A SOLID STATE DEVICE FOR THE DETERMINATION OF OSMOTIC AND INTERSTITIAL FLUID PRESSURES: CLINICAL AND EXPERIMENTAL APPLICATIONS

Classical equations from nonequilibrium thermodynamics describe the fundamental parameters which govern movement of solvent (water) and solute (proteins) across the semipermeable walls of the microcirculatory system. Two of these parameters which have been difficult to quantitate are the colloid osmotic pressure of the interstitial fluid (IFCOP) and the hydrostatic interstitial fluid pressure (IFP). If the lymph flowing from an organ is considered to have the same protein concentration as interstitial fluid, normal techniques for colloid osmometry may be utilized when a sufficient lymph volume can be obtained. We have constructed a device which can: 1) determine the colloid osmotic pressure of very small volumes of interstitial fluid of lymph and 2) when chronically or acutely implanted within the interstitium can record IFP with great fidelity at high physiologic frequencies. For the determination of IFP a solid state silicon strain gauge is inserted into a 1. 5 mm diameter stainless steel needle. A thin layer of porous polyethylene matrix is introduced into the front of the needle to prevent solid tissue elements from coming into contact with the transducer. The needle is fluid filled and sealed around the transducer cable.

A SOLID STATE DEVICE FOR THE DETERMINATION OF OSMOTIC AND INTERSTITIAL FLUID PRESSURES: CLINICAL AND EXPERIMENTAL APPLICATIONS Conference Paper