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US5134998A
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System and method for predicting the value of a compositional parameter of blood
Assignee: Terumo Cardiovascular Systems Corp
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Filing: 1990-04-26
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Granted: 1992-08-04
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Expires: 2010-04-26
Abstract
Abstract A system for determining the value of a compositional parameter of blood, including a sensor for producing a signal related to the value of the compositional parameter. A computer analyzes the signal and produces an output representing the value of the compositional parameter of blood. There is a delayed response in the system such that the signal has a time-varying waveform that varies from an initial value to an equilibrated value. The equilibrated value is predicted by detecting the occurrence of an inflection point and then computing an estimate of the equilibrated value based upon the assumption that the waveform varies exponentially from the inflection point to the equilibrated value.
Inventors
- 👤 James K. Tusa
- 👤 William W. Miller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 14:43
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/145; A61B5/1455; G; G01; G01N; G01N33/00; G01N33/48; G01N33/483; G01N33/487; G01N33/49; G01N33/4925
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
192 words
A system for determining the value of a compositional parameter of blood, comprising: means for containing blood; sensor means on the containing means for producing a signal related to the value of the compositional parameter of blood; computer means coupled to the sensor means for analyzing the signal and producing an output representing the value of the compositional parameter of blood; wherein there is a delayed response such that the signal has a time-varying waveform P(t) that deviates from an exponential function as it varies from an initial value P(t 0 ) occurring at a time t 0 at which the sensor means is subjected to the blood toward an equilibrated value P(t E ) occurring at a time t E thereafter; and wherein the computer means includes means for detecting the occurrence of an inflection point P(t I ) occurring between the initial value P(t 0 ) and the equilibrated value P(t E ); and means for computing an estimate of the equilibrated value P(t E ) based upon the assumption that the waveform P(t) varies exponentially from the inflection point P(t I ) to the equilibrated value P(t E ).
Claim 2
Independent Claim
192 words
A system for determining the value of a compositional parameter of blood, comprising: means for containing blood; sensor means on the containing means for producing a signal related to the value of the compositional parameter of blood; computer means coupled to the sensor means for analyzing the signal and producing an output representing the value of the compositional parameter of blood; wherein there is a delayed response such that the signal has a time-varying waveform P(t) that deviates from an exponential function as it varies from an initial value P(t 0 ) occurring at a time t 0 at which the sensor means is subjected to the blood toward an equilibrated value P(t E ) occurring at a time t E thereafter; and wherein the computer means includes means for detecting the occurrence of an inflection point P(t I ) occurring between the initial value P(t 0 ) and the equilibrated value P(t E ); and means for computing an estimate of the equilibrated value P(t E ) based upon the assumption that the waveform P(t) varies exponentially from the inflection point P(t I ) to the equilibrated value P(t E ).
Claim 3
Dependent Claim
39 words
A system as defined in claim 1, wherein the compositional parameter of blood is a blood gas, the sensor means is responsive to such blood gas, and said signal is related to the partial pressure of such blood gas.
Claim 4
Dependent Claim
20 words
A system as defined in claim 2 wherein the sensor means includes a fluorescent sensor responsive to the blood gas.
Claim 5
Dependent Claim
26 words
A system as defined in claim 3, wherein the compositional parameter of blood is CO 2 and the fluorescent sensor is responsive to CO 2 .
Claim 6
Dependent Claim
36 words
A system as defined in claim 1, wherein the compositional parameter of blood is carbon dioxide, the sensor means is responsive to carbon dioxide and said signal is related to the partial pressure of carbon dioxide.
Claim 7
Dependent Claim
33 words
A system as defined in claim 1, wherein the compositional parameter of blood is oxygen, the sensor means is responsive to oxygen, and said signal is related to the partial pressure of oxygen.
Claim 8
Dependent Claim
31 words
A system as defined in claim 1, wherein the compositional parameter of blood is pH, the sensor means is responsive to pH, and said signal is related to the pH value.
Claim 9
Dependent Claim
56 words
A system as recited in claim 1, wherein the means for computing an estimate of the equilibrated value P(t E ) uses the relationship (A+B).sub.est =P(t.sub.I)+[Tau * MAX(dp/dt)] where (A+B) est is the estimate of the equilibrated value, Tau is a constant, and MAX(dp/dt) is the slope of P(t) at the inflection point P(t I ).
Claim 10
Dependent Claim
72 words
A system as recited in claim 8, wherein the means for computing an estimate of the equilibrated value P(t E ) includes means for computing an estimated value of Tau using the relationship TAU.sub.est =K.sub.1 +K.sub.2 /MAX(dp/dt) where TAU est is the estimated value of Tau, K 1 is a first constant, K 2 is a second constant, and MAX(dp/dt) is the slope of P(t) at the inflection point P(t I ).
Claim 11
Dependent Claim
25 words
A system as recited in claim 9, wherein the value of K 1 is approximately 15 and the value of K 2 is approximately 5.5.
Claim 12
Dependent Claim
94 words
A system as recited in claim 8, wherein the means for computing an estimate of the equilibrated value P(t E ) includes means for computing an estimated value of TAU using the relationship TAU.sub.est =K.sub.1 +K.sub.2 * MAX(dp/dt).sup.K3 +K.sub.4 * MAX(dp/pdt).sup.K5 where MAX (dp/dt) is the slope of P(t) at the inflection point P(t 1 ) and MAX (dp/pdt) is the maximum value of the proportional slope of P(t) occurring near the inflection point P(t I ), and K 1 , K 2 , K 3 , K 4 and K 5 are constants.
Claim 13
Independent Claim
78 words
A system for determining the value of a compositional parameter of blood comprising: a sensor exposable to blood for providing a signal related to the compositional parameter of the blood, said signal varying non-exponentially until it reaches an inflection point and approximately exponentially after the inflection point to a final value; means for detecting the inflection point; and means for estimating the final value based on the assumption that the signal varies approximately exponentially after the inflection point.
Claim 14
Independent Claim
78 words
A system for determining the value of a compositional parameter of blood comprising: a sensor exposable to blood for providing a signal related to the compositional parameter of the blood, said signal varying non-exponentially until it reaches an inflection point and approximately exponentially after the inflection point to a final value; means for detecting the inflection point; and means for estimating the final value based on the assumption that the signal varies approximately exponentially after the inflection point.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-08-04 | 1996-02-03 | 1996-08-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-08-04 | 2000-02-03 | 2000-08-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-08-04 | 2004-02-03 | 2004-08-04 | $7700.00 | Window Closed / Lapsed |