EP0417796A2
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EP
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Hematocrit measuring instrument
Assignee: Toyota Central R&D Labs Inc
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Filing: 1990-09-13
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Granted: —
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Expires: 2010-09-13
Abstract
Abstract A hematocrit measuring instrument for measuring a value of the hematocrit based on impedances of blood includes a low-frequency impedance measuring device (20) for measuring a low-frequency impedance of the blood and a high-frequency impedance measuring device (30) for measuring a high-frequency impedance of the blood. The hematocrit value is calculated based on the measured low and high-frequency impedances of the blood. Low and high-frequency measuring electrode pairs (26a/26b and 28a/28b) are disposed substantially at the same position in the blood flow direction in the blood flow passage (10) thereby enabling the hematocrit measuring instrument to measure the hematocrit value without being influenced due to temperature variations of the blood.
Inventors
- 👤 Toshikazu Ishihara
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 05:10
CPC Classifications
A; A61; A61M; A61M1/00; A61M1/36; A61M1/3621; A61M1/3669; A61M1/3607; A61M1/3609; G; G01; G01N; G01N33/00; G01N33/48; G01N33/483; G01N33/487; G01N33/49; G01N33/4915
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
202 words
A hematocrit measuring instrument for deriving a hematocrit value from the impedance of the blood and comprising: (a) a blood flow passage (10); (b) a low-frequency impedance measuring device (20) in which at least a pair of low-frequency impedance measuring electrodes (26a/26b, 27a/27b) are disposed in said blood flow passage and are applied a low-frequency current in which a cell membrane impedance is much larger than a blood plasma impedance or an intra-cellular fluid impedance, so as to measure a low-frequency impedance of the blood; (c) a high-frequency impedance measuring device (30) in which at least a pair of high-frequency impedance measuring electrodes (28a/28b) are disposed in said blood flow passage and are applied a high-frequency current in which the cell membrane impedance is negligible compared with the blood plasma impedance or the intracellular fluid impedance, so as to measure a high-frequency impedance in the blood; and (d) an arithmetic unit (40) for calculating a hematocrit value based on the low and high-frequency impedances of the blood; said pair of low-frequency impedance measuring electrodes (26a/26b, 27a/27b) and said pair of high-frequency measuring electrodes (28a/28b) being disposed substan tially at the same position in said blood flow passage in the blood flowing direction.
Claim 2
Dependent Claim
202 words
A hematocrit measuring instrument for deriving a hematocrit value from the impedance of the blood and comprising: (a) a blood flow passage (10); (b) a low-frequency impedance measuring device (20) in which at least a pair of low-frequency impedance measuring electrodes (26a/26b, 27a/27b) are disposed in said blood flow passage and are applied a low-frequency current in which a cell membrane impedance is much larger than a blood plasma impedance or an intra-cellular fluid impedance, so as to measure a low-frequency impedance of the blood; (c) a high-frequency impedance measuring device (30) in which at least a pair of high-frequency impedance measuring electrodes (28a/28b) are disposed in said blood flow passage and are applied a high-frequency current in which the cell membrane impedance is negligible compared with the blood plasma impedance or the intracellular fluid impedance, so as to measure a high-frequency impedance in the blood; and (d) an arithmetic unit (40) for calculating a hematocrit value based on the low and high-frequency impedances of the blood; said pair of low-frequency impedance measuring electrodes (26a/26b, 27a/27b) and said pair of high-frequency measuring electrodes (28a/28b) being disposed substan tially at the same position in said blood flow passage in the blood flowing direction.
Claim 3
Dependent Claim
182 words
A hematocrit measuring instrument according to claim 1, wherein one of said low-frequency impedance measuring electrodes (26a, 27a) is disposed facing said blood flow passage (10) while the other low-frequency impedance measuring electrode (26a/27b) is disposed across said blood flow passage (10) at a position which is on the opposite side of said low-frequency impedance measuring electrode and is at a certain distance from said electrode (26a, 27a) in the direction of the central axis of said blood flow passage; and one of said high-frequency impedance measuring electrodes (28a) is disposed facing said blood flow passage (10) while the other high-frequency impedance measuring electrode (28b) is disposed across said blood flow passage (10) at a position which is on the opposite side of said high-frequency impedance measuring electrode and is at a certain distance from said electrode in the direction of the central axis of said blood flow passage, so that said high-frequency current flow passage through said high-frequency impedance measuring electrodes and said low-frequency current flow passage through said low-frequency measuring electrodes intersect with each other in said blood flow passage.
Claim 4
Dependent Claim
47 words
A hematocrit measuring instrument according to claim 1, wherein both of said low and high-frequency impedance measuring electrode pairs are disposed so that their low-frequency current passage and high-frequency current passage intersect in a plane which is perpendicular to the central axis of said blood flow passage.
Claim 5
Dependent Claim
38 words
A hematocrit measuring instrument according to any of claims 1 to 3, wherein both of said low and high-frequency impedance measuring electrode pairs are disposed on an insulated resistance measuring cell (21) in said blood flow passage (10).
Claim 6
Dependent Claim
179 words
A hematocrit measuring instrument according to any of claims 1 to 4, wherein said low-frequency impedance measuring device includes a low-frequency constant current source (22) for supplying a low-frequency current to the blood through said pair of low-frequency impedance measuring electrodes (26a/26b, 27a/27b) a low pass filter (23) for passing a low-frequency voltage signal generated between said pair of low-frequency impedance measuring electrodes (26a/26b, 27a/27b) and low-frequency impedance outputting means (24) for measuring a voltage of the low-frequency voltage signal outputted from said low-pass filter and for outputting a signal indicating the low-frequency impedance of the blood; and said high-frequency impedance measuring device includes a high-frequency constant current source (31) for supplying a high-frequency current to the blood through said pair of high-frequency impedance measuring electrodes (28a/28b), a high-pass filter (32) for passing a high-frequency voltage signal generated between said pair of high-frequency impedance measuring electrodes (28a/28b), and high-frequency impedance outputting means (33) for measuring a voltage of the high-frequency voltage signal outputted from said high-pass filter and for outputting a signal indicating the high-frequency impedance of the blood.
Claim 7
Dependent Claim
40 words
A hematrocrit measuring instrument according to claim 5, wherein said low-frequency impedance measuring device (20) includes a pair of voltage detecting electrodes (27a/27b) disposed adjacent to said pair of low-frequency impedance measuring electrodes (26a/26b) and connected to said low-pass filter.
Claim 8
Dependent Claim
42 words
A hematocrit measuring instrument according to any of claims 1 to 6, wherein at least one of said pair of high-frequency impedance measuring electrodes is also used as a low-frequency impedance measuring electrode so as to decrease the number of said electrodes.
Claim 9
Dependent Claim
66 words
A hematocrit measuring instrument according to any of claims 1 to 7, wherein said low-frequency impedance measuring device measures a low-frequency impedance of the blood by means of a low-frequency of 5 KH Z to 50 KH Z , and said high-frequency impedance measuring device measures a high-frequency impedance of the blood by means of a high-frequency of 20 MH Z to 200 MH Z .
References Cited (Backward Citations)
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