In-vivo measurement of end-tidal carbon monoxide concentration apparatus and methods
First Claim
1. Apparatus for monitoring a patient'"'"'s end-tidal gas flow during breathing comprising:
- a first gas detector for monitoring the concentration of a first selected gas in a gas sample and having an output corresponding to the monitored first selected gas concentration;
a first means for monitoring a parameter corresponding to the patient'"'"'s breathing and determining the ratio of said parameter corresponding to the patient'"'"'s end-tidal breath portion to said parameter corresponding to inspired air as a duty cycle and having an output corresponding to the determined duty cycle;
first means for providing a sample of room air to the first gas detector for measuring a background concentration of the first gas;
second means for providing a sample of the patient'"'"'s breath to the first gas detector for measuring a breath sample concentration of the first gas in the patient'"'"'s breath; and
first means for receiving the output of the first gas detector and the first monitoring means for determining a end-tidal concentration of the first gas in response to the determined duty cycle, the determined background concentration of the first gas in room air, and the determined breath sample concentration of the first gas in the patient'"'"'s breath.
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Accused Products
Abstract
A noninvasive device and methods for measuring the end-tidal carbon monoxide concentration in a patient'"'"'s breath, particularly newborn and premature infants. The patient'"'"'s breath is monitored. An average carbon monoxide concentration is determined based on an average of discrete samples in a given time period. The ratio of the end-tidal portion of the breath flow sample is separately determined, preferably based on monitoring the level of carbon dioxide in the gas sample and identifying the carbon dioxide concentration levels corresponding to the end-tidal portion of the breath sample. The sensed carbon monoxide level is converted to the end-tidal carbon monoxide level by subtracting the ambient carbon monoxide level and dividing the remainder by the ratio of end-tidal breath to breath in the breath sample. An easy to use microcontroller-based device containing a carbon dioxide detector, a carbon monoxide detect and a pump for use in a hospital, home, physician'"'"'s office or clinic by persons not requiring high skill and training is described.
140 Citations
50 Claims
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1. Apparatus for monitoring a patient'"'"'s end-tidal gas flow during breathing comprising:
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a first gas detector for monitoring the concentration of a first selected gas in a gas sample and having an output corresponding to the monitored first selected gas concentration; a first means for monitoring a parameter corresponding to the patient'"'"'s breathing and determining the ratio of said parameter corresponding to the patient'"'"'s end-tidal breath portion to said parameter corresponding to inspired air as a duty cycle and having an output corresponding to the determined duty cycle; first means for providing a sample of room air to the first gas detector for measuring a background concentration of the first gas; second means for providing a sample of the patient'"'"'s breath to the first gas detector for measuring a breath sample concentration of the first gas in the patient'"'"'s breath; and first means for receiving the output of the first gas detector and the first monitoring means for determining a end-tidal concentration of the first gas in response to the determined duty cycle, the determined background concentration of the first gas in room air, and the determined breath sample concentration of the first gas in the patient'"'"'s breath. - View Dependent Claims (2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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4. The apparatus of clam 3 wherein the second gas detector further comprises a carbon dioxide gas analyzer.
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25. A method of measuring end-tidal carbon monoxide concentration in expired breath comprising the steps of:
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(a) measuring a carbon monoxide concentration in ambient room air (COroom); (b) sampling a patient'"'"'s breath over a first period of time; (c) measuring the carbon monoxide concentration (CO) in a sampled patient'"'"'s breath during the first time period; (d) determining a duty cycle of an end-tidal portion of the patient'"'"'s breath during the first time period; and (e) determining an end-tidal carbon monoxide level based on the determined duty cycle, the measured COroom, and the measured CO. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44)
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45. Apparatus for determining the carbon monoxide concentration in the end tidal portion of the exhaled breath flow of a patient, comprising:
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a carbon monoxide gas analyzer having a gas input for receiving a gas sample and a signal output CO representative of the measured concentration of carbon monoxide in the gas sample, said carbon monoxide gas analyzer having a response time that is not sufficiently fast to distinguish the carbon monoxide concentration of the end tidal portion from other portions of a gas sample that is a patient breath flow; a carbon dioxide gas analyzer having an input for receiving a gas sample and a signal output CO2 representative of the measured concentration of carbon dioxide in the gas sample, said carbon dioxide gas analyzer having a response time that is sufficiently fast to distinguish the carbon dioxide concentration of the end tidal portion form other portions of a gas sample that is a patient breath flow; means for analyzing the signal output CO2 over a given time period and determining a duty cycle for said signal output relative to a preselected signal parameter; first means for providing a room air gas sample flow to the carbon monoxide gas analyzer for a first duration so that the carbon monoxide gas analyzer signal output CO corresponds to a background carbon monoxide concentration; second means for providing a patient breath flow gas sample flow of a second duration to the carbon monoxide gas analyzer and to the carbon dioxide gas analyzer, wherein the carbon monoxide gas analyzer signal output CO corresponds to an average carbon monoxide concentration near the end of the second duration, the preselected signal parameter corresponds to the patient'"'"'s end tidal carbon dioxide concentration, and the analyzing means determines the duty cycle of the end tidal portion of the breath flow sample; and calculating means for receiving the background carbon monoxide concentration, the average carbon monoxide concentration and the determined duty cycle and calculating therefrom the end tidal carbon monoxide concentration. - View Dependent Claims (46, 47, 48, 49, 50)
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Specification