Title:
FILTER SELECTION AND GAS CONCENTRATION COMPUTATION FOR SHUTTERLESS OPTICALLY STABILIZED CAPNOGRAPH
Document Type and Number:
WIPO Patent Application WO1993009413
Kind Code:
A3
Abstract:
Methods and apparatus for constructing optically stabilized, shutterless infrared capnographs are disclosed. The capnographs of the present invention provide the absolute concentration of the constituents of the respiratory airstream of a patient, without thermal drift problems normally associated with thermopile detectors, thereby providing a device with a high degree of accuracy. The present invention eliminates the need for a mechanical shutter to modulates the incident infrared beam and the need for a modulated source, thereby increasing the reliability and response time of the devices disclosed. Capnographs which are substantially unaffected by changes in the ambient temperature at which they operate are provided by connecting pairs of optically filtered thermopiles in series and processing the resulting differential pair. In addition, techniques are provided for selecting overlapping optical filters for use with thermopiles with a minimum level of cross-talk. A processing technique is also given which allows the concentrations of two or more airstream constituents to be separately quantified even when such overlapping optical filters are used.
Inventors:
YELDERMAN MARK L (US)
BRAIG JAMES R (US)
GOLDBERGER DANIEL S (US)
BRAIG JAMES R (US)
GOLDBERGER DANIEL S (US)
Application Number:
PCT/US1992/009028
Publication Date:
June 10, 1993
Filing Date:
October 21, 1992
Export Citation:
Assignee:
CRITIKON INC (US)
International Classes:
A61B5/083; G01N21/35; G01J5/12; (IPC1-7): G01J3/36
Foreign References:
| US4423739A | 1984-01-03 | |||
| US4914719A | 1990-04-03 |
Other References:
COMPUTERIZED QUANTITATIVE INFRARED ANALYSIS, 1987, D.M. HAALAND, 78-94.
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