Interstitial Fluid Presure. Ii. Pressure-volume Curves of Interstitial Space .

• In a previous study we found the interstitial fluid pressure, as measured in tissue cavities created by implanting perforated capsules, to be —6 to —7 mm Hg in most normal tissues, though it rose to positive values in edema. Very slight changes of interstitial fluid volume changed the interstitial fluid pressure markedly in normal tissues but only slightly in edematous tissues. The present study is an attempt to quantitate earlier findings by recording pressure-volume curves for the interstitial spaces. Also, a physical model was constructed to exhibit some of the physical principles that govern the nature of the pressure-volume relationships of the interstitial spaces, and curves determined in this model are compared with those from the interstitial spaces themselves.