Journal of Applied Physiology, Vol 65, Issue 4 1634-1641, Copyright © 1988 by American Physiological Society
Erythrocyte deformability and segmental pulmonary vascular resistance: osmolarity and heat treatment
T. S. Hakim
Department of Physiology, McGill University, Montreal, Quebec, Canada.
The site and nature of change in resistance to blood flow in canine left
lung lobe preparation after changes in blood viscosity were assessed by
using the arterial and venous occlusion (AVO) technique and the vascular
pressure-flow relationship. Blood viscosity was changed by erythrocyte
(RBC) shrinkage and swelling with hypertonic and hypotonic NaCl solutions
and by RBC membrane rigidification with heat treatment (49 degrees C for 1
h). The results show that although all three methods of changing blood
viscosity increased the pulmonary vascular resistance (PVR) by 15-50%, the
site and nature of the change in PVR were different in each case. The AVO
data showed that the increase in PVR with heat treatment of RBC's was due
entirely (100%) to increased resistance of the middle microvascular
segment, whereas deviation from normal osmolarity potentiated the
resistance in arterial, middle, and venous segments. By examining the
effect of osmolarity in plasma-perfused lobes, it was possible to separate
the increase in PVR due to changes in RBC deformability from those due to
other factors. The increase in arterial and venous resistances with
hypertonic solution was attributed in part (approximately 50%) to factors
other than RBC's; however, the increase in middle resistance was entirely
due to RBC crenation. The increase in arterial and venous resistances with
hypotonic solutions was small and was apparently caused by factors other
than RBC swelling, whereas the increase in middle resistance was partially
(approximately 50%) due to RBC swelling and partially to other factors
(e.g., endothelial cell hydration).(ABSTRACT TRUNCATED AT 250 WORDS)
