Maximal skin vascular conductance in subjects aged 5 to 85.
Martin, Heidi L., Joseph L. Loomis, and W. Larry Kenney.
Noll Physiological Research Center and The Department of Exercise
and Sport Science, The Pennsylvania State University, University
Park, Pennsylvania 16802
APStracts 2:0098A, 1995.
Prolonged local heating of the skin at 42 C elicits complete
relaxation of the cutaneous vascular smooth muscle and thus maximal
vascular conductance (minimal resistance). This study examined
maximal forearm skin vascular conductance (FVCmax) as a function of
age in 74 healthy male and female subjects ranging in age from 5 to
85 years. We also investigated the relative influence of age vs other
characteristics (gender, blood pressure, level of regular physical
activity, adiposity, and body surface area) on FVCmax. Subjects sat
in a 24+/-1 C climatic chamber with their left forearm suspended in a
plexiglass cylinder. Uniform forearm surface heating was achieved by
spraying a fine mist of water from 12 sprays located within the
cylinder and inlet water temperature was adjusted to uniformly clamp
the skin of the forearm at 42 C. Forearm blood flow (FBF) was
measured 6-10 times over a 2-min period at baseline (no heating) and
every 15 min thereafter by venous occlusion plethysmography using a
Hg-in-Silastic strain gauge. After 60 min of heating, a reactive
hyperemia maneuver was performed to verify that forearm skin blood
flow was maximal, using laser Doppler flowmetry to isolate the skin
component of the FBF response. The maximal FBF of each subject was
then divided by mean arterial pressure and multiplied by 100 to yield
FVCmax (ml.100ml-1.min-1.100mm Hg-1). The model which best fit the
data was curvilinear, and described by: FVCmax = 13.1 + 86.9 (age
-0.75) (r2 = 0.52, p < 0.001). Excluding subjects younger than 18
years of age simplified the model to a linear fit with a slope of
-0.16 conductance units.year-1 for adults. Interindividual variability
remained constant across the entire age span. Once the age effect was
considered, there were no significant effects of gender, adiposity,
resting blood pressure, physical activity level, or body surface area
on FVCmax.
Received 20 October 1994; accepted in final form 7 March 1995.
APS Manuscript Number A1080-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.