Blood flow measuring apparatus

• US 20040147967A1
• Filed: 11/13/2003
• Published: 07/29/2004
• Est. Priority Date: 05/31/2001
• Status: Active Grant

• Current Assignee: St. Jude Medical AB (Abbott Laboratories Incorporated)
• Original Assignee: St. Jude Medical AB (Abbott Laboratories Incorporated)
• Inventors: Strandberg, Hans
• Granted Patent: US 7,011,633 B2
• Time in Patent Office: Days
• US Class Current: 607/17
• CPC Class Codes: A61B 2562/164 the sensor is mounted in or on a conformable substrate or carrier
• CPC Class Codes: A61B 5/026 Measuring blood flow A61B3/1233, A61B3/1241 take precedence
• CPC Class Codes: A61B 5/6862 Stents
• CPC Class Codes: A61B 5/6876 Blood vessel
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36571 controlled by blood flow rate, e.g. blood velocity or cardiac output

Abstract

A blood flow measuring apparatus has a measuring electrode and a counter-electrode adapted to be brought into contact with the blood of a patient. A measuring unit measures a voltage or a current between the measuring electrode and the counter-electrode and determines the flow of blood therefrom. The measuring electrode is ring-shaped and sized to fit within a blood vessel in the body of the patient. An inner surface of the ring-shaped electrode forms an active measuring electrode surface. The blood flow measuring apparatus is suitable for use in a cardiac pacemaker.

Claims

1. A blood flow measuring apparatus comprising a measuring electrode (8, 14, 16, 24, 30) and a counter electrode (12) intended to be brought into contact with the blood of a patient, and a measuring unit adapted to measure the voltage or current between said electrodes to determine therefrom the flow of blood, characterized in that said measuring electrode (8, 14, 16, 24, 30) is ring-shaped and sized to fit within a blood vessel (10) within the patient'"'"'s body, and in that an inner surface (40) of said ring-shaped electrode is adapted to form an active measuring electrode surface.

2. The apparatus according to claim 1, characterized in that said measuring unit is adapted to measure the current to the ring-shaped measuring electrode (8, 14, 16, 24, 30) while maintaining a constant voltage between said measuring and counter electrodes (8, 14, 16, 24, 30;

12).

3. The apparatus according to claim 1 or 2, characterized in that the active surfaces of the measuring electrode (8, 14, 16, 24, 30) and the counter electrode (12) are of the same order of magnitude.

4. The apparatus according to any one of the preceding claims, characterized in that said ring-shaped electrode (8, 14, 16, 24, 30) is sized to surround substantially the total flow in said vessel.

5. The apparatus according to any one of the preceding claims, characterized in that said ring-shaped electrode (8,14, 16, 24, 30) comprises plastic material with said inner surface at least partly coated by an electrically conducting electrode material (40).

6. The apparatus according to claim 5, characterized in that a platinum foil is attached to said inner surface of the ring (8,14, 16, 24, 30).

7. The apparatus according to any one of the preceding claims, characterized in that the outer surface of said ring-shaped measuring electrode (8,14, 16, 24, 30) is insulated.

8. The apparatus according to any one of the claims 1-6, characterized in that a second electrode is provided on the outer surface of the plastic ring.

9. The apparatus according to any one of the preceding claims, characterized in that said ring-shaped measuring electrode includes a metal net.

10. The apparatus according to any one of the preceding claims, characterized in that said ring-shaped electrode (14) is foldable to enable reduction of its diameter for implantation.

11. The apparatus according to claim 10, characterized in that said ring-shaped electrode is made up of several mutually foldable segments.

12. The apparatus according to any one of the claims 1-9, characterized in that said ring-shaped electrode (16) is slotted to be wound together to reduce the cross-section area for implantation.

13. The apparatus according to any one of the claims 10-12, characterized in that said ring-shaped electrode (24) is designed for introduction, in its folded or wound together state, into a catheter (22) suitable for insertion into a blood vessel, and further designed to be pressed out of the catheter by a stiff wire (26) to then relax to its ring-shape.

14. The apparatus according to any one of the preceding claims, characterized in that the ends of said ring-shaped electrode (30) are flexible.

15. The apparatus according to any one of the preceding claims, characterized in that a plurality of axial slits are formed in said ends of said ring-shaped electrode.

16. The apparatus according to any one of the claims 1-14, characterized in that said ends of the ring-shaped electrode (30) are wave-shaped, the curvature of the wave-shape being small compared to the curvature of the ring.

17. The apparatus according to any one of the preceding claims, a lead (32) connecting said ring-shaped electrode (30) to said measuring unit, characterized in that an elongated part (34) of plastic material is attached to said ring-shaped electrode (30) to extend along said lead (32) to serve as a support therefor.

18. The apparatus according to claim 17, characterized in that the lead (32) is passing through holes (36) in said elongated part.

19. A pacemaker, characterized by an apparatus according to any one of the preceding claims.