Development of a low cost microP-based blood gas monitor

A low cost microprocessor-based system for continuous in-vivo measurement of blood pH and pCO2 using a biosensor is being developed. The biosensor is a pH Ti2O3 ISFET (Ion Sensitive Field Effect Transistor) with a sensitivity of -56 mV/pH and a linear response over physiologically meaningful blood pH range of 6.5 to 8.0. The ISFET chip is bonded onto a printed circuit board substrate to enable reliable and robust connections to three wires. The small sensor tip sized of 0.95 mm facilitates its incorporation into a catheter tip and its placement into a rat's artery. A microcontroller supervises preusage calibration, data logging, display of alphanumeric information on a LCD (liquid crystal display) unit, and resettable visual & audio alarm indicators. Preliminary clinical testing are underway to perfect the system and use it on a routine basis to monitor the physiological state of laboratory animals during neurophysiological experiments.