Method of analyzing and processing signals

• US 9,198,616 B2
• Filed: 08/20/2012
• Issued: 12/01/2015
• Est. Priority Date: 02/27/2003
• 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): D'ANGELO, MICHAEL J
• Application Number:
  US13/590,095
• Publication Number:
  US 20130046187A1
• Time in Patent Office: 1,198 Days
• Field of Search: 600/323, 600/309, 600/310, 600/324, 600/481, 600/502, 600/529, 600/534
• US Class Current: 1/1
• CPC Class Codes: A61B 2503/06 Children, e.g. for attention deficit diagnosis
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0082 adapted for particular medical purposes
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• 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 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6829 Foot or ankle
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: A61B 5/6896 Toys
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7214 using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths
• 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: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence

Abstract

A physiological measurement system is disclosed which can take a pulse oximetry signal such as a photoplethysmogram from a patient and then analyze the signal to measure physiological parameters including respiration, pulse, oxygen saturation and movement. The system comprises a pulse oximeter which includes a light emitting device and a photodetector attachable to a subject to obtain a pulse oximetry signal; analog to digital converter means arranged to convert said pulse oximetry signal into a digital pulse oximetry signal; signal processing means suitable to receive said digital pulse oximetry signal and arranged to decompose that signal by wavelet transform means; feature extraction means arranged to derive physiological information from the decomposed signal; an analyzer component arranged to collect information from the feature extraction means; and data output means arranged in communication with the analyzer component.

Claims

1. A method for determining physiological information, comprising:

obtaining a photoplethysmographic (PPG) biosignal from a subject at least in part using a signal acquisition unit;

decomposing, using a signal processor, the PPG biosignal at least in part using wavelet transform analysis;

identifying, using the signal processor, a locus of points on a transform surface constructed by the wavelet transform analysis that define a path displaced from a ridge of a band;

determining, using the signal processor, wavelet phase information based at least in part on the wavelet transform analysis; and

determining, using the signal processor, based at least in part on the locus of points that define the path and the wavelet phase information at least one of;

timing of individual breaths of the subject, respiration rate of the subject, presence of an abnormal breathing pattern, timing of individual heart beats of the subject, heart rate of the subject, and presence of heart beat anomalies.

2. The method of claim 1, wherein determining physiological information based at least in part on the locus of points that define the path and the wavelet phase information comprises:

mapping the band and the wavelet phase information; and

analyzing the phase cycling of the wavelet phase information along the band.

3. The method of claim 1, wherein the signal acquisition unit comprises a photodetector.

4. The method of claim 1, wherein decomposing the PPG biosignal using the wavelet transform analysis comprises performing a continuous wavelet transform of the PPG biosignal.

5. A monitoring system for determining physiological information, the system comprising:

a signal acquisition unit attachable to a subject to obtain a photoplethysmographic (PPG) biosignal; and

a signal processor configured to;

receive the PPG biosignal;

decompose the PPG biosignal at least in part using wavelet transform analysis;

identify a locus of points on a transform surface constructed by the wavelet transform analysis that define a path displaced from a ridge of a band;

determine wavelet phase information based at least in part on the wavelet transform analysis; and

determine based at least in part on the locus of points that define the path and the wavelet phase information at least one of;

timing of individual breaths of the subject, respiration rate of the subject, presence of an abnormal breathing pattern, timing of individual heart beats of the subject, heart rate of the subject, and presence of heart beat anomalies.

6. The system of claim 5, wherein the signal processor is further configured to:

map the band and the wavelet phase information; and

analyze the phase cycling of the wavelet phase information along the band.

7. The system of claim 5, wherein the signal acquisition unit comprises a photodetector.

8. The system of claim 5, wherein the signal processor is configured to decompose the PPG biosignal by performing a continuous wavelet transform of the PPG biosignal.