Systems and methods for detecting pulses

• US 8,574,162 B2
• Filed: 09/30/2008
• Issued: 11/05/2013
• Est. Priority Date: 06/30/2008
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Watson, James
• Primary Examiner(s): Blumel, Benjamin P
• Application Number:
  US12/242,908
• Publication Number:
  US 20090326395A1
• Time in Patent Office: 1,862 Days
• Field of Search: None
• US Class Current: 600/502
• 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 system for detecting pulses in a signal, the system comprising:

processing circuitry capable of;

receiving an input signal;

detecting local minima and local maxima points in the input signal, comparing segments formed by pairs of the local minima and local maxima points to a number of respective neighboring segments, and

determining based at least in part upon the comparison if each segment is a pulse segment.

2. The system of claim 1 wherein the local minima and local maxima points are turning points.

3. The system of claim 1 wherein the comparing comprises comparing the amplitude of a segment to amplitudes of the number of respective neighboring segments.

4. The system of claim 3 wherein the determining comprises determining that the segment is a pulse segment at least in part on whether the amplitude is greater or less than a threshold value computed based at least in part on the amplitudes of the number of respective neighboring segments.

5. The system of claim 1 wherein the comparing comprises comparing the temporal length of a segment to temporal lengths of the number of respective neighboring segments.

6. The system of claim 5 wherein the determining comprises determining that the segment is a pulse segment based at least in part on whether the temporal length is greater or less than a threshold value computed based at least in part on the temporal lengths of the number of respective neighboring segments.

7. The system of claim 1 wherein the comparing comprises comparing the amplitude of a segment to the amplitudes of a percentage of the number of respective neighboring segments having the greatest amplitudes.

8. The system of claim 7 wherein the percentage is generally 25%.

9. The system of claim 1 wherein the processing circuitry is further capable of generating pulse information based at least in part on the determination.

10. The system of claim 9 wherein the pulse information comprises a signal containing pulse segments, and wherein the generating comprises:

identifying neighboring segments separated by notches; and

splicing the neighboring segments to form single pulse segments.

11. The system of claim 1 wherein the processing circuitry is further capable of applying a sliding time window to the input signal, and wherein detecting the local minima and local maxima points comprises detecting the minimum and maximum points in the sliding time window.

12. The system of claim 11 wherein a length of the sliding time window is greater than the temporal length of one pulse, less than the temporal length of two pulses, and adjusted dynamically.