Journal of Applied Physiology, Vol 41, Issue 5 719-726, Copyright © 1976 by American Physiological Society
Effects of lower body negative pressure (LBNP) on the distribution of body fluids
A. Foux, R. Seliktar and A. Valero
Reduction of pressure on the lower part of the human body is believed to be
capable of altering the normal fluid distribution. This could serve as a
therapeutic method for emergency relief of the effects of hypertension, or
it could be used as counterbalance for zero gravity and assist in preparing
astronauts for reentry into the gravitational field. The present work
describes a technique of assessment of the fluid shift caused by such
pressure reduction. Thirty experiments were performed on four healthy
subjects. The shift of fluid was assessed by measuring changes in body
weight distribution of the tested subjects. The shift of fluid was assessed
by measuring changes in body weight distribution of the tested subjects.
The experimental results show that two processes may have taken place
within the human body: shift of blood within the vascular system and
diffusion of fluids from the circulatory system to the tissues. The total
fluid shift ranges between 1 and 2 kg. It was proportional to the pressure
gradient and exponential with time. The systolic blood pressure was reduced
with the pressure reduction while the pulse rate increased.
