Journal of Applied Physiology, Vol 58, Issue 5 1528-1535, Copyright © 1985 by American Physiological Society
Measurement of subcutaneous tissue fluid pressure using a skin-cup method
T. H. Adair and A. C. Guyton
We developed a new method for measuring tissue fluid pressure in
subcutaneous tissue. Porous Teflon cylinders were permanently implanted
subcutaneously into the inguinal area of 10 dogs, and after several weeks a
skin concavity formed in the center of each of the cylinders. A small
needle attached to a recording system was inserted into the free tissue
fluid lining the concavity, and the tissue fluid pressure averaged -8.8 +/-
2.7 (SD) mmHg. Next, a hollow Plexiglas cup was placed over the concavity
and glued to the skin. The air pressure in the skin cup was continually
adjusted (using an electromechanical servo-control system) to pull the skin
upward and to hold it perfectly flat across the upper ridge of the Teflon
cylinder. The simultaneously recorded needle and cup pressures averaged
-9.1 +/- 2.4 and -8.6 +/- 2.6 mmHg, respectively, during steady-state
conditions with the skin in a flat position. Both pressures also responded
appropriately to dynamic changes in tissue fluid pressure caused by
increasing and decreasing the volume of the free tissue fluid. Because the
skin was flat, the equivalences of pressures above and below the skin is
consistent with the hypothesis that the skin was not tethered significantly
to the underlying tissues and that cup pressure accurately estimates the
tissue free fluid pressure.
