SYSTEM FOR DETECTION OF BLOOD PRESSURE USING A PRESSURE SENSING GUIDE WIRE

• US 20130296722A1
• Filed: 01/30/2012
• Published: 11/07/2013
• Est. Priority Date: 01/30/2011
• Status: Active Grant

• Current Assignee: Guided Interventions, Incorporated
• Original Assignee: Guided Interventions, LLC
• Inventors: Warnking, Reinhard J., Pollman, Matthew J.
• Granted Patent: US 9,456,756 B2
• Time in Patent Office: Days
• US Class Current: 600/488
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 5/0015 characterised by features of the telemetry system
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/02152 specially adapted for venous pressure
• CPC Class Codes: A61B 5/6851 Guide wires
• CPC Class Codes: A61M 2025/09175 having specific characteristics at the distal tip
• CPC Class Codes: A61M 25/09 Guide wires

Abstract

A guide wire has a distal end incorporating a coil and a capacitive element that form a resonance circuit with a resonance frequency that is responsive to the pressure of blood external to the guide wire. The resonance frequency can be detected wirelessly, or through two contacts at the proximal wire end, or through one brush contact located inside an insertion sheath and a ground electrode. Wireless detection can be implemented via a second resonance circuit, and electronics for determining the frequency when the first and second circuits are in resonance with each other.

Claims

1. A system for detection of blood pressure in a blood vessel comprising:

a guide wire;

a coil provided at a distal end of said guide wire; and

a capacitor provided at a distal end of said guide wire, said coil and said capacitor being coupled to each other to form a resonance circuit, at least one of said coil and said capacitor being responsive to changes in pressure of fluid external to said guide wire such that said resonance circuit has a resonance frequency that varies in accordance with changes in pressure of the external fluid.

2. The system defined in claim 1 wherein said coil is configured to have an inductance that is variable depending on changes in pressure of fluid external to said guide wire.

3. The system defined in claim 2 wherein said coil is provided with a ferromagnetic core that is movably mounted to said guide wire and partially disposed inside said coil so that changes in pressure of said external fluid results in a shifting of said core relative to said coil, thereby varying an inductance of said coil and concomitantly the resonance frequency of said resonance circuit.

4. The system defined in claim 2 wherein said resonance circuit has a movable contact shiftable relative to said coil so that changes in pressure of said external fluid results in shifting of said contact relative to said coil and changing the active length of said coil, thereby varying an inductance of said coil and concomitantly the resonance frequency of said resonance circuit.

5. The system defined in claim 2 wherein said coil has windings that are shiftably mounted to said guide wire so that changes in pressure of said external fluid results in a change in an effective length of said coil, thereby varying an inductance of said coil and concomitantly the resonance frequency of said resonance circuit.

6. The system defined in claim 1 wherein said capacitor is configured to have a capacitance that varies in response to changes in said external pressure.

7. The system defined in claim 6 wherein said capacitor includes a first plate element and a second plate element, at least said second plate element being movably mounted to said guide wire so that changes in pressure of said external fluid results in a shifting of said second plate element and a change in a distance or separation between said first plate element and said second plate element, thereby varying said capacitance and concomitantly the resonance frequency of said resonance circuit.

8. The system defined in claim 1, further comprising a detector operatively connected to said resonance circuit for monitoring said resonance frequency and determining the pressure of said external fluid.

9. The system defined in claim 8 wherein said resonance circuit is a first resonance circuit, said detector including a second resonance circuit disposable outside of a patient, said second resonance circuit being electromagnetically couplable to said first resonance circuit for determining said resonance frequency by detecting when said first and said second resonance circuits are in resonance.

10. The system defined in claim 9 wherein said detector is configured for monitoring power consumption of second resonance circuit.

11. The system defined in claim 9 wherein said second resonance circuit includes a printed disposable coil attachable to a patient near an intervention site.

12. The system defined in claim 9 wherein said second resonance circuit is mounted on a sheath, said guide wire extending through said sheath.

13. The system defined in claim 8 wherein said guide wire has a core member and a hypotube, said detector being connected to said resonance circuit via two electrical contacts located at a proximal end of said guide wire, one of said electrical contacts being connected to said core member and another of said electrical contacts being connected to said hypotube.

14. The system defined in claim 8, further comprising an insertion sheath, said guide wire extending through said insertion sheath, said resonance circuit being operatively connected to said detector via a ground electrode at a distal end of said guide wire and via a brush contact inside said insertion sheath.

15. The system defined in claim 8 wherein said detector includes a radio transmitter/receiver operatively connectable to said resonance circuit via a proximal wire end acting as a receive/transmit antenna.

16. The system defined in claim 8, further comprising an insertion sheath, said guide wire extending through said insertion sheath, a metal layer or a braid being disposed inside the sheath, said metal layer or a braid coacting together with said guide wire to form a capacitor that couples said detector to said resonance circuit.

17. A method measuring blood pressure, comprising:

inserting a distal end portion of an elongate wire into a cardiovascular system of a patient, said distal end portion being provided with an LC resonance circuit;

detecting a resonance frequency of said LC resonance circuit while said circuit is inside the vascular system of the patient;

determining a blood pressure value from the detected resonance frequency.

18. The method defined in claim 17 wherein said LC resonance circuit includes a circuit element with an LC parameter varying in accordance with pressure of a fluid surrounding said distal end portion of said wire, further comprising monitoring said resonance circuit for a change in said resonance frequency owing to a variation in said LC parameter induced by a blood pressure change;

determining a second blood pressure value from the changed resonance frequency.

19. The method defined in claim 18 wherein said LC parameter is inductance, further comprising varying said inductance in accordance with blood pressure by changing a physical parameter taken from the group consisting of coil length, number of active windings in an inductor, and extent of insertion of a movable ferromagnetic core member into an inductor or coil.