pH Changes in Front of the Hydrogen Generating Electrode During Measurements with an Electrolytic Hydrogen Clearance Sensor
The electrolytic hydrogen clearance according to Lübbers and Stosseck (1970) uses a sensor which combines an electrode generating electrochemically molecular hydrogen with another electrode which measures hydrogen polarographically (pH2/H2 sensor). Although a separating membrane could be applied, up to now the sensor is used only in direct contact with the tissue so that the measurements may directly influence local tissue. Using a transparent sensor Stosseck et al. (1974) found that generating currents of 0.2–2μAof a duration of 1–2 s did not show any change of the vascular diameters (brain cortex), but that larger currents of 3–4 μ A of the same duration caused local vasoconstriction and produced visible gas bubbles. For explanation, a direct effect of the electrical current on the smooth muscle was discussed. However, since during the generation of molecular hydrogen hydroxyl ions are produced, possible pH changes and their effect on microcirculation have to be considered, especially if large generating currents are recommended, as in recent publications (for example, 100 μ A during 2–6 s (Koshu et al., 1982), to guarantee better results.
KeywordsBuffer Capacity Quasi Steady State Local Vasoconstriction Quasi Steady State Condition Special Measuring Condition
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