Method and device for measuring systolic and diastolic blood pressure and heart rate in an environment with extreme levels of noise and vibrations

• US 6,705,998 B2
• Filed: 04/29/2002
• Issued: 03/16/2004
• Est. Priority Date: 11/24/2000
• Status: Expired due to Fees

• Current Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Original Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Inventors: Zachariah, Ronald, Pinto, Lisa, Dhanantwari, Amar, Stergiopoulos, Stergios
• Primary Examiner(s): Nasser, Robert L.
• Assistant Examiner(s): MALLARI, PATRICIA C
• Application Number:
  US10/133,575
• Publication Number:
  US 20020143259A1
• Time in Patent Office: 687 Days
• Field of Search: 600/485, 600/490, 600/493, 600/495, 600/499, 600/500
• US Class Current: 600/493
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/02208 using the Korotkoff method
• CPC Class Codes: A61B 5/025 within occluders, e.g. responsive to Korotkoff sounds electric stethoscopes A61B7/04
• CPC Class Codes: A61B 7/045 Detection of Korotkoff sounds A61B5/0225 takes precedence; measuring blood pressure A61B5/021

Abstract

A method and a device for measuring systolic and diastolic blood pressure and heart rate in an environment comprising extreme levels of noise and vibrations is disclosed. Blood pressure signals corresponding to the Korotkoff sounds are detected using a first acoustic sensor, or array of sensors, placed on the patient'"'"'s skin over the brachial artery. A second acoustic transducer is placed on the outside of a pressure cuff the patient away for detecting noise and vibrations. Pressure is applied to the artery using the pressure cuff forcing the artery to close. The pressure is then reduced and while reducing the pressure the acoustic signals detected by the first and second acoustic sensor as well as a signal indicative of the pressure applied to the artery are provided to a processor. The signal of the first acoustic sensor is then processed using an adaptive interferer canceller algorithm with the signal of the second acoustic sensor as interferer. From the processed signal heart beat pulses are determined and relating the heart beat pulses to the pressure signal provides the systolic and diastolic blood pressure. Use of the adaptive interferer canceller provides good results for measurements performed under extreme levels of noise and vibrations such as aboard a helicopter, naval vessels, ambulances and noisy emergency rooms.

Claims

1. A method for measuring systolic and diastolic blood pressure of a patient comprising the steps of:

applying pressure to a brachial artery of the patient by wrapping a pressure cuff around a limb of the patient, the pressure cuff having a first surface being in contact with skin of the patient'"'"'s limb and a second surface opposite the first surface facing away from the skin of the patient'"'"'s limb;

sensing blood pressure signals corresponding to Korotkoff sounds using a first acoustic sensor placed on the skin of the patient'"'"'s limb over the brachial artery, the first acoustic sensor for producing a first acoustic signal in dependence upon the blood pressure signals;

sensing noise and vibrations using a second acoustic sensor for producing a second acoustic signal in dependence upon noise and vibrations, the second sensor being attached to the second surface and acoustically isolated therefrom;

sensing the pressure applied to the brachial artery using a pressure transducer for sensing pressure and for providing a pressure signal in dependence upon the sensed pressure;

providing the first acoustic signal, the second acoustic signal and the pressure signal to a processor while the pressure is applied to the brachial artery;

processing the first acoustic signal for removing interference due to noise and vibrations using the second acoustic signal in an adaptive interferer canceller;

detecting Korotkoff sound pulses within the processed first acoustic signal; and

,

determining systolic and diastolic pressure by relating the detected Korotkoff sound pulses to the pressure signal.

2. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 1, wherein the pressure is applied to the brachial artery such that the brachial artery is forced closed.

3. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 2, comprising the step of reducing the pressure applied to the brachial artery.

4. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 2, wherein the blood pressure signals are sensed while performing the step of applying pressure to the brachial artery until the brachial artery is forced closed.

5. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 2, wherein the first acoustic sensor is placed on the skin of the patient'"'"'s limb over the brachial artery of the patient downstream of a location where the pressure is applied to the brachial artery.

6. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 5, wherein the pressure applied to the brachial artery is distributed substantially equally along the brachial artery.

7. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 6, wherein the first acoustic sensor is supported by a support contacting the patient'"'"'s skin, the support having a surface area for contacting the patient'"'"'s skin being sufficiently large for substantially reducing pressure exerted by the support onto the brachial artery due to inflation of the pressure cuff.

8. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 1, wherein the Korotkoff sound pulses are detected using a peak discriminator.

9. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 8, wherein peaks greater than a floor noise level are isolated.

10. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 9, wherein peaks not satisfying periodicity and constancy in repetition are discarded.

11. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 10, wherein peaks corresponding to Korotkoff sound pulses not perceptible to an average human ear are discarded.

12. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 10, comprising the step of determining a heart rate from the detected Korotkoff sound pulses.

13. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 12, comprising the step of updating the heart rate with each pulse found during searching for the systolic and diastolic pressure.

14. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 13, comprising the step of tracking gaps in a sequence of detected Korotkoff sound pulses.

15. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 14, comprising the step of determining a new value for the systolic and diastolic blood pressures if a new sequence of Korotkoff sound pulses is found.

16. A device for measuring systolic and diastolic blood pressure of a patient in an environment with extreme levels of noise and vibration, the device comprising:

a pressure cuff for being wrapped around a limb of the patient for applying pressure to a brachial artery of the patient, the pressure cuff having a first surface for being in contact with skin of the patient'"'"'s limb and a second surface opposite the first surface for facing away from the skin of the patient'"'"'s limb;

a pressure transducer for sensing the pressure applied to the brachial artery and for providing a pressure signal in dependence thereupon;

a first acoustic sensor for placement on the skin of the patient'"'"'s limb over the brachial artery for sensing blood pressure signals corresponding to Korotkoff sounds and for producing a first acoustic signal in dependence thereupon;

a second acoustic sensor attached to the second surface and acoustically isolated therefrom for sensing noise and vibration and for producing a second acoustic signal in dependence thereupon; and

,

a processor for processing the first acoustic signal and the second acoustic signal using adaptive interference cancellation, for detecting Korotkoff sound pulses within the processed first acoustic signal and for determining systolic and diastolic blood pressure using the detected Korotkoff sound pulses and the pressure signal.

17. A device for measuring systolic and diastolic blood pressure of a patient as defined in claim 16, wherein the second acoustic sensor is attached to the second surface approximately diametrically opposite to the location of the first acoustic sensor with respect to the patient'"'"'s limb.

18. A device for measuring systolic and diastolic blood pressure of a patient as defined in claim 17, wherein the second acoustic sensor is attached to the second surface at an upstream end of the pressure cuff with respect to the blood flow in the brachial artery.

19. A device for measuring systolic and diastolic blood pressure of a patient as defined in claim 16, comprising an array of first acoustic sensors for placement on the skin of the patient'"'"'s limb across the brachial artery.

20. A device for measuring systolic and diastolic blood pressure of a patient as defined in claim 19, wherein the array of first acoustic sensors is housed in a bell shaped housing using an acoustic isolator.

21. A device for measuring systolic and diastolic blood pressure of a patient as defined in claim 20, wherein the second acoustic sensor is housed in a bell shaped housing using an acoustic isolator.

22. A device for measuring systolic and diastolic blood pressure of a patient as defined in claim 21, wherein the second acoustic sensor is removably attached to the second surface.

23. A device for measuring systolic and diastolic blood pressure of a patient as defined in claim 16, wherein the first acoustic sensor is housed in a bell shaped housing using an acoustic isolator.

24. A device for measuring systolic and diastolic blood pressure of a patient as defined in claim 23 wherein the first acoustic sensor is attached to the first surface.

25. A device for measuring systolic and diastolic blood pressure of a patient as defined in claim 24, wherein the pressure applied to the brachial artery is distributed substantially equally along the brachial artery.

26. A device for measuring systolic and diastolic blood pressure of a patient as defined in claim 25, wherein the bell shaped housing has a surface area for contacting the patient'"'"'s skin being sufficiently large for substantially reducing pressure exerted by the bell onto the brachial artery due to inflation of the pressure cuff.

27. A device for measuring systolic and diastolic blood pressure of a patient as defined in claim 16, wherein the pressure cuff comprises a non inflatable extension for attaching the first acoustic sensor thereto.

28. A device for measuring systolic and diastolic blood pressure of a patient in an environment with extreme levels of noise and vibration, the device comprising:

a pressure cuff for being wrapped around a limb of the patient for applying pressure to a brachial artery of the patient, the pressure cuff having a first surface for being in contact with skin of the patient'"'"'s limb and a second surface opposite the first surface for facing away from the skin of the patient'"'"'s limb;

a pressure transducer for sensing the pressure applied to the brachial artery and for providing a pressure signal in dependence thereupon;

a first acoustic sensor attached to the first surface for placement on the skin of the patient'"'"'s limb over the brachial artery at a downstream end of the pressure cuff with respect to the blood flow in the brachial artery for sensing blood pressure signals corresponding to Korotkoff sounds and for producing a first acoustic signal in dependence thereupon;

a second acoustic sensor attached to the second surface and acoustically isolated therefrom for sensing noise and vibration and for producing a second acoustic signal in dependence thereupon, the second acoustic sensor being attached approximately opposite to the location of the first acoustic sensor with respect to the patient'"'"'s limb at an upstream end of the pressure cuff; and

,

a processor for processing the first acoustic signal and the second acoustic signal using adaptive interference cancellation, for detecting Korotkoff sound pulses within the processed first acoustic signal and for determining systolic and diastolic blood pressure using the detected Korotkoff sound pulses and the pressure signal.