RU2489088C2 - Device for investigation of viscous properties of blood and method of its application - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to medical equipment, namely to devices and methods of investigating biomechanical properties of blood. Device contains coaxial engine starter, external transparent cylinder and internal cylinder, floating in free way in blood located in clearance. From external side of external cylinder installed are light source and photoreceiver for measuring intensity of backscattered light from blood layer, sensor, made with possibility of registering moment of stop of internal cylinder rotation. Processor is made with possibility of changing rotation frequency of external cylinder, fixation by sensor of moment of freely-floating cylinder stop and carrying out measurements of intensity and calculation of viscous and aggregation properties of blood. Method lies in bringing freely-floating cylinder into rotation by magnetic field of starter, measurement intensity of back light scattering at the moment of its stop and registration of curve of intensity change in time, calculation and building curve s of apparent blood viscosity, shear stress, average size, rate and time of formation of erythrocyte aggregates by means of processor. Freely-floating in blood internal cylinder rotates in opposite direction, with frequency of starter current being changed until internal cylinder stops when balance of moments of forces created by magnetic field of starter and viscous forces of blood on the wall of freely-floating internal cylinder is achieved; moment of its stop id fixed by sensor for formation of control signal of carrying out measurements of back light scattering intensity and frequency of starter current, which in accordance with calibration by liquids with known viscosity are used to calculate apparent blood viscosity and shear stress, to determine average volume of erythrocyte aggregates, by which curves of blood flow and erythrocyte aggregates are built.

EFFECT: application of the invention makes it possible to extend possibilities of viscosimetry method.

2 cl, 3 dwg

Description

The invention relates to blood rheology (hematology, physiology, biophysics, clinical hemorheology), and in particular to the biomechanical properties of blood.

Known devices for determining the viscosity of a liquid, in particular blood, consisting of two coaxial cylinders, of which the outer cylinder is stationary, and the inner one freely floats in the liquid (blood) located between the cylinders:

1. V.N.Zakharchenko, USSR Copyright Certificate No. 16851818 / P, 1965, B No. 4.

2. N. A. Dobrovolsky et al. USSR Author's Certificate No. 779862 1980

In the design of V.N.Zakharchenko, the torque is set by the rotation of a cylindrical mixer, lowered into a viscous fluid that transmits torque and is located in the free-floating cylinder. The measured value is the time of one revolution of the floating cylinder. The disadvantages of this device are:

1. The need for rigorous thermal stabilization, since the viscosity of a moment-transmitting fluid depends on temperature.

2. Difficulties in accurately measuring the time of one revolution, especially at low (about 1 s ^-1 ) and high (over 100 s ^-1 ) shear rates when working with blood.

3. The inability to simultaneously determine the viscous and aggregation parameters of the blood.

4. The need for periodic replacement of the transfer fluid.

In N.A.Dobrovolsky’s device, a free-floating electrically conductive cup rotates under the action of a rotating magnetic field of a motor stator located outside a stationary external cylinder.

The disadvantages of the device N.A.Dobrovolsky:

1. The inability to accurately set the shear rate at their low values (about 1 s ^-1 ).

2. Inability to measure aggregation (micro-rheological) parameters of blood.

The invention is aimed at expanding the capabilities of the method of viscometry by simultaneously measuring not only all viscometric parameters characterizing the micro-rheological properties of blood, but also measuring parameters characterizing the kinetics of aggregation of red blood cells, the hydrodynamic strength of erythrocyte aggregates of various sizes. The device allows you to obtain curves of blood flow, as the dependence of the average size of red blood cells from shear stress or blood viscosity. This is achieved by the fact that a light source and a photodetector for measuring the intensity of backscattered light from the blood layer are installed on the outer side of the external cylinder, and a sensor is arranged on the outside of the external cylinder that is capable of detecting the stopping moment of rotation of the inner cylinder, and the processor is configured to change the rotational speed of the outer cylinder, fixing the stop moment of the free-floating cylinder with the sensor and measuring the intensity of the scattered light and calculating the viscous x and aggregation properties of blood.

A method for simultaneously measuring the viscous and aggregation properties of blood consists in bringing the free-floating cylinder into rotation by means of the stator magnetic field, measuring the intensity of backscattering at the moment of its stop and registering the intensity change curve over time, calculating and plotting the curves of apparent blood viscosity, shear stress, average size, the speed and time of formation of red blood cell aggregates by means of a processor, characterized in that the free-floating cylinder is morning and installed with a gap in the outer cylinder, which is rotated with a frequency specified by the frequency of the stator current, while the inner cylinder rotates in the opposite direction, measure the frequency of the stator current until the inner cylinder stops when the balance of the moments of forces created by the stator magnetic field and the moment is reached viscous forces of blood on the wall of a free-floating inner cylinder, the moment of its stop is fixed by a sensor to form a control signal for measuring the intensity scattering and stator current frequencies. The light source forms a beam of light that is scattered by blood flowing in the gap between the cylinders, and only that part of the scattered light that is directed at an angle of 180 ° relative to the incident beam is recorded by the photodetector (back light scattering). Automatically measured values using the built-in program are processed by a computer in accordance with the calibration of the instrument with standard Newtonian liquids with a known viscosity. In accordance with the Programs, the control computer constructs the blood flow curves: η _a = η _a (γ), τ = τ (γ), τ (γ) = <N> (γ), where η _a is the apparent viscosity, τ is the shear stress , γ is the shear rate, <N> is the average size of the aggregates. All parameters recommended by the Rheological Society are calculated.

The advantage of the proposed "Application" and "Method" is as follows:

1. The completeness of the description of macro and micro-rheological properties of blood.

2. A significant reduction in the time of determination of all hemorheological parameters of the blood.

3. The exact task of the necessary shear rate, as a necessary condition for the standardization of measurements.

4. Full automation of measurements from the introduction of a blood sample to print a protocol with the results.

5. Ease of use of the device, not requiring high qualification of the operator.

6. The possibility of expanding the parameters characterizing the suspension stability of blood by introducing an additional program: measuring the deformation ability of red blood cells and blood thixotropy.

List of figures

Figure 1 presents a block diagram of a device.

The device contains an external transparent cylinder (1) inserted into the glass (2) located on the axis of the stepper motor (3). The inner cylinder (4), freely floating in the analyzed blood sample (5), can rotate under the influence of the magnetic field of the stator (6). A light source (7) and a photodetector (8) are located on the outer side of the outer cylinder (1); moreover, only that part of the scattered light that is directed at an angle of 180 ° relative to the incident beam (back light scattering), as well as a sensor (9) are detected by the photodetector moment of stopping rotation of the inner cylinder (4).

Figure 2 presents a graph of the apparent viscosity of the blood from the logarithm of the average size of erythrocyte aggregates Ln <N> before (1 and 2) and after (1 ¹ and 2 ¹ ) plasmapheresis.

. Напряжение сдвига на левой абсцисе рассчитано как $$\tau =\mathrm{3,5}\dot{\gamma }\left({\eta }_{pl}+\ln \left|\frac{I_0}{I(\dot{\gamma })}\right|\right)$$

, где I₀ и I(&) - интенсивности светорассеяния, а & - скорость сдвига (сек^-1).Figure 3 shows the curves of blood flow and erythrocyte aggregates in standard Caisson coordinates $$\left(\sqrt{\tau }=\sqrt{{\tau }_0}+\sqrt{K\dot{\gamma }.}\right)$$

. The shear stress on the left abscissa is calculated as $$\tau =\mathrm{3,5}\dot{\gamma }\left({\eta }_{pl}+\ln \left|\frac{I_0}{I(\dot{\gamma })}\right|\right)$$

where I ₀ and I (&) are the light scattering intensities, and & is the shear rate (sec ^-1 ).

A method for measuring viscous and aggregation properties of blood at the same time is described with specific examples:

Example 1. Blood stabilized by Trilon B is placed in the cuvette of the device (Figure 1). In accordance with the program, shear rates (γ) are sequentially set from 1 to 125 reverse seconds, the intensity of backscattering (I) and the frequency of the generator when the inner cylinder is stopped are measured. Figure 2 clearly shows a linear relationship between the measured apparent blood viscosity and the logarithm of the average size of the aggregates, which is confirmed by the existing theory. This dependence is not violated during the patient's plasmapheresis procedure.

Example 2. Blood in accordance with Example 1 undergoes the same test procedure. Figure 3 shows that the flow of erythrocyte aggregates is fully consistent with the empirical law of Caisson, which was established for blood back in the 60s of the last century, which confirms the possibility of studying the curve of blood flow, as the dependence of the size of the aggregates on shear stress.

Claims (2)

1. A device for simultaneously measuring the viscous and aggregation properties of blood, containing a coaxial motor stator, an external transparent cylinder and an inner cylinder floating freely in the blood gap, a light source and a photodetector for measuring the intensity of backscattered light from the blood layer are installed on the outside of the external cylinder , characterized in that on the outer side of the outer cylinder there is a sensor configured to record the moment of stop of rotation of the inner cylinder, and the percent quarrel configured to change the rotational speed of the outer cylinder, fixation of free-stop torque sensor cylinder and measuring the intensity and calculating the viscous properties of blood and aggregation. 2. A method for simultaneously measuring the viscous and aggregation properties of blood, which consists in bringing the free-floating cylinder into rotation by means of the stator magnetic field, measuring the intensity of backscattering at the moment of its stop and registering the intensity change curve over time, calculating and plotting the curves of apparent blood viscosity, shear stress, the average size, speed and time of formation of red blood cell aggregates, by means of a processor, characterized in that the free-floating cylinder in the blood is internal and installed with a gap in the outer cylinder, which is rotated at a frequency specified by the frequency of the stator current, while the inner cylinder rotates in the opposite direction, the stator current frequency is changed until the inner cylinder stops reaching a balance of the moments of forces created by the stator magnetic field and viscous forces of blood on the wall of a free-floating inner cylinder, the moment of its stop is fixed by a sensor to form a control signal for measuring the intensity of the return of light scattering and the frequency of the stator current, which in accordance with the calibration of liquids of known viscosity is calculated apparent blood viscosity and shear stress determines the average size of the erythrocyte aggregates, which construct the flow curves and blood erythrocyte aggregates.

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