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Proceedings Paper

Mainstream sensor unit for closed-circle anesthetic gas monitoring
Author(s): Stephan Junger; Norbert O. Lutter; Johannes Schwider; Dieter Goettler; Norbert Weber; Edmund Burte
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Paper Abstract

The use of closed circle systems in anesthesia requires accurate real-time anesthetic gas monitoring. A demonstration system was designed in order to test monitoring feasibilities for volatile anesthetics, N2O, carbon-dioxide, and water based on nondispersive infrared spectroscopy (NDIR) in the wavelength range from 3 to 13 microns. Calibration curves have been obtained using mass flow controllers. These results are compared with simulations thus representing the basis for the selection of interference filters with optimized central wavelengths and bandwidths. The paper describes the design of a miniaturized sensor unit that permits integration into the breathing circuit yielding a decrease of response time and measurement delay when compared with sidestream sampling devices. This mainstream sensor unit consists of a miniaturized infrared spectroscopic cell to detect gas concentrations, as well as a pressure and a temperature sensor. A stabilized infrared source is coupled to the spectroscopic cell using a silver halide glass fiber bundle. The radiation passes two different absorption lengths adapted to the typical concentrations and extinction coefficients and is focused onto multispectral detectors by aspheric reflective surfaces. Six signal and two reference channels are amplified by miniaturized multichannel lock-in modules and transferred to a PC for acquisition, calibration, processing and display.

Paper Details

Date Published: 24 April 1996
PDF: 8 pages
Proc. SPIE 2676, Biomedical Sensing, Imaging, and Tracking Technologies I, (24 April 1996); doi: 10.1117/12.238799
Show Author Affiliations
Stephan Junger, Univ. Erlangen-Nurnberg (Germany)
Norbert O. Lutter, Univ. Erlangen-Nurnberg (Germany)
Johannes Schwider, Univ. Erlangen-Nurnberg (Germany)
Dieter Goettler, Fraunhofer Institut fuer Integrierte Schaltungen (Germany)
Norbert Weber, Fraunhofer Institut fuer Integrierte Schaltungen (Germany)
Edmund Burte, Fraunhofer Institut fuer Integrierte Schaltungen (Germany)

Published in SPIE Proceedings Vol. 2676:
Biomedical Sensing, Imaging, and Tracking Technologies I
Robert A. Lieberman; Halina Podbielska M.D.; Tuan Vo-Dinh, Editor(s)

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