Continuous non-invasive blood pressure monitoring system

• US 5,450,852 A
• Filed: 04/14/1994
• Issued: 09/19/1995
• Est. Priority Date: 11/09/1993
• Status: Expired due to Term

• Current Assignee: Medwave, Inc.
• Original Assignee: Medwave, Inc.
• Inventors: Thede, Roger C., Curran, Timothy G., Poliac, Marius O., Archibald, G. Kent, Danielson, Orland H.
• Primary Examiner(s): Sykes, Angela D.
• Application Number:
  US08/227,506
• Time in Patent Office: 523 Days
• Field of Search: 128/672, 128/677, 128/687-690, 128/678-683
• US Class Current: 600/485
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence

Abstract

A transducer having a sensing surface for sensing blood pressure within an underlying artery of a patient includes a transducer, a sidewall, a flexible diaphragm and a fluid coupling medium. The sidewall supports the transducer above the underlying artery. The flexible diaphragm is spaced from the sensing surface of the transducer. The fluid coupling medium is coupled between the sensing surface of the transducer and the flexible diaphragm and transmits blood pressure pulses within the underlying artery from the flexible diaphragm to the sensing surface of the transducer. The fluid coupling medium is isolated from the sidewall so that forces are not transmitted from the sidewall through the fluid coupling medium to the transducer.

Claims

1. A sensor for sensing blood pressure within an underlying artery of a patient, the sensor comprising:

a pressure transducer for sensing blood pressure pulses of the underlying artery, the transducer having a sensing surface;

a flexible diaphragm having an active portion for transmitting blood pressure pulses of the underlying artery;

interface means coupled between the sensing surface of the transducer and the flexible diaphragm for transmitting the blood pressure pulses within the underlying artery from the flexible diaphragm to the sensing surface of the transducer; and

means isolated from the interface means and surrounding the active portion for conforming to the anatomy surrounding the underlying artery.

2. The sensor of claim 1 wherein the means for conforming includes means for equalizing pressure around the active portion.

3. The sensor of claim 2 wherein the means for equalizing pressure includes a compressible ring surrounding the active portion having a top surface and a bottom surface, the ring being partially filled with a fluid so that the distance between the top surface and the bottom surface varies along the ring to conform to the anatomy of the patient surrounding the underlying artery.

4. The sensor of claim 3 including:

a foam rubber ring surrounding the active portion and positioned between the compressible ring and the anatomy of the patient.

5. The sensor of claim 1 including means isolated from the interface means and at least partially surrounding the active portion for dampening forces in a direction parallel to the underlying artery which are exerted by the blood pressure pulses on the sensor so that a substantially zero pressure gradient exists within the interface means across the pressure transducer.

6. The sensor of claim 5 wherein the means for dampening includes a compressible sidewall surrounding the active portion.

7. The sensor of claim 1 wherein the tissue surrounding the underlying artery exerts a force as the underlying artery is compressed, and wherein the sensor includes means isolated from the interface means and surrounding the active portion for neutralizing the force exerted by the tissue surrounding the underlying artery.

8. The sensor of claim 7 wherein means for neutralizing includes a compressible sidewall surrounding the active portion.

9. A sensor for sensing blood pressure within an underlying artery, the sensor comprising:

a pressure transducer for sensing blood pressure pulses of the underlying artery, the transducer having a sensing surface;

a flexible diaphragm spaced from the sensing surface, the flexible diaphragm having an active portion for receiving forces exerted by the blood pressure pulses;

interface means coupled between the sensing surface of the transducer and the flexible diaphragm for transmitting the blood pressure pulses within the underlying artery from the flexible diaphragm to the sensing surface of the transducer; and

means isolated from the interface means and at least partially surrounding the active portion for dampening forces in a direction parallel to the underlying artery which are exerted by the blood pressure pulses on the sensor so that a substantially zero pressure gradient exists across the active portion of the flexible diaphragm.

10. A sensor for measuring blood pressure pulses within an underlying artery surrounded by tissue as the underlying artery is compressed, wherein the tissue surrounding the underlying artery exerts a force as the underlying artery is compressed, the sensor comprising:

a pressure transducer for sensing blood pressure pulses of the underlying artery, the transducer having a sensing surface;

a flexible diaphragm spaced from the sensing surface, the diaphragm having an active portion for receiving forces exerted by the blood pressure pulses;

interface means coupled between the sensing surface of the transducer and the flexible diaphragm for transmitting the blood pressure pulses within the underlying artery from the flexible diaphragm to the sensing surface of the transducer; and

means isolated from the interface means and surrounding the active portion for neutralizing the force exerted by the tissue surrounding the underlying artery.

11. A sensor for sensing blood pressure within an underlying artery, the sensor comprising:

a pressure transducer for sensing blood pressure pulses of the underlying artery, the transducer having a sensing surface;

supporting means for supporting the transducer above the underlying artery;

a flexible diaphragm spaced from the sensing surface; and

interface means coupled between the sensing surface of the transducer and the flexible diaphragm for transmitting the blood pressure pulses within the underlying artery from the flexible diaphragm to the sensing surface of the transducer, wherein the interface means are isolated from the supporting means.

12. The sensor of claim 11 wherein the interface means comprises a fluid coupling medium and wherein the flexible diaphragm partially defines an interface chamber extending between the flexible diaphragm and the sensing surface of the transducer, the interface chamber containing the fluid coupling medium and being substantially isolated from the supporting means so as to prevent pressure from the support means from being transmitted to the fluid coupling medium and to the sensing surface of the transducer.

13. The sensor of claim 12 wherein the flexible diaphragm includes:

a first flexible member having an active portion encircled by the supporting means, wherein the active portion receives forces exerted by the blood pressure pulses; and

a second flexible member supported between the supporting means and the first flexible member and bonded to the first flexible member, the second flexible member having a portion above the active portion which is isolated from the supporting means so that the isolated portion of the second flexible member and the active portion of the first flexible member at least partially define the interface chamber.

14. The sensor of claim 13 wherein the supporting means defines an expansion cavity so that the isolated portion of the second flexible member is permitted to move into the expansion cavity without changing the volume of the interface chamber when the sensor is conforming to the anatomy of the patient surrounding the underlying artery.

15. The sensor of claim 12 wherein the means for supporting includes a compressible sidewall at least partially surrounding the sensing surface of the transducer.

16. The sensor of claim 15 wherein the compressible sidewall includes:

a fluid filled wall for conforming to the anatomy surrounding the underlying artery, the fluid filled wall equalizing pressure around the sensing surface of the transducer.

17. The sensor of claim 15 wherein the compressible sidewall includes:

a foam wall for dampening forces in a direction parallel to the underlying artery which are exerted by the blood pressure pulses on the sensor so that a substantially zero pressure gradient exists within the interface means across the pressure transducer.

18. The sensor of claim 15 wherein the tissue surrounding the underlying artery exerts a force as the underlying artery is compressed and wherein the compressible sidewall includes:

a foam wall for neutralizing the force exerted by the tissue surrounding the underlying artery.

19. A sensor for sensing blood pressure within an underlying artery, the sensor comprising:

a pressure transducer for sensing blood pressure pulses of the underlying artery, the transducer having a sensing surface;

a flexible diaphragm spaced from the sensing surface;

a sidewall coupled to the transducer, wherein the sidewall supports the transducer above the underlying artery; and

a fluid coupling medium coupled between the sensing surface of the transducer and the flexible diaphragm and isolated from the sidewall so that blood pressure pulses within the underlying artery are transmitted from the flexible diaphragm to the sensing surface of the transducer and so that external forces from the sidewall are not transmitted through the fluid coupling medium to the sensing surface of the transducer.

20. A sensor or claim 19 wherein the flexible diaphragm at least partially defines an interface chamber isolated from the sidewall and wherein the interface chamber contains the fluid coupling medium.

21. A sensor for sensing blood pressure within an underlying artery of a patient, the sensor comprising:

a pressure transducer for sensing blood pressure pulses of the underlying artery, the transducer having a sensing surface;

a flexible diaphragm spaced from the sensing surface, wherein the flexible diaphragm at least partially defines an interface chamber in communication with the sensing surface of the pressure transducer;

a fluid coupling medium within the interface chamber for transmitting blood pressure pulses within the underlying artery from the flexible diaphragm to the sensing surface of the transducer; and

a supporting structure for supporting the transducer above the underlying artery, wherein the supporting structure defines an expansion cavity adjacent the flexible diaphragm so that the interface chamber containing the fluid coupling medium may undergo a change in shape without a corresponding change in volume and pressure.