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US3620207A
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Blood flowmeter
Assignee: Iowa State University Research Foundation Inc
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Filing: 1969-05-14
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Granted: 1971-11-16
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Expires: 1989-05-14
Abstract
Abstract This invention relates to a blood flowmeter comprising a catheter suitable for insertion into a blood vessel, thermal resistors (thermistors) connected in electrical circuits disposed in the catheter near the insertable end of the catheter; and moving means for moving the thermistors out of the insertable end of the catheter into the blood flow and, when desired, back into the catheter. Means are also provided for measuring electrical response through the thermistors. Flow characteristics in the blood vessels are determined by observing changes in measured electrical response through the thermistor circuits.
Inventors
- 👤 John C Sinclair
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 23:38
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/68; A61B5/6846; A61B5/6886; A61B5/02; A61B5/026; A61B5/0275; A61B5/028
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
196 words
A device for use in measuring fluid flow comprising: a catheter having an insertable end and a measurement end, said catheter being elongate and flexible and having an opening therethrough; a pair of wires extending longitudinally through said catheter and movable longitudinally through said opening therein, each of said wires being electrically insulated and electrically conductive and having ends disposed proximate opposite ends of said catheter; a thermistor having an electrical resistance which is variable with slight variations in ambient temperature, said thermistor being electrically insulated, disposed near said insertable end of said catheter, and electrically connected between the ends of said wires; moving means connected to said wires for longitudinally moving said wires and said thermistor connected thereto into and out of said insertable end of said catheter; means for introducing a liquid through the opening in said catheter through which said wires move and out the insertable end of said catheter such that the liquid introduced may flow around and in contact with said thermistor; and connecting means for connecting said ends of said wires proximate said measurement end of said catheter to an instrument capable of measuring the electrical response through said thermistor.
Claim 2
Independent Claim
196 words
A device for use in measuring fluid flow comprising: a catheter having an insertable end and a measurement end, said catheter being elongate and flexible and having an opening therethrough; a pair of wires extending longitudinally through said catheter and movable longitudinally through said opening therein, each of said wires being electrically insulated and electrically conductive and having ends disposed proximate opposite ends of said catheter; a thermistor having an electrical resistance which is variable with slight variations in ambient temperature, said thermistor being electrically insulated, disposed near said insertable end of said catheter, and electrically connected between the ends of said wires; moving means connected to said wires for longitudinally moving said wires and said thermistor connected thereto into and out of said insertable end of said catheter; means for introducing a liquid through the opening in said catheter through which said wires move and out the insertable end of said catheter such that the liquid introduced may flow around and in contact with said thermistor; and connecting means for connecting said ends of said wires proximate said measurement end of said catheter to an instrument capable of measuring the electrical response through said thermistor.
Claim 3
Dependent Claim
49 words
The device of claim 1 adapted for measuring blood flow through blood vessels wherein a plurality of pairs of said wires extend through said catheter, each of said pairs of wires having a thermistor disposed near the insertable end of the catheter, and said thermistors being spaced apart longitudinally.
Claim 4
Dependent Claim
22 words
The device of claim 2 wherein at least three thermistors are disposed near said insertable end, said thermistors being spaced apart longitudinally.
Claim 5
Dependent Claim
75 words
The device of claim 3 wherein said means for introducing a liquid comprises: a fitting having a leg and two arms, all having interconnecting passageways formed therethrough; means on one of said arms for attaching the measurement end of said catheter; means on the second of said arms for attaching the means for longitudinally moving said wires in said catheter; means on said leg for introducing liquid through said catheter and into the blood vessel.
Claim 6
Dependent Claim
48 words
The device of claim 4 wherein said moving means comprises: a tubular element slidably inserted into said second arm and rigidly affixed to said wires; said tubular element having annular gradations formed therearound; and a handle member affixed to said tubular element and having said wires running therethrough.
Claim 7
Dependent Claim
36 words
The device of claim 5 wherein centering means comprising a plurality of flexible loops disposed about the catheter are formed on the insertable end of said catheter to center said catheter laterally in the blood vessel.
Claim 8
Dependent Claim
19 words
The device of claim 6 wherein a plurality of holes are formed through said catheter proximate said insertable end.
Claim 9
Dependent Claim
30 words
The device of claim 7 wherein said insertable end of said catheter and said insulation for said wires and said thermistors are manufactured from a material innocuous to mammalian tissue.
Claim 10
Dependent Claim
22 words
The device of claim 8 wherein said wires are formed from platinum alloy and have an outside diameter of about 0.0025 inches.
Claim 11
Dependent Claim
17 words
The device of claim 9 wherein the time constant of said thermistors is more than 100 Hz.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-15 | 1975-05-17 | 1975-11-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-15 | 1979-05-17 | 1979-11-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-15 | 1983-05-17 | 1983-11-16 | $7700.00 | Window Closed / Lapsed |