Chemical apparatus and process disinfecting – deodorizing – preser – Control element responsive to a sensed operating condition
Reexamination Certificate
2000-12-21
2003-09-02
Alexander, Lyle A. (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Control element responsive to a sensed operating condition
C422S091000, C422S105000, C422S105000, C422S073000, C436S069000, C436S180000
Reexamination Certificate
active
06613286
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to detection of changes in a property of a liquid that is mixed with one or more reagents. This invention is particularly concerned with detecting changes in viscosity of human blood that is mixed with blood viscosity changing reagents such as heparin and protamine.
2. Statement of Problem
The ability to detect changes in a property of a liquid that has been placed under the influence of a reagent that is capable of changing that property has great practical value. Changes in viscosity, translucence, color, electrical conductivity, optical density, chemical component concentration, and many other properties have been used in a wide variety of tests. For example, detection of changes in the viscosity of liquids such as blood, food products, and various other liquid compositions (e.g., industrial fluids, oil well injection fluids, etc.) form the basis of many very practical tests.
Indeed, the ability to detect changes in the viscosity of human blood can even have life and death consequences. This follows from the fact that a proper balance between normal hemostasis and coagulation or anticoagulation is absolutely essential in maintaining the integrity of the human circulatory system—and in stopping both external and internal bleeding. It is, however, sometimes necessary to modify the natural coagulation system, either by increasing or decreasing the rate of blood coagulation. During open heart surgery for example, a patient is usually supported by a heart/lung bypass machine that provides extracorporeal blood circulation while the heart is stopped. To prevent blood from clotting upon exposure to the bypass system, the patient is treated with high doses of heparin, a naturally occurring substance that significantly prolongs the clotting time of blood. When the time comes to remove the patient from the heart/lung bypass machine, however, it is desirable for the patient's blood to regain its normal coagulation characteristics so that it will again be able to clot and assist in healing incisions and stopping internal or external bleeding. This reversal of the effects of heparin is achieved by treating the patient's blood with an anticoagulant-reversing substance (e.g., protamine) capable of neutralizing heparin or other anticoagulating substances.
To successfully maintain anticoagulation during a surgical procedure, and neutralize the heparin at the conclusion of surgery, it is highly desirable to be able to quickly and accurately determine the concentration of heparin in the patient's blood. Unfortunately, since the activity of heparin varies significantly from batch to batch, and from patient to patient, these determinations cannot be made simply on the basis of the amount of heparin administered. Protamine also varies in potency from batch to batch and from patient to patient. Furthermore, protamine itself can act as an anticoagulant. Thus, for optimal reversal of a given heparin action, it is essential to use only that amount of protamine that will directly neutralize the amount of active heparin in a particular patient's blood.
Such reversals of a heparin action are detected by dose-response tests which measure changes in blood clotting time in response to differing doses of anticoagulant in order to determine the correct dose of anticoagulant for a particular patient. Clotting time or activated clotting time tests are used to determine whether a patient's blood has achieved the desired level of anticoagulation. Heparin/protamine (anticoagulant
eutralizer) titration tests have been developed to provide accurate determinations of heparin (anticoagulant) levels. Such tests are based on measuring the time necessary for the blood to coagulate. Consequently, these titration tests measure coagulation time as an empirical measure of blood viscosity. These titration tests are accurate; but they have three major drawbacks. They require relatively long times to conduct, they require relatively large blood samples and they are subject to variable results and inaccuracies due to operator related variances. Consequently, various alternative methods and apparatus have been proposed to address these drawbacks.
By way of example only, U.S. Pat. No. 5,629,209 (“the '209 patent”) discloses apparatus and methods for detecting changes in human blood viscosity through use of cartridges that, in conjunction with a test apparatus, are used to detect changes in blood viscosity. Heparinized blood is introduced into the cartridge through an injection port and fills the blood receiving/dispensing reservoir. The blood then moves from the reservoir through at least one conduit into at least one blood-receiving chamber where it is subjected to a viscosity test. In this test, a freely movable ferromagnetic object is placed within the blood-receiving chamber. The ferromagnetic object is moved up and down by an electromagnet in the test apparatus. Changes in the viscosity of the blood through which the ferromagnetic object falls are detected by determining the position of the ferromagnetic object in the blood-receiving chamber over a given time period or a given number of rises and falls of the ferromagnetic object. The incoming blood sample can be mixed with a blood viscosity altering agent (e.g., protamine) as it passes through the conduit to the blood-receiving chamber. Any air in the fluid communication system in front of the incoming blood sample is vented through an air vent/fluid plug device.
Applicants are co-inventors in the '209 patent and regard it as the closest prior art to the present invention. Therefore, its teachings are hereby fully incorporated into the present patent disclosure. The apparatus and methods described in the '209 patent are concerned with the same general issues e.g., test accuracy, test speed and operator safety that are further addressed in the present patent disclosure. Applicants' continued concern for these issues follows from the fact that the apparatus and methods of the '209 patent proved to have various drawbacks. These drawbacks have been eliminated or greatly diminished by the present invention. Many of these drawbacks were ultimately traced to the fact that a blood sample and the reagents (e.g., protamine) mixed into that blood sample by the apparatus and methods of the '209 patent were not uniformly mixed. This lack of uniformity of mixture resulted in test readings that sometimes proved to be unreliable. It would therefore be desirable to continue to employ, and enhance, the advantages originally brought about by the apparatus and methods taught in the '209 patent, while improving upon the reliability of the tests in which they are used. It also would be desirable to use these improvements in conducting other tests (e.g., those based upon changes in translucence, color, electrical conductivity, optical density, component concentration, electromotive response, etc.) on liquids other than human blood.
SUMMARY OF THE INVENTION
As was the case with the apparatus and methods of the '209 patent, the present invention is carried out through use of a disposable cartridge containing one or more simple testing chambers. This use of multiple chambers allows several tests to be performed simultaneously using uniform samples in a single cartridge. Thus, a second, third, etc. test carried out in that single cartridge can be a duplication of another test (to ensure greater reliability), or two or more entirely different tests can be conducted simultaneously. Here again, the amount of fluid contained within each test chamber is automatically determined. Hence, it will not vary from chamber to chamber or from test to test. The disposable cartridges of the present invention also are relatively small in size (thereby reducing the amount of storage space needed) and, likewise, relatively easy and inexpensive to manufacture.
The apparatus and methods of the present patent disclosure can be used in virtually any test where a re
Braun Steven P.
Braun, Jr. Walter J.
Braun, Sr. Walter J.
Alexander Lyle A.
Dorr, Carson , Sloan & Birney, P.C.
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