SYSTEMS AND METHODS FOR DETERMINING RESPIRATION INFORMATION USING FREQUENCY DEMODULATION

• US 20140221852A1
• Filed: 02/05/2013
• Published: 08/07/2014
• Est. Priority Date: 02/05/2013
• Status: Abandoned Application

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Van Slyke, Braddon M., Kadlec, Ron J., McGonigle, Scott
• Application Number:
  US13/759,956
• Publication Number:
  US 20140221852A1
• Time in Patent Office: Days
• US Class Current: 600/484
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• 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 5/7228 Signal modulation applied to the input signal sent to patient or subject; demodulation to recover the physiological signal modulation H03C
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: H04L 27/1525 using quadrature demodulation

Abstract

A patient monitoring system may receive a physiological signal such as a photoplethysmograph (PPG) signal. The PPG signal may include a pulsatile component that functions as a carrier signal and a frequency modulation component that represents respiration information. The patient monitoring system may more the frequency modulation component to a baseline component of the PPG signal. Respiration information may be calculated based on the frequency modulation component.

Claims

1. A method for determining respiration information for a patient, the method comprising:

receiving a photoplethysmograph (PPG) signal that includes a frequency modulation component caused at least in part by respiration;

processing, with processing equipment, the PPG signal to move the frequency modulation component into a baseline component of the PPG signal to generate a processed PPG signal; and

analyzing, with the processing equipment, the processed PPG signal to determine the respiration information based on the frequency modulation component.

2. The method of claim 1, wherein processing the PPG signal comprises:

identifying a frequency and phase associated with a pulsatile component of the PPG signal;

establishing a phase shift;

generating a reference signal based on the identified frequency, the identified phase, and the phase shift; and

mixing the PPG signal with the reference signal.

3. The method of claim 2, wherein the frequency and phase associated with the pulsatile component of the PPG signal are identified based on a phase locked loop.

4. The method of claim 1, wherein analyzing the processed PPG signal comprises:

identifying the frequency modulation component based on a frequency range associated with respiration; and

determining the respiration information based on the identified frequency modulation component.

5. The method of claim 1, wherein analyzing the processed PPG signal comprises:

transforming the processed PPG signal based at least in part on a continuous wavelet transform to generate a scalogram;

identifying for a particular time, a scale in the scalogram associated with respiration information; and

determining the respiration information based at least in part on the scale.

6. The method of claim 1, wherein analyzing the processed PPG signal comprises performing a Fourier transform to identify a frequency associated with the frequency modulation component.

7. The method of claim 1, wherein the respiration information comprises a respiration rate.

8. A non-transitory computer-readable storage medium for use in determining respiration information for a patient, the computer-readable medium having computer program instructions recorded thereon for:

receiving a photoplethysmograph (PPG) signal that includes an frequency modulation component caused at least in part by respiration;

processing the PPG signal to move the frequency modulation component into a baseline component of the PPG signal to generate a processed PPG signal; and

analyzing the processed PPG signal to determine the respiration information based on the frequency modulation component.

9. The computer-readable medium of claim 8, wherein processing the PPG signal comprises:

identifying a frequency and phase associated with a pulsatile component of the PPG signal;

establishing a phase shift;

generating a reference signal based on the identified frequency, the identified phase, and the phase shift; and

mixing the PPG signal with the reference signal.

10. The computer-readable medium of claim 9, wherein the frequency and phase associated with the pulsatile component of the PPG signal are identified based on a phase locked loop.

11. The computer-readable medium of claim 8, wherein analyzing the processed PPG signal comprises:

identifying the frequency modulation component based on a frequency range associated with respiration; and

determining the respiration information based on the identified frequency modulation component.

12. The computer-readable medium of claim 8, wherein analyzing the processed PPG signal comprises:

transforming the processed PPG signal based at least in part on a continuous wavelet transform to generate a scalogram;

identifying for a particular time, a scale in the scalogram associated with respiration information; and

determining the respiration information based at least in part on the scale.

13. The computer-readable medium of claim 8, wherein analyzing the processed PPG signal comprises performing a Fourier transform to identify a frequency associated with the frequency modulation component.

14. A patient monitoring system comprising processing equipment configured to:

receive a photoplethysmograph (PPG) signal that includes an frequency modulation component caused at least in part by respiration;

process the PPG signal to more the frequency modulation component into a baseline component of the PPG signal to generate a processed PPG signal; and

analyze the processed PPG signal to determine the respiration information based on the frequency modulation component.

15. The patient monitoring system of claim 14, wherein the patient monitoring system is configured to:

identify a frequency and phase associated with a pulsatile component of the PPG signal;

establish a phase shift;

generate a reference signal based on the identified frequency, the identified phase, and the phase shift; and

mix the PPG signal with the reference signal to generate the processed PPG signal.

16. The patient monitoring system of claim 15, wherein the frequency and phase associated with the pulsatile component of the PPG signal are identified based on a phase locked loop.

17. The patient monitoring system of claim 14, wherein the patient monitoring system is configured to:

identify the frequency modulation component based on a frequency range associated with respiration; and

determine the respiration information based on the identified frequency modulation component.

18. The patient monitoring system of claim 14, wherein the patient monitoring system is configured to:

transform the processed PPG signal based at least in part on a continuous wavelet transform to generate a scalogram;

identify for a particular time, a scale in the scalogram associated with respiration information; and

determine the respiration information based at least in part on the scale.

19. The patient monitoring system of claim 14, wherein the patient monitoring system is configured to perform a Fourier transform to identify a frequency associated with the frequency modulation component.

20. The patient monitoring system of claim 14, wherein the respiration information comprises a respiration rate.