Systems and methods for normalizing a plethysmograph signal for improved feature analysis

• US 8,463,347 B2
• Filed: 09/30/2009
• Issued: 06/11/2013
• Est. Priority Date: 09/30/2009
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Watson, James N., Sethi, Rakesh, Stoughton, Robert, Addison, Paul Stanley
• Primary Examiner(s): Kahelin, Michael
• Assistant Examiner(s): ALTER, MITCHELL E
• Application Number:
  US12/571,172
• Publication Number:
  US 20110077486A1
• Time in Patent Office: 1,350 Days
• Field of Search: 600/331, 600/485, 600/475
• 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 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/72 Signal processing specially adapted for physiological signals or for diagnostic purposes character recognition, recognising digital ink, document-oriented image-based pattern recognition G06V30/00; recognition or understanding of postal images G06V30/424
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B

Abstract

The present disclosure relates to systems and methods for analyzing and normalizing signals, such as PPG signals, for use in patent monitoring. The PPG signal may be detected using a continuous non-invasive blood pressure monitoring system and the normalized signals may be used to determine whether a recalibration of the system should be performed.

Claims

1. A method for normalizing a signal using a continuous non-invasive blood pressure monitoring system, comprising:

detecting a photoplethysmograph (PPG) signal at a first time and a second time with a sensor coupled to a processor;

determining, using the processor, whether a difference in a metric of the PPG signal at the first time and a metric of the PPG signal at the second time exceeds a threshold;

normalizing the PPG signal at the second time when the threshold is determined to be exceeded;

comparing, using the processor, the normalized PPG signal and the PPG signal at the first time; and

generating a signal, using the processor, if the normalized PPG signal and the PPG signal at the first time do not correspond.

2. The method of claim 1 wherein normalizing, using the processor, the signal at the second time comprises a calculation based at least in part on a change in amplitude, area, pulse period, baseline, or any combination thereof.

3. The method of claim 1 wherein the signal indicates:

an alarm, a request to perform a recalibration operation, or a combination thereof.

4. The method of claim 1 further comprising detecting a second PPG signal with a second sensor.

5. The method of claim 1 wherein the PPG signal is capable of being used to calculate blood pressure, blood oxygen saturation, or a combination thereof.

6. The method of claim 1 wherein the metric of the PPG signal at the first time and the metric of the PPG signal at the second time comprises:

peak amplitude, area, period, baseline, or any combination thereof.

7. A system for analyzing photoplethysmograph (PPG) signals in patient monitoring, comprising:

a sensor having at least one emitter and at least one detector configured to detect a PPG signal, the sensor coupled to a processor, the processor capable of;

detecting a PPG signal at a first time and a second time with the sensor;

determining whether a difference in a metric of the PPG signal at the first time and a metric of the PPG signal at the second time exceeds a threshold;

normalizing the PPG signal at the second time when the threshold is determined to be exceeded;

comparing the normalized PPG signal and the PPG signal at the first time; and

generating a signal if the normalized PPG signal and the PPG signal at the first time do not correspond.

8. The system of claim 7 wherein the normalizing the PPG at the second time comprises a calculation based at least in part on a change in amplitude, area, pulse period, baseline, or any combination thereof.

9. The system of claim 7 wherein the signal indicates:

an alarm, a request to perform a recalibration operation, or a combination thereof.

10. The system of claim 7 further comprising a second sensor having at least one emitter and at least one detector configured to detect a second PPG signal, the second sensor coupled to the processor.

11. The system of claim 7 wherein the PPG signal is capable of being used to calculate blood pressure, blood oxygen saturation, or a combination thereof.

12. The system of claim 7 wherein the metric of the PPG signal at the first time and the metric of the PPG signal at the second time comprises:

peak amplitude, area, period, baseline, or any combination thereof.