CARDIAC OUTPUT MEASURING METHOD AND APPARATUS

• US 3,820,530 A
• Filed: 02/16/1973
• Issued: 06/28/1974
• Est. Priority Date: 02/16/1973
• Status: Expired due to Term

• Current Assignee: Bauman J, Freeman G, Gilford S
• Original Assignee: Bauman J, Freeman G, Gilford S
• Inventors: GILFORD S, FREEMAN G, BAUMAN J
• Application Number:
  US05/332,929
• Time in Patent Office: 497 Days
• US Class Current: 600/526
• CPC Class Codes: A61B 5/02755 Radioactive tracers

Abstract

Apparatus and method for practicing the Stewart-Hamilton method of measuring cardiac output but with dynamic calibration. The apparatus includes a chamber into which a precise quantity of dye can be introduced for admixture with blood in the chamber. The flow of a subject'"'"''"'"'s blood can then be switched from normal measuring flow through the densitometer to calibrating flow through the densitometer by a simple mechanical operation without stopping the procedure and without need for sterilization of any apparatus or changing of any equipment. An important component of the apparatus is a combined mixing chamber and cuvette which is disposable.

Claims

1. Apparatus for use in measuring cardiac output and calibrating such measurement, which comprises:

A. a cuvette and means for leading a flow of blood from a subject through the cuvette to measure the density of any test substance which may have been introduced into the blood, B. a mixing chamber of known volume, C. means for introducing an accurate amount of test substance into said chamber without permitting discharge of any fluid from said chamber, D. valve means upstream of said cuvette and interposed in said flow leading means and including means for directing flow into said chamber for a temporary zero flow condition and then through said chamber passing through said cuvette in one condition of said valve means, or to direct flow to said cuvette by-passing said chamber in a second condition of said valve means, and E. structure operable to place said valve means in either of said two conditions.

2. The apparatus as claimed in claim 1 in which said introducing means includes a septum facing the interior of said chamber and a sharp cannula adapted to pierce said septum.

3. The apparatus as claimed in claim 1 in which said introducing means comprises an elastomeric septum closing off an access opening to said chamber and an adjustable volume pump having a hollow pointed needle output passageway adapted to be pierced through the septum so that the pump may be emptied into said chamber and withdrawn from said septum.

4. The apparatus as claimed in claim 1 in which said introducing means comprises an elastomeric septum closing said chamber, a pre-settable syringe and means for holding the syringe in position with its needle arranged to be introduced through said septum to enable discharge of the contents thereof into said chamber.

5. The apparatus as claimed in claim 1 in which means are provided for mixing the fluid in said chamber comprising a mixing device within the chamber and a rotary magnetic member exterior of said chamber magnetically coupled with said mixing device.

6. The apparatus as claimed in claim 1 in whIch said valve means includes a closure for said chamber rendering said chamber liquid tight but for the passage of blood as aforesaid.

7. The apparatus as claimed in claim 1 in which said valve means includes a cylindrical plug rotatable in and serving as the closure for said chamber.

8. The apparatus as claimed in claim 1 in which said chamber has a cylindrical entrance at the upper end thereof, said valve means includes a cylindrical plug in fluidtight yet rotatable engagement with said entrance, said flow leading means including a pair of opposed but aligned passageways comprising upstream and downstream passageways opening to said chamber, said plug having a transverse passageway adapted to connect said aligned passageway openings when the plug is rotated to an angular disposition in said cylindrical entrance so that said transverse passageway is so connected and said angular disposition comprising the said second condition of said valve means.

9. The apparatus as claimed in claim 1 in which said cuvette and mixing chamber comprises a unitary component including said valve means, a holder is provided for receiving said unitary component and said holder having an externally operable lever adapted to be brought into coupled engagement with said valve means when said unitary component is in operative position in said holder.

10. The apparatus as claimed in claim 7 in which said plug has flow directing passageways therein and said flow leading means includes ports in said chamber, said plug adapted to be rotated to bring its passageways into different relationships with said ports for achieving said first and second conditions.

11. The apparatus as claimed in claim 7 in which said structure operable to place said valve means in either of said two conditions comprises a swingable lever and a separable nonrotatable connection between the lever and the plug.

12. The apparatus as claimed in claim 11 in which means are provided for indexing and limiting the movement of said lever to achieve said two positions.

13. The apparatus as claimed in claim 12 in which means are provided to bias the lever and plug together but permitting overcoming said bias to enable disassociation of said plug from said lever.

14. The apparatus as claimed in claim 8 in which said plug has a recess formation angularly spaced from said transverse passageway adapted when the plug is rotated to a different angular disposition to align with the upstream one of the opposed passageways to direct entering fluid into said chamber and the plug having a configuration at the same time uncovering the downstream one of said opposed passageways while blocking said transverse passageway, said different angular disposition comprising said first condition of said valve means.

15. The apparatus as claimed in claim 14 in which the angular dispositions are at most 90* apart.

16. The apparatus as claimed in claim 14 in which the plug has means for emptying air bubbles from said chamber when said plug is in said different angular disposition.

17. The apparatus as claimed in claim 9 in which said unitary component comprises an integral cylindrical portion having said chamber formed therein, a flanged portion having the cuvette formed therein, a first passageway from the chamber to the cuvette, said holder having means for directing radiation across the flanged portion and through said cuvette, a second passageway comprising a part of said leading means and adapted to convey blood from said subject to said chamber, said first and second passageways having ports opening into said chamber, and a third passageway for carrying blood away from said cuvette, said holder having a conduit for said third passageway, said valve means comprising a rotatable closure for said chamber provided with a transverse connecting passageway and a recess and being so configured so that in one rotational position comprising the first condition of said valve means the transverse connecting passageway is blockEd and blood enters from said second passageway, passes through its port into the chamber, flows through the chamber and into the other port, through the first passageway and the cuvette and the third passageway, while in a second rotational position of said closure comprising the second condition of said valve means only the transverse connecting passageway is between the ports so that blood entering the second passageway passes directly to the cuvette by-passing the chamber.

18. The apparatus as claimed in claim 9 in which the introducing means comprises a syringe having a hollow needle mounted to said holder, a bore for the needle in the holder and an elastomeric septum in the unitary component facing and closed to the chamber and aligned with said bore when said unitary component is in place in said holder.

19. A unitary component for apparatus for use in measuring cardiac output and calibrating such measurement, the component adapted to be disposable and adapted to be mounted to a holder which has mixing means, structure including a needle guide for introducing a fluid substance into said unitary component, valve manipulating means, a radiation path for densitometric purposes, said component comprising:

A. a cylindrical portion having a mixing chamber with a closure having valving structure formed therein comprising means for establishing two conditions intwo different angular dispositions of the closure, B. a lateral portion connected to the cylindrical portion and adapted to be secured to said holder, C. an input passageway in the cylindrical portion adapted to be connected to a source of blood flowing to said apparatus and having an input port opening into the chamber, D. a discharge port in the lateral portion for leading blood from said unitary component, E. a cuvette formed in the lateral portion and adapted to be aligned with the radiation path when the unitary component is in place in said holder so that radiation may pass transversely through said cuvette, F. a cuvette discharge passageway in said lateral portion connecting the cuvette to said discharge port, G. a cuvette connecting passageway in said lateral portion extending from said cuvette to said chamber and having a chamber discharge port opening to said chamber to lead fluid from said chamber to said cuvette, H. the valving structure of the closure having means for cooperating with the valve manipulating means when the unitary component is connected to said holder, I. one condition of the valving structure providing a direct connection between the input port and chamber discharge port, and the second condition providing means for flow of blood into said chamber for a temporary zero flow condition and then through said chamber into said cuvette connecting passageway.

20. A structure as claimed in claim 19 in which said chamber has an elastomeric septum adapted to align with said needle guide when said unitary component is mounted to said holder whereby said substance may be introduced into said chamber through said septum without loss of fluid from said chamber.

21. A structure as claimed in claim 19 in which the valving structure comprises a transverse straightthrough passageway adapted to have its ends aligned with the respective input port and chamber discharge port during said one condition of the valving structure.

22. A structure as claimed in claim 21 in which the valving structure additionally comprising a diverting recess in said closure and an angled surface of the bottom of said closure, the diverting recess adapted to be aligned with said input port while the angled surface uncovers said chamber discharge port in said second condition of said valving structure so that any fluid entering said input port must pass through the chamber before passing into said chamber discharge port.

23. A structure as claimed in claim 19 in which the lateral portion is radiation transmissive and a radiation opaque guide is alIgned with said cuvette and adapted to be aligned with said radiation path when the component is mounted in the holder substantially to confine radiation passing through said cuvette and thereafter passing through said lateral portion while substantially excluding radiation by-passing said radiation path.

24. A method of measuring cardiac output by the Stewart-Hamilton technique and calibrating such measurement which includes commencing a flow of the subject'"'"''"'"'s blood through a densitometer, providing a chamber with an aliquot of the subject'"'"''"'"'s blood in said chamber in a temporary zero flow condition, introducing a precise proportion of a trace material into said chamber while under said condition of zero flow through said chamber and mixing the trace material with said blood, maintaining said zero flow condition until the trace material in said aliquot has stabilized, then resuming and directing the the flow through the chamber to said densitometer so that the densitometer indicates the dilution characteristics of the trace material in said aliquot.

25. A method of measuring cardiac output by the Stewart-Hamilton technique and calibrating such measurement which includes establishing a continuous flow of subject blood through a densitometer, establishing in a dye-dilution chamber an aliquot of blood in a temporary zero flow condition for an accurate proportional measurement of dye and said aliquot of subject blood, and switching the flow between said chamber and by-passing the chamber without interrupting said flow.

26. The method as claimed in claim 25 in which dye is injected into said chamber and mixed therein while said flow is by-passing the chamber.

27. The method as claimed in claim 26 in which the dye is permitted to remain in the chamber after injection for a sufficient length of time before switching flow into said chamber to enable equilibration of said dye in said aliquot.