CO.sub.2 mainstream capnography sensor
First Claim
1. A capnography system comprising:
- a breathing passage for breathing gases between a patient and an exhaust;
an optical path across said breathing passage permitting the transmission of radiation therethrough;
an LED source of pulsed radiation, positioned adjacent said breathing passage, for emitting radiation of approximately 4.2 micron wavelength and of a bandwidth encompassing the absorption band of CO2 in said optical path;
a detector for pulsed radiation positioned adjacent said breathing passage for the receipt of radiation emitted by said LED source and to provide a pulsed waveform output in response to the received pulsed radiation from said LED source; and
processing electronics electrically connected to said detector, said processing electronics responsive to the pulsed waveform output provided by said detector and generating an output capnogram representation of the concentration of CO2 in said breathing passage.
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Accused Products
Abstract
A capnography system has a 4.2 micron LED emitter of narrow-band radiation having a center wavelength very close to the 4.26 micron absorption band of CO2 breathing gas in a breathing tube. The radiation passes through windows in an insert in the breathing passage between the LED source and an infrared detector in an opposite side of the insert. A mirror is optionally placed in the opposite wall to reflect the radiation back to the detector which is then placed on the same side as the emitter. The LED emitter is pulsed at a low frequency repetition rate with a regulated voltage from a power supply. The detector output is applied to processing electronics which includes amplification and dual integrators that integrate the detector output on two signal paths, one the integration of each pulse and the other the integration of detector background with the two differences to provide self calibration against drift and noise. A heater heats the emitter, infrared detector, local electronics and the windows thereby stabilizing these temperature sensitive components to minimize the measured CO2 value error to a few mm of mercury and to prevent condensation on the insert particularly in the windows. A second emitter is optionally used as a reference and/or to detect additional gas concentrations.
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Citations
52 Claims
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1. A capnography system comprising:
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a breathing passage for breathing gases between a patient and an exhaust; an optical path across said breathing passage permitting the transmission of radiation therethrough; an LED source of pulsed radiation, positioned adjacent said breathing passage, for emitting radiation of approximately 4.2 micron wavelength and of a bandwidth encompassing the absorption band of CO2 in said optical path; a detector for pulsed radiation positioned adjacent said breathing passage for the receipt of radiation emitted by said LED source and to provide a pulsed waveform output in response to the received pulsed radiation from said LED source; and processing electronics electrically connected to said detector, said processing electronics responsive to the pulsed waveform output provided by said detector and generating an output capnogram representation of the concentration of CO2 in said breathing passage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A capnography system comprising:
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a breathing passage for breathing gases between a patient and a breathing gas source and an exhaust; an LED source of pulsed radiation positioned adjacent said breathing passage, the radiation having a narrow band emission spectrum coinciding with an absorption band of CO2 gas within said breathing passage; a detector positioned adjacent said breathing passage for detecting pulsed radiation from said LED source through said passage and providing a pulsed waveform output in response to the reception of pulsed radiation from said LED source; a mirror mounted adjacent said breathing passage; an optical access disposed transversely through said breathing passage enabling the transmission of radiation across said breathing passage between said LED source and said detector by reflection of the pulsed radiation by said mirror from an opposite side to provide multiple traversals through the breathing gas by said radiation; processing electronics electrically connected to said detector, said processing electronics responsive to the pulsed waveform output provided by said detector and generating an output capnogram representation of the concentration of CO2 in said breathing passage. - View Dependent Claims (21, 22, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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- 23. The capnography system of clam 20 wherein said LED source is an InAsSbP/InAs emitter.
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39. A capnography system comprising:
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a breathing passage for breathing gases between a patient and a breathing gas source and an exhaust; an LED source of pulsed radiation positioned adjacent said breathing passage, the radiation having a narrow band emission spectrum coinciding with an absorption band of CO2 gas within said breathing passage; a detector positioned adjacent said breathing passage for detecting pulsed radiation from said LED source through said passage and providing a pulsed waveform output in response to the reception of pulsed radiation from said LED source; an optical access disposed transversely through said breathing passage providing for the transmission of radiation through said breathing passage between said LED source and said detector; processing electronics electrically connected to said detector, said processing electronics responsive to the pulsed waveform output provided by said detector and generating an output capnogram representation of the concentration of CO2 in said breathing passage, said processing electronics further including a first integrator for providing an integration of the detector pulsed waveform output above an adjusted baseline. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46)
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47. A capnography system comprising:
- a breathing passage for breathing gases between a patient and a breathing gas source and an exhaust;
an LED source of pulsed radiation positioned adjacent said breathing passage, the radiation having a wavelength within the absorption band of CO2 gas within said breathing passage; a detector positioned adjacent said breathing passage for detecting pulsed radiation from said LED source and providing a pulsed waveform output in response to the detected pulsed radiation from said LED source; an optical access disposed transversely through said breathing passage providing the transmission of radiation across said breathing passage between said LED source and said detector; processing electronics electrically connected to said detector, said processing electronics responsive to the pulsed waveform output provided by said detector and generating an output capnogram representation of the concentration of CO2 in said breathing passage, said processing electronics further including a first integrator for providing an integration of the detector pulsed waveform output above an adjusted baseline; a heater for at least one of said detector and source to limit an error in the representation of CO2 ; and a housing cooperative with said breathing passage for said heater, said source, and said detector for maintaining the temperature thereof. - View Dependent Claims (48, 49, 50, 51, 52)
- a breathing passage for breathing gases between a patient and a breathing gas source and an exhaust;
Specification