitivity, of peripheral baroreflex responses during heat stress. Laser-Doppler techniques detected thermoregulatory responses in the skin, but no significant change in CVC occurred during mild-to-moderate LBNP. Interestingly, very high levels of LBNP produced cutaneous vasodilation in some subjects.
authors.affiliation: Children's Hospital, Technical University of Munich, 80804 Munich, Germany.
authors.forename: J K
authors.initials: JK
authors.lastname: Peters
authors.forename: T
authors.initials: T
authors.lastname: Nishiyasu
authors.forename: G W
authors.initials: GW
authors.lastname: Mack
mesh_terms: D000328:Adult; D017704:Baroreflex / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology*; D002496:Central Venous Pressure / Q000502:physiology; D003080:Cold Temperature; D005260:Female; D005542:Forearm / Q000098:blood supply; D006439:Hemodynamics; D006358:Hot Temperature; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D012039:Regional Blood Flow / Q000502:physiology; D012867:Skin / Q000098:blood supply*; D013312:Stress, Physiological / Q000503:physiopathology