A preliminary in-vitro evaluation and comparative study of various tissue pH sensors

An investigation is being pursued to determine the best pH sensor for assessing tissue viability during the process of reconstructive surgery. Two different pH sensors are being evaluated in a preliminary study designed to improve upon the standard glass pH electrode: an ion-selective field effect transistor (ISFET) sensor and a conventional glass electrode. Preliminary test results show that the ISFET sensor responds more quickly to changes in pH than the glass electrode does. Each electrode responds quickly enough to adequately monitor physiological pH changes. However, more importantly, the glass electrode displayed very little drift over a 72 hour period, whereas the ISFET sensor displayed an unacceptably large drift for patient monitoring. The accuracy of both the ISFET and the glass electrodes in the 7.0 pH buffer was found to be satisfactory for tissue monitoring. The accuracy tests in the 6.84 and 7.38 buffers showed a less than ideal accuracy for tissue monitoring. However, the results may be a result of using weak ionic strength buffers and not due to electrode inaccuracy at particular pH levels.