FORMIKROSYS

RESEARCH ASSOCIATION MICROSYSTEM TECHNOLOGY

TP 1 Real time sensor unit for pulmonary function testing

Field of work:

Oxygen consumption, carbon dioxide production, active lung volume and diffusion resistance of the lung tissue are substantial characteristics of the lung function of healthy persons and in the medical case. A-part from other causes these parameters are determined more extensively because the frequency of lung illness has been increasing for years. These measurements are made in several, partially very time-consuming single steps and in many cases can be carried out only in special lung function laboratories due to the up-to-date available device technology and because of the size of the measuring instruments. The aim of the biomedical engineering project "Real time sensor unit for pulmonary function testing" is the development of a miniaturized multi-functional device for the measurement of the lung function, which can be used at the same time for patient monitoring in the operating room as well and on intensive care units. Old and new measured variables can be determined in only one measuring process fast and easily. The main feature of the new device are miniaturized, fast and inexpensive sensors for carbon dioxide, o-xygen, carbon monoxide and methane. The device under development uses the principle of fluorescence extinction for detecting oxygen and infrared absorption for the measurement of carbon dioxide, carbon monoxide and methane. This is achieved by analyzing the inhaled gases directly at the patient (i. e. in mainstream technique) using nondispersive infrared spectroscopy. From the signal reduction after ab-sorption the respective gas concentrations can be determined. For the oxygen measurement additionally a special fiber-optic sensor is integrated into the multi-sensor module, whose advantages are short res-ponse time and its miniaturization potential. Conventional measuring instruments measure the inhaled gas concentrations in a measuring chamber far from the patient (sidestream technique). This accompa-nies with serious disadvantages: due to the filling time of the measuring chamber the measuring signal is delayed and distorted and thus the results of the measurement are falsified. In order to precisely detect the small signal changes caused by the moving gases in the mainstream, the application of modern sensor and signal processing technologies is necessary. This is achieved by using new multi-channel infrared detectors, the design of a miniaturized optical sensor unit and by the applicati-on of preamplifiers (ASIC) integrated into the sensor which are developed particularly for this purpose. A subsequent multi-channel lock-in amplifier rejects the noise very efficiently. The project results will start up a new device generation, whose innovative functionality corresponds to three different single devices necessary at the moment. The advantage for the physician is that all rele-vant aspects of the lung functions can be determined time-saving with the help of only one device. The patient profits by the fact that the new device will be very much smaller, light-weight and portable, so that lung function can be measured directly at the patient bed and in the operating room - without the need of so-called "function departments" of the hospital. The industrial partners expect development leads, a sub-stantial cost advantage by this new device and thus an improved position in the market.