Systems and methods for pulse processing

• US 8,679,027 B2
• Filed: 09/30/2008
• Issued: 03/25/2014
• 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
• Primary Examiner(s): Blumel, Benjamin P
• Application Number:
  US12/242,828
• Publication Number:
  US 20100016738A1
• Time in Patent Office: 2,002 Days
• Field of Search: None
• US Class Current: 600/501
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

According to embodiments, techniques for using continuous wavelet transforms to process pulses from a photoplethysmographic (PPG) signal are disclosed. The continuous wavelet transform of the PPG signal may be used to identify and characterize features and their periodicities within a signal. Regions, phases and amplitudes within the scalogram associated with these features may then be analyzed to identify, locate, and characterize a true pulse within the PPG signal. Having characterized and located the pulse in the PPG (possibly also using information gained from conventional pulse processing techniques such as, for example, by identifying turning points for candidate pulse maxima and minima on the PPG, frequency peak picking for candidate scales of pulses, etc.), the PPG may be parameterized for ease of future processing.

Claims

1. A method for processing pulses from a PPG signal, comprising:

receiving a PPG signal;

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

generating a scalogram from the transformed signal;

identifying regions in the scalogram corresponding to desired components of the PPG signal;

identifying pulse locations in the PPG signal based on the identified regions; and

replacing at least one pulse in at least one of the identified pulse locations in the PPG signal with a pulse selected from the group comprising a triangular pulse, a square pulse, and a sinusoid pulse.

2. The method of claim 1, further comprising modifying the received PPG signal to produce a processed PPG signal.

3. The method of claim 2, wherein modifying the received PPG signal to produce the processed PPG signal comprises filtering the received PPG signal.

4. The method of claim 2, further comprising performing a continuous wavelet transform of the modified PPG signal to produce a modified wavelet transformed signal and wherein generating the scalogram comprises generating a combined scalogram from the wavelet transformed signal and the modified wavelet transformed signal.

5. The method of claim 1, wherein identifying regions in the scalogram comprises identifying a plurality of pulse locations in the scalogram.

6. The method of claim 5, wherein identifying a plurality of pulse locations in the scalogram comprises determining localized high energy regions at high scales within the scalogram.

7. A system for processing pulses from a PPG signal, comprising:

a wavelet processor capable of performing a continuous wavelet transform of the PPG signal to produce a wavelet transformed signal and generating a scalogram from the transformed signal; and

a pulse processor capable of identifying regions in the scalogram corresponding to desired components of the PPG signal, identifying pulse locations in the PPG signal based on the identified regions, and replacing at least one pulse in at least one of the identified pulse locations in the PPG signal with a pulse selected from the group comprising a triangular pulse, a square pulse, and a sinusoid pulse.

8. The system of claim 7, further comprising a signal filter capable of modifying the received PPG signal to produce a processed PPG signal.

9. The system of claim 8, wherein the wavelet processor is further capable of performing a continuous wavelet transform of the modified PPG signal to produce a modified wavelet transformed signal and generating a combined scalogram from the wavelet transformed signal and the modified wavelet transformed signal.

10. The system of claim 7, wherein the pulse processor is capable of identifying a plurality of pulse locations in the scalogram.

11. The system of claim 10, wherein the pulse processor is capable of determining localized high energy regions at high scales within the scalogram.

12. Non-transitory computer-readable medium for use in processing pulses from a PPG signal, the non-transitory 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;

generating a scalogram from the transformed signal;

identifying regions in the scalogram corresponding to desired components of the PPG signal;

identifying pulse locations in the PPG signal based on the identified regions; and

replacing at least one pulse in at least one of the identified pulse locations in the PPG signal with a pulse selected from the group comprising a triangular pulse, a square pulse, and a sinusoid pulse.

13. The non-transitory computer-readable medium of claim 12, further comprising computer program instructions recorded thereon for performing a continuous wavelet transform of the modified PPG signal to produce a modified wavelet transformed signal and wherein generating the scalogram comprises generating a combined scalogram from the wavelet transformed signal and the modified wavelet transformed signal.