EP0271109A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Respiratory CO2 detector circuit with high quality waveform
Assignee: Applied Biosystems Inc
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Filing: 1987-12-10
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Granted: —
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Expires: 2007-12-10
Abstract
Abstract A respiratory CO₂ detector (10) comprising an infrared lamp source (44) and an infrared detector (50) responsive thereto forming an optical path for detecting the change in CO₂ concentration, or an obstruction in a cuvette (42). The output of the infrared detector (50) provides a continuous high and low voltage signal to be applied to a feedback control loop (12) and to an output circuit (14). The feedback control loop (12) includes a peak detector (22), a contamination detector (24), a pulse-width modulator (26) and a low pass filter (28), the latter providing a DC bias on the infrared lamp (44). The peak detector (22) is connected to the pulse-width modulator (26) to maintain the lamp voltage constant and is connected to comparators (56,62) to compare both outputs of the peak and contamination detectors (22,24). The contamination detector (24) will respond to blockage in the cuvette (42). The output control circuit (14) includes a sample-and-hold circuit (30) to direct the high and low voltage signal from the detector to a subtractor (32), the output of which is then inverted to provide a high quality waveform.
Inventors
- 👤 Bruce E. Mount
- 👤 Douglas P. Becker
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 18:00
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/25; G01N21/31; G01N21/35; G01N21/3504; G01N21/27; G01N33/00; G01N33/48; G01N33/483; G01N33/497; G01J; G01J1/00; G01J1/10; G01J1/16; G01J1/18; G01J2001/182; G01J1/42; G01J1/44; G01J2001/444; G01N2201/00; G01N2201/06; G01N2201/069; G01N2201/12; G01N2201/127
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
127 words
A CO₂ detector including a cuvette, an infrared lamp responsive to the voltage applied thereto, and an infrared detector and detector preamplifier having a reference (baseline) voltage, said lamp being positioned to illuminate an optical path through said cuvette so that infrared detector will produce a signal representative of the quantity of CO₂ in said cuvette, the improvement comprising, first means responsive to said signal to maintain the baseline voltage (minimum CO₂ concentration) of the detector preamplifier output at a nearly constant value, second means responsive to said signal to return the detector preamplifier baseline voltage to a reference level if the optical path is partially blocked, and means for providing a high quality output signal waveform corresponding to the CO₂ concentration changes occuring within said cuvette.
Claim 2
Dependent Claim
127 words
A CO₂ detector including a cuvette, an infrared lamp responsive to the voltage applied thereto, and an infrared detector and detector preamplifier having a reference (baseline) voltage, said lamp being positioned to illuminate an optical path through said cuvette so that infrared detector will produce a signal representative of the quantity of CO₂ in said cuvette, the improvement comprising, first means responsive to said signal to maintain the baseline voltage (minimum CO₂ concentration) of the detector preamplifier output at a nearly constant value, second means responsive to said signal to return the detector preamplifier baseline voltage to a reference level if the optical path is partially blocked, and means for providing a high quality output signal waveform corresponding to the CO₂ concentration changes occuring within said cuvette.
Claim 3
Dependent Claim
21 words
The detector as claimed in Claim 1 further including a signal which can be used for warning if contamination is present.
Claim 4
Dependent Claim
30 words
The detector as claimed in Claim 1 wherein said first means includes a peak detector whose output is connected through a pulse-width modulator and low pass filter to said lamp.
Claim 5
Dependent Claim
51 words
The detector as claimed in Claim 3 wherein said second means includes a contamination detector whose output is connected to the input of said peak detector to change the last voltage level sensed by said peak detector to a reference (baseline) voltage level when the optical path has become partially occluded.
Claim 6
Dependent Claim
71 words
The detector as claimed in Claim 4 wherein said peak detector has an RC network with a relatively short charging time and a long discharge time constant, and wherein said contamination detector has an RC network with a relatively short charging time constant, and a shorter discharge time than the peak detector whereby the output signal from said peak detector may be interrupted and returned to said reference (baseline) voltage level.
Claim 7
Dependent Claim
33 words
The detector as claimed in Claim 5 wherein a pulse-width modulator is connected between the output of said peak detector to provide a predetermined voltage level baseline at the output of said preamplifier.
Claim 8
Dependent Claim
53 words
The detector as claimed in Claim 6 wherein the output of said preamplifier is connected to a sample-and-hold circuit and to a subtractor whereby said subtractor eliminates the baseline voltage provided by said pulse-width modulator and returns the output waveform from said preamplifier to a zero baseline for a high quality output waveform.
Claim 9
Dependent Claim
26 words
The combination claimed in Claim 7 wherein a warning signal may be taken at the output of said pulse-width modulator and low pass filter (lamp voltage).
Claim 10
Dependent Claim
192 words
A CO₂ detector for monitoring a patient's breath inhalation and exhalation including a cuvette connected to the patient's airway, an infrared lamp responsive to the voltage applied thereto, and an infrared detector and preamplifier, said lamp being positioned to provide an optical path through said cuvette so that the infrared detector will produce an electrical waveform representative of the quantity of CO₂ in said cuvette, the improvement comprising, a peak detector with an RC network connected to said preamplifier and whose output is connected to said lamp through a pulse-width modulator and lowpass filter, a contamination detector with an RC network connected to said preamplifier and whose output is connected to the input of said peak detector, the output of said peak detector and said contamination detector being continuously monitored by comparators with the discharge time of the RC network of said contamination detector having a time constant shorter than the discharge time constant of the RC network of said peak detector to override the RC network of the peak detector and raise the voltage on said lamp in the event the preamplifier output remains below the contamination detector positive input voltage.
Claim 11
Dependent Claim
192 words
A CO₂ detector for monitoring a patient's breath inhalation and exhalation including a cuvette connected to the patient's airway, an infrared lamp responsive to the voltage applied thereto, and an infrared detector and preamplifier, said lamp being positioned to provide an optical path through said cuvette so that the infrared detector will produce an electrical waveform representative of the quantity of CO₂ in said cuvette, the improvement comprising, a peak detector with an RC network connected to said preamplifier and whose output is connected to said lamp through a pulse-width modulator and lowpass filter, a contamination detector with an RC network connected to said preamplifier and whose output is connected to the input of said peak detector, the output of said peak detector and said contamination detector being continuously monitored by comparators with the discharge time of the RC network of said contamination detector having a time constant shorter than the discharge time constant of the RC network of said peak detector to override the RC network of the peak detector and raise the voltage on said lamp in the event the preamplifier output remains below the contamination detector positive input voltage.
Claim 12
Dependent Claim
60 words
The CO₂ detector as claimed in Claim 9, wherein said pulse-width modulator causes the voltage level of said preamplifier to remain at a baseline DC level and wherein said voltage level is reduced by a subtractor in order that the waveform output from said subtractor will represent a waveform representative of the concentration of CO₂ in said cuvette, but inverted.
Claim 13
Dependent Claim
21 words
The CO₂ detector as claimed in Claim 10 wherein said last mentioned waveform is inverted for a high quality waveform output.
Claim 14
Dependent Claim
27 words
The CO₂ detector as claimed in Claim 11 wherein the output of said detectors create a signal for triggering an alarm representative an obstruction in said cuvette
Claim 15
Independent Claim
100 words
A method of producing a high qualiity waveform representative of the amount of CO₂ in the expired breath of a patient which is directed to a cuvette, comprising the steps of, generating a waveform varying with the amount of CO₂ in the patient's breath, sampling the negative, or minimum concentration, peaks of said waveform continuously, processing said waveform in conjunction with said sampling to produce an output signal representative of said breath, and generating a signal responsive to any contamination in said cuvette to warn of said contamination to prevent false measurement of actual CO₂ concentration in the patient's breath.
Claim 16
Independent Claim
100 words
A method of producing a high qualiity waveform representative of the amount of CO₂ in the expired breath of a patient which is directed to a cuvette, comprising the steps of, generating a waveform varying with the amount of CO₂ in the patient's breath, sampling the negative, or minimum concentration, peaks of said waveform continuously, processing said waveform in conjunction with said sampling to produce an output signal representative of said breath, and generating a signal responsive to any contamination in said cuvette to warn of said contamination to prevent false measurement of actual CO₂ concentration in the patient's breath.
References Cited (Backward Citations)
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