Continuous non-invasive blood pressure monitoring system

• US 5,649,542 A
• Filed: 05/03/1995
• Issued: 07/22/1997
• Est. Priority Date: 11/09/1993
• Status: Expired due to Fees

• 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): Cohen, Lee S.
• Assistant Examiner(s): GILBERT, SAMUEL G
• Application Number:
  US08/434,264
• Time in Patent Office: 811 Days
• Field of Search: 128/672, 128/677, 128/678-690
• 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 sensor for sensing blood pressure within an underlying artery as the underlying artery is compressed includes a transducer and a compressible sidewall. The transducer senses blood pressure of blood pressure pulses as the pulses travel beneath the sensor. As each blood pressure pulses crosses an edge of the sensor, each pulse exerts a force on the sensor in a direction parallel to the underlying artery. Tissue surrounding the underlying artery also exerts a force. The compressible sidewall is distant from the transducer and engages tissue surrounding the underlying artery. The compressible side wall neutralizes the force exerted by the tissue surrounding the underlying artery and dampens the force parallel to the underlying artery so that a substantially zero pressure gradient exists across the transducer.

Claims

1. A sensor for measuring blood pressure pulses within an underlying artery surrounded by tissue of a patient as the underlying artery is compressed, the sensor comprising:

sensing means for sensing blood pressure of each pulse as each pulse travels beneath the sensor; and

a variable height side wall distinct from and adjacent to the sensing means for engaging the tissue proximate the underlying artery and capable of conforming to the anatomy of the patient.

2. The sensor of claim 1 wherein the means for sensing blood pressure comprises a transducer.

3. The sensor of claim 2 further including a flexible diaphragm spaced from the transducer.

4. The sensor of claim 3 further including interface means coupled between the transducer and the flexible diaphragm for transmitting blood pressure pulse signals from the underlying artery to the transducer.

5. The sensor of claim 4 wherein the interface means comprises a fluid coupling medium.

6. The sensor of claim 1 wherein each blood pressure pulse exerts a force on the sensor in a direction parallel to the underlying artery as each pulse crosses an edge of the sensor, and wherein the spacing means further includes means for dampening the force parallel to the underlying artery.

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 variable height side wall further includes means for neutralizing the force exerted by the tissue proximate the underlying artery.

8. The sensor of claim 1 wherein the side wall is compressible.

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

an external 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; 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; and

means for dampening forces in a direction parallel to the underlying artery which are exerted by the blood pressure pulses on the sensor.

10. The sensor of claim 9 wherein the interface means comprises a fluid coupling medium.

11. The sensor of claim 10 wherein the means for dampening comprise a compressible side wall surrounding sensing surface of the transducer and supporting the flexible diaphragm.

12. The sensor of claim 11 wherein the side wall is constrained from expanding parallel to the sensing surface of the transducer.

13. The sensor of claim 11 wherein the side wall is made of foam.

14. The sensor of claim 9 further including means for applying a variable hold down pressure to the sensor.

15. The sensor of claim 14 wherein the means for applying a variable hold down pressure to the sensor comprises:

a base plate;

means for supporting the base plate with reference to the underlying artery;

movable coupling means for movably coupling the sensor to the base plate; and

means for moving the moveable coupling means so that a variable hold down pressure is applied to the sensor.

16. The sensor of claim 14 wherein the means for applying a variable hold down pressure to the sensor comprises:

a base plate;

means for supporting the base plate with reference to the underlying artery;

an outer sleeve coupled to the base plate;

a threaded inner sleeve rotatably supported within the outer sleeve;

a threaded screw shaft coupled to the sensor, the screw shaft slidably engaging the base plate and threadably engaging the inner sleeve so that rotation of the inner sleeve causes the screw shaft to move the sensor up and down to vary the hold down pressure of the sensor; and

a motor for rotating the inner sleeve to vary hold down pressure of the sensor.

17. The sensor of claim 9 further including means for calculating blood pressure based upon the sensed pressure pulses within the underlying artery.

18. The sensor of claim 17 wherein the means for calculating comprise:

a microprocessor for receiving signals representing the sensed blood pressure pulses and the hold down pressure applied to the underlying artery and for calculating blood pressure based upon the received signals representing the blood pressure pulses and the hold down pressures.

19. The sensor of claim 9 further including means for mounting the sensor above the underlying artery.

20. The sensor of claim 19 wherein the means for mounting comprises:

a frame coupled to the sensor, the frame including a stabilizing support protruding from the frame and supporting the frame above the underlying artery; and

a flexible strap coupled to the frame and extending below the underlying artery.

21. A sensor for sensing blood pressure in an underlying artery surrounded by tissue, the sensor comprising:

a transducer element for sensing blood pressure pulses within the underlying artery;

a compressible wall distant from the transducer element, wherein the compressible wall dampens and absorbs forces exerted upon the wall in a direction parallel to the underlying artery and neutralizes forces exerted by the tissue proximate the underlying artery;

a flexible diaphragm supported by the compressible wall and constrained from tension, wherein the compressible wall and the flexible diaphragm at least partially define a chamber in communication with the transducer element; and

a pressure coupling medium within the chamber, whereby the transducer element senses blood pressure pulses transmitted across the flexible diaphragm and through the pressure coupling medium when the flexible diaphragm is placed over the underlying artery.

22. A blood pressure monitoring system for continuous external measurements of blood pressure in an underlying artery surrounded by tissue of a patient, the system comprising:

a sensor for sensing blood pressure pulses in the underlying artery;

means for applying a variable hold down pressure to the sensor;

means for calculating blood pressure based upon the sensed pressure pulses within the underlying artery; and

means for neutralizing forces exerted by the tissue proximate the underlying artery while conforming to the anatomy of the patient.

23. The system of claim 22 wherein the sensor includes:

a transducer having a sensing surface;

a flexible diaphragm for being positioned over the underlying artery;

interface means between the flexible diaphragm and the sensing surface of the transducer for transmitting pressure pulses from the diaphragm to the transducer; and

flexible means for supporting the flexible diaphragm above the underlying artery and for conforming to the anatomy of the patient.

24. The system of claim 23 wherein the interface means comprises a fluid.

25. The system of claim 23 wherein the flexible means for supporting comprises a semi-rigid side wall encircling the interface means and supporting the flexible diaphragm.

26. The system of claim 25 wherein the semi-rigid side wall comprises foam.

27. The system of claim 22 wherein the means for applying the variable hold down pressure to the sensor comprises:

a base plate;

an outer sleeve coupled to the base plate;

a threaded inner sleeve rotatably supported within the outer sleeve;

bearings between the inner sleeve and the outer sleeve for rotatably supporting the inner sleeve relative to the outer sleeve;

a threaded screw shaft coupled to the sensor, the screw shaft slidably engaging the base plate and threadably engaging the inner sleeve so that rotation of the inner sleeve causes the screw shaft to move the sensor up and down to vary the hold down pressure of the sensor; and

a motor for rotating the inner sleeve to vary hold down pressure of the sensor.

28. The system of claim 27 further including means for controlling the motor to control the hold down pressure applied to the sensor.

29. The system of claim 22 wherein the means for calculating blood pressure based upon sensed pressure pulses comprises:

a microprocessor for receiving data representing the sensed pressure pulses and the hold down pressures applied to the underlying artery and for calculating blood pressure based upon the received data representing the pressure pulses and the hold down pressures.

30. The system of claim 22 further including means for mounting the sensor above the underlying artery.

31. The system of claim 30 wherein the means for mounting comprises:

a frame coupled to the sensor, the frame including a stabilizing support protruding from the frame and supporting the frame above the underlying artery; and

a flexible strap coupled to the frame and extending below the underlying artery so that the underlying artery is positioned between the flexible strap and the stabilizing support of the frame.

32. The system of claim 31 further including:

a socket coupled to the frame; and

a ball coupled to the outer sleeve and frictionally set within the socket for properly orienting the sensor with respect to the underlying artery.

33. The system of claim 22 further including:

means for dampening and absorbing forces exerted by the blood pressure pulses in directions not perpendicular to the underlying artery.

34. An apparatus for sensing blood pressure pulses within an underlying artery surrounded by tissue as the underlying artery is compressed, the apparatus comprising:

a transducer;

a flexible diaphragm for placement above the underlying artery;

a flexible compressible sidewall distant from the transducer and positioned for engaging tissue adjacent the underlying artery; and

a fluid coupling medium coupled between the transducer and the flexible diaphragm, wherein the fluid coupling medium transmits blood pressure pulse signals from the underlying artery to the transducer.

35. A sensor for sensing blood pressure within an artery surrounded by tissue, the sensor comprising:

a transducer;

a flexible diaphragm;

a fluid coupling medium coupled between the flexible diaphragm and the transducer; and

a compressible wall supported above the artery to at least partially surround the artery and to engage tissue proximate the artery.

36. In a sensor for sensing blood pressure within an underlying artery of a patient, the sensor having a transducer for sensing blood pressure of each pulse as each pulse travels beneath the sensor, an improvement comprising:

a flexible sidewall spaced from the transducer for engaging the tissue and capable of conforming to the anatomy of the patient.

37. In the sensor of claim 36, the improvement further including:

a flexible diaphragm spaced from the transducer; and

the fluid coupling medium coupled between the flexible diaphragm and the transducer.

38. For use in a system for non-invasively determining the intraarterial blood pressure of an artery surrounded by tissue, a sensing apparatus comprising:

a compressible sidewall for engaging tissue at least partially surrounding the underlying artery;

a transducer having a sensing surface spaced from the sidewall;

a flexible diaphragm for transmitting blood pressure pulses of the underlying artery; and

a fluid coupling medium between the sensing surface of the transducer and the flexible diaphragm.

39. A sensor for sensing blood pressure pulses within an underlying artery surrounded by tissue of a patient as the underlying artery is compressed, the sensor comprising:

a transducer;

a flexible diaphragm for placement above the underlying artery;

a fluid coupling medium coupled between the transducer and the flexible diaphragm for transmitting blood pressure pulse signals from the underlying artery to the transducer; and

a flexible sidewall distinct from the transducer and positioned for engaging tissue proximate the underlying artery while being capable of conforming to the anatomy of the patient.

40. The sensor of claim 39 wherein the flexible sidewall is compressible.

41. A sensor for sensing blood pressure pulses within an underlying artery surrounded by tissue as the underlying artery compressed, the sensor comprising:

a transducer;

a flexible diaphragm for placement above the underlying artery;

a variable height body conforming side wall positioned adjacent the flexible diaphragm for engaging tissue proximate to the underlying artery; and

a fluid coupling medium between the transducer and the flexible diaphragm, wherein the fluid coupling medium transmits blood pressure pulse signals from the underlying artery to the transducer.

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

a fluid filled sensing chamber having a diaphragm and a body conforming side wall; and

a pressure transducer fluidly coupled to the fluid filled sensing chamber.

43. The sensor of claim 42 further including:

means for positioning the fluid filled sensing chamber and the diaphragm over the artery of the patient.

44. The sensor of claim 42 including:

means for applying a variable hold down pressure to the sensor.

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

a fluid filled sensing chamber having a diaphragm;

a transducer fluidly coupled to the fluid filled sensing chamber, wherein the transducer senses fluid pressure within the chamber; and

a body conformable wall proximate the sensing chamber for applying force to the artery while preventing pressure in a direction generally parallel to the artery from being applied to the sensing chamber.