PHYSIOLOGICAL EVENT DETECTION SYSTEMS AND METHODS

• US 20070213599A1
• Filed: 03/13/2006
• Published: 09/13/2007
• Est. Priority Date: 03/13/2006
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Hatlestad, John, Siejko, Krzysztof
• Granted Patent: US 7,713,213 B2
• Time in Patent Office: Days
• US Class Current: 600/300
• CPC Class Codes: A61B 5/00 Measuring for diagnostic purposes radiation diagnosis A61B6/00; diagnosis by ultrasonic, sonic or infrasonic waves A61B8/00; Identification of persons
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• 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: A61B 7/023 for introduction into the body, e.g. into the oesophagus oesophageal ECG probes A61B5/285
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/36514 controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by two or more physical parameters A61N1/36585
• CPC Class Codes: G16H 40/40 for the management of medical equipment or devices, e.g. scheduling maintenance or upgrades
• CPC Class Codes: G16H 40/63 for local operation

Abstract

Systems and methods using constant false alarm rate techniques for event detection. One example of an event detection method includes collecting a first distribution of measurements for a first physiological parameter. In another example, the first distribution of measurements includes only non-event measurements. One or more values are determined corresponding to at least a first tail area of the first distribution from at least one measurement of the first physiological parameter toward an end point of the distribution. A threshold is established based on a specified false alarm rate. The one or more values are compared to the threshold. The method includes determining if the measurement is representative of a detected event using the comparison.

Claims

1. A method comprising:

determining a first distribution of values for a first physiological parameter;

determining one or more values corresponding to at least a first tail area of the first distribution, the first tail area extending from at least one measurement of the first physiological parameter toward an end point of the distribution;

receiving a specified false alarm rate;

establishing a threshold based on the specified false alarm rate;

comparing the one or more values to the threshold; and

determining that the measurement is representative of a detected event using the comparison.

2. The method of claim 1, wherein determining the first distribution of values for the first physiological parameter includes collecting only non-event measurements of the first physiological parameter.

3. The method of claim 1, wherein determining the first distribution of values includes collecting a first distribution of measurements for a first cardiac parameter.

4. The method of claim 1, wherein determining one or more values corresponding to at least the first tail area of the first distribution includes determining a first probability of false alarm for the measurement of the first physiological parameter.

5. The method of claim 1, wherein receiving the specified false alarm rate includes inputting the specified false alarm rate independent of at least the first distribution of values for the first physiological parameter.

6. The method of claim 1, further comprising updating the first distribution of values for the first physiological parameter by collecting additional non-event values of the first physiological parameter.

7. The method of claim 6, wherein updating the first distribution of values for the first physiological parameter includes excluding at least one of corrupted, confounded, or event-related measurements.

8. The method of claim 1, further comprising transforming the one or more values corresponding to at least the first tail area of the first distribution into one or more transformed values with observable significance with respect to at least one of other transformed values and the threshold.

9. The method of claim 1, further comprising:

determining a first value corresponding to the first tail area of the first distribution, the first tail area extending from a first measurement of the first physiological parameter toward an end point of the distribution;

determining a second value corresponding to a second tail area of the first distribution, the second tail area extending from a second measurement of the first physiological parameter toward an end point of the distribution;

combining the first value with the second value to form a joint metric; and

comparing the one or more values to the threshold includes comparing the joint metric to the threshold.

10. A method comprising:

using a first distribution representative of measurements for a first physiological parameter;

receiving a specified false alarm rate;

computing an event detection threshold value based on the specified false alarm rate for the first distribution, and the event detection threshold value corresponds to a first tail area of the first distribution extending from the event detection threshold value toward an end point of the first distribution;

obtaining a measurement of the first physiological parameter;

comparing the measurement of the first physiological parameter to the event detection threshold value; and

declaring the measurement as representative of a detected event if the measurement falls within the tail area.

11. The method of claim 10, wherein using the first distribution includes using only non-event measurements of the first physiological parameter.

12. The method of claim 11, further comprising:

updating the first distribution of measurements for the first physiological parameter; and

excluding from the updating at least one of corrupted, confounded, or event-related measurements.

13. A method comprising:

collecting a first distribution of measurements for a first physiological parameter;

determining a first value corresponding to a first tail area of the first distribution, the first tail area extending from a first physiological parameter measurement toward an end point of the first distribution;

collecting a second distribution of measurements for a second physiological parameter;

determining a second value corresponding to a second tail area of the second distribution, the second tail area extending from a second physiological parameter measurement toward an end point of the second distribution;

combining the first value with the second value to form a joint metric;

receiving a specified false alarm rate;

establishing a threshold based on a specified false alarm rate;

comparing the joint metric with the threshold; and

determining that the first and second physiological parameter measurements are representative of a detected event using the comparison.

14. The method of claim 13, wherein determining the first and second values includes determining first and second probabilities of false alarm for the physiological parameter measurements of the first and second physiological parameters.

15. A method comprising:

collecting a first distribution of measurements for a first physiological parameter;

determining at least one composite measurement based on the distribution;

determining at least one threshold value based on the composite measurement;

comparing at least a first measurement with the threshold value;

counting the first measurement if the measurement equals or exceeds the threshold value;

receiving at least one specified false alarm rate;

comparing the count against the at least one specified false alarm rate; and

determining whether the count is representative of a detected event using the comparison.

16. The method of claim 15, wherein determining the at least one threshold value based on the composite measurement includes determining a first threshold value and a second threshold value.

17. The method of claim 16, wherein counting the first measurement includes counting the first measurement in a first count if the measurement equals or exceeds the first threshold value, and counting the first measurement in a second count if the measurement equals or exceeds the second threshold value.

18. The method of claim 17, wherein comparing the count against the at least one specified false alarm rate includes comparing the first count against a first specified false alarm rate and comparing the second count against a second specified false alarm rate.

19. The method of claim 15, wherein receiving the at least one specified false alarm rate includes inputting the at least one specified false alarm rate independent of the first distribution of measurements for the first physiological parameter.

20. An apparatus comprising:

an implantable medical device comprising;

a physiological sensor to collect at least a first distribution of measurements for a first physiological parameter; and

a processor circuit comprising;

a value determination module to determine one or more values corresponding to at least a first tail area of the first distribution of the first physiological parameter toward an end point of the distribution,

a comparator to compare the one or more values with a threshold, the threshold based on a specified false alarm rate, and

an event indicator to provide an event indication if the measurement is representative of a detected event using the comparison.

21. The apparatus of claim 20, wherein the implantable medical device includes a pulse generator.

22. The apparatus of claim 20, wherein the physiological sensor is adapted to collect at least the first distribution of measurements for the first physiological parameter selected from the group consisting essentially of heart sound and thoracic impedance.

23. The apparatus of claim 20, wherein the physiological sensor is adapted to collect only non-event measurements of the first physiological parameter.

24. The apparatus of claim 20, wherein the value determination module is adapted to determine a first probability of false alarm for the measurement of the first physiological parameter.

25. The apparatus of claim 24, wherein the value determination module is adapted to determine a heart failure condition confidence for the measurement of the first physiological parameter.

26. The apparatus of claim 20, further comprising a joint metric module adapted to combine a plurality of values into a joint metric.

27. The apparatus of claim 20, further comprising a therapy circuit in communication with the event indicator, wherein the therapy circuit is adapted to control therapy delivered by the implantable medical device in response to the event indicator.

28. The apparatus of claim 20, wherein the implantable medical device includes the processor circuit.

29. The apparatus of claim 20, further comprising an input module adapted to receive the specified false alarm rate independent of the first distribution of measurements for the first physiological parameter.