Journal of Applied Physiology, Vol 72, Issue 2 535-542, Copyright © 1992 by American Physiological Society
Compliance of the main pulmonary artery during the ventilatory cycle
B. J. Grant and B. B. Lieber
Department of Medicine, State University of New York, Buffalo 14215.
Transmural pulmonary arterial pressure (Ppa), diameter (D), and length (L)
of a segment of the main pulmonary artery (MPA) were measured
simultaneously in anesthetized open-chest dogs. The instantaneous volume
was calculated from D and L. Pulmonary arterial elasticity for diameter
(EpD) was calculated as the ratio of the amplitude of Ppa to D oscillation
normalized by the mean D. Similar indexes were calculated for L (EpL) and V
(Epv). Compliance per unit length was calculated from the dimensions and
elasticity of the MPA. Under control conditions with 5 cmH2O positive
end-expiratory pressure, EpD, EpL, and Epv at cardiac frequency were 175
+/- 27, 147 +/- 27, and 55 +/- 7 cmH2O, respectively. EpD increased with
positive end-expiratory pressure, but EpL decreased and Epv was unaffected.
EpD, EpL, Epv, and compliance per unit length were not significantly
different between the start of inspiration and the start of expiration. In
addition, there were no significant phase differences between the
oscillations of Ppa and V at respiratory frequency. We conclude that the
previously reported time variation of pulmonary arterial compliance during
the ventilatory cycle is not due to time-varying properties of the MPA.
