Blood Rheology Testing Laboratory
Blood Rheology Testing Laboratory
Blood rheology is the science that focuses on the flow and deformability patterns of blood and its components. The rheology of blood consists of three aspects: the macroscopic fluidity of blood (viscosity), the rheology of blood cells (aggregation and deformability of red blood cells), and the influence of blood biochemical substances on the rheology of blood (fibrinogen, globulin). Abnormalities in blood rheology play an important role in the etiology and pathogenesis of certain diseases, especially thrombotic diseases. Blood is a very special suspension, as the solvent plasma is not homogeneous, but contains various proteins with different molecular weights, molecular shapes and contents; as the blood cells suspended in the plasma are not only very large in number, but also visco-elastic and malleable, and these cells, under certain conditions, can be aggregated in strings, or even in multidimensional clusters, thus creating a great resistance to flow. On the other hand, such blood cell aggregates may be completely dispersed into individual blood cells, and even individual blood cells can be elongated and deformed along the direction of flow, and these changes will make the resistance to flow greatly reduced, and these characteristics make the blood show more complex rheological characteristics than general non-Newtonian fluids. The purpose of blood rheology testing is to understand and master the flow and coagulation properties of blood and its changing patterns under physiological and pathological conditions. The basic indexes of the test include blood viscosity, hematocrit (HCT), aggregation and deformability of erythrocytes, platelet adhesion and aggregation, and plasma fibrinogen content. Measurement of blood viscosity is one of the most important indicators; blood viscosity is a comprehensive indicator reflecting the rheological properties of blood, the level of blood viscosity is closely related to the advantages and disadvantages of blood circulation or the amount of blood supply, all factors that can affect the rheological properties of the blood can be manifested from the changes in blood viscosity. An increase in blood viscosity is considered to be one of the indicators of possible thrombosis, while a decrease in blood viscosity can be used to determine the amount of bleeding and is an important indicator of disease prediction.
Operation method
Blood Rheology Testing Laboratory
Principle
Blood rheology is the science that focuses on the flow and deformability patterns of blood and its components. The rheology of blood consists of three aspects: the macroscopic fluidity of blood (viscosity), the rheology of blood cells (aggregation and deformability of red blood cells), and the influence of blood biochemical substances on the rheology of blood (fibrinogen, globulin). Abnormalities in blood rheology play an important role in the etiology and pathogenesis of certain diseases, especially thrombotic diseases. Blood is a very special suspension, as the solvent plasma is not homogeneous, but contains various proteins with different molecular weights, molecular shapes and contents; as the blood cells suspended in the plasma are not only very large in number, but also visco-elastic and malleable, and these cells, under certain conditions, can be aggregated in strings, or even in multidimensional clusters, thus creating a great resistance to flow. On the other hand, such blood cell aggregates may be completely dispersed into individual blood cells, and even individual blood cells can be elongated and deformed along the direction of flow, and these changes will make the resistance to flow greatly reduced, and these characteristics make the blood show more complex rheological characteristics than general non-Newtonian fluids. The purpose of blood rheology testing is to understand and master the flow and coagulation properties of blood and its changing patterns under physiological and pathological conditions. The basic indexes of the test include blood viscosity, hematocrit (HCT), aggregation and deformability of erythrocytes, platelet adhesion and aggregation, and plasma fibrinogen content. Measurement of blood viscosity is one of the most important indicators; blood viscosity is a comprehensive indicator reflecting the rheological properties of blood, the level of blood viscosity is closely related to the advantages and disadvantages of blood circulation or the amount of blood supply, all factors that can affect the rheological properties of the blood can be manifested from the changes in blood viscosity. An increase in blood viscosity is considered to be one of the indicators of possible thrombosis, while a decrease in blood viscosity can be used to determine the amount of bleeding and is an important indicator of disease prediction.
Materials and Instruments
Blood Move Basic operation of cone plate viscometer Caveat Blood viscosity is a comprehensive index, which is a combination of plasma viscosity, hematocrit, erythrocyte deformation and aggregation capacity, platelet and leukocyte rheological properties. In the blood viscosity test, attention should be paid to:1. No matter what type of viscometer is taken, it should be strictly controlled according to the specific operation requirements. 2. the working temperature, in general, the temperature rise makes the body fluid viscosity decrease, the temperature drop makes the body fluid viscosity increase. However, the blood situation is very complex, elevated temperature will lead to increased red blood cell aggregation, so that the blood low shear rate viscosity increased, while the plasma viscosity and high shear rate blood viscosity are reduced. The relative viscosity of blood, especially at high shear rates, is determined using a rotational viscometer and does not change with temperature (15°C-40°C). However, blood viscosity determined by capillary viscometer decreased with increasing temperature. When the temperature rises above 41℃, the blood viscosity increases due to changes in both plasma proteins and red blood cell membranes, resulting in increased hardness of red blood cells. 3. blood sample preparation, blood collection process, pay attention to shear may cause damage to the red blood cells; room temperature storage of blood samples should not be more than 4h, blood samples can not have air bubbles, fibrous filaments, debris and so on. 4. Anticoagulant, generally use heparin or EDTA as anticoagulant. Common Problems Methods of Blood Rheology Determination For more product details, please visit Aladdin Scientific website.
Cone-Plate Rotational Viscometer
1. Before turning on the machine, adjust the horizontal position of the main machine by using bubble level.
2. Relax the positioning lever and rotate it by 180 degrees, remove the specimen cup, connect the specimen cup with the thermostatic water bath and make the thermostatic water bath run.
3. Load the blood sample to be measured. Use a syringe to extract a certain amount of blood sample to be measured, remove air bubbles, inject the blood sample into the specimen cup, and load the main unit.
4. Viscosity measurement. It should be carried out under the condition that the water temperature of the circulating thermostatic water bath is balanced, i.e. the temperature of the specimen cup is stabilized; firstly, rotate the speed knob to the low-speed frame, and the rotary shaft locking handle is placed in the release position, turn on the power, start the rotary switch, and then carry out the viscosity measurement.
Blood viscosity is the most basic rheological property of blood. Blood viscosity measurements include whole blood viscosity (η b) and plasma viscosity (η b) measurements. The unit of blood viscosity is expressed in mPa-s (millipascal per second).
The methods of blood viscosity determination are divided into two main categories, one is capillary viscosity determination and the other is rotational viscosity determination.
(A) Capillary Viscometer Measurement Method
The theoretical basis for the capillary method of blood viscosity measurement is Poiseuille's law. When the liquid flows through the capillary tube, it will follow the following formula: Q = πr4 P/8ηL, i.e., the flow rate Q is directly proportional to the pressure difference between the two ends of the pipe, P, the radius of the pipe, r, and inversely proportional to the length of the pipe, L, and the viscosity of the fluid, η. The flow rate Q in the formula is also equal to V/t, V is the volume flowing through the capillary tube, t is the time of flow, i.e., V/t = πr4P/8ηL.
Usually, r, L, and P can be constant under the experimental conditions, and if the flow rate Q is constant, η ∝ t. Therefore, the fluid viscosity η can be calculated by determining the time of liquid flow through the capillary tube, t.
The method for the determination of the capillary tube viscosity is only applicable to the determination of the viscosity of blood plasma.
(ii) Rotational viscosity measurement
The principle of rotational viscosity measurement is to an object that can actively rotate at different speeds, through the action of the liquid to be measured, driving another object with the same axis to passively rotate and produce a certain size of the moment, as long as we know the geometry of the actively rotating object, the speed of rotation, as well as the magnitude of the torque produced by the passively rotating object, it can be calculated by the liquid to be measured by the tangential stress (τ). The shear stress (τ) and the shear rate (γ), using the formula η = τ / γ, you can calculate the viscosity of the measured liquid. The use of this principle for the manufacture of viscometer rotational viscometer. Currently in common use are cone-plate viscometer and drum type viscometer. The main structure of a rotating drum or plate and the same axis of the inner drum or cone, the narrow gap between the two samples of the liquid to be measured, the inner drum or cone by the metal twisted wire K suspension up. The biggest advantage of this type of viscometer is that the shear rate can be changed by changing the rotational speed, and the liquid viscosity can be measured under a wide range of shear rate (0.04~4000s-1). In addition, the gap between the two rotating objects is very small, so very few liquid samples can be measured, and have a high degree of accuracy, especially for whole blood viscosity measurement.
1. Cone - plate type rotational viscometer
also known as cone - plate type rotational viscometer, the main components of a large apex angle of the cone and a flat plate, cone-plate viscometer only requires the cone and the plate have a relative motion, if the plate below the rotation is known as the lower rotational, if the cone rotates on top, it is called upper rotational. If the plate below rotates, it is called the lower rotating type, if the cone above rotates, it is called the upper rotating type.
Cone - plate type rotational viscometer, there is a wide range of shear rate, can be measured in different shear rate under the corresponding apparent viscosity value, so that the viscosity of blood samples can be made with the shear rate of the curve, so the cone - plate viscometer, is the determination of non-Newtonian fluids is more ideal equipment.
2. coaxial cylinder viscometer
that is, the hanging wire viscometer for the frictionless structure of the blood rheometer, the viscometer can be accurately measure the shear rate of This type of viscometer can accurately measure blood viscosity in the range of shear rate from 1s-1 to 200s-1 with high sensitivity and long service life.
(III) Main factors affecting blood viscosity
1. Hematocrit (HCT) Blood cells in the blood are mainly red blood cells, accounting for about 95% of the volume of blood cells, therefore, HCT is the most important factor affecting blood viscosity.
2. Erythrocyte Aggregation and Deformation Erythrocyte aggregation mainly affects blood viscosity under low shear. When erythrocyte aggregation increases, the apparent viscosity of blood under low shear increases; when erythrocyte deformability decreases or is lost, the viscosity of erythrocytes increases when they flow in microvessels.
3. Plasma Protein Plasma protein is the main factor affecting plasma viscosity and is an influencing factor of blood viscosity. The effect of plasma proteins on plasma viscosity is determined by the content of plasma proteins, the shape and size of the molecules, and the higher the protein content, the higher the plasma viscosity. Fibrinogen has the greatest effect on plasma viscosity.
4. pH and osmolality pH and osmolality affect blood rheology mainly because they cause changes in red blood cell aggregation and deformability. A decrease in pH can cause the red blood cell membrane to stiffen and cell deformation to decrease. Hypotonic conditions cause erythrocytes to sphericalize and become less deformable. Hypertonic conditions can lead to intracellular water efflux and increased intracellular viscosity. Thus, all these factors can reduce the viscosity at low shear rate and increase the viscosity at high shear rate.