Characteristics of Non-Aqueous Electrolytes for Transcutaneous Oxygen Electrodes

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Abstract
We investigated the characteristics of non-aqueous solvents for tcPO2 electrolytes, using a tcPO2 electrode with three 15 micrometer platinum cathodes set in a polished glass surface, a 17.8 mm2 silver anode covered with a 25 micrometer Telfon membrane, with and without a 12 micrometer cellophane spacer, and polarized at--0.8v. We examined the effect of ethylene glycol (EG) concentration, in water, on O2 sensitivity, stirring effect, in vitro drift, in vitro response time, behaviour on the skin of newborn infants and in vivo response time. We found the following: (1) O2 sensitivity was reduced by increasing EG concentration. (2) phi, the stirring effect (gas/50% glycerine) was 1.01 at 90% EG with cellophane, but higher without cellophane. (3) In vitro drift at 44 degree C electrode temperature, in 43 degree C water (simulating skin), was reduced with 90% EG, 25 micrometer Telfon and no spacer, but increased with a spacer. (4) In vitro response time was increased with EG. (5) Correlations with arterial PO2 in a group of newborns was as excellent with an electrode made with 90% EG and 25 micrometer Telfon, without spacer, as it was with our previous study using aqueous electrolyte and 12 micrometer Telfon wint 12 micrometer cellophane: (tcPO2 = 1.32 + 0.988 PaO2 r = 0.987). In vivo response time was not prolonged. Using EG, the tc PO2 electrode membrane required changing only after 7--9 days, compared with 1--2 days when using aqueous electrolytes. No advantage of using cellophane spacers was identified in these in vivo studies.

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