Methods and systems for qualifying calculated values based on a statistical metric

• US 9,186,110 B2
• Filed: 09/11/2012
• Issued: 11/17/2015
• Est. Priority Date: 09/11/2012
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Rodriguez-Llorente, Fernando, Engelbrecht, Pirow, Wooder, Nicholas James
• Primary Examiner(s): ZEMAN, MARY K
• Application Number:
  US13/609,480
• Publication Number:
  US 20140073865A1
• Time in Patent Office: 1,162 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: G06F 2218/10 by analysing the shape of a waveform, e.g. extracting parameters relating to peaks
• CPC Class Codes: G06F 2218/14 by matching peak patterns
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

A physiological monitoring system may determine physiological information, such as physiological rate information, from a physiological signal. The system may receive a calculated value indicative of a physiological rate. The system may generate value pairs from a first collection of values of the physiological signal and another collection of corresponding value of the physiological signal spaced from the first collection based on the calculated value. The system may determine a best fit linear relationship based on the value pairs and determine at least one statistical metric based on the linear relationship and the value pairs. The system may qualify or disqualify the calculated value based on the at least one statistical metric.

Claims

1. A subject monitoring pulse oximetry system for updating a display rate for a subject, comprising:

a pulse oximetry sensor configured to detect light attenuated by the subject and generate a photoplethysmographic (PPG) signal based on the detected attenuated light;

a pulse oximeter coupled to the pulse oximetry sensor; and

a display coupled to the pulse oximeter, wherein the display is configured to display the display rate for the subject, and wherein;

the pulse oximeter is configured to;

receive a calculated value that may be indicative of a physiological rate of the subject;

generate a plurality of value pairs each comprising a first sample point of the PPG signal and a second point of the PPG signal spaced apart by a particular spacing, wherein the particular spacing is based on the calculated value;

determine a best fit linear relationship based on the plurality of value pairs;

determine at least one statistical metric based on the linear relationship and the plurality of value pairs;

qualify the calculated value based on the at least one statistical metric; and

update the display rate on the display based on the qualified value.

2. The system of claim 1, wherein the pulse oximeter is further configured to determine a standard error between the plurality of value pairs and the linear relationship, and a slope of the linear relationship.

3. The system of claim 1, wherein the pulse oximeter is further configured to determine a value indicative of the probability, relative to a predetermined probability distribution function, of the at least one statistical metric being outside of a set of bounding values.

4. The system of claim 3, wherein the pulse oximeter is further configured to:

determine at least one additional spacing other than the particular spacing, and for each of the at least one additional spacing;

generate a plurality of value pairs each comprising a first sample point of the PPG signal and a second point of the PPG signal spaced apart by the respective spacing,

determine a best fit linear relationship based on the respective plurality of value pairs,

determine at least one statistical metric based on the respective linear relationship and the respective plurality of value pairs; and

determine a value indicative of the probability, relative to a predetermined probability distribution function, of the respective at least one statistical metric being outside of the set of bounding values;

calculate a sum based on the values indicative of the probability of the respective at least one statistical metric being outside of the set of bounding values for the at least one additional lag value and the value indicative of the probability of the at least one statistical metric being outside of the set of bounding values for the particular spacing; and

qualify the calculated value based on the sum.

5. The system of claim 3, wherein the pulse oximeter is further configured to:

access a reference look-up table comprising a plurality of probability values; and

determine the value indicative of the probability based on at least one of the plurality of probability values in the reference look-up table.

6. A pulse oximetry processing module for updating a display rate for a subject on a display, wherein the pulse oximetry processing module is coupled to the display and comprises non-transitory computer readable media configured to store instructions that instruct the pulse oximetry processing module to:

receive a photoplethysmographic (PPG) signal from a pulse oximetry sensor, wherein the pulse oximetry sensor detector detects light attenuated by the subject and generates the PPG signal based on the detected attenuated light;

receive a calculated value that may be indicative of a physiological rate of the subject;

generate a plurality of value pairs each comprising a first sample point of the PPG signal and a second point of the PPG signal spaced apart by a particular spacing, wherein the particular spacing is based on the calculated value;

determine a best fit linear relationship based on the plurality of value pairs;

determine at least one statistical metric based on the linear relationship and the plurality of value pairs;

qualify the calculated value based on the at least one statistical metric; and

update the display rate on the display based on the qualified value.

7. The pulse oximetry processing module of claim 6, wherein the non-transitory computer-readable media is further configured to store instructions that instruct the pulse oximetry processing module to determine a standard error between the plurality of value pairs and the linear relationship, and a slope of the linear relationship.

8. The pulse oximetry processing module of claim 6, wherein the non-transitory computer-readable media is further configured to store instructions that instruct the pulse oximetry processing module to determine a value indicative of the probability, relative to a predetermined probability distribution function, of the at least one statistical metric being outside of a set of bounding values.

9. The pulse oximetry processing module of claim 8, wherein the non-transitory computer-readable media is further configured to store instructions that instruct the pulse oximetry processing module to:

determine at least one additional spacing other than the particular spacing, and for each of the at least one additional spacing;

generate a plurality of value pairs each comprising a first sample point of the PPG signal and a second point of the PPG signal spaced apart by the respective spacing,

determine a best fit linear relationship based on the respective plurality of value pairs,

determine at least one statistical metric based on the respective linear relationship and the respective plurality of value pairs; and

determine a value indicative of the probability, relative to a predetermined probability distribution function, of the respective at least one statistical metric being outside of the set of bounding values;

calculate a sum based on the values indicative of the probability of the respective at least one statistical metric being outside of the set of bounding values for the at least one additional lag value and the value indicative of the probability of the at least one statistical metric being outside of the set of bounding values for the particular spacing; and

qualify the calculated value based on the sum.

10. The pulse oximetry processing module of claim 8, wherein the non-transitory computer-readable media is further configured to store instructions that instruct the pulse oximetry processing module to:

access a reference look-up table comprising a plurality of probability values; and

determine the value indicative of the probability based on at least one of the plurality of probability values in the reference look-up table.

11. A method for updating a display rate for a subject on a display, comprising:

receiving, using a pulse oximeter, a photoplethysmographic (PPG) signal derived from a pulse oximetry sensor detector output, wherein the pulse oximetry sensor detects light attenuated by the subject and generates the PPG signal based on the detected attenuated light;

receiving, using the pulse oximeter, a calculated value that may be indicative of a physiological rate of the subject;

generating, using the pulse oximeter, a plurality of value pairs each comprising a first sample point of the PPG signal and a second point of the PPG signal spaced apart by a particular spacing, wherein the particular spacing is based on the calculated value;

determining, using the pulse oximeter, a best fit linear relationship based on the plurality of value pairs;

determining, using the pulse oximeter, at least one statistical metric based on the linear relationship and the plurality of value pairs;

qualifying, using the pulse oximeter, the calculated value based on the at least one statistical metric; and

updating, using the pulse oximeter, the display rate on the display based on the qualified value.

12. The method of claim 11, wherein determining the at least one statistical metric comprises determining a standard error between the plurality of value pairs and the linear relationship, and a slope of the linear relationship.

13. The method of claim 11, wherein qualifying the calculated value comprises determining a value indicative of the probability, relative to a predetermined probability distribution function, of the at least one statistical metric being outside of a set of bounding values.

14. The method of claim 13, further comprising:

determining at least one additional spacing other than the particular spacing, and for each of the at least one additional spacing;

generating a plurality of value pairs each comprising a first sample point of the PPG signal and a second point of the PPG signal spaced apart by the respective spacing,

determining a best fit linear relationship based on the respective plurality of value pairs,

determining at least one statistical metric based on the respective linear relationship and the respective plurality of value pairs; and

determining a value indicative of the probability, relative to a predetermined probability distribution function, of the respective at least one statistical metric being outside of the set of bounding values; and

calculating a sum based on the values indicative of the probability of the respective at least one statistical metric being outside of the set of bounding values for the at least one additional lag value and the value indicative of the probability of the at least one statistical metric being outside of the set of bounding values for the particular spacing, wherein qualifying the calculated value is based on the sum.

15. The method of claim 13, wherein determining the value indicative of the probability of the respective at least one statistical metric being outside of the set of bounding values comprises:

accessing a reference look-up table comprising a plurality of probability values, and

determining the value indicative of the probability based on at least one of the plurality of probability values in the reference look-up table.

16. A non-transitory computer-readable medium for use in updating a display rate for a subject on a display, the non-transitory computer-readable medium comprising:

computer program instructions recorded thereon for causing a pulse oximeter to;

receive a photoplethysmographic (PPG) signal derived from a pulse oximetry sensor output, wherein the pulse oximetry sensor detects light attenuated by the subject and generates the PPG signal based on the detected attenuated light;

receive a calculated value that may be indicative of a physiological rate of the subject;

generate a plurality of value pairs each comprising a first sample point of the PPG signal and a second point of the PPG signal spaced apart by a particular spacing, wherein the particular spacing is based on the calculated value;

determine a best fit linear relationship based on the plurality of value pairs;

determine at least one statistical metric based on the linear relationship and the plurality of value pairs;

qualify the calculated value based on the at least one statistical metric; and

update the display rate on the display based on the qualified value.

17. The non-transitory computer-readable medium of claim 16, comprising further computer program instructions recorded thereon for causing the pulse oximeter to determine a standard error between the plurality of value pairs and the linear relationship, and a slope of the linear relationship.

18. The non-transitory computer-readable medium of claim 16, comprising further computer program instructions recorded thereon for causing the pulse oximeter to determine a value indicative of the probability, relative to a predetermined probability distribution function, of the at least one statistical metric being outside of a set of bounding values.

19. The non-transitory computer-readable medium of claim 18, comprising further computer program instructions recorded thereon for causing the pulse oximeter to:

determine at least one additional spacing other than the particular spacing, and for each of the at least one additional spacing;

generate a plurality of value pairs each comprising a first sample point of the PPG signal and a second point of the PPG signal spaced apart by the respective spacing,

determine a best fit linear relationship based on the respective plurality of value pairs,

determine at least one statistical metric based on the respective linear relationship and the respective plurality of value pairs; and

determine a value indicative of the probability, relative to a predetermined probability distribution function, of the respective at least one statistical metric being outside of the set of bounding values;

calculate a sum based on the values indicative of the probability of the respective at least one statistical metric being outside of the set of bounding values for the at least one additional lag value and the value indicative of the probability of the at least one statistical metric being outside of the set of bounding values for the particular spacing; and

qualify the calculated value based on the sum.

20. The non-transitory computer-readable medium of claim 18, comprising further computer program instructions recorded thereon for causing the pulse oximeter to:

access a reference look-up table comprising a plurality of probability values; and

determine the value indicative of the probability based on at least one of the plurality of probability values in the reference look-up table.