Patent US4730623A successfully refreshed from Google Patents.
US4730623A
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Cardiac output estimation method and apparatus
Assignee: Individual
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Filing: 1985-06-14
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Granted: 1988-03-15
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Expires: 2005-06-14
Abstract
Abstract Thermocouple pairs measure the temperatures at a cold-fluid injection point and a downstream point. The reference thermocouple of each pair sees the temperature of a thermally floating heat sink of unknown temperature that has high thermal conductivity and mass, and is well insulated from the environment. Consequently the heat-sink temperature drift is practically constant. To the extent that heat-sink temperature drift is significant, the invention overcomes the effects of drift to a first approximation by providing electronic circuitry that in effect registers the drift in measurement voltage before fluid injection, extrapolates this voltage drift into the measurement time period, and automatically subtracts the extrapolated voltage drift from the measurement voltages.
Inventors
- 👤 Arnold St. J. Lee
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 18:09
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/02; A61B5/026; A61B5/0275; A61B5/028
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
180 words
An apparatus for estimating the flow rate of blood in a bloodstream comprising: means for injecting into such bloodstream a quantity of fluid whose temperature is distinctly different from that of the blood; means, having a reference thermocouple, for measuring changes in the temperature of the blood at a point downstream from the injection point; and a reference heat sink which is not temperature-controlled, thermally connected to the reference thermocouple of the means for measuring changes; the change-measuring means including: a sensing thermocouple disposed at the downstream point, a reference thermocouple disposed to substantially assume the temperature of the reference heat sink, and means for measuring the voltage produced by the sensing and reference thermocouples, operating as an opposed thermocouple pair, while the injected fluid passes the downstream point; and electronic means responsive to the measured voltage for determining the blood temperature changes sensed by the sensing thermocouple independently of the temperature of the reference thermocouple considered singly wherein said electronic means compensates for changes in the temperature of the heat sink while the injected fluid passes the downstream point.
Claim 2
Independent Claim
180 words
An apparatus for estimating the flow rate of blood in a bloodstream comprising: means for injecting into such bloodstream a quantity of fluid whose temperature is distinctly different from that of the blood; means, having a reference thermocouple, for measuring changes in the temperature of the blood at a point downstream from the injection point; and a reference heat sink which is not temperature-controlled, thermally connected to the reference thermocouple of the means for measuring changes; the change-measuring means including: a sensing thermocouple disposed at the downstream point, a reference thermocouple disposed to substantially assume the temperature of the reference heat sink, and means for measuring the voltage produced by the sensing and reference thermocouples, operating as an opposed thermocouple pair, while the injected fluid passes the downstream point; and electronic means responsive to the measured voltage for determining the blood temperature changes sensed by the sensing thermocouple independently of the temperature of the reference thermocouple considered singly wherein said electronic means compensates for changes in the temperature of the heat sink while the injected fluid passes the downstream point.
Claim 3
Dependent Claim
23 words
The apparatus of claim 1, wherein: the heat sink is very generally at an ambient temperature distinctly different from that of the blood.
Claim 4
Dependent Claim
32 words
The apparatus of claim 1, wherein: the heat sink has high thermal conductivity; whereby thermal effects at any part of the heat sink tend to be averaged over the entire heat sink.
Claim 5
Dependent Claim
113 words
The apparatus of claim 1, further comprising: means for measuring the temperature of the fluid substantially at the injection point, the fluid-temperature measuring means including: a second sensing thermocouple disposed substantially at the injection point, a second reference thermocouple disposed to assume the temperature of the reference heat sink, means for measuring the voltage produced by the second sensing and reference thermocouples, operating as a second opposed thermocouple pair, while the fluid is injected; and second electronic means responsive to the measured voltage produced by the second opposed thermocouple pair for determining the blood temperature changes sensed by the second sensing thermocouple independently of the temperature of the second reference thermocouple considered singly.
Claim 6
Dependent Claim
32 words
The apparatus of claim 4 wherein said second electronic means is further comprising: means for approximately integrating the measured voltage produced by the second thermocouple pair over injected volume of the fluid.
Claim 7
Dependent Claim
91 words
The apparatus of claim 1, wherein the electronic means further comprises: means for registering an approximation to the effects of drift in heat-sink temperature upon the measured voltage before the fluid is injected; means for extrapolating said registered approximation into the time period in which the injected fluid passes the downstream point; and means for correcting the measured voltage to compensate for the extrapolated approximation; said electronic means therein tending to compensate for drift in the electronic means itself, except for drift in the registering means and in the extrapolating means.
Claim 8
Dependent Claim
55 words
The apparatus of claim 6, wherein: the approximation-registering means respond to the mean rate of drift of the measured voltage before the fluid is injected; the extrapolation means provide a compensation signal that drifts at said mean rate after the fluid is injected; and the correction means subtract the compensation signal from the measured voltage.
Claim 9
Independent Claim
128 words
A method for use in estimating the flow rate of blood in the bloodstream from a living being's heart, comprising: injecting into such bloodstream, at a particular point near such heart, a quantity of fluid whose temperature is distinctly different from that of the blood; while the injected fluid passes the downstream point, measuring changes in the voltage output of an opposed thermocouple pair whose sensing junction is disposed downstream from the injection point and whose reference junction is disposed to substantially assume the temperature of a reference heat sink which is not temperature-controlled; said measuring step being independent of the temperature of the reference heat sink considered singly; and compensating for changes in the temperature of the heat sink while the injected fluid passes the downstream point.
Claim 10
Independent Claim
128 words
A method for use in estimating the flow rate of blood in the bloodstream from a living being's heart, comprising: injecting into such bloodstream, at a particular point near such heart, a quantity of fluid whose temperature is distinctly different from that of the blood; while the injected fluid passes the downstream point, measuring changes in the voltage output of an opposed thermocouple pair whose sensing junction is disposed downstream from the injection point and whose reference junction is disposed to substantially assume the temperature of a reference heat sink which is not temperature-controlled; said measuring step being independent of the temperature of the reference heat sink considered singly; and compensating for changes in the temperature of the heat sink while the injected fluid passes the downstream point.
Claim 11
Dependent Claim
23 words
The method of claim 8, wherein: the heat sink is very generally at an ambient temperature distinctly different from that of the blood.
Claim 12
Dependent Claim
32 words
The method of claim 8, wherein: the heat sink has high thermal conductivity; whereby thermal effects at any part of the heat sink tend to be averaged over the entire heat sink.
Claim 13
Dependent Claim
68 words
The method of claim 8, further comprising: while the injected fluid passes the downstream point, also measuring the voltage output of a second opposed thermocouple pair whose sensing junction is disposed substantially at the injection point and whose reference junction is disposed to substantially assume the temperature of a reference heat sink; said second-pair measuring step being independent of the temperature of the reference heat sink considered singly.
Claim 14
Dependent Claim
24 words
The method of claim 11, further comprising: approximately integrating the measured voltage produced by the second thermocouple pair over injected volume of the fluid.
Claim 15
Dependent Claim
58 words
The method of claim 8, wherein the compensating step includes: registering an approximation to the effects of drift in heat-sink temperature upon the measured voltage before the fluid is injected; extrapolating said registered approximation into the time period in which the injected fluid passes the downstream point; and correcting the measured voltage to compensate for the extrapolated approximation.
Claim 16
Dependent Claim
54 words
The method of claim 13, wherein: the approximation-registering step registers the mean rate of drift of the measured voltage before the fluid is injected; the extrapolation step provides a compensation signal that drifts at said mean rate after the fluid is injected; and the correction step subtracts the compensation signal from the measured voltage.
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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) | 1991-03-15 | 1991-09-14 | 1992-03-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-03-15 | 1995-09-14 | 1996-03-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-03-15 | 1999-09-14 | 2000-03-15 | $7700.00 | Window Closed / Lapsed |