Cutaneous microvascular flow in the foot during simulated variable
gravities.
Chang, David S., Gregory A. Breit, Jorma R. Styf, and Alan R. Hargens.
Life Science Division, NASA Ames Research Center, Moffett Field, CA
94035-1000
APStracts 3:0225R, 1996.
Our objective was to understand how weight bearing with varying
gravitational fields affects blood perfusion in the sole of the foot.
Human subjects underwent whole-body tilting at four angles: upright
(1 Gz), 22 (.38 Gz), 10 (.17 Gz), and supine (0 Gz), simulating the
gravitational fields of Earth, Mars, Moon, and microgravity,
respectively. Cutaneous capillary blood flow was monitored on the
plantar surface of the heel by laser Doppler flowmetry while weight
-bearing load was measured. At each tilt angle, subjects increased
weight bearing on one foot in graded load increments of one kilogram
beginning with zero. The weight bearing at which null flow first
occurred was determined as the Closing Load. Subsequently, the weight
bearing was reduced in reverse steps until blood flow returned
(Opening Load). Mean Closing Loads for simulated Earth gravity, Mars
gravity, Moon gravity, and microgravity were 9.1, 4.6, 4.4, and 3.6
kg, respectively. Mean Opening Loads were 7.9, 4.1, 3.5, and 3.1, kg,
respectively. Mean arterial pressures in the foot MAPfoot calculated
for each simulated gravitational field were 192, 127, 106, and 87 mm
Hg, respectively. Closing Load and Opening Load were significantly
correlated with MAPfoot (r = 0.70, 0.72, respectively) and were
significantly different (p < 0.001) from each other. The data suggest
that decreased local arterial pressure in the foot lowers tolerance
to external compression. Consequently, the human foot sole may be
more prone to cutaneous ischemia during load bearing in microgravity
than on Earth.
Received 31 August 1995; accepted in final form 8 April 1996.
APS Manuscript Number R540-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 June 96