Limb blood flowmeter
First Claim
Patent Images
1. A limb blood flowmeter comprising:
- occluding pressure means for applying pressure to a limb to be examined on the side of the heart to occlude only the venous return;
admittance measuring means for measuring the admittance of the limb;
means for holding an initial admittance of the limb at the start of measurement;
a subtractor for deriving an admittance change Δ
Y from the difference tetween the initial admittance and an admittance measured subsequently and operative to produce an electrical signal corresponding to Δ
Y;
means for setting the value of the blood resistivity ρ
of the limb and operative to produce a corresponding electrical signal;
means for setting the value of the length L of the region of the limb to be examined and operative to produce a corresponding electrical signal;
means for setting the value of the tissue volume VO of the region to be examined and operative to produce a corresponding electrical signal;
a calculator responsive to said electrical signals for calculating ρ
L2 Δ
Y/VO based on the output Δ
Y from the subtractor and the blood resistivity ρ
, the length L and the volume VO set in the setting means; and
a controller for controlling the occluding pressure means and the holding of the initial admittance of the limb.
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Abstract
A human limb to be examined is pressurized on the side of the heart to occlude the venous return alone for the measurement of admittance of the limb, and the measured initial admittance is retained and compared with subsequently measured admittance to detect a difference ΔY therebetween. The blood resistivity ρ, the length L of the limb segment to be examined and its tissue volume VO are respectively set, and ρL2 ΔY/VO is computated. The initial gradient of the computation result to time is indicative of the blood flow rate in the limb being examined.
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Citations
13 Claims
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1. A limb blood flowmeter comprising:
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occluding pressure means for applying pressure to a limb to be examined on the side of the heart to occlude only the venous return; admittance measuring means for measuring the admittance of the limb; means for holding an initial admittance of the limb at the start of measurement; a subtractor for deriving an admittance change Δ
Y from the difference tetween the initial admittance and an admittance measured subsequently and operative to produce an electrical signal corresponding to Δ
Y;means for setting the value of the blood resistivity ρ
of the limb and operative to produce a corresponding electrical signal;means for setting the value of the length L of the region of the limb to be examined and operative to produce a corresponding electrical signal; means for setting the value of the tissue volume VO of the region to be examined and operative to produce a corresponding electrical signal; a calculator responsive to said electrical signals for calculating ρ
L2 Δ
Y/VO based on the output Δ
Y from the subtractor and the blood resistivity ρ
, the length L and the volume VO set in the setting means; anda controller for controlling the occluding pressure means and the holding of the initial admittance of the limb. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A limb blood flow rate measuring method comprising the steps of:
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appling pressure to a limb to be examined on the side of the heart to occlude only the venous return; measuring the admittance of the limb and holding the initial admittance of the limb at the start of measurement; measuring the admittance of the limb after holding of the initial admittance and subtracting the measured value from the initial admittance to obtain an admittance change Δ
Y;calculating Δ
V=ρ
L2 Δ
Y/VO based on the blood resistivity ρ
of the limb to be measured and the length L and the tissue volume VO of the region of the limb to be examined; andobtaining the limb blood flow rate from an initial gradient of the calculated Δ
V.
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Specification