US 5,854,423 A · Apparatus and method for assessment of visco-elasticity and shear adherence strength properties of blood clots

Abstract

The present invention, a thrombo visco-elastogram (TVE), measures the changes in blood elastic and viscous properties in the magnitude and phase of the hydro-dynamic impedance of a tubular blood sample as the thrombus is formed. The present invention is an apparatus and method for assessment of visco-elasticity and shear adherence strength properties of blood clots. An apparatus for practicing the invention includes a tubular conduit connected to a fluid-filled cylindrical chamber and a fluid-filled reservoir, a piezo-electric bender attached to the fluid-filled cylindrical chamber, which creates a volume variation in the fluid-filled cylindrical chamber, a fluid source capable of injecting a fluid into the tubular conduit, a blood source capable of injecting blood into the tubular conduit, and a microprocessor to supply a sinusoidal wave form or limited band frequency content signal to the piezo-electric bender and record and analyze resulting pressure signals. A method for practicing the invention measures the viscosity and elastic shear modulus of a blood sample over time obtaining the average and maximum viscosity and shear modulus for the blood sample as it clots, and further includes applying a forcing signal, which displaces the clotted blood sample, while measuring the applied pressure for clot dislodgement from the walls of the test section. The adherence strength properties of the blood clot are calculated.

Claims20

Dependent claims

An apparatus for assessment of visco-elasticity and/or shear adherence strength properties of blood as it clots, said apparatus comprising:

a tubular conduit having a first section, a second section, and an intermediate zone therebetween for blood under test;
a fluid chamber connected to said first section of said tubular conduit and in fluid communication with said intermediate zone;
a piezo-electric bender attached to said fluid chamber, said bender deformable in response to a signal to cause a volume variation in said fluid chamber, which causes a pressure variation and displacement effect in fluid in said tubular conduit including said intermediate zone, the shape and amplitude of which effect when detected reflect clotting properties in blood in said intermediate zone.

A method for detecting blood thrombus properties comprising the steps of:

applying to a bolus of blood in a conduit a fluid force varying at two or more frequencies and inducing an effect manifested in fluid pressure and displacement in said conduit wherein a piezo-electric bender is attached to a fluid chamber connected to said conduit, said bender deformable in response to a signal to cause a volume variation in said fluid chamber, which causes a pressure variation and displacement effect in fluid in said conduit, the shape and amplitude of which effect when detected reflect clotting properties in blood in said conduit;
sensing said effect in said conduit in response to the applied force;
analyzing in the frequency domain a transfer function between the applied force and the sensed effect at said two or more frequencies over time for changes in real and imaginary components of said transfer function representing changes in viscosity and shear modulus of elasticity of the blood in said conduit.

A method for assessment of visco-elasticity and shear adherence strength properties of blood clots, said method comprising the steps of:

calibrating a blood test system to establish a calibration factor using a forcing signal, a fluid displacement signal for a first reference fluid within a conduit, a fluid displacement signal for a second reference fluid within said conduit, a cross-talk signal for a bender in fluid communicating with said conduit;
mixing a sample of citrated blood with a clotting activation agent such as calcium chloride to initiate a clotting cascade;
supplying and confining said blood sample to a test section of said conduit;
applying said forcing signal to said bender in fluid communication with said conduit;
obtaining an initial viscosity as a function of said forcing signal and said cross talk signal for a fluid in said test section;
repeatedly obtaining viscosity and thrombus elastic shear modulus values of a blood sample in said test section while said blood sample coagulates and forms a blood clot attached to the walls of said test section;
calculating and storing peak viscosity and elastic shear modulus values of said blood during clotting;
gradually increasing pressure across said blood clot in said test section and measuring a pressure in said conduit until the detachment of a blood clot from walls of said test section;
and
calculating and storing peak viscosity and rate of change of viscosity and peak elastic shear modulus and peak rate of change of elastic shear modulus as a function of the times of their occurrence relative to the addition of the clotting activation agent before detachment.

7 more elements

Dependencies are inferred from the claim text.

Apparatus and method for assessment of visco-elasticity and shear adherence strength properties of blood clots

Life of this patent

Apparatus and method for assessment of visco-elasticity and shear adherence strength properties of blood clots

Life of this patent

Abstract

Claims20