Indwelling chemical sensors based on semiconductor technology.

Indwelling chemical sensors have been designed and built which operate on similar principles to field effect transistors, the fundamental structural unit of the computer. By appropriate use of ion-filtering membranes with these devices, it is possible to measure, continuously, serum electrolytes, including hydrogen ion, and CO2 tension. Semiconductor processing techniques allow incorporation of multiple ion sensors on a single miniaturized chip. Chip-based signal processing can also allow compensation for temperature effects and other sources of instability. Because these devices can be produced inexpensively, they seem to be promising for patient monitoring in the critical care environment. Problems with stability, blood compatibility, and reference electrode design are addressed and potential solution methods are proposed. The performance of preliminary devices in vitro and in vivo is discussed.