Journal of Applied Physiology, Vol 54, Issue 2 445-452, Copyright © 1983 by American Physiological Society
Dynamic response of local pulmonary blood flow to alveolar gas tensions: analysis
B. J. Grant and A. M. Schneider
It has been reported that left lower lobe pulmonary blood flow (Q) and
alveolar CO2 decrease then oscillate in a progressively damped manner when
the lobar inspirate is changed from pure O2 to N2. This damped oscillatory
response of lobar Q is abolished by maintaining lobar CO2 constant. We set
out to develop the simplest mathematical model that can simulate these
experimental results by using techniques derived from control theory.
Different models were tested. The simplest model that predicts the
experimental data incorporates an exponential decrease of lobar Q to local
alveolar hypoxia (time constant 3 min) and a damped oscillatory response of
lobar Q to local alveolar hypocapnia. The response to hypocapnia has two
components: a vasodilator effect possibly related to intracellular [H+] and
a vasoconstrictor effect possibly related to changes of molar CO2. Both
these components (time constants of 4.8 min) interact with each other by
cross-coupled elements (time constants of 4.8 min). This model can be used
to forecast results so that its validity can be tested by experiment.
