AJP - Heart and Circulatory Physiology, Vol 243, Issue 6 1018-H1026, Copyright © 1982 by American Physiological Society
Direct measurement of microvessel hematocrit, red cell flux, velocity, and transit time
I. H. Sarelius and B. R. Duling
A method is presented for the in vivo study of red cell flow dynamics. The
method permits direct measurement of the red cell volume fraction in
microvessel blood without resort to in vitro calibration curves.
Furthermore, the method does not require extensive mathematical
manipulation and can be applied to any microvascular network in any tissue.
The method also enables direct measurement of red cell velocity, flux, and
capillary transit time. Fluorescently labeled erythrocytes in tracer
quantities, but known concentrations, are used as indicators of the
behavior of the total cell population. Erythrocyte transit time across
vascular networks and erythrocyte velocity are determined directly by
following the behavior of the labeled cells. Hematocrit and red cell flux
are measured by standard microcirculatory methods using labeled cells
instead of the total cell population. Data are then converted to absolute
values from the measured fraction of labeled cells. The method is thus
absolutely dependent on the labeled cells being rheologically normal, and
the conditions under which this requirement is satisfied are defined.
Microvascular data obtained by the use of this method are presented for
hamster cheek pouch and cremaster muscle.
