Dew-point hygrometry system for measurement of evaporative water
loss in infants.
Ariagno, Ronald L., Steven F. Glotzbach[acute]a, Roger B. Baldwin,
David M. Rector, Susan M. Bowley[tilde]n, and Robert J. Moffat.
Department of Pediatrics, Stanford University, School of Medicine,
Stanford, CA 94305-5119, Program in Human Biology, Stanford
University, Stanford, CA 94305-2160, Brain Research Institute,
Universty of California at Los Angeles, Los Angeles, CA, 90095, NASA
Ames Research Center, Moffett Field, CA, 94035-1000, Department of
Mechanical Engineering, Stanford University, Stanford, CA 94305
-3030
APStracts 3:0506A, 1996.
Evaporation of water from the skin is an important mechanism in
thermal homeostasis. Resistance hygrometry, in which the water vapor
pressure gradient above the skin surface is calculated, has been the
measurement method of choice in the majority of pediatric
investigations. However, resistance hygrometry is influenced by
changes in ambient conditions such as relative humidity, surface
temperature, and convection currents. We have developed a ventilated
capsule method that minimized these potential sources of measurement
error and that allowed second-by-second, long-term, continuous
measurements of evaporative water loss in sleeping infants. Air with
a controlled reference humidity (dew-point temperature = 0[acute]iC)
is delivered to a small, light weight skin capsule and mixed with the
vapor on the surface of the skin. The dew-point of the resulting
mixture is measured using a chilled mirror dew-point hygrometer. The
system indicates leaks, is mobile, and is accurate within 2% as
determined by gravimetric calibration. Examples from a recording of a
13 week old full-term infant using the system give evaporative water
loss rates of approximately 0.02 mgH2O/cm2/min for normothermic
baseline conditions and values up to 0.4 mgH2O/cm2/min when the
subject was being warmed. The system is effective for clinical
investigations which require dynamic measurements of water loss.
Received 15 November 1995; accepted in final form 28 October
1996.
APS Manuscript Number A1198-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996