Chemistry: analytical and immunological testing – Clotting or clotting factor level tests
Patent
1998-12-11
2000-12-12
Snay, Jeffrey
Chemistry: analytical and immunological testing
Clotting or clotting factor level tests
422 73, 73 6441, G01N 3386
Patent
active
061597414
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the measurement of the aggregation of blood platelets or the coagulation of blood according to the preamble of patent claim 1 and to a device for carrying out this process according to the preamble of patent claim 12.
The DE 35 41 057 C2 discloses such a process, in which blood is sucked into a capillary with the aid of a piston located in a cylinder, which is connected to the capillary and in which the actual pressure that prevails in the space between the piston and the aspirated blood is measured. This actual pressure is maintained at a desired value by moving the piston as a function of the difference between the actual pressure and a desired value. As a measure for the aggregation or the coagulation, the quantity of blood flow in the capillary is determined by detecting the movement of the piston.
One problem with such a process is the fact that the capillaries to be used are extremely difficult to produce, because the flow resistance of the capillary is a function of the fourth power of the radius of the capillary.
This is of the magnitude of 100 .mu.m. This means that the capillaries must be produced with a very precise diameter. This requirement results in high costs. Another problem lies in the fact that the capillaries can clog, a state that leads to errors in the measurements. In addition, the interior surface of the capillary has to be of the highest quality and totally cleaned of foreign substances (e.g. grease), so that the blood platelets do not adhere, a state that would result in clogging or undesired effects on the flow. The outflow ends must be rounded so that the blood cells are not injured by shearing. In addition to the cost of production that is increased hereby, expenses are incurred by the requisite quality controls. Handling the capillaries with such small dimensions for further automatic processing is extremely difficult. The capillaries that result in the said drawbacks are, however, absolutely necessary due to physiological reasons, because they simulate the resistance of the arterioles. The preceding capillaries make the process of hemostasis more effective, because, when the aperture is open, the shear of a large flow is limited at the start of the measuring process and in this manner the interaction between the thrombocytes and the collagen is more effective.
Therefore, the object of the present invention is to provide a process and a device for the measurement of the aggregation of the blood platelets or the coagulation of the blood, in which process or with which device the problems attributable to the capillaries are avoided.
This problem is solved by a process with the features of patent claim 1 and by a system with the features of patent claim 12.
The essential advantage of the invention lies in the fact that the capillaries used in the prior art can be omitted, because those conditions, which are actually produced during the measurement with a capillary, are simulated by a volume flow/pressure control without capillary. The present device for the measurement of the aggregration of the blood platelets or the coagulation of the blood is advantageously significantly less expensive because the capillaries, which can be produced only quite expensively in the prior art, are superfluous.
In the following the invention and its embodiments are explained in detail with reference to the figures.
FIG. 1 depicts a circuit diagram in order to explain the process according to the invention.
FIG. 2 depicts the dependence between the volume flow and the pressure in order to explain the process according to the invention.
FIG. 3 depicts the time-dependent pressure curve at the aperture.
FIG. 4 depicts a device according to the invention in order to carry out the present process, and
FIGS. 5 and 6 depict other devices to carry out the present process.
FIG. 1 shows the equivalent circuit diagram of a known device with a capillary, as known, for example, from the DE 35 41 057 C2. The flow resistance R.sub.v of the capillary, which is constant, is labe
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Freiherr Von Der Goltz Volker
Kratzer Michael
Dr. Michael Kratzer GmbH
Snay Jeffrey
VDG-Von Der Goltz GmbH
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