Systems And Methods For Identifying Pulse Rates

• US 20100016693A1
• Filed: 10/10/2008
• Published: 01/21/2010
• Est. Priority Date: 07/15/2008
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Addison, Paul Stanley, Watson, James Nicholas
• Granted Patent: US 8,285,352 B2
• Time in Patent Office: Days
• US Class Current: 600/324
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

According to embodiments, techniques for using continuous wavelet transforms and spectral transforms to identify pulse rates from a photoplethysmographic (PPG) signal are disclosed. According to embodiments, candidate pulse rates of the PPG signal may be identified from a wavelet transformed PPG signal and a spectral transformed PPG signal. A pulse rate may be determined from the candidate pulse rates by selecting one of the candidate pulse rates or by combining the candidate pulse rates. According to embodiments, a spectral transform of a PPG signal may be performed to identify a frequency region associated with a pulse rate of the PPG signal. A continuous wavelet transform of the PPG signal at a scale corresponding to the identified frequency region may be performed to determine a pulse rate from the wavelet transformed signal.

Claims

1. A method for determining a pulse rate from a photoplethysmographic (PPG) signal, comprising:

receiving a PPG signal;

performing a continuous wavelet transform of the PPG signal to produce a wavelet transformed signal;

performing a spectral transform of the PPG signal to produce a spectrum;

identifying a first candidate pulse rate of the PPG signal from the wavelet transformed signal;

identifying a second candidate pulse rate of the PPG signal from the spectrum; and

determining a pulse rate from the first candidate pulse rate and the second candidate pulse rate.

2. The method of claim 1 wherein the spectral transform comprises a Fourier transform.

3. The method of claim 1 wherein determining the pulse rate from the first candidate pulse rate and the second candidate pulse rate comprises selecting one of the candidate pulse rates.

4. The method of claim 3 wherein selecting one of the candidate pulse rates comprises selecting the candidate pulse rate based at least in part on its source.

5. The method of claim 3 wherein selecting one of the candidate pulse rates comprises selecting the candidate pulse rate based at least in part on its value.

6. The method of claim 3 further comprising determining confidence values associated with each of the first and the second candidate pulse rates and wherein selecting one of the candidate pulse rates comprises selecting the candidate pulse rate based at least in part on the confidence values.

7. The method of claim 1 wherein determining the pulse rate from the first candidate pulse rate and the second candidate pulse rate comprises combining the candidate pulse rates.

8. The method of claim 7 further comprising determining confidence values associated with each of the first and the second candidate pulse rates and wherein combining the candidate pulse rates comprises combining the candidate pulse rates weighted by the confidence values.

9. A system for determining a pulse rate from a photoplethysmographic (PPG) signal, comprising:

a wavelet processor capable of performing a continuous wavelet transform of a received PPG signal to produce a wavelet transformed signal and identifying a first candidate pulse rate of the PPG signal from the wavelet transformed signal;

a spectral processor capable of performing a spectral transform of the received PPG signal to produce a spectrum and identifying a second candidate pulse rate of the PPG signal from the spectrum; and

a pulse rate discriminator capable of determining a pulse rate from the first candidate pulse rate and the second candidate pulse rate.

10. The system of claim 9 wherein the spectral transform comprises a Fourier transform.

11. The system of claim 9 wherein the pulse rate discriminator is capable of selecting one of the candidate pulse rates.

12. The system of claim 11 wherein the pulse rate discriminator is capable of selecting one of the candidate pulses based at least in part on its source.

13. The system of claim 11 wherein the pulse rate discriminator is capable of selecting one of the candidate pulses based at least in part on its value.

14. The system of claim 11 wherein the a wavelet processor and the Fourier processor are capable of determining confidence values associated the first and the second candidate pulse rates and wherein the pulse rate discriminator is capable of selecting one of the candidate pulse rates based at least in part on the confidence values.

15. The system of claim 9 wherein the pulse rate discriminator is capable of combining the candidate pulse rates.

16. The system of claim 15 wherein the wavelet processor and the spectral processor are capable of determining confidence values associated the first and the second candidate pulse rates and wherein the pulse rate discriminator is capable of combining the pulse rate candidates weighted by the confidence values.

17. A method for determining a pulse rate from a photoplethysmographic (PPG) signal, comprising:

receiving a PPG signal;

performing a spectral transform of the PPG signal to produce a spectrum;

identifying from the spectrum a frequency region associated with a pulse rate of the PPG signal;

performing a continuous wavelet transform of the PPG signal at a scale corresponding to the identified frequency region to produce a wavelet transformed signal; and

determining a pulse rate from the wavelet transformed signal.

18. The method of claim 17 wherein the spectral transform comprises a Fourier transform.

19. The method of claim 17 wherein identifying the frequency region associated with a pulse rate of the PPG signal comprises identifying peaks in the spectral transformed signal.

20. The method of claim 17 wherein determining the pulse rate from the wavelet transformed signal comprises determining a set of pulse rates over time.

21. A system for determining a pulse rate from a photoplethysmographic (PPG) signal, comprising:

a spectral processor capable of performing a spectral transform of a received PPG signal to produce a spectrum and identifying a frequency region associated with a pulse rate of the PPG signal from the spectrum; and

a wavelet processor capable of performing a continuous wavelet transform of the received PPG signal at a scale corresponding to the identified frequency region to produce a wavelet transformed signal and determining a pulse rate from the wavelet transformed signal.

22. The system of claim 21 wherein the spectral processor is capable of identifying peaks in the spectral transformed signal to identify the frequency region associated with the pulse rate.

23. The system of claim 21 wherein the wavelet processor is capable of determining a set of pulse rates over time.

24. Computer-readable medium for use in determining a pulse rate from a photoplethysmographic (PPG) signal, the computer-readable medium having computer program instructions recorded thereon for:

performing a continuous wavelet transform of a PPG signal to produce a wavelet transformed signal;

performing a spectral transform of the PPG signal to produce a spectrum;

identifying a first candidate pulse rate of the PPG signal from the wavelet transformed signal;

identifying a second candidate pulse rate of the PPG signal from the spectrum; and

determining a pulse rate from the first candidate pulse rate and the second candidate pulse rate.

25. Computer-readable medium for use in determining a pulse rate from a photoplethysmographic (PPG) signal, the computer-readable medium having computer program instructions recorded thereon for:

performing a spectral transform of a PPG signal to produce a spectrum;

identifying from the spectrum a frequency region associated with a pulse rate of the PPG signal;

performing a continuous wavelet transform of the PPG signal at scales with characteristic frequencies corresponding to the identified frequency region to produce a wavelet transformed signal; and

determining a pulse rate from the wavelet transformed signal.