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

• US 20030139674A1
• Filed: 01/15/2003
• Published: 07/24/2003
• Est. Priority Date: 11/24/2000
• Status: Active Grant

• 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: Dhanantwari, Amar, Stergiopoulos, Stergios, Zachariah, Ronald, Pinto, Lisa, Wong, Man Yee Winnie
• Granted Patent: US 6,805,671 B2
• Time in Patent Office: Days
• US Class Current: 600/490
• 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 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 an array of primary acoustic sensors, placed on the patient'"'"'s skin over the brachial artery. A secondary 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 signals provided by the primary acoustic sensors are then processed using a combination of focused beamforming and planar wave beamforming. The final beam time series is then processed using an adaptive interferer canceller algorithm with the signal provided by the secondary acoustic sensor as interferer. Use of an array of acoustic sensors in combination with beamforming substantially enhances signal detection as well as accurate isolation of the signal source which is highly beneficial for blood pressure measurements measurements performed under extreme levels of noise and vibrations.

Claims

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

sensing Korotkoff sounds using an array of primary acoustic sensors placed on skin of a patient'"'"'s limb over an artery occluded by applying pressure thereupon, the primary acoustic sensors being placed in rows and columns forming a planar array, the planar array being placed on the patient'"'"'s skin such that the rows are oriented approximately perpendicular to the artery and the columns are oriented approximately parallel to the artery, each primary acoustic sensor for producing a first acoustic signal in dependence upon the Korotkoff sounds;

sensing noise and vibrations using a secondary acoustic sensor for producing a secondary acoustic signal in dependence upon noise and vibrations;

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

providing the first acoustic signal of each primary acoustic sensor, the secondary acoustic signal and the pressure signal to a processor;

using the processor beamforming the first acoustic signals based on a focused beamformer for beamforming approximately perpendicular to the artery and a plane wave beamformer for beamforming approximately parallel to the artery in order to produce an output beam time series in dependence thereupon;

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

detecting the Korotkoff sounds based on the beam time series; and

,

determining at least one of systolic and diastolic pressure by relating the detected Korotkoff sounds to the pressure signal.

2. A method for measuring blood pressure of a patient as defined in claim 1 wherein the step of beamforming the first acoustic signals comprises the steps of:

beamforming the first acoustic signals produced by the primary acoustic sensors placed in a same row based on a focused beamformer producing a first beam time series for each row;

beamforming the first beam time series based on a plane wave beamformer producing the output beam time series.

3. A method for measuring blood pressure of a patient as defined in claim 2 wherein each of the first beam time series is assumed to be a directional acoustic sensor signal.

4. A method for measuring blood pressure of a patient as defined in claim 2 wherein the interference due to noise and vibrations is removed from the first acoustic signal of each primary acoustic sensor.

5. A method for measuring blood pressure of a patient as defined in claim 2 wherein the interference due to noise and vibrations is removed from each of the first beam time series.

6. A method for measuring blood pressure of a patient as defined in claim 2 wherein the interference due to noise and vibrations is removed from the output beam time series.

7. A method for measuring blood pressure of a patient as defined in claim 1 wherein the step of beamforming the first acoustic signals comprises the steps of:

beamforming the first acoustic signals produced by the primary acoustic sensors placed in a same column based on a plane wave beamformer producing a first beam time series for each column; and

,

beamforming the first beam time series based on a focused beamformer producing the output beam time series.

8. A method for measuring blood pressure of a patient comprising the steps of:

sensing Korotkoff sounds using an array of primary acoustic sensors placed on skin of a patient'"'"'s limb over an artery occluded by applying pressure thereupon, each primary acoustic sensor for producing a first acoustic signal in dependence upon the Korotkoff sounds;

providing the first acoustic signal of each primary acoustic sensor to a processor;

using the processor beamforming the first acoustic signal produced by each primary acoustic sensor in order to produce a beam time series in dependence thereupon; and

, detecting the Korotkoff sounds based on the beam time series.

9. A method for measuring blood pressure of a patient as defined in claim 8 wherein the first acoustic signal produced by each primary acoustic sensor is beamformed using an adaptive beamformer.

10. A method for measuring blood pressure of a patient as defined in claim 9 wherein the primary acoustic sensors are placed in rows and columns forming a planar array, the planar array being placed on the patient'"'"'s skin such that the rows are oriented approximately perpendicular to the artery and the columns are oriented approximately parallel to the artery.

11. A method for measuring blood pressure of a patient as defined in claim 9 wherein the first acoustic signals are beamformed based on a focused beamformer for beamforming approximately perpendicular to the artery and a plane wave beamformer for beamforming approximately parallel to the artery.

12. A method for measuring blood pressure of a patient as defined in claim 8 comprising the steps of:

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

providing the pressure signal to the processor; and

,

determining at least one of systolic and diastolic pressure by relating the detected Korotkoff sounds to the pressure signal.

13. A method for measuring blood pressure of a patient as defined in claim 12 comprising the steps of:

sensing noise and vibrations using a secondary acoustic sensor for producing a secondary acoustic signal in dependence upon noise and vibrations;

providing the secondary acoustic signal to the processor; and

,

processing the first acoustic signals for removing interference due to noise and vibrations using the secondary acoustic signal in an adaptive interferer canceller.

14. A device for measuring blood pressure of a patient comprising:

an array of primary acoustic sensors for being placed on skin of a patient'"'"'s limb over an artery occluded by applying pressure thereupon, each primary acoustic sensor for producing a first acoustic signal in dependence upon Korotkoff sounds;

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

,

a processor for receiving the first acoustic signals and the pressure signal, for beamforming the first acoustic signals in order to produce a beam time series in dependence thereupon, for detecting Korotkoff sounds based on the beam time series and for determining at least one of systolic and diastolic blood pressure using the detected Korotkoff sounds and the pressure signal.

15. A device for measuring blood pressure of a patient as defined in claim 14 wherein the primary acoustic sensors are placed in rows and columns forming a planar array, the planar array for being placed on the patient'"'"'s skin such that the rows are oriented approximately perpendicular to the artery and the columns are oriented approximately parallel to the artery.

16. A device for measuring blood pressure of a patient as defined in claim 15 wherein the primary acoustic sensors placed in a row are spaced less than ½

a wavelength of the first acoustic signal.

17. A device for measuring blood pressure of a patient as defined in claim 15 wherein the primary acoustic sensors placed in a column are spaced less than ½

a wavelength of the first acoustic signal.

18. A device for measuring blood pressure of a patient as defined in claim 14 comprising a secondary acoustic sensor for sensing noise and vibration and for producing a secondary acoustic signal in dependence thereupon, the secondary acoustic signal for provision to the processor for removing interference due to noise and vibrations from the first acoustic signal using adaptive interference cancellation.

19. A device for detecting Korotkoff sounds of a patient comprising:

an array of primary acoustic sensors for being placed on skin of a patient'"'"'s limb over an artery, the primary acoustic sensors being placed in rows and columns forming a planar array, the planar array for being placed on the patient'"'"'s skin such that the rows are oriented approximately perpendicular to the artery and the columns are oriented approximately parallel to the artery, each primary acoustic sensor for producing a first acoustic signal in dependence upon the Korotkoff sounds; and

,

a processor for receiving the first acoustic signals, for beamforming the first acoustic signals based on a focused beamformer for beamforming approximately perpendicular to the artery and a plane wave beamformer for beamforming approximately parallel to the artery in order to produce a beam time series in dependence thereupon and for detecting Korotkoff sounds based on the beam time series.