Intravascular monitoring: problems and promise.

Intravascular monitoring of arterial blood gases provides the means to detect precipitous change in cardiopulmonary function almost instantaneously, promising major improvement in the ability to manage critically ill patients. Attempts to miniaturize and repackage conventional electrodes for continuous intravascular use have met insurmountable problems, and only the application of new technology involving fiber-optic chemical sensors (FOCS) has proved that in vivo monitoring of blood gas chemistry is truly feasible. Although a wide range of analytes of clinical significance may potentially be monitored by using FOCS technology, the analytes of choice for the management of the critically ill patient are pHa, paCO2, and paO2, because of their dynamic nature and importance for critical-care diagnosis and monitoring. Although intravascular FOCS blood gas monitors currently under clinical investigation exhibit promising performance, clinical acceptance and commercial success will depend on the creative solution of several problems, the most challenging of which are related to physiological factors at the interface between the sensors and their intravascular sensing environment.