| 摘要 |
2064892 9103204 PCTABS00003 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 the 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 modulate 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 filtered (60, 61, 62, 16, 18, 26, 28, 36, 38) thermopiles (12, 14, 22, 24, 32, 34) in series and processing the resulting differential signal (242).
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