SYSTEMS AND METHODS FOR DETERMINING RESPIRATION INFORMATION USING HISTORICAL DISTRIBUTION

• US 20130137936A1
• Filed: 11/30/2011
• Published: 05/30/2013
• Est. Priority Date: 11/30/2011
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Baker, Clark R. Jr., Ochs, James, Addison, Paul S., Dripps, James H.
• Granted Patent: US 9,693,736 B2
• Time in Patent Office: Days
• US Class Current: 600/300
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• 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

A patient monitoring system may generate an autocorrelation sequence for a physiological signal such as a photoplethysmograph signal. A series of peak values may be identified for the autocorrelation sequence. The peak values may be modified based on a historical distribution of a physiological parameter. A physiological parameter such as respiration rate may be determined based on the modified peak values.

Claims

1. A method for determining a physiological parameter from a physiological signal, the method comprising:

determining, using processing equipment, a plurality of peak values of an autocorrelation sequence based on the physiological signal;

modifying, using processing equipment, the plurality of peak values based on a historical distribution of the physiological parameter; and

determining, using processing equipment, the physiological parameter based on the modified peak values.

2. The method of claim 1, wherein determining the plurality of peak values comprises:

generating a plurality of morphology metric signals based on the physiological signal;

generating the autocorrelation sequence based on the plurality of morphology metric signals; and

selecting the plurality of peak values based on the autocorrelation sequence.

3. The method of claim 1, wherein modifying the plurality peak values comprises:

accessing the historical distribution of the physiological parameter; and

for each of the plurality of peak values;

associating the peak value with a first portion of the historical distribution of the physiological parameter; and

adjusting the peak value based on the first portion of the historical distribution of the physiological parameter.

4. The method of claim 3, wherein adjusting the peak value comprises weighting the peak value based on a total distribution of the physiological parameter within the first portion of the historical distribution.

5. The method of claim 1, wherein determining the physiological parameter comprises:

comparing the modified peak values to a threshold;

selecting the first modified peak value that exceeds the threshold; and

determining the physiological parameter based on the selected modified peak value.

6. The method of claim 1, wherein determining the physiological parameter comprises:

selecting the maximum modified peak value within a window of interest; and

determining the physiological parameter based on the selected modified peak value.

7. The method of claim 1 further comprising updating the historical distribution based on the physiological parameter.

8. The method of claim 7 wherein updating the historical distribution comprises:

identifying a portion of the historical distribution associated with the physiological parameter;

increasing one or more historical distribution values associated the identified portion; and

decreasing one or more historical distribution values that are not associated with the identified portion.

9. The method of claim 1, further comprising generating, using processing equipment, a confidence value based on the plurality of peak values, wherein the physiological parameter is determined based on the confidence value and the modified peak values.

10. The method of claim 1, wherein the physiological parameter comprises a respiration rate.

11. A patient monitoring system comprising:

an interface configured to receive a physiological signal; and

a processor configured to;

determine a plurality of peak values of an autocorrelation sequence based on the physiological signal;

modify the plurality of peak values based on a historical distribution of the physiological parameter; and

determine the physiological parameter based on the modified peak values.

12. The patient monitoring system of claim 11, wherein the processor is further configured to:

generate a plurality of morphology metric signals based on the physiological signal;

generate the autocorrelation sequence based on the plurality of morphology metric signals; and

determine the plurality of peak values based on the autocorrelation sequence.

13. The patient monitoring system of claim 11, wherein the processor is further configured to:

access the historical distribution of the physiological parameter; and

for each of the plurality of peak values;

associate the peak value with a first portion of the historical distribution of the physiological parameter; and

adjust the peak value based on the first portion of the historical distribution of the physiological parameter.

14. The patient monitoring system of claim 13, wherein the processor is further configured to adjust the peak value based on a total distribution of the physiological parameter within the first portion of the historical distribution.

15. The patient monitoring system of claim 11, wherein the processor is further configured to:

compare the modified peak values to a threshold;

select the first modified peak value that exceeds the threshold; and

determine the physiological parameter based on the selected modified peak value.

16. The patient monitoring system of claim 11, wherein the processor is further configured to:

select the maximum modified peak value within a window of interest; and

determine the physiological parameter based on the selected modified peak value.

17. The patient monitoring system of claim 11 wherein the processor is further configured to update the historical distribution based on the physiological parameter.

18. The patient monitoring system of claim 17 wherein the processor is further configured to:

identify a portion of the historical distribution associated with the physiological parameter;

increase one or more historical distribution values associated the identified portion; and

decrease one or more historical distribution values that are not associated with the identified portion.

19. The patient monitoring system of claim 11, wherein the processor is further configured to generate a confidence value based on the plurality of peak values, wherein the physiological parameter is determined based on the confidence value and the modified peak values.

20. The patient monitoring system of claim 11, wherein the physiological parameter comprises a respiration rate.