SYSTEMS AND METHODS FOR DETECTING ARRHYTHMIA FROM A PHYSIOLOGICAL SIGNAL

• US 20140243621A1
• Filed: 05/08/2014
• Published: 08/28/2014
• Est. Priority Date: 11/30/2011
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Weng, Binwei, Ochs, James
• Granted Patent: US 9,060,746 B2
• Time in Patent Office: Days
• US Class Current: 600/301
• 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 5/14551 for measuring blood gases
• 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 5/7267 involving training the classification device
• 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

Abstract

Arrhythmia may impact the determination of physiological information from a physiological signal. A patient monitoring system may detect the presence of arrhythmia based on changes in the physiological signal. Derived value data sets may be extracted from the physiological signal and calculations performed to generate arrhythmia features. The arrhythmia features may be used to generate an arrhythmia indicator that may indicate the presence of arrhythmia in the physiological signal.

Claims

1. A physiological monitoring system for detecting arrhythmia in a subject, the system comprising:

an interface configured to receive a plethysmograph signal; and

processing equipment configured to;

filter the plethysmograph signal based on a pulse rate of the subject to generate a filtered signal;

perform an FM demodulation of the filtered signal to generate a demodulated signal;

filter the demodulated signal based on respiration to generate a filtered demodulated signal; and

subsample the filtered demodulated signal to generate a demodulated derived value signal;

determine a plurality of arrhythmia features from the demodulated derived value signal; and

generate an arrhythmia indicator based on the arrhythmia features.

2. The system of claim 1, wherein the plurality of arrhythmia features comprise at least one of an entropy feature and a standard deviation feature.

3. The system of claim 1, wherein the processor is further configured to determine respiration information based on the arrhythmia indicator.

4. The system of claim 1, wherein the filtering the plethysmograph signal based on the pulse rate of the subject comprises band pass filtering the plethysmograph signal with a band pass range determined based on the pulse rate of the subject.

5. The system of claim 4, wherein the band pass range is set at 0.1 to 1.9 times the pulse rate of the subject.

6. The system of claim 1, wherein the filtering the demodulated signal based on respiration comprises band pass filtering the demodulated signal with a frequency window corresponding to 3 to 40 breaths per minute.

7. The system of claim 1, wherein the subsampling the filtered demodulated signal comprises subsampling the filtered demodulated signal based on the pulse rate of the subject.

8. The system of claim 1, wherein the plurality of arrhythmia features comprise a dot product feature.

9. The system of claim 1, wherein generating the arrhythmia indicator comprises:

calculating a distance value based on the plurality of arrhythmia features;

comparing the distance value to a threshold distance value; and

generating the arrhythmia indicator value based on the distance value and the threshold distance value.

10. A method for detecting arrhythmia from a plethysmograph signal, the method comprising:

extracting, using processing equipment, a plurality of derived value data sets associated with the plethysmograph signal;

determining, using processing equipment, a plurality of arrhythmia features based on the derived value data sets, wherein the arrhythmia features comprise an entropy feature; and

generating, using processing equipment, an arrhythmia indicator based on the arrhythmia features.

11. The method of claim 10, wherein the derived value data sets comprise at least one of a pulse rate data set, a kurtosis data set, and a b/a ratio data set.

12. The method of claim 10, wherein the arrhythmia features further comprise a standard deviation feature.

13. The method of claim 10, wherein the arrhythmia features further comprise a dot product feature.

14. The method of claim 10, wherein generating the arrhythmia indicator comprises:

calculating a distance value based on the plurality of arrhythmia features;

comparing the distance value to a threshold distance value; and

generating the arrhythmia indicator based on the distance value and the threshold distance value.

15. The method of claim 14, wherein comparing the distance value comprises determining whether the distance value falls within a range of values based on the threshold distance value.

16. The method of claim 15, wherein the range of values is less than a positive threshold distance value and greater than a negative threshold distance value.

17. The method of claim 14, wherein calculating the distance value comprises:

modifying each of the plurality of arrhythmia features based on one or more weighting factors; and

calculating the distance value based on the modified arrhythmia features and a bias term.

18. The method of claim 10, wherein generating the arrhythmia indicator comprises determining a confidence value.

19. The method of claim 10, further comprising determining respiration information based on the arrhythmia indicator.

20. A patient monitoring system comprising:

an interface configured to receive a plethysmograph signal; and

a processor configured to;

extract a plurality of derived value data sets associated with the plethysmograph signal;

determine a plurality of arrhythmia features based on the derived value data sets, wherein the arrhythmia features comprise an entropy feature; and

generate an arrhythmia indicator based on the arrhythmia features.