Theory and methods of local tissue-pO2 monitoring in experimental angiology

The platinum-multiwire-surface electrode after Kessler and Lübbers gives the opportunity of direct measuring of the local tissue-pO2-pressure; this 8-wire electrode with a Pt-wire-diameter of 15 microns operates on the polarographic principle. Each Pt-wire has a hemispheric collecting area of about 30 microns. Pressure ischemia by compression of capillaries is prevented by proportioning the weight (2.1 g) of the electrode. Data output is done by continuous pO2 measuring; pO2 histograms. During the continuous pO2 measurement the electrode stays on the tissue measuring point thus enabling the direct record of quickly proceeding reactions. The pO2-histogram exhibits the statistical distribution of the local partial oxygen pressures in a studied organ, a quasi sample inquiry is performed in the tissue, based on minimum 100 single values that are obtained by repeated manual repositioning of the electrode. By this, values are obtained on the level and distribution of local pO2 in the tissue so that condition and function of the microcirculation can be objectively assessed. Immediate alterations in the local tissue pO2 suggest regulatory adjustment after hemodynamic changes. Technical problems connected with pO2 measurement in clinical use (sterilization, data acquisition and presentation) are described. The presented technique gives the chance to exactly assess the effects of vasoactive drugs on the microcirculation and to quantify the results of operations, for example after bypass-surgery.