AJP - Gastrointestinal and Liver Physiology, Vol 251, Issue 4 446-G452, Copyright © 1986 by American Physiological Society
Quantitative assessment of the two-component model of intestinal circulation
P. R. Kvietys, C. A. Navia, A. J. Premen and D. N. Granger
Recently a two-component model of the intestinal circulation was proposed
to explain the effects of vasodilators on intestinal oxygenation. This
model assumes that the intestine is composed of two regions: one region in
which oxygen uptake is blood flow independent (well perfused and normoxic)
and a second region in which oxygen uptake is blood flow dependent
(under-perfused and hypoxic). The model predicts that total intestinal
oxygen uptake is increased by a vasodilator only if the blood
flow-dependent region is affected. We used a systems analysis approach to
predict the various boundary conditions that must be imposed on the
two-component model for it to simulate experimental observations. The
mathematical model was based on current concepts and available data
regarding intestinal hemodynamics and oxygen exchange. The model
simulations predict that 30-70% of the intestine must be hypoxic (regions
where oxygen uptake is blood flow dependent) for the two-component
hypothesis to adequately explain published observations. Since the
existence of such an extensive hypoxic region seems unlikely for the normal
intestine, the predictive value of the two-component hypothesis may be of
limited value for describing the effects of vasodilators on oxygen uptake
in the normal intestine. However, the two-component model may be useful in
predicting the effects of vasodilators on intestinal oxygen uptake in the
ischemic intestine.
