METHOD AND APPARATUS FOR DETECTING RESPIRATORY EFFORT IN A MEDICAL DEVICE

• US 20100076324A1
• Filed: 10/31/2008
• Published: 03/25/2010
• Est. Priority Date: 09/19/2008
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Greenhut, Saul E., Kleckner, Karen J., Erickson, Mark K., Cho, Yong K., Bennett, Tommy D., Sperling, Charles P., Corey, Robert A., Shrivastav, Maneesh
• Granted Patent: US 8,231,536 B2
• Time in Patent Office: Days
• US Class Current: 600/484
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• 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 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/6846 specially adapted to be brought in contact with an internal body part, i.e. invasive
• 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: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: A61N 1/37258 Alerting the patient

Abstract

A medical device for determining a respiratory effort having a pressure sensor to sense pressure signals, a housing having system components positioned therein, and a microprocessor positioned within the housing, wherein the microprocessor detects an inspiration and an expiration in response to the pressure signals, detects a breath in response to the detected inspiration and the detected expiration, and determines the respiratory effort in response to the detected breath.

Claims

1. A medical device for determining a respiratory effort, comprising:

a pressure sensor to sense pressure signals;

a housing having system components positioned therein; and

a microprocessor positioned within the housing, wherein the microprocessor detects an inspiration and an expiration in response to the pressure signals, detects a breath in response to the detected inspiration and the detected expiration, and determines the respiratory effort in response to the detected breath.

2. The device of claim 1, wherein the microprocessor detects the inspiration in response to a first predetermined number of sample points corresponding to the sensed pressure signals being less than a detection threshold, and detects the expiration in response to a second predetermined number of sample points corresponding to the sensed pressure signals, occurring subsequent to the first predetermined number of sample points, being greater than the detection threshold.

3. The device of claim 2, wherein the microprocessor detects a peak inspiration associated with a first detected breath during a first interval, and detects a peak expiration associated with the first detected breath during a second interval, wherein the first interval is defined by a sample point of second predetermined sample points associated with a breath detected prior to the first detected breath and a sample point of the second predetermined number of sample points associated with the first detected breath, and wherein the second interval is defined by a sample point of the first predetermined number of sample points associated with the first detected breath and a sample point of the first predetermined number of sample points associated with a breath detected subsequent to the first detected breath.

4. The device of claim 2, wherein the microprocessor determines a slope between a sample point of the first predetermined number of sample points and a sample point of the second predetermined number of sample points.

5. The device of claim 2, wherein the microprocessor continuously adjusts a breath detection threshold in response to the generated sample points to generate a current adjusted breath detection threshold, compares a current generated sample point to the current adjusted breath detection threshold, suspends the continuous adjusting of the breath detection threshold and sets the breath detection threshold equal to the most current adjusted breath detection threshold generated prior to the suspending, compares a next sample point, generated subsequent to the suspending, to the set detection threshold, and detects one of the inspiration and the expiration in response to the comparing of a next sample point.

6. The device of claim 1, further comprising a signal filtering system filtering the sensed pressure signal in response to a determined heart rate to generate a heart-rate dependent frequency response, wherein the microprocessor derives a filtered signal in response to the heart rate dependent frequency response, and wherein the sample points are generated in response to the derived filtered signal.

7. The device of claim 6, wherein the signal filtering system comprises:

a first filter having a first frequency response corresponding to a heart rate greater than a heart rate threshold; and

a second filter having a second frequency response different from the first frequency response, the second frequency response corresponding to a heart rate being less than the heart rate threshold.

8. The device of claim 7, wherein the microprocessor selects the first filter and the second filter one at a time in a sequential manner in response to the determined heart rate, and derives the respiration signal as a continuous signal comprising sequential outputs of the first filter and the second filter.

9. The device of claim 7, wherein the microprocessor selects the first filter and the second filter simultaneously for parallel filtering of the pressure signals, and wherein the filtered signal comprises a first signal component corresponding to an output of the first filter and a second signal component corresponding to an output of the second filter.

10. The device of claim 7, wherein the first and second filters each comprise multiple filtering stages, the first filter is a subset of the multiple stages of the second filter, and wherein the signal filtering system decimates the pressure signal following at least one of the multiple stages.

11. A medical device for determining respiratory effort, comprising:

means for sensing cardiac pressure signals;

means for sensing cardiac signals and determining a heart rate in response to the sensed cardiac signals;

means for filtering the sensed pressure signals in response to the determined heart rate to generate a heart-rate dependent frequency response;

means for deriving a filtered signal in response to the heart rate dependent frequency response;

means for generating sample points in response to the derived filtered signal;

means for detecting an inspiration in response to a first predetermined number of sample points corresponding to the sensed pressure signals being less than a detection threshold;

means for detecting an expiration in response to a second predetermined number of sample points corresponding to the sensed pressure signals, occurring subsequent to the first predetermined number of sample points, being greater than the detection threshold;

means for detecting a breath in response to the detected inspiration and the detected expiration; and

means for determining the respiratory effort in response to the detected breath.

12. The device of claim 11, further comprising:

means for detecting a peak inspiration and a peak expiration; and

means for determining a difference between the peak inspiration and the peak expiration.

13. The device of claim 11, further comprising:

means for continuously adjusting the detection threshold in response to the generated sample points to generate a current adjusted detection threshold;

means for comparing a current generated sample point to the current adjusted detection threshold;

means for suspending the continuous adjusting of the detection threshold and setting the detection threshold equal to the most current adjusted detection threshold generated prior to the suspending;

means for comparing a next sample point, generated subsequent to the suspending, to the set detection threshold; and

means for detecting one of the inspiration and the expiration in response to the comparing of a next sample point.

14. The device of claim 11, further comprising:

means for detecting a peak inspiration associated with a first detected breath during a first interval; and

means for detecting a peak expiration associated with the first detected breath during a second interval, wherein the first interval is defined by a sample point of second predetermined sample points associated with a breath detected prior to the first detected breath and a sample point of the second predetermined number of sample points associated with the first detected breath, and wherein the second interval is defined by a sample point of the first predetermined number of sample points associated with the first detected breath and a sample point of the first predetermined number of sample points associated with a breath detected subsequent to the first detected breath.

15. The device of claim 11, further comprising means for determining a slope between a sample point of the first predetermined number of sample points and a sample point of the second predetermined number of sample points.

16. The device of claim 11, further comprising means for filtering the sensed pressure signals using a first filter having a first frequency response corresponding to the determined heart rate being greater than a heart rate threshold and a second filter having a second frequency response different from the first frequency response, the second frequency response corresponding to the determined heart rate being less than the heart rate threshold.

17. The device of claim 16, further comprising means for selecting the first filter and the second filter one at a time in a sequential manner in response to the determined heart rate and obtaining the filtered signal as a continuous signal comprising sequential outputs of the first filter and the second filter.

18. The device of claim 16, further comprising means for selecting the first filter and the second filter simultaneously for parallel filtering of the pressure signals, and wherein the filtered signal comprises a first signal component corresponding to an output of the first filter and a second signal component corresponding to an output of the second filter.

19. The device of claim 16, wherein the first and second filters each comprise multiple filtering stages, the first filter is a subset of the multiple stages of the second filter, and further comprising means for decimating the pressure signal following at least one of the multiple stages.

20. The device of claim 11, further comprising:

means for detecting a peak inspiration and a peak expiration; and

means for determining a difference between the peak inspiration and the peak expiration.