Tonometry sensor calibration apparatus

• US 5,195,522 A
• Filed: 06/18/1991
• Issued: 03/23/1993
• Est. Priority Date: 11/30/1990
• Status: Expired due to Term

• Current Assignee: Carefusion 303 Incorporated (Becton, Dickinson & Co)
• Original Assignee: Ivax Corporation (Teva Pharmaceutical Industries, Ltd.)
• Inventors: Butterfield, Robert D., Martin, Stephen A., Pytel, Kenneth J.
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): CASLER, BRIAN L
• Application Number:
  US07/717,224
• Time in Patent Office: 644 Days
• Field of Search: 128/748, 128/774, 128/687, 128/688, 128/689, 128/690, 73/4 V, 73/1 B
• US Class Current: 600/493
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02241 of small dimensions, e.g. adapted to fingers
• CPC Class Codes: A61B 5/02422 within occluders

Abstract

A calibration apparatus for use in calibrating a tissue stress sensor used in a blood pressure monitoring system. The calibration apparatus includes a calibration head which is adapted to be retained in close proximity to a tissue stress sensor. The calibration head includes means for heating the tissue stress sensor. A calibration system is also disclosed for calibrating a blood pressure monitoring system, the blood pressure monitoring system employing a stress sensor for generating an electric output signal representative of tissue stress data. The calibration system comprises a tissue stress sensor having a displaceable diaphragm and a sealed chamber. The chamber has a continuous wall defining an inner volume and an outer volume. The displaceable diaphragm comprises a portion of the continuous wall, whereby the displaceable diaphragm is responsive to a pressure differential between the inner chamber volume and the outer chamber volume. The vacuum means is fluidly coupled to the inner volume of the sealed chamber for applying a controlled vacuum to the inner volume of the chamber whereby the diaphragm is displaced in response to the application of the vacuum. Calibration means is provided for detecting the sensors response to heating and displacing of the sensor diaphragm and for generating corrective data for use in correcting the effects of sensor temperture on the data generated by the sensor.

Claims

1. A calibration apparatus for use in calibrating a tissue stress sensor used in a blood pressure monitoring system, said apparatus comprising:

a calibration head,

means, attached to said calibration head, for retaining said calibration head in close proximity to said tissue stress sensor, and

means, attached to said calibration head, for heating said tissue stress sensor.

2. The calibration apparatus of claim 1, wherein said calibration head generally includes a "C" shaped body adapted to engage a portion of an outer support structure surrounding said tissue stress sensor.

3. The calibration head of claim 2, wherein said retaining means includes a thumb screw threadedly engaged through said "C" shaped body, whereby rotating said thumb screw causes said thumb screw to engage said outer support structure of said tissue stress sensor thereby retaining said "C" shaped body to said outer support structure of said tissue stress sensor.

4. A calibration system for use in calibrating a sensor, comprising:

a tissue stress sensor including a sensor support structure to house said tissue stress sensor,

a calibration head, adapted to engage said support structure,

means for retaining said calibration head to said sensor support structure, and

means, attached to said calibration head, for heating said tissue stress sensor.

5. The calibration system of claim 4, wherein said sensor support structure includes a wrist strap for fastening said sensor support structure to a wrist of a wearer.

6. The calibration system of claim 5, wherein said calibration head generally includes a "C" shaped body adapted to engage an outer surface portion of said support structure.

7. The calibration system of claim 6, wherein said retaining means includes a thumb screw threadedly engaged to said "C" shaped body, whereby rotating said thumb screw causes said thumb screw to engage said sensor support structure thereby retaining said "C" shaped body to said sensor support structure.

8. The calibration system of claim 4, wherein said tissue stress sensor further includes a continuous, stress sensitive diaphragm and a continuous wall defining a hermetically sealable chamber, said continuous wall adapted to separate an inner chamber pressure from a pressure outside said chamber, wherein said continuous, stress sensitive diaphragm comprises at least a portion of said continuous wall, whereby said diaphragm is responsive to a pressure differential between said inner chamber pressure and said pressure outside said chamber.

9. A calibration system for use in calibrating a tissue stress sensor used in a blood pressure monitoring system, said sensor of the type having a stress sensitive portion for sensing tissue stress, said tissue stress sensor generating an electrical output signal representative of tissue stress, comprising:

means, adapted to be in thermal communication with said stress sensitive portion of said tissue stress sensor, for heating said stress sensitive portion of said tissue stress sensor,

means, adapted to be coupled to said tissue stress sensor, for displacing said stress sensitive portion of said tissue stress sensor,

calibrating means, adapted to be coupled to said electrical output signal of said tissue stress sensor, for

detecting a response of said stress sensitive portion of said sensor to said heating and displacing of said stress sensitive portion of said tissue stress sensor, and

correcting the effects of temperature on said electrical output signal of said tissue stress sensor.

10. The calibration system of claim 9, wherein said calibration means further includes means for sensing the temperature of said heating means.

11. The calibration system of claim 9, wherein said means for displacing includes a vacuum pump adapted to be in fluid communication with said stress sensitive portion of said tissue stress sensor.

12. The calibration system of claim 11, wherein said calibration means includes means for sensing a vacuum of said vacuum pump.

13. The calibration system of claim 9, wherein said heating means and said displacing means are connected to, and controlled by, said calibration means.

14. The calibration system of claim 13, wherein said heating means is adapted to heat said stress sensitive portion of said tissue stress sensor in response to a first control signal from said calibration means, and wherein displacing means is adapted to displace said stress sensitive portion of said tissue stress sensor in response to a second control signal from said calibration means.

15. A calibration system for use in calibrating a blood pressure monitoring system, comprising:

a tissue stress sensor having a stress sensitive diaphragm and a continuous wall defining a sealable chamber;

said continuous wall defining an inner chamber volume and wherein said stress sensitive diaphragm comprises a portion of said continuous wall, whereby said stress sensitive diaphragm is responsive to a pressure differential between the pressure of said inner chamber volume and a pressure outside of the inner chamber volume,

means, in thermal communication with said stress sensitive diaphragm, for heating said stress sensitive diaphragm,

vacuum means, fluidly coupled to said inner volume of said sealable chamber, for applying a controlled vacuum to said inner chamber volume of said sealable chamber, whereby said stress sensitive diaphragm is displaced in response to said application of said vacuum, and

calibration means, coupled to an electrical output signal of said tissue stress sensor, for

detecting said sensor'"'"'s response to said heating and displacing of said stress sensitive diaphragm, and

generating corrective data for use in correcting the effects of tissue stress sensor temperature on the electrical output signal of said tissue stress sensor.

16. The calibration system of claim 15, wherein said calibration means further includes means for sensing the temperature of said heating means.

17. The calibration system of claim 15, wherein said vacuum means includes a vacuum pump.

18. The calibration system of claim 17, wherein said calibration means includes means for sensing a vacuum of said vacuum pump.

19. The calibration system of claim 15, wherein said heating means and said vacuum means are connected to, and controlled by, said calibration means.

20. The calibration system of claim 19, wherein said heating means is adapted to heat said stress sensitive diaphragm in response to a first control signal from said calibration means, and wherein said vacuum means is adapted to displace said stress sensitive diaphragm in response to a second control signal from said calibration means.

21. The calibration system of claim 15, wherein said tissue stress sensor includes a sensor support structure which includes a wrist strap for fastening said sensor support structure to a wrist of a wearer.

22. The calibration system of claim 21, further including a calibration head, adapted to engage said support structure, and wherein said calibration head is adapted to engage said heating means thereby keeping said heating means in thermal communication with said stress sensitive diaphragm, and wherein said calibration head generally includes a "C" shaped body adapted to engage an outer surface portion of said sensor support structure.

23. The calibration system of claim 22, wherein said calibration head "C" shaped body includes a thumb screw threadedly engaged to said "C" shaped body, whereby rotating said thumb screw causes said thumb screw to engage said sensor support structure thereby retaining said "C" shaped body to said sensor support structure.

24. A tissue stress sensor of the type used to non-invasively determine intra-arterial blood pressure, said tissue stress sensor comprising:

a continuous stress sensitive diaphragm including means for placing said diaphragm in direct communication with tissue overlying an artery of interest,

a continuous wall,

a vacuum port through said continuous wall,

wherein said continuous stress sensitive diaphragm comprises a portion of said continuous wall, and

wherein said continuous wall and said continuous stress sensitive diaphragm form a sealable air tight chamber,

whereby said tissue stress sensor is used as a stress sensor and said continuous diaphragm is responsive to stresses imparted to it from said tissue overlying an artery of interest, and whereby when said tissue stress sensor is calibrated, a calibrated vacuum is applied to said vacuum port thereby lowering the pressure within said air tight chamber, whereby said continuous diaphragm responds to a pressure differential established between the sealable air tight chamber and a pressure upon an outer surface of said continuous diaphragm, said response of said continuous diaphragm to said pressure differential being in part due to the magnitude of said calibrated vacuum, whereby said application of said calibrated vacuum to said vacuum port enables said tissue stress sensor to be calibrated.

25. The tissue stress sensor of claim 24, further including calibrated vacuum means connected to said vacuum port for lowering the pressure within said air tight chamber.

26. The tissue stress sensor of claim 25, wherien said calibrated vacuum means includes a vacuum source and a vacuum tube connected between said vacuum source and said vacuum port, wherein said vacuum tube includes an end portion adapted to engage a seal along an inne surface of said vacuum port thereby forming an air tight seal between said port and said vacuum tube.