Journal of Applied Physiology, Vol 60, Issue 1 133-140, Copyright © 1986 by American Physiological Society
Effects of arterial pressure on lung capillary pressure and edema after microembolism
I. C. Ehrhart, W. M. Granger and W. F. Hofman
The effect of increased arterial pressure (Pa) on microvessel pressure (Pc)
and edema following microvascular obstruction (100-micron glass spheres)
was examined in the isolated ventilated dog lung lobe pump perfused with
blood. Lobar vascular resistance (PVR) increased 2- to 10-fold following
emboli when either Pa or flow was held constant. Microbead obstruction
increased the ratio of precapillary to total PVR from 0.60 +/- 0.05 to 0.84
+/- 0.02 (SE) or to 0.75 +/- 0.06 (n = 6), as determined by the venous
occlusion and the isogravimetric capillary pressure techniques,
respectively. Isogravimetric Pc (5.0 +/- 0.7) did not differ from Pc
obtained by venous occlusion (3.8 +/- 0.2 Torr, n = 6). After embolism, Pc
in constant Pa decreased from 6.2 +/- 0.3 to 4.4 +/- 0.3 Torr (n = 16). In
the constant-flow group, embolism doubled Pa while Pc increased only 40%
(6.7 +/- 0.6 to 9.2 +/- 1.4 Torr, n = 6) with no greater edema formation
than in the constant Pa groups. These data indicate poor transmission of Pa
to filtering capillaries. Microembolism, even when accompanied by elevated
Pa and increased flow velocity of anticoagulated blood of low leukocyte and
platelet counts, caused little edema. Our results suggest that mechanical
effects alone of lung microvascular obstruction cause minimal pulmonary
edema.
