INSTRUMENT FOR MEASURING BLOOD CLOTTING TIMES

• US 3,840,806 A
• Filed: 08/20/1973
• Issued: 10/08/1974
• Est. Priority Date: 08/20/1973
• Status: Expired due to Term

• Current Assignee: Glenn E. Stoner, Thompson H. Boyd III
• Original Assignee: Glenn E. Stoner, Thompson H. Boyd III
• Inventors: Stoner, Glenn E., Boyd, Thompson H. III
• Primary Examiner(s): Krawczewicz, Stanley T.
• Application Number:
  US05/389,672
• Time in Patent Office: 414 Days
• Field of Search: 324/65R,65P,3B 128/2G,2.1R,2.1E,2E 73/15A,64.1 23/23B
• US Class Current: 324/722
• CPC Class Codes: G01N 27/07 Construction of measuring vessels; Electrodes therefor
• CPC Class Codes: G01N 33/4905 Determining clotting time of blood by chemical methods G01N33/86, C12Q1/54
• CPC Class Codes: G01R 27/22 Measuring resistance of fluids

Abstract

An improved method and apparatus for monitoring and studying blood clotting times are disclosed. The method includes the step of passing a direct current through a blood or plasma sample and observing the electrical resistance of the sample during the clotting process. The electrical resistance, when plotted against time, is found to form a sigmoid curve having distinct inflections which signify the occurrence of both gellation and fibrin cross-linking within the clotting sample. The apparatus of the present invention includes a sample container which is preferably a disposable cup having a pair of electrodes suitably mounted in it and connected to an electrical connector. A current source is provided for supplying a constant current to the plasma or blood sample, and is equipped with an electrical coupling for mating with the connector on the disposable sample container. A chart recorder is coupled to the constant current source for providing a continuous indication of the sample resistance.

Claims

1. A method of measuring the times of formation of fibrin and the cross-linking of fibrin in whole blood comprising the steps:

placing a pair of electrodes into a blood sample;

supplying a direct current to said electrodes;

measuring the electrical impedance of said sample between said electrodes; and

detecting inflections in said electrical impedance which occur during said step of measuring, said inflections denoting the occurrence of fibrin formation and cross-linking of said fibrin.

2. A method as in claim 1, further comprising the step of:

maintaining said direct current at a constant amplitude.

3. A method as in claim 2, wherein said step of maintaining includes the step of:

fixing said direct current at an amplitude of approximately 0.8 microamp.

4. A method as in claim 1, further comprising the step of:

recording said inflections of said electrical impedance after said step of measuring.

5. A method as in claim 1 further comprising the step of:

timing the occurrence of said inflections.

6. A method as in claim 1, further comprising the step of:

differentiating said inflections to produce clearer indications of the occurrence of said inflections.

7. A method as in claim 1, wherein said step of measuring includes the step of:

continuously monitoring the direct current electrical resistance of said sample.

8. A method as in claim 4, further comprising the step of:

recording timing marks representing standard times for fibrin formation and cross-linking in juxtaposition with said inflections to permit comparison of the behavior of said sample with a reference standard.

9. A method as in claim 1, wherein said step of placing includes the steps of:

obtaining a sample of whole blood, placing said whole blood sample into a sample container having a pair of micro-electrodes mounted therein; and

coupling said micro-electrodes to a source of direct current.

10. An apparatus for detecting changes in the impedance of a biological fluid comprising:

sample container means for holding a sample of said biological fluid, electrode means positioned within said sample container means for continuously engaging said sample of biological fluid, power source means coupled to said electrode means for passing a direct current through said sample, measuring means coupled across said electrode means for measuring changes in the resistance of said sample; and

indicator means coupled to said measuring means for indicating the output of said measuring means whereby changes occurring in the molecular structure of said biological fluid are detected through indications of said changes in resistance.

11. An apparatus as in claim 10, further comprising:

differentiating means coupled between said measuring means and said indicator means for emphasizing changes in the output of said measuring means.

12. An apparatus as in claim 10, further comprising:

timing means coupled to said indicator means for providing a standard for comparison with the output of said measuring means.

13. An apparatus as in claim 10, wherein:

said sample container means comprises a disposable vessel formed of a plastic material and said electrode means are mounted within said vessel.

14. An apparatus as in claim 13, wherein said sample container means further comprises:

an electrical connector mounted to a bottom portion of said vessel and electrically connected to said electrode means for connecting said electrode means to said power source.

15. An apparatus as in claim 10, wherein said electrode means comprises:

a pair of electrodes, each including a spherical gold micro-electrode coupled to a fine conductive wire, said fine wire surrounded by a firm tube of insulating material.

16. An apparatus as in claim 10, wherein said power source means comprises:

an electric circuit for generating a fixed amplitude direct current.

17. An apparatus as in claim 10, wherein said measuring means comprises:

a very high impedance voltmeter.

18. An apparatus as in claim 10, wherein said indicator means comprises:

a chart recorder for continuously recording the output of said measuring means.

19. A disposable sample container for use with an apparatus for detecting changes in the impedance of a biological fluid comprising:

a cup-shaped vessel formed of a plastic material, a reinforced base member secured to a bottom portion of said vessel, a pair of electrodes mounted in said reinforced base member and protruding into the interior volume of said vessel; and

an electrical connector mounted in said reinforced base member for coupling said electrodes to a power source.

20. A disposable sample container as in claim 19, wherein each of said electrodes comprises:

a spherical gold micro-electrode coupled to a fine conductive wire, said fine wire surrounded by a firm tube of insulating material.