Closing the Loop

In order to establish automatic glycaemic control, the decision support system needed to be enhanced by a body interface and a glucose sensor for automatic glucose measurement. Several components were developed both for the subcutaneous and the vascular route.

All three sensor types developed within CLINICIP, i.e. the fibre-optic, the amperometric and IR-spectrometric glucose sensors were developed and clinically implemented for the subcutaneous body interface. This approach will be of special interest for critically ill patient populations that do not have routinely placed large vascular access catheters, e.g. paediatric patients or patients at cardiac care units.

In addition, the infrared spectroscopic and amperometric glucose sensors were developed, implemented and clinically tested for the vascular access principle. This measurement technology has the major advantage that it is capable of monitoring additional metabolic parameters in parallel to glucose. The vascular concept is an ideal solution for patients at intensive care units with large vascular access lines or the general requirement of more frequent metabolic monitoring due to the severe level of disease.

A clinical study was carried out to provide proof of concept for this approach to closed-loop insulin infusion. The clinical study included testing the vascular body interface based on newly developed microdialysis membrane technology in combination with a spectroscopic glucose sensor and the computer algorithm developed for the decision support system.