Methods and systems for determining whether to trigger an alarm

• US 8,370,080 B2
• Filed: 10/10/2008
• Issued: 02/05/2013
• Est. Priority Date: 07/15/2008
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Watson, James Nicholas, Addison, Paul Stanley
• Primary Examiner(s): Brusca, John S
• Application Number:
  US12/249,632
• Publication Number:
  US 20100016691A1
• Time in Patent Office: 1,579 Days
• Field of Search: None
• US Class Current: 702/24
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• 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
• CPC Class Codes: G08B 21/02 Alarms for ensuring the safety of persons

Abstract

According to embodiment, systems and methods for processing a physiological measurement and generating alarms based on the measurement are provided. Multiple features of a single physiological measurement may be concurrently monitored to generate alarms. One or more of the features may be based on a trend of the physiological measurement. One or more of the features may be based on a wavelet transform of the physiological measurement. Different features may be used in different combinations to lower the percentage of false alarms while still recognizing valid alarm events.

Claims

1. A method for determining whether to trigger an alarm, the method comprising:

using a processor for;

receiving an SpO₂ signal;

performing a continuous wavelet transform of the SpO₂ signal to generate a scalogram;

determining features of the scalogram; and

determining whether to trigger an alarm based at least in part on the determined features.

2. The method of claim 1, wherein the features comprise features indicative of signal quality.

3. The method of claim 1, wherein the features comprise features indicative of a probe condition.

4. The method of claim 1, wherein the features comprise a moving average of the scalogram and a slope of the scalogram.

5. The method of claim 4, wherein the determining comprises triggering an alarm if the moving average of the scalogram is below a threshold and the slope of the scalogram is non-positive.

6. The method of claim 1, further comprising:

determining a characteristic of the SpO₂ signal in parallel with the determining features of the scalogram, wherein the determining whether to trigger an alarm comprises determining whether to trigger an alarm based at least in part on the features and the characteristic.

7. The method of claim 6, wherein:

the characteristic of the SpO₂ signal comprises a moving average of the SpO₂ signal; and

the determining whether to trigger an alarm comprises determining whether to trigger an alarm based at least in part on whether the moving average of the SpO₂ signal is below a threshold.

8. The method of claim 1, further comprising:

generating an alarm based at least in part on the determining whether to trigger an alarm.

9. A system capable of determining whether to trigger an alarm, the system comprising:

a sensor capable of generating a photoplethysmograph (PPG) signal;

an SpO₂ signal generator coupled to the sensor and capable of generating an SpO₂ signal based at least in part on the PPG signal;

a wavelet transform generator coupled to the SpO₂ signal generator and capable of performing a continuous wavelet transform of the SpO₂ signal to generate a scalogram;

a plurality of feature analyzers, each feature analyzer coupled to the wavelet transform generator and capable of determining a feature of the scalogram and providing an output; and

an alarm generator coupled to the outputs of the plurality of feature analyzers and capable of triggering an alarm based at least in part on the outputs.

10. The system of claim 9, wherein the features comprise features indicative of signal quality.

11. The system of claim 9, wherein the features comprise features indicative of a probe condition.

12. The system of claim 9, wherein the plurality of feature analyzers comprises:

a first feature analyzer capable of determining a moving average of the scalogram; and

a second feature analyzer capable of determining a slope of the scalogram.

13. The system of claim 12, wherein the alarm generator is capable of generating an alarm if the output of the first feature analyzer indicates that the moving average of the scalogram is below a threshold and the output of the second feature analyzer indicates that the slope of the scalogram is non-positive.

14. The system of claim 9, further comprising a criteria processor coupled to the SpO₂ signal generator and capable of determining at least one characteristic of the SpO₂ signal and providing an output, wherein the alarm generator is coupled to the output of the criteria processor and capable of determining whether to trigger an alarm based at least in part on the output of the criteria processor.

15. The system of claim 14, wherein:

the plurality of feature analyzers comprises a first feature analyzer capable of determining a slope of the scalogram;

the criteria processor is capable of determining a moving average of the SpO₂ signal;

and the alarm generator is capable of generating an alarm if the output of the criteria processor indicates that the moving average of the SpO₂ signal is below a threshold and the output of the first feature analyzer indicates that the slope of the scalogram is non-positive.

16. Non-transitory computer-readable medium for use in determining whether to trigger an alarm, the non-transitory computer-readable medium having computer program instructions recorded thereon for:

receiving an SpO₂ signal;

performing a continuous wavelet transform of the SpO₂ signal to generate a scalogram;

determining features of the scalogram; and

determining whether to trigger an alarm based at least in part on the determined features.

17. The non-transitory computer-readable medium of claim 16 having further computer program instructions recorded thereon for:

determining a characteristic of the SpO₂ signal in parallel with the determining features of the scalogram, wherein the determining whether to trigger an alarm comprises determining whether to trigger an alarm based at least in part on the features and the characteristic.