Journal of Applied Physiology, Vol 63, Issue 3 962-968, Copyright © 1987 by American Physiological Society
Skin blood flow in sheep: comparison of xenon-133 washout and radioactive microsphere techniques
U. Midtgard, J. R. Hales, A. A. Fawcett and P. Sejrsen
Institute of Cell Biology and Anatomy, University of Copenhagen, Denmark.
Blood flow was measured in leg and torso skin of conscious or anesthetized
sheep by using 15-micron radioactive microspheres (Qm) and the 133Xe
washout method (QXe). There was a good relationship between Qm in the
cutaneous compartment and QXe calculated from the fast component of the
biexponential washout curves (QXe = 0.40.Qm + 6.2, r = 0.90, P less than
0.001) with QXe values substantially below those determined with
microspheres. Only at low blood flow levels was there a tendency for QXe to
overestimate capillary blood flow as assessed with microspheres, but at
higher blood flow levels the 133Xe washout method resulted in values
substantially below those determined with microspheres. The slope of the
slow component of the washout curves was inversely related to the
tissue-blood partition coefficient in the subcutaneous tissue (r = 0.52, P
less than 0.001), indicating an influence of the amount of subcutaneous fat
on the washout rate. QXe calculated from the slow component of the washout
curves was not significantly correlated with Qm in the subcutaneous
compartment (r = 0.19, P greater than 0.10). In leg skin with dilated
arteriovenous anastomoses, QXe was generally higher than in torso skin and
leg skin with constricted arteriovenous anastomoses, indicating that shunt
blood flow increases the washout of 133Xe.
