Noninvasive method of measuring blood density and hematocrit
First Claim
1. A method of noninvasively measuring fluid density of a pulsed flow system with non-rigid vessel walls, comprising:
- a) noninvasively measuring a local relative fluid volume ratio Vb/Δ
Vb, where Vb is a basal volume of fluid in a vessel and Δ
Vb is a volume change of the fluid in the vessel due to the pulse;
b) noninvasively measuring a fluid pulse propagation velocity ν
;
c) noninvasively measuring a basal fluid pressure P and a local change in fluid pressure Δ
P;
d) calculating fluid density ρ
b as a function of the local relative fluid volume ratio, the fluid pulse propagation velocity, the basal fluid pressure, and local change in fluid pressure according to the generalized functional relationship or its derivatives.
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Accused Products
Abstract
Apparatus and methods for noninvasively measuring blood density and hematocrit in a human subject can include an appliance for applying pressure around a segment of a subject'"'"'s limb or appendage that includes a pressure sensing means and encloses an array of impedance sensing devices applied to the subject'"'"'s skin for independent fluid volume measurements. While applying pressure to the limb segment by the pressure appliance, measurements of blood pressure, blood pulse wave velocity, and limb segment impedance are recorded. The measurements are subsequently processed to yield changes of arterial blood volume during pulse wave passage. Then pressure, wave velocity, and derived volume data are combined to yield the density of the blood. Blood density is converted to hematocrit by means of a linear relationship between the two. Independent of the blood hematocrit, such apparatus and means may also be used to measure the density of enclosed fluid in other pulsed flow non-rigid wall vessel systems.
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Citations
19 Claims
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1. A method of noninvasively measuring fluid density of a pulsed flow system with non-rigid vessel walls, comprising:
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a) noninvasively measuring a local relative fluid volume ratio Vb/Δ
Vb, where Vb is a basal volume of fluid in a vessel and Δ
Vb is a volume change of the fluid in the vessel due to the pulse;
b) noninvasively measuring a fluid pulse propagation velocity ν
;
c) noninvasively measuring a basal fluid pressure P and a local change in fluid pressure Δ
P;
d) calculating fluid density ρ
b as a function of the local relative fluid volume ratio, the fluid pulse propagation velocity, the basal fluid pressure, and local change in fluid pressure according to the generalized functional relationshipor its derivatives. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An apparatus for noninvasively measuring fluid density of a pulsed flow system with non-rigid vessel walls at a local measurement area, comprising:
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a) means for noninvasively measuring a local relative fluid volume ratio Vb/Δ
Vb, where Vb is a basal volume of fluid in a vessel and Δ
Vb is a volume change of the fluid in the vessel due to the pulse;
b) means for noninvasively measuring a fluid pulse propagation velocity ν
;
c) means for noninvasively measuring a basal fluid pressure P and a local change in fluid pressure Δ
P; and
d) a calculator for determining fluid density ρ
b as a function of the local relative fluid volume ratio, the fluid pulse propagation velocity, the basal fluid pressure, and local change in fluid pressure according to the generalized functional relationshipor its derivatives. - View Dependent Claims (8, 9, 10, 11, 12)
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13. An apparatus for noninvasively measuring fluid density of a pulsed flow system with non-rigid vessel walls at a local measurement area, comprising:
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a) a pressure applicator for applying external pressure to the local measurement area, b) an impedance measurer coextensive with the pressure applicator; and
c) a calculator operably connected to the pressure applicator and the impedance measurer for calculating a fluid density value of the local measurement area. - View Dependent Claims (14, 15)
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16. A method of noninvasively measuring fluid density of a pulsed flow system with non-rigid vessel walls, comprising:
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a) noninvasively measuring a local relative fluid volume ratio Vb/Δ
Vb, where Vb is a basal volume of fluid in a vessel and Δ
Vb is a volume change of the fluid in the vessel due to the pulse;
b) noninvasively measuring a fluid pulse propagation velocity ν
;
c) noninvasively measuring a local change in fluid pressure Δ
P;
d) calculating fluid density ρ
b as a function of the local relative fluid volume ratio, the fluid pulse propagation velocity, and local change in fluid pressure according to the relationshipor its derivatives. - View Dependent Claims (17)
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18. A method of noninvasively measuring a local relative fluid volume ratio Vb/Δ
- Vb in a pulsed flow system with non-rigid vessel walls comprising;
a) measuring the electrical admittance (Yb) of the local basal fluid volume;
b) measuring the electrical admittance change (Δ
Yb) due to increased local volume from pulsed flow; and
c) equating whereby the need to know the resistivity of the fluid in determining the local fluid volume ratio is eliminated.
- Vb in a pulsed flow system with non-rigid vessel walls comprising;
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19. A method of determining a hematocrit value of blood comprising:
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a) measuring density of the blood (ρ
b); and
b) determining the hematocrit value according to the relationship
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Specification