RU2278381C1 - Device for studying blood platelets aggregation - Google Patents

Abstract

FIELD: medical engineering.

SUBSTANCE: device has stabilized light source, reservoir for collecting blood enriched in blood platelets, photodetector, analog-to-digital converter and recording unit. The reservoir for enriching blood plasma with blood platelets is formed by two horizontal parallel-sided plates the lower of which has cylindrical cavity in the center. The cavity forms chamber when being engaged with the upper plate. The plates are rotatable in counter polar directions for stirring blood plasma without foreign bodies introduced into it and making strictly defined shear rate mode in the reservoir containing blood promoting spontaneous blood platelets aggregation.

EFFECT: high sensitivity in measuring spontaneous blood platelets aggregation.

2 cl, 4 dwg

Description

The present invention relates to medicine, in particular to devices for studying platelet aggregation.

Platelets play a major role in the primary arrest of bleeding during damage to the vascular wall, as well as in the occurrence of micro- and macrovascular disorders in various diseases. An increase in platelet aggregation activity is the basis of intravascular thrombosis in case of myocardial infarction, atherosclerosis, chronic coronary heart disease, hypertension, cerebrovascular accident, and its decrease leads to bleeding in congenital platelet pathology (thrombocytopathies) or in case of leukemia, thrombosis, liver diseases, DIC, the effects of drugs, etc.

A measure of aggregation is a graphically recorded decrease in the optical density of blood plasma as a result of platelet consumption in aggregates formed under the influence of inducers. The turbidimetric method for studying platelet aggregation underlies the work of most aggregometers, with which it is possible to evaluate platelet aggregation induced by various agents (ADP, collagen, adrenaline, etc.). However, it is impossible to register spontaneous platelet aggregation using these aggregometers due to their insufficient sensitivity.

Closest to the proposed technical solution is the platelet aggregation analyzer "Solar" AP2110 manufactured by Spectroscopy, Optics, Lasers - Avant-Garde Development CJSC (Minsk, Republic of Belarus), which is designed to study only induced platelet aggregation by the turbidimetric method by continuously measuring changes in light transmission coefficient, occurring in a stirred and thermostatically controlled cell suspension, with the output of the measurement results to an external recording device.

This platelet aggregation analyzer consists of a light source, a heat shield, a filter block, a lens in the diaphragm plane, a rotary mirror, a beam splitter and a polystyrene cylindrical cell with the test fluid - blood plasma enriched with platelets and standardized by their quantity, an electronic magnetic stirrer and photodetector.

However, in this device, as in other similar devices of domestic and foreign manufacture, a cylindrical cuvette is used, which leads to uncontrolled reflection, re-reflection and loss of light flux, and, consequently, to a significant decrease in the sensitivity of the device and the reliability of the results. Insufficient sensitivity makes it impossible to register spontaneous platelet aggregation, as well as the formation of small aggregates (50-100 platelets).

The objective of the proposed technical solution is to increase the sensitivity of the device for the ability to measure spontaneous platelet aggregation.

This problem is solved due to the fact that the capacity for platelet-rich blood plasma is formed by two horizontally located plane-parallel disk-shaped quartz plates, in the center of the bottom of which there is a cylindrical recess, forming a chamber at contact with the upper plate, the depth of which is selected so that platelet aggregation causes the maximum change in the optical density of blood plasma. The plates are placed in the field of view of a light microscope and are made to rotate in opposite directions to mix blood plasma without introducing foreign bodies into it and create a strictly specified shear rate inside the blood plasma reservoir at which spontaneous platelet aggregation occurs.

The essence of the proposed technical solution is illustrated by drawings, in which Fig. 1 is a block diagram of a device, Fig. 2 is a design of a main unit, Fig. 3 is a graph of spontaneous platelet aggregation of a healthy donor, Fig. 4 is a graph of spontaneous aggregation of red blood cells healthy donor.

The device consists of a stabilized light source 1, a main unit 2, an electric motor 3 connected to the main unit 2 by means of a friction clutch 4, a light binocular microscope 5, a photodetector 6, an analog-to-digital converter 7, and a recorder 8.

The main unit 2, which is the main part of the device, is made in the form of two - bottom 9 and top 10 - horizontally located plane-parallel disk-shaped quartz plates with a diameter of 20 mm. In the center of the bottom plate 9 there is a cylindrical recess, which upon contact with the top plate 10 forms a chamber 11 with a depth of 0.9 mm and a diameter of 12 mm. In the chamber 11 is placed blood plasma enriched in platelets. The tight fit of the plates 9 and 10 is ensured by the weight of the glass 12, at the bottom of which there is an upper plate 10 attached to it by means of a cushioning system in the form of a steel ring 13 and rubber gaskets 14. The main unit is placed in the housing 15.

In the process, the upper 10 and lower 9 plates rotate in opposite directions relative to each other, providing mixing of the plasma and stimulating spontaneous platelet aggregation.

The shear rate in the chamber 11 is clearly defined and calculated by the formula

γ = R / δ (ω _upper + ω _lower ),

where R is the average radius of the chamber, δ is the depth of the chamber, ω _upper is the angular velocity of rotation of the upper plate, ω _lower is the angular velocity of rotation of the lower plate.

A shear rate of 20 s ^{-1 is} used to evaluate spontaneous platelet aggregation.

When the plates 9 and 10 are rotated in different directions, shear stress is created, but the platelets remain almost motionless, which makes it possible to visually observe their aggregation using a microscope 5.

The study of spontaneous platelet aggregation using the described device is as follows. Prepare a blood plasma enriched with platelets, standardizing their concentration with a spectrophotometer up to 100,000 in mm ³ . Platelet-rich blood plasma in an amount of 0.1 ml is placed in a cylindrical recess on the lower plate 9, after which a glass 12 with the upper plate 10 attached to it is lowered onto it so that the platelet suspension is between the plates in the closed chamber 11. Then, a stream of light is supplied through the chamber 11, the electric motor 3 and the recorder are turned on 8. The upper 10 and lower 9 plates begin to rotate in different directions, creating a certain shear rate inside the chamber 11 with the blood plasma, at which plasma Ita spontaneously begin to aggregate. In the process of aggregation, a change in the optical density of blood plasma is detected by the photodetector 6 and, after processing the signal in the analog-to-digital converter 7, is recorded by the recorder 8 in the form of a curve (see Fig. 3). The calculation of the parameters of the platelet aggregation curve is carried out by the standard method.

The proposed device can also be successfully used for research and registration of spontaneous aggregation of red blood cells. To this end, replace the bottom plate 9 of the main unit 2 with a similar, but with a cylindrical recess of 90 microns. In this case, 30 μl of blood stabilized with sodium citrate and standardized for hematocrit (30%) is placed in chamber 11 between plates 9 and 10. At a shear rate of 250 s ⁻¹ , erythrocytes are hydrodynamically dispersed for 20 seconds, during which they orient themselves in the flow. At the moment of stopping the rotation of the plates 9 and 10, the orientation of the red blood cells is disturbed, followed by their spontaneous aggregation. The change in the optical density of blood, as in the case of platelet aggregation, is recorded by a photodetector 6 and, after processing the signal in an analog-to-digital converter 7, is recorded by a recorder 8 in the form of a curve (see Fig. 4).

Thus, the use of a flat horizontal camera with a short optical path length (0.9 mm) and minimization of the effects of reflection and re-reflection of the light flux provide high sensitivity of the device, which allows recording spontaneous platelet aggregation, and when replacing the lower plate of the main unit with a similar one, but with a cylindrical a smaller recess, it is possible to register spontaneous aggregation of red blood cells. The advantages of the proposed device also include the use of a small volume of the studied blood plasma (0.1 ml), dosing of the shear rate and mixing of the blood plasma without the use of foreign objects (magnets, paddle stirrers) due to the rotation of the plates in mutually opposite directions, which ensures measurement accuracy. In addition, the proposed device allows you to visually monitor the process of aggregation of blood cells, as well as conduct research with an initially low platelet count - thrombocytopenia.

Claims (2)

1. A device for studying platelet aggregation by a turbidimetric method based on measuring changes in the optical density of blood plasma enriched in platelets during their aggregation, consisting of a source of stabilized light, a container with blood plasma enriched in platelets, a blood plasma mixing system, a photodetector, and analog a digital converter registering the unit, characterized in that the capacity for platelet-rich blood plasma is formed by two horizontally located plane-parallel disc-shaped optically transparent plates, in the center of the lower of which there is a cylindrical recess, which forms a chamber upon contact with the upper plate, and the plates themselves are rotatable in mutually opposite directions to mix blood plasma. 2. The device for studying platelet aggregation by a turbidimetric method according to claim 1, characterized in that the plates are placed in the field of view of a light microscope, and their rotation ensures the creation of a shear rate inside the vessel with blood plasma sufficient for spontaneous platelet aggregation to occur.

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