Journal of Applied Physiology, Vol 58, Issue 2 506-513, Copyright © 1985 by American Physiological Society
Influence of G-suit abdominal bladder inflation on gas exchange during +GZ stress
H. I. Modell, P. Beeman and J. Mendenhall
Available data relating duration of +GZ stress to blood gas exchange status
is limited. Furthermore, studies focusing on pulmonary gas exchange during
+GZ stress when abdominal restriction is imposed have yielded conflicting
results. To examine the time course of blood gas changes occurring during
exposure to +GZ stress in dogs and the influence of G-suit abdominal
bladder inflation on this time course, seven spontaneously breathing
pentobarbital-anesthetized adult mongrel dogs were exposed to 60 s of up to
+5 GZ stress with and without G-suit abdominal bladder inflation. Arterial
and mixed venous blood were sampled for blood gas analysis during the first
and last 20 s of the exposure and at 3 min postexposure. Little change in
blood gas status was seen at +3 GZ regardless of G-suit status. However,
with G-suit inflation, arterial PO2 fell by a mean of 14.7 Torr during the
first 20 s at +4 Gz (P less than 0.01, t test) and 20.6 Torr at +5 GZ (P
less than 0.01). It continued to fall an additional 10 Torr during the next
40 s at both +4 and +5 GZ. Arterial PO2 was still 5-10 Torr below control
values (P less than 0.05) 3 min postexposure. A second series of
experiments paralleling the first focused on blood gas status during
repeated exposure to acceleration. Blood gas status was assessed in five
dogs during the late 20 s of two 60-s exposures separated by 3 min at 0 GZ.
No significant differences between the initial and repeated exposures were
detected. The data indicate that G-suit abdominal bladder inflation
promotes increased venous admixture.
