Noninvasive apparatus and method for estimating blood pressure

• US 7,828,740 B2
• Filed: 08/01/2006
• Issued: 11/09/2010
• Est. Priority Date: 08/03/2005
• Status: Active Grant

• Current Assignee: Luca Longhini
• Original Assignee: Luca Longhini
• Inventors: Longhini, Luca, Peretto, Lorenzo
• Primary Examiner(s): Bockelman; Mark W
• Assistant Examiner(s): Dinga; Roland
• Application Number:
  US11/496,754
• Publication Number:
  US 20070032728A1
• Time in Patent Office: 1,561 Days
• Field of Search: 600/485, 600493-496, 600/508, 600/513, 600/514, 600/528, 600/586
• US Class Current: 600/528
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 7/00 Instruments for auscultation
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R

Abstract

Methods and apparatus for noninvasively estimating a blood pressure are provided. A pulmonic (P) component extracted from a second heart sound (S2) signal is analyzed to obtain a number of oscillations in the P component. A predetermined relationship between the number of oscillations and PAP is used to generate a blood pressure estimate. A PCG sensor including a mechanical filter for receiving heart sounds from a chest wall is also provided. The pressure of the PCG sensor on the chest wall is adjustable.

Claims

1. A method for noninvasively estimating a blood pressure, the method comprising the steps of:

a) extracting a pulmonic (P) component from a second heart sound (S2) signal;

b) analyzing the extracted P component to obtain a number of oscillations in the P component;

c) determining a value that corresponds to the number of oscillations; and

d) applying a predetermined relationship between the value and blood pressure to generate a blood pressure estimate.

2. The method according to claim 1, wherein the blood pressure includes a pulmonary artery pressure (PAP) and step (d) includes applying the predetermined relationship between the value and PAP to generate a PAP estimate.

3. The method according to claim 1, the method further including the steps of, prior to step (a):

receiving a phonocardiogram (PCG) signal; and

extracting the S2 signal from the received PCG signal,

wherein step (a) extracts the P component from the extracted S2 signal.

4. The method according to claim 1, wherein the S2 signal is a time-domain S2 signal and step (a) extracts the P component using the time-domain S2 signal.

5. The method according to claim 1, wherein step (b) determines the number of oscillations using a derivative with respect to time of the P component.

6. The method according to claim 1, wherein the predetermined relationship is determined by a linear regression between a plurality of measured numbers of oscillations and a respective plurality of measured blood pressures corresponding to the measured numbers of oscillations.

7. The method according to claim 1, step (a) includes the steps of:

determining a P component onset time according to a maximum absolute value of a time derivative of the S2 signal; and

selecting a predetermined portion of the S2 signal as the P component using the determined P component onset time.

8. The method according to claim 1, wherein the S2 signal includes a plurality of S2 signals, and

step (a) includes extracting a corresponding plurality of P components from the plurality of S2 signals,

wherein the blood pressure estimate is generated according to the extracted plurality of P components.

9. The method according to claim 8, further including the step of determining a confidence interval measure associated with the blood pressure estimate.

10. The method according to claim 8, further including the steps of:

repeating steps (b), (c) and (d) over the plurality of S2 signals to generate a corresponding plurality of blood pressure estimates; and

determining a mode of the plurality of blood pressure estimates to generate an average blood pressure estimate.

11. The method according to claim 8, further including the steps of:

determining a mean S2 signal from the plurality of S2 signals; and

repeating steps (b), (c) and (d) using the mean S2 signal to generate the blood pressure estimate.

12. The method according to claim 11, wherein the step of determining the mean S2 signal further includes the steps of:

determining a plurality of discrete Fourier transform (DFT) signals corresponding to the plurality of S2 signals;

computing a mean DFT signal from the plurality of DFT signals; and

determining an inverse discrete Fourier transform (IFDT) signal from the mean DFT signal, the IFDT signal forming the mean S2 signal.

13. The method according to claim 1, the method further including the steps of, prior to step (a):

synchronously receiving a phonocardiogram (PCG) signal and an electrocardiogram (ECG) signal for a predetermined duration of time; and

extracting the S2 signal from the received PCG signal using the received ECG signal,

wherein step (a) extracts the P component from the extracted S2 signal.

14. The method according to claim 13, the step of extracting the S2 signal includes the steps of:

determining two consecutive QRS complex onset times from the received ECG signal;

calculating a time interval from the determined QRS complex onset times;

determining an S2 onset time according to the calculated time interval; and

selecting a predetermined portion of the PCG signal using the determined S2 onset time as the extracted S2 signal.

15. The method according to claim 13, wherein the PCG signal includes a plurality of PCG signals and the ECG signal includes a plurality of ECG signals corresponding to the plurality of PCG signals,

the step of synchronously receiving the PCG signal and the ECG signal includes synchronously receiving the plurality of PCG signals and the plurality of ECG signals, and

the step of extracting the S2 signal includes extracting a corresponding plurality of S2 signals,

wherein the blood pressure estimate is generated according to the extracted plurality of S2 signals.

16. The method according to claim 15, further including the step of determining a confidence interval measure associated with the blood pressure estimate.

17. The method according to claim 16, further including the step of storing at least one of the received PCG signal, the received ECG signal, the extracted S2 signal, the P component, the blood pressure estimate and the confidence interval measure.

18. The method according to claim 16, further including the step of presenting, on a display device, the blood pressure estimate and at least one of the received PCG signal, the received ECG signal, the extracted S2 signal, the P component and the confidence interval measure.

19. A non-transitory computer-readable medium including computer program instructions that cause a computer to perform a method for noninvasively estimating a blood pressure, the method comprising the steps of:

a) extracting a pulmonic (P) component from a second heart sound (S2) signal;

b) analyzing the extracted P component to obtain a number of oscillations in the P component;

c) determining a value that corresponds to the number of oscillations; and

d) applying a predetermined relationship between the value and blood pressure to generate a blood pressure estimate.

20. Apparatus for noninvasively estimating a blood pressure, the apparatus comprising:

a) means for extracting a pulmonic (P) component from a second heart sound (S2) signal;

b) means for analyzing the extracted P component to obtain a number of oscillations in the P component;

c) means for determining a value that corresponds to the number of oscillations; and

d) means for applying a predetermined relationship between the value and blood pressure to generate a blood pressure estimate.

21. Apparatus according to claim 20, wherein the blood pressure includes a pulmonary artery pressure (PAP) and the means for applying the predetermined relationship includes means for applying the predetermined relationship between the value and PAP to generate a PAP estimate.

22. Apparatus according to claim 20, the apparatus further comprising:

means for receiving a phonocardiogram (PCG) signal; and

means for extracting the S2 signal from the received PCG signal,

wherein the means for extracting the P component includes means for extracting the P component from the extracted S2 signal.

23. Apparatus according to claim 20, the apparatus further comprising:

means for synchronously receiving a phonocardiogram (PCG) signal and an electrocardiogram (ECG) signal for a predetermined duration of time; and

means for extracting the S2 signal from the received PCG signal using the received ECG signal,

wherein the means for extracting the P component includes means for extracting the P component from the extracted S2 signal.