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24 April 1996 Mainstream sensor unit for closed-circle anesthetic gas monitoring
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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.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Stephan Junger, Norbert O. Lutter, Johannes Schwider, Dieter Goettler, Norbert Weber, and Edmund Burte "Mainstream sensor unit for closed-circle anesthetic gas monitoring", Proc. SPIE 2676, Biomedical Sensing, Imaging, and Tracking Technologies I, (24 April 1996);

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