A HYDROGEN CATHETER ELECTRODE FOR THE DETERMINATION OF BLOOD FLOW THROUGH ORGAN TISSUE AND CORONARY BLOOD FLOW UNDER CONTINUOUS HYPDXIA

Abstract

In order to develop an applicable H2 Pt electrode for the determination of average blood flow through organs, a catheter tip electrode covered with a Teflon membrane was designed. The properties of the covered electrode were studied polarographically mainly with reference to the effects of the applied voltage on the linearity, reproducibility and response time of the H2 current against PH2. Next the coronary blood flow was measured by placing an electrode in the coronary sinus and also in the aorta. In a wide range of the applied voltage an addition of H2 to the solution caused an increase in the positive current through the electrodes. But the H2 current was influenced to a considerable extent by the applied voltage. It was observed that a linear relation between the H2 current and PH2 was obtained in a range of applied voltage of -0.1 to +0.3V, when the external resistance was fixed at 5MΩ. However, at the applied voltage of +0.3V the response time was found to be markedly prolonged. Thus, the following conditions were selected as reasonable for practical use in vivo: 1) The platinisation was performed for 10 seconds with -1.5V in an 1% H2 (PtCl6) 6H2O solution with 0.01% Pb (CH3COO) 23H2O, 2) the applied voltage was about -0.1V against an Ag-AgCl electrode, and 3) the external resistance was 5MΩ. Even under these conditions the H2 current was influenced by PO2 the stirring of the medium and the temperature. Therefore, to obtain reproducibility, these factors should be kept unchanged.In order to ascertain the applicability of the present method to blood flow measurement, coronary blood flow was simultaneously determined by use of the H2 and N2O methods. The values obtained by both methods were in fairly good agreement, with only a small difference. The H2 currents alone were then recorded at various inspired PH2's and the coronary blood flow was calculated by using the saturation and desaturation curves of PH2. It was revealed that the change in the inspired PH2 caused no remarkable influence on the calculated value, and that the desaturation curve gave more reliable values for the blood flow than the saturation curve. As an application of this electrode the coronary blood flow was measured under hypoxia over a 2 hour interval. As the result it was shown that the coronary blood flow was significantly increased during continuous hypoxia of over 2 hours compared with that in air respiration.