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US6076392A
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Method and apparatus for real time gas analysis
Assignee: Metasensors Inc
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Filing: 1998-06-26
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Granted: 2000-06-20
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Expires: 2018-06-26
Abstract
Abstract A method and apparatus for real time gas analysis involving determining individual concentrations of fluid constituents in a mixture of known constituents by measuring properties of the mixture and solving a set of equations, which relate the individual gas concentrations to the measured properties of the mixture, for the unknown individual gas concentrations. The individual concentrations of four gasses in a mixture are determined by: passing the mixture through a flowmeter, a capillary, an orifice, and a sonic oscillator; transducing temperature, pressure and acoustic frequency measurements taken from the sensors; determining the density, viscosity, and the specific heat of the mixture; forming three equations which respectively relate these three properties to individual gas concentrations; and solving the three equations and the constitutive equation which requires that the sum of the concentrations equal unity, for the four unknown individual gas concentrations. A single oscillator can serve as both a sensor (e.g., flowmeter, acoustic velocimeter) and an orifice. The fluidic sensors can be formed as a single chip disposable sensor module. By modifying only the processing software, the same sensors or a subset of the sensors can be used to verify or determine the identity of an unknown gas which is supplied by itself in a pure form or in a mixture of other gasses whose identities are known. By measuring N-1 properties of the gas mixture as a whole, the capabilities of an existing sensor system for measuring M gas concentrations can be extended to measure N additional gas concentrations, provided the identities of the gasses in the mixture are known. Similarly, by modifying only the processing software the same sensor can be used to analyze any sets of gas mixtures.
Inventors
- 👤 Tadeusz M. Drzewiecki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 11:20
CPC Classifications
G; G01; G01F; G01F1/00; G01F1/05; G01F1/20; G01F1/32; G01F1/3227; G01N; G01N31/00; A; A61; A61M; A61M16/00; A61M16/0051; A61M16/021; A61M16/08; A61M16/0816; A61M16/0841; A61M16/085; A61M16/0808; A61M16/10; A61M16/1005; A61M2016/102; A61M2016/1025; A61M2016/103; A61M2016/1035; A61M2230/00; A61M2230/40; A61M2230/43; A61M2230/432; A61M2230/435; G01N2291/00; G01N2291/02; G01N2291/028; G01N2291/02872; G01N2291/02881; Y; Y10; Y10T; Y10T137/00; Y10T137/206; Y10T137/2229; Y10T137/2234; Y10T137/2496; Y10T137/2499; Y10T137/2506
Claims Analysis
Total Claims: 59
Claim 1
Independent Claim
118 words
A method of determining individual concentrations of at least L fluid constituents and identities of at least M fluid constituents of a mixture of fluids, where L and M are non-negative integers, the method comprising the steps of: a) measuring characteristics of the mixture flowing through a plurality of sensing devices; b) determining values of N-1 properties of the mixture from the measured characteristics, where N is equal to L+M; c) establishing N-1 equations relating the individual concentrations of the fluid constituents to the N-1 properties of the mixture; and d) solving the N-1 equations and a constitutive equation for the individual concentrations of L of the fluid constituents and for identities of M of the fluid constituents.
Claim 2
Independent Claim
118 words
A method of determining individual concentrations of at least L fluid constituents and identities of at least M fluid constituents of a mixture of fluids, where L and M are non-negative integers, the method comprising the steps of: a) measuring characteristics of the mixture flowing through a plurality of sensing devices; b) determining values of N-1 properties of the mixture from the measured characteristics, where N is equal to L+M; c) establishing N-1 equations relating the individual concentrations of the fluid constituents to the N-1 properties of the mixture; and d) solving the N-1 equations and a constitutive equation for the individual concentrations of L of the fluid constituents and for identities of M of the fluid constituents.
Claim 3
Dependent Claim
35 words
The method of claim 1, wherein the mixture of fluids comprises N fluids, and wherein step d) includes solving the N-1 equations and the constitutive equation for the N individual concentrations of the fluid constituents.
Claim 4
Dependent Claim
18 words
The method according to claim 2, wherein step a) is performed using a plurality of fluidic sensing devices.
Claim 5
Dependent Claim
12 words
The method according to claim 2, wherein the fluid constituents are gasses.
Claim 6
Dependent Claim
12 words
The method according to claim 2, wherein the fluid constituents are liquids.
Claim 7
Dependent Claim
23 words
The method according to claim 2, wherein the identity of each of the fluid constituents is known, and M is equal to zero.
Claim 8
Dependent Claim
19 words
The method according to claim 2, wherein the individual concentrations of the fluid constituents are determined in real time.
Claim 9
Dependent Claim
79 words
The method according to claim 2, wherein step a) includes: a1) measuring absolute pressure of the mixture; a2) measuring absolute temperature of the mixture; a3) measuring a frequency of oscillation of the mixture in an oscillator flowmeter; a4) measuring the pressure drop of the mixture across an orifice; and a5) measuring the pressure drop of the mixture across a capillary; and step b) includes: b1) calculating a density of the mixture; and b2) calculating a viscosity of the mixture.
Claim 10
Dependent Claim
25 words
The method according to claim 8, wherein steps a3) and a4) are performed using a single oscillator serving as both said flowmeter and said orifice.
Claim 11
Dependent Claim
29 words
The method according to claim 8, wherein the capillary is one of a plurality of parallel capillaries, and wherein step a5) includes passing the mixture through said parallel capillaries.
Claim 12
Dependent Claim
36 words
The method according to claim 8, wherein step a) further includes: a6) measuring an acoustic frequency of the mixture in a sonic oscillator; and step b) further includes: b3) calculating the specific heat of the mixture.
Claim 13
Dependent Claim
75 words
The method according to claim 2, wherein, said mixture includes an N+1th fluid and two of said fluid constituents are treated as a single fluid in steps c) and d), such that a combined concentration of the two fluid constituents is determined in step d), the method further comprising the step of: e) determining the individual concentrations of the two fluid constituents by determining changes in the combined concentration of the two fluid constituents overtime.
Claim 14
Dependent Claim
152 words
The method according to claim 12, wherein step e) includes: e1) determining the combined concentration of the two fluid constituents at a plurality of times during a single breath cycle, one of said times corresponding to a time in the single breath cycle when the combined concentration of the two fluid constituents is substantially at a minimum; e2) determining a concentration of a first of the two fluid constituents over the single breath cycle as a function of the combined concentration of the two fluid constituents determined at said one of said times; and e3) making a plurality of determinations of a concentration of a second of the two fluid constituents during the single breath cycle by subtracting the concentration of the first of the two fluid constituents determined in step e2) from the combined concentration of the two fluid constituents determined at said plurality of times during the single breath cycle.
Claim 15
Independent Claim
65 words
The method according to 13, wherein: in step e1), at said one of said times, the concentration of the second of the fluid constituents is substantially zero; and in step e2), the concentration of the first of the two fluid constituents is assumed to be, over the single breath cycle, the combined concentration of the two fluid constituents determined at said one of said times.
Claim 16
Independent Claim
65 words
The method according to 13, wherein: in step e1), at said one of said times, the concentration of the second of the fluid constituents is substantially zero; and in step e2), the concentration of the first of the two fluid constituents is assumed to be, over the single breath cycle, the combined concentration of the two fluid constituents determined at said one of said times.
Claim 17
Dependent Claim
17 words
The method according to claim 12, wherein the two fluid constituents are carbon dioxide and nitrous oxide.
Claim 18
Dependent Claim
151 words
The method according to claim 2, wherein the identity of one of the fluid constituents is initially unknown, and wherein step c) includes assuming that the unknown fluid constituent is one of P fluids whose properties are known, where P is a positive integer, the method further comprising the steps of: e) indicating that the unknown fluid constituent is said one of the P fluids if the individual concentrations solved for in step d) fall within respective predetermined concentration ranges; and f) if the individual concentrations solved for in step d) do not fall within the respective predetermined concentration ranges, repeating steps c) through e) by assuming the unknown fluid constituent is different ones of said P fluids, until the individual concentrations solved for in step d) fall within the respective predetermined concentration ranges or until the unknown fluid constituent has been assumed to be every one of said P fluids.
Claim 19
Dependent Claim
208 words
The method according to claim 2, wherein: the identity of one of the fluid constituents is initially unknown; step b) includes determining a value of an Nth property of the mixture from the measured characteristics; and step c) includes assuming that the unknown fluid constituent is one of P fluids whose properties are known, where P is a positive integer; the method further comprising the steps of: e) calculating a value of an Nth property of the unknown fluid constituent from an equation relating the Nth property of the mixture to individual concentrations of the constituent components, where the Nth property of the mixture is not used in step c); f) determining whether the calculated value of the Nth property of the unknown fluid constituent matches, to within a predetermined threshold, a known value of the Nth property of said one of the P fluids; g) if a match is found in step f), indicating that the unknown fluid constituent is said one of the P fluids; and h) if a match is not found in step f), repeating steps c) through g) with different ones of said P fluids until a match is found or until a match has been attempted with all of said P fluids.
Claim 20
Dependent Claim
72 words
The method according to claim 2, wherein said mixture comprises P+N fluids, where P is a positive integer, the method further comprising the step of: e) prior to step c), determining the individual concentrations of P of the fluid constituents, wherein step c) includes establishing N-1 equations relating the individual concentrations of the fluid constituents, including the determined individual concentrations of the P fluid constituents, to the N-1 properties of the mixture.
Claim 21
Dependent Claim
20 words
The method of claim 12. wherein the fluid constituents of the mixture of fluids are gasses respired during anesthesia administration.
Claim 22
Dependent Claim
106 words
The method according to claim 19, wherein step a) includes the steps of: a1) measuring absolute temperature of the mixture; a2) measuring absolute pressure of the mixture; a3) measuring a first oscillation frequency of the mixture flowing through a first fluidic oscillator; a4) measuring a pressure drop of the mixture flowing through the first fluidic oscillator; a5) measuring a pressure drop of the mixture flowing through a fluidic capillary; and a6) measuring a second oscillation frequency of the mixture flowing through a second fluidic oscillator; and step b) includes calculating a density, a viscosity and specific heat of the mixture from characteristics measured in step a).
Claim 23
Dependent Claim
19 words
The method according to claim 19, wherein the individual concentrations of the gas constituents are determined in real time.
Claim 24
Dependent Claim
34 words
The method according to claim 19, wherein the gas constituents of the mixture include: oxygen, carbon dioxide, nitrous oxide, a potent, volatile anesthetic agent, and one of nitrogen and another potent, volatile anesthetic agent.
Claim 25
Dependent Claim
38 words
The method according to claim 1, wherein the mixture includes oxygen in an initially undetermined concentration and an initially unidentified potent, volatile anesthetic agent in an initially undetermined concentration, such that L equals 2 and M equals 1.
Claim 26
Dependent Claim
27 words
The method according to claim 1, wherein the mixture includes two initially unknown fluids in initially undetermined concentrations, such that L equals 2 and M equals 2.
Claim 27
Independent Claim
117 words
An apparatus for determining individual concentrations of at least L fluid constituents and identities of at least M fluid constituents of a mixture of fluids, where L and M are non-negative integers, the apparatus comprising: a plurality of sensors adapted to measure physical conditions of the mixture; and a processor configured to: determine values of N-1 properties of the mixture from the measured physical conditions, where N is equal to L+M; establish N-1 equations relating the individual concentrations of the fluid constituents to the N-1 properties of the mixture; and solve the N-1 equations and a constitutive equation for the individual concentrations of L of the fluid constituents and for identities of M of the fluid constituents.
Claim 28
Independent Claim
117 words
An apparatus for determining individual concentrations of at least L fluid constituents and identities of at least M fluid constituents of a mixture of fluids, where L and M are non-negative integers, the apparatus comprising: a plurality of sensors adapted to measure physical conditions of the mixture; and a processor configured to: determine values of N-1 properties of the mixture from the measured physical conditions, where N is equal to L+M; establish N-1 equations relating the individual concentrations of the fluid constituents to the N-1 properties of the mixture; and solve the N-1 equations and a constitutive equation for the individual concentrations of L of the fluid constituents and for identities of M of the fluid constituents.
Claim 29
Dependent Claim
33 words
The apparatus of claim 25. wherein the mixture of fluids comprises N fluids, and wherein said processor solves the N-1 equations and the constitutive equation for the individual concentrations of the fluid constituents.
Claim 30
Dependent Claim
78 words
The apparatus according to claim 26, wherein said plurality of sensors includes: a fluidic oscillator through which the mixture flows; a plurality of microphones adapted to measure an oscillation frequency of the mixture in the fluidic oscillator; a capillary through which the mixture flows; a first pressure transducer adapted to measure a pressure drop of the mixture across said fluidic capillary; and a second pressure transducer adapted to measure a pressure drop of the mixture across an orifice.
Claim 31
Dependent Claim
17 words
The apparatus according to claim 27, wherein a nozzle of said fluidic oscillator serves as said orifice.
Claim 32
Dependent Claim
16 words
The apparatus according to claim 27, further comprising said orifice disposed downstream of said fluidic oscillator.
Claim 33
Dependent Claim
17 words
The apparatus according to claim 27, wherein said fluidic oscillator is a fluidic amplifier feedback oscillator flowmeter.
Claim 34
Dependent Claim
29 words
The apparatus according to claim 27, wherein said capillary is one of a plurality of capillaries arranged to provide parallel resistance to flow of the mixture through said capillaries.
Claim 35
Dependent Claim
14 words
The apparatus according to claim 31, wherein said capillaries are situated substantially in parallel.
Claim 36
Dependent Claim
36 words
The apparatus according to claim 27, wherein said plurality of sensors further includes: a temperature sensor adapted to measure absolute temperature of the mixture; and a pressure sensor adapted to measure absolute pressure of the mixture.
Claim 37
Dependent Claim
40 words
The apparatus according to claim 27, wherein said plurality of sensors further includes: a sonic oscillator through which the mixture flows; and a second plurality of microphones adapted to measure an oscillation frequency of the mixture in the sonic oscillator.
Claim 38
Dependent Claim
74 words
The apparatus according to claim 27, further comprising an electronic amplifier, wherein said plurality of microphones includes a first microphone disposed in a first feedback path of said fluidic oscillator and a second microphone disposed in a second feedback path of said fluidic oscillator, and wherein outputs of said first and second microphones are 180° out of phase and are differenced in said electronic amplifier, thereby providing isolation from ambient noise by active cancellation.
Claim 39
Dependent Claim
18 words
The apparatus according to claim 26, wherein said processor calculates a density and a viscosity of the mixture.
Claim 40
Dependent Claim
16 words
The apparatus according to claim 35, wherein said processor further calculates specific heat of the mixture.
Claim 41
Dependent Claim
24 words
The apparatus according to claim 26, further comprising a display configured to display the individual concentrations of the fluid constituents determined by said processor.
Claim 42
Dependent Claim
12 words
The apparatus according to claim 26, wherein the fluid constituents are gasses.
Claim 43
Dependent Claim
12 words
The apparatus according to claim 26, wherein the fluid constituents are liquids.
Claim 44
Dependent Claim
23 words
The apparatus according to claim 26, wherein the identity of each of the fluid constituents is known, and M is equal to zero.
Claim 45
Dependent Claim
20 words
The apparatus according to claim 26, wherein said processor determines the individual concentrations of the fluid constituents in real time.
Claim 46
Dependent Claim
51 words
The apparatus according to claim 26, wherein, said mixture includes an N+1th fluid and said processor determines a combined concentration of two of said fluid constituents, said processor determining the individual concentrations of the two fluid constituents by determining changes in the combined concentration of the two fluid constituents over time.
Claim 47
Dependent Claim
144 words
The apparatus according to claim 43, wherein said processor: determines the combined concentration of the two fluid constituents at a plurality of times during a single breath cycle, one of said times corresponding to a time in the single breath cycle when the combined concentration of the two fluid constituents is substantially at a minimum; determines a concentration of a first of the two fluid constituents over the single breath cycle as a function of the combined concentration of the two fluid constituents determined at said one of said times; and makes a plurality of determinations of a concentration of a second of the two fluid constituents during the single breath cycle by subtracting the concentration of the first of the two fluid constituents from the combined concentration of the two fluid constituents determined at said plurality of times during the single breath cycle.
Claim 48
Independent Claim
59 words
The apparatus according to 44, wherein the concentration of the second of the fluid constituents is substantially zero at said one of said times, and the concentration of the first of the two fluid constituents is assumed to be, over the single breath cycle, the combined concentration of the two fluid constituents determined at said one of said times.
Claim 49
Independent Claim
59 words
The apparatus according to 44, wherein the concentration of the second of the fluid constituents is substantially zero at said one of said times, and the concentration of the first of the two fluid constituents is assumed to be, over the single breath cycle, the combined concentration of the two fluid constituents determined at said one of said times.
Claim 50
Dependent Claim
17 words
The apparatus according to claim 43, wherein the two fluid constituents are carbon dioxide and nitrous oxide.
Claim 51
Dependent Claim
32 words
The apparatus according to claim 43, wherein the N+1 fluid constituents include: oxygen, carbon dioxide, nitrous oxide, a potent, volatile anesthetic agent, and one of nitrogen and another potent, volatile anesthetic agent.
Claim 52
Dependent Claim
17 words
The apparatus according to claim 26, further comprising a memory for storing properties of the fluid constituents.
Claim 53
Dependent Claim
169 words
The apparatus according to claim 26, wherein: the identity of one of the fluid constituents is initially unknown; said processor establishes the N-1 equations by assuming that the unknown fluid constituent is one of P fluids whose properties are known, where P is a positive integer; said processor determines that the unknown fluid constituent is said one of the P fluids if the individual concentrations solved for fall within respective predetermined concentration ranges; and if the individual concentrations solved for do not fall within the respective predetermined concentration ranges, said processor establishes N-1 equations relating the individual concentrations of the fluid constituents to the N-1 properties of the mixture by assuming the unknown fluid constituent is different ones of said P fluids and solves the N-1 equations and a constitutive equation for the individual concentrations of the fluid constituents, until the individual concentrations solved for fall within the respective predetermined concentration ranges or until the unknown fluid constituent has been assumed to be every one of said P fluids.
Claim 54
Dependent Claim
18 words
The apparatus according to claim 49, further comprising a look-up table for storing properties of said P fluids.
Claim 55
Dependent Claim
240 words
The apparatus according to claim 26, wherein: the identity of one of the fluid constituents is initially unknown; said processor determines a value of an Nth property of the mixture from the measured physical conditions; said processor establishes the N-1 equations by assuming that the unknown fluid constituent is one of P fluids whose properties are known, where P is a positive integer; said processor calculates a value of an Nth property of the unknown fluid constituent from an equation relating the Nth property of the mixture to individual concentrations of the constituent components, where the Nth property of the mixture is not used to establish the N-1 equations; said processor determines whether the calculated value of the Nth property of the unknown fluid constituent matches, to within a predetermined threshold, a known value of the Nth property of said one of the P fluids; said processor determines that the unknown fluid constituent is said one of the P fluids if a match is found; and if a match is not found, said processor establishes N-1 equations relating the individual concentrations of the fluid constituents to the N-1 properties of the mixture by assuming the unknown fluid constituent is different ones of said P fluids and solves the N-1 equations and a constitutive equation for the individual concentrations of the fluid constituents, until a match is found or until a match has been attempted with all of said P fluids.
Claim 56
Dependent Claim
18 words
The apparatus according to claim 51, further comprising a look-up table for storing properties of said P fluids.
Claim 57
Dependent Claim
66 words
The apparatus according to claim 26, wherein: said mixture comprises P+N fluids, where P is a positive integer; individual concentrations of P of the fluid constituents are known prior to establishing the N-1 equations; and said processor establishes the N-1 equations relating the individual concentrations of the fluid constituents, including the known individual concentrations of the P fluid constituents, to the N-1 properties of the mixture.
Claim 58
Dependent Claim
20 words
The apparatus of claim 43, wherein the fluid constituents of the mixture of fluids are gasses respired during anesthesia administration.
Claim 59
Dependent Claim
139 words
The apparatus according to claim 54, wherein said plurality of sensors includes: a temperature sensor adapted to measure absolute temperature of the mixture; a pressure sensor adapted to measure absolute pressure of the mixture; a fluidic oscillator through which the mixture flows; a plurality of microphones adapted to measure an oscillation frequency of the mixture in the fluidic oscillator; a first pressure transducer adapted to measure a pressure drop of the mixture across said fluidic oscillator; a capillary through which the mixture flows; a second pressure transducer adapted to measure a pressure drop of the mixture across said capillary; a sonic oscillator through which the mixture flows; and a second microphone adapted to measure an oscillation frequency of the mixture in the sonic oscillator; and wherein said processor calculates a density, a viscosity and specific heat of the mixture.
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