SYSTEMS AND METHODS FOR DETECTING PULSES

• US 20140058231A1
• Filed: 10/29/2013
• Published: 02/27/2014
• Est. Priority Date: 06/30/2008
• Status: Abandoned Application

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Watson, James
• Application Number:
  US14/065,926
• Publication Number:
  US 20140058231A1
• Time in Patent Office: Days
• US Class Current: 600/324
• 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 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/02433 for infrared radiation
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence

Abstract

According to embodiments, systems and methods are provided for detecting pulses in a PPG signal. Local minima and maxima points may be identified in the PPG signal. Each minimum may be paired with an adjacent maximum forming an upstroke segment. Noise may be removed by comparing adjacent segments and ignoring segments that are too long or too large. Notches in the pulse may be identified and ignored by analyzing adjacent segments. Adjacent upstroke segments may be combined as a single upstroke if the lengths of adjacent upstroke segments are about the same, have similar slopes, and the end point of one segment is close to the start point of an adjacent segment. Segments having small temporal or amplitude difference relative to adjacent segments may be disregarded. The remaining segments may represent the pulse upticks. A sliding time window may be used instead to detect pulses in the PPG signal.

Claims

1. A method for detecting pulses in a photoplethysmograph (PPG) signal, the method comprising:

receiving, using processing equipment, a PPG signal from a subject;

identifying, using the processing equipment, segments in the PPG signal, wherein each segment comprises a portion of a potential pulse;

comparing, using the processing equipment, a feature of a segment to features of respective neighboring segments; and

determining, using the processing equipment, whether each of the segments comprises a pulse portion based on the comparison.

2. The method of claim 1, further comprising applying a sliding time window to the PPG signal, and wherein identifying segments in the PPG signal comprises identifying segments in the sliding time window.

3. The method of claim 2, wherein the sliding time window is associated with a temporal length, and wherein the temporal length of the sliding time window is based on a pulse rate of the subject.

4. The method of claim 3, further comprising dynamically adjusting the temporal length of the sliding time window based on the pulse rate of the subject.

5. The method of claim 1, wherein comparing a feature of a segment to features of respective neighboring segments comprises comparing an amplitude of a segment to a threshold value based on amplitudes of respective neighboring segments.

6. The method of claim 5, wherein the threshold value is based on a running average of amplitudes of a number of respective neighboring segments.

7. The method of claim 5, wherein the threshold value is based on a median of amplitudes of a number of respective neighboring segments.

8. The method of claim 1, wherein comparing a feature of a segment to features of respective neighboring segments comprises comparing a temporal length of a segment to a threshold value, wherein the threshold value is based on temporal lengths of respective neighboring segments.

9. The method of claim 8, wherein the threshold value is based on a running average of temporal lengths of a number of respective neighboring segments.

10. The method of claim 8, wherein the threshold value is based on a median of temporal lengths of a number of respective neighboring segments.

11. The method of claim 1, wherein each of the segments comprises an upstroke or a downstroke, the method further comprising determining, using the processing equipment, whether a segment comprises an upstroke or a downstroke based on a slope of the segment.

12. The method of claim 11, wherein comparing a feature of a segment to features of respective neighboring segments comprises comparing a feature of a segment to a threshold value, wherein the threshold value is based on whether the segment is an upstroke or a downstroke.

13. The method of claim 1, further comprising generating, using the processing equipment, a signal representative of pulses in the PPG signal based on the segments comprising pulse portions.

14. The method of claim 1, further comprising determining, using the processing equipment, whether a segment comprises artifact based on the comparison.

15. The method of claim 14, wherein determining whether a segment is artifact comprises determining whether a segment comprise a notch based on the comparison.

16. The method of claim 15, wherein a notch corresponds to one of a dicrotic notch, ankle notch, or shoulder notch.

17. The method of claim 16, further comprising:

generating, using the processing equipment, a signal representative of pulses in the PPG signal by removing segments comprising artifact from the PPG signal.

18. The method of claim 16, further comprising:

generating, using the processing equipment, a signal representative of pulses in the PPG signal by ignoring segments comprising artifact in the PPG signal.

19. The method of claim 1, further comprising determining a pulse rate of the subject based on the segments comprising pulse portions.

20. The method of claim 1, further comprising determining a pulse intensity of the subject based on the segments comprising pulse portions.