Bernhard Montag

Online blood electrolyte monitoring with a ChemFET microcell system

Abstract A sample-taking sensor system for online pH and electrolyte monitoring of blood is described. The system consists of a two-lumen catheter with a ChemFET flow-through cell, a syringe pump unit with ChemFET instrumentation and a personal computer. Suitable operation of the pump unit allows the sensor to be calibrated every 2 min before each measurement. The blood sample volume withdrawn from the patient is on the order of 10 μl. Solvent polymeric membrane ISFETs serve as measurement sensors as well as reference sensors. For this purpose they are spatially separated by a flow-through channel where a liquid junction can be established between the calibration solution and blood. In this way the arrangement saves a conventional reference electrode with the bridge solution. In vivo experiments in pigs show a very good correlation between sensor and analyzer values. There was no blood clotting in the sensor system.

Combination of amperometric and potentiometric sensor principles for on-line blood monitoring

Abstract Low-cost disposable multiparameter chemical sensors not only require monolithic and hybrid integration of different sensors, but also a combination of different measuring principles within a small area of a silicon chip. Miniaturized sensors can be implemented using potentiometric ISFETs and three-electrode amperometric sensors. ISFET-transducers need a signal ground reference to the analyte which would shunt the counter electrode of a three-electrode amperometric oxygen sensor without an isolating membrane. The working electrode potential of the oxygen sensor is used as the signal ground reference for the ISFETs. Despite the fact that the working electrode potential is varied cyclically for the purpose of electrode regeneration, no interference between the different sensors occurs.

Monitoring of blood pO/sub 2/ with a thin film amperometric sensor

A sample-taking sensor system for online pO/sub 2/ monitoring of blood is described. The system consists of a two-lumen catheter with a thin-film amperometric sensor cell, a pump unit with instrumentation, and a personal computer. The planar three-electrode system is only covered by a hydrophilic pHEMA membrane to avoid alterations in the composition of any internal electrolyte solution. To overcome the problem of electrode poisoning, the surface of the working electrode is regenerated during the calibration mode of the calibration/measurement cycle. Animal studies have been performed with anaesthetized pigs. The comparison of the sensor values with blood gas analyzer data shows a curved but reproducible correlation.<<ETX>>

A micro transmission cell for monitoring of oxygen saturation and hemoglobin concentration

Abstract Oxygen uptake and transport into cells are important mechanisms for metabolism. There is a demand for sensors which measure oxygen saturation ( Sa O 2 ) and hemoglobin concentration ( c Hb ) for automated monitoring systems. An ex vivo optoelectrical flow-through cell is connected to a catheter and a pump system, originally developed for a ChemFET measuring system. The system is in vitro calibrated and has been tested in vivo with anesthetized pigs. It is capable of monitoring Sa O 2 and c Hb with high accuracy and stability with an expected lifetime greater than monitoring periods experienced in intensive care.