METHOD AND APPARATUS FOR DETERMINING A RESPIRATION PARAMETER IN A MEDICAL DEVICE

• US 20100076323A1
• Filed: 10/31/2008
• Published: 03/25/2010
• Est. Priority Date: 09/19/2008
• Status: Abandoned Application

• 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
• Application Number:
  US12/262,300
• Publication Number:
  US 20100076323A1
• 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

An apparatus for determining a respiration parameter in a medical device in which a pressure sensor senses pressure signals, and a signal processor, coupled to the pressure sensor, receives the sensed pressure signals and generates corresponding sample points. A 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, and determines the respiration parameter in response to a comparing of a next generated sample point to the set breath detection threshold

Claims

1. An apparatus for determining a respiration parameter in a medical device, comprising:

a pressure sensor to sense pressure signals;

a signal processor coupled to the pressure sensor to receive the sensed pressure signals and generate corresponding sample points; and

a microprocessor to continuously adjust a breath detection threshold in response to the generated sample points to generate a current adjusted breath detection threshold, compare a current generated sample point to the current adjusted breath detection threshold, suspend the continuous adjusting of the breath detection threshold and set the breath detection threshold equal to the most current adjusted breath detection threshold generated prior to the suspending, and determine the respiration parameter in response to a comparing of a next generated sample point to the set breath detection threshold.

2. The apparatus of claim 1, further comprising a storage device to store a predetermined number of generated sample points, wherein the microprocessor sets the breath detection threshold equal to one of a minimum amplitude and a maximum amplitude of the current stored sample points, and updates the stored predetermined number of generated sample points to include a subsequently generated sample point.

3. The apparatus of claim 1, wherein the respiration parameter is a breath count.

4. The apparatus of claim 1, further comprising:

an electrode to sense cardiac signals; and

a signal filtering system to filter the sensed pressure signal, wherein the microprocessor determines a heart rate in response to the sensed cardiac signals, and the signal filtering system filters the sensed pressure signals in response to the determined heart rate to generate a heart-rate dependent frequency response to derive a filtered signal, wherein the signal processor generates the sample points in response to the derived filtered signal.

5. The apparatus of claim 4, further comprising:

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.

6. The apparatus of claim 5, wherein the signal processor selects the first filter and the second filter one at a time in a sequential manner in response to the determined heart rate and, the derives the filtered signal as a continuous signal comprising sequential outputs of the first filter and the second filter.

7. The apparatus of claim 5, wherein the signal processor 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.

8. The apparatus of claim 5, wherein the first and second filters each comprise multiple filtering stages, and the first filter is a subset of the multiple stages of the second filter, and wherein the signal processor decimates the pressure signal following at least one of the multiple stages.

9. An apparatus for determining a respiration parameter in a medical device, comprising:

means for sensing pressure signals to generate corresponding sample points;

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

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

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

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

means for determining the respiration parameter in response to the comparing of a next sample point to the set breath detection threshold.

10. The apparatus of claim 9, wherein the means for continuously adjusting a breath detection threshold comprises:

means for storing a predetermined number of generated sample points;

means for setting the breath detection threshold equal to one of a minimum amplitude and a maximum amplitude of the current stored sample points; and

means for updating the stored predetermined number of generated sample points to include a subsequently generated sample point.

11. The apparatus of claim 9, further comprising means for determining whether both an inspiration detection threshold and an expiration detection threshold are sequentially detected in response to the comparing a next sample point.

12. The apparatus of claim 9, wherein the respiration parameter is a breath count.

13. The apparatus of claim 9, further comprising:

means for confirming detection of an one of an inspiration and an expiration;

means for resuming the continuous adjusting of the breath detection threshold;

means for comparing a current sample point, generated subsequent to the resuming, to the current adjusted breath detection threshold;

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

means for confirming detection of the other of an inspiration and an expiration; and

means for incrementing a breath count in response to the confirming detection of the other of an inspiration and an expiration.

14. The apparatus of claim 9, further comprising:

means for determining a heart rate;

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

means for deriving a filtered signal in response to the heart rate dependent frequency response, wherein the sample points are generated in response to the derived filtered signal.

15. The apparatus of claim 14, wherein the means for filtering the sensed pressure signals comprises 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.

16. The apparatus of claim 15, wherein the first filter and the second filter are selected one at a time in a sequential manner in response to the determined heart rate, and the filtered signal is obtained as a continuous signal comprising sequential outputs of the first filter and the second filter.

17. The apparatus of claim 15, wherein the means for filtering the sensed pressure signals 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.

18. The apparatus of claim 15, 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 means for filtering the sensed pressure signals decimates the pressure signal following at least one of the multiple stages.

19. An apparatus for determining a respiration parameter in a medical device, comprising:

means for sensing pressure signals to generate corresponding sample points;

means for continuously adjusting a breath detection threshold in response to a minimum amplitude of a predetermined number of the generated sample points to generate a first detection threshold;

means for determining whether a current generated sample point is less than the first inspiration detection threshold;

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

means for determining whether a first predetermined number of next sample points, generated subsequent to the suspending, is less than the first respiration detection threshold;

means for resuming the continuous adjusting of the breath detection threshold to continuously adjust the breath detection threshold in response to a maximum amplitude of the generated sample points to generate a second respiration detection threshold;

means for determining whether a current generated sample point is greater than the second respiration detection threshold;

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

means for determining whether a second predetermined number of next sample points, generated subsequent to the suspending, is greater than the second respiration detection threshold; and

means for determining the respiration parameter in response to the predetermined number of next sample points being greater than the second respiration detection threshold.

20. The apparatus of claim 19, wherein the first respiration detection threshold is generated using a first computation scheme and the second respiration detection threshold is generated using a second computation scheme different from the first computation scheme.

21. The apparatus of claim 19, wherein the first predetermined number of next sample points is equal to the second predetermined number of next sample points.