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

• US 6,520,918 B1
• Filed: 11/24/2000
• Issued: 02/18/2003
• Est. Priority Date: 11/24/1999
• Status: Expired due to Term

• 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: Stergiopoulos, Stergios, Dhanantwari, Amar C.
• Primary Examiner(s): Nasser, Robert L.
• Assistant Examiner(s): MALLARI, PATRICIA C
• Application Number:
  US09/718,515
• Time in Patent Office: 816 Days
• Field of Search: 600/485, 600/490, 600/586
• US Class Current: 600/490
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• 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 heart beat are detected using a first acoustic sensor placed on a patient near an artery. A second acoustic transducer is placed on the patient away from the artery for detecting noise and vibrations. Pressure is applied to the artery 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 processing unit. 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.

Claims

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

sensing blood pressure signals corresponding to heart beat using a first acoustic sensor placed on the patient near a location of an artery of the patient, 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 placed at a location away from an artery such that the second acoustic signal enables reliable signal processing for measuring systolic and diastolic blood pressure using non-linear adaptive interference cancellation;

sensing pressure applied to the 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 processing unit while the pressure is applied to the artery;

processing the first acoustic signal for removing interference due to noise and vibrations in the first acoustic signal by subtracting the second acoustic signal from the first acoustic signal using the adaptive interference cancellation;

detecting heart beat pulses within the processed first acoustic signal; and

,

determining systolic and diastolic pressure by relating the detected heart beat pulses to the pressure signal.

2. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 1, comprising the steps of:

applying pressure to the artery such that the artery is forced closed; and

,

reducing the pressure applied to the artery.

3. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 2, comprising the step of:

sensing the blood pressure signals while performing the step of applying pressure to the artery until the artery is forced closed.

4. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 2, wherein the first acoustic sensor is placed near the artery downstream of a location where the pressure is applied to the artery.

5. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 1, wherein the first acoustic signal is band pass filtered.

6. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 1, wherein the second acoustic signal is band pass filtered.

7. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 1, wherein the processed first acoustic signal is band pass filtered.

8. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 1, wherein the second acoustic signal is processed using an adaptive filter.

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

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

11. 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.

12. A method for measuring systolic and diastolic blood pressure of a patient as defined in claim 1, comprising the step of:

determining a heart rate from the detected heart beat pulses.

13. A method for monitoring heart beat of a patient within a noisy environment comprising the steps of:

sensing blood pressure signals corresponding to heart beat using a first acoustic sensor placed on the patient near a location of an artery of the patient, 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 placed at a location away from an artery such that the second acoustic signal enables reliable signal processing for measuring systolic and diastolic blood pressure using non-linear adaptive interference cancellation;

providing the first acoustic signal and the second acoustic signal to a processing unit;

removing interference due to noise and vibrations in the first acoustic signal by subtracting the second acoustic signal from the first acoustic signal using the adaptive interference cancellation;

detecting heart beat pulses within the first acoustic signal; and

,

determining a heart rate from the detected heart beat pulses.

14. A method for monitoring heart beat of a patient as defined in claim 13, wherein a pressure above diastolic blood pressure is applied to the artery.

15. A method for monitoring heart beat of a patient as defined in claim 14, wherein the first acoustic sensor is placed near the artery downstream of a location where the pressure is applied to the artery.

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 applying pressure to an artery of the patient;

a pressure transducer for providing a pressure signal in dependence upon the pressure applied to the artery;

a first acoustic sensor for producing a first acoustic signal in dependence upon blood pressure signals corresponding to heart beat;

a second acoustic sensor for producing a second acoustic signal in dependence upon noise and vibration, the second sensor being placed such that the second acoustic signal enables reliable signal processing for measuring systolic and diastolic blood pressure using non-linear adaptive interference cancellation; and

,

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

17. A device for measuring systolic and diastolic blood pressure of a patient in an environment with extreme levels of noise and vibration as defined in claim 16, wherein the processing unit is used for determining a heart rate from the detected heart beat pulses.

18. A device for measuring systolic and diastolic blood pressure of a patient in an environment with extreme levels of noise and vibration as defined in claim 16, comprising a band pass filter for filtering the first and the second acoustic signal.

19. A device for measuring systolic and diastolic blood pressure of a patient in an environment with extreme levels of noise and vibration as defined in claim 16, comprising a band pass filter for filtering the processed first acoustic signal.