Enslaved active implantable medical device with reduced power consumption

• US 5,766,228 A
• Filed: 10/11/1996
• Issued: 06/16/1998
• Est. Priority Date: 10/13/1995
• Status: Expired due to Term

• Current Assignee: Sorin CRM USA (MicroPort Scientific Corp.)
• Original Assignee: Ela Medical S.A. (LivaNova Plc)
• Inventors: Dubreuil, Anne, Bonnet, Jean-Luc
• Primary Examiner(s): Getzow, Scott M.
• Application Number:
  US08/730,735
• Time in Patent Office: 613 Days
• Field of Search: 607/16, 607/9, 607/17, 607/29, 607/28
• US Class Current: 607/16
• CPC Class Codes: A61N 1/36542 controlled by body motion, e.g. acceleration
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters

Abstract

An active implantable medical device, particularly a rate responsive cardiac pacemaker having reduced power consumption. The device has a first sensor to measure a parameter that is used to control at least one function of the device, particularly a cardiac stimulation frequency, and a first sensing circuit for receiving and processing the output signals delivered by the first sensor. A switch is used to switch in and out of service the first sensing circuit according to the determined activity level of the patient bearing the device. The first sensing circuit determines a state of activity of the first sensor, this state being susceptible to take, according to predetermined criteria, a calculated value that is representative of a state of rest of the patient. The first sensing circuit is then switched according to the determined state of activity of the first sensor being established at the state of rest. Advantageously, a second sensor is used to measure a parameter representative of the activity of the patient and a second sensing circuit is used to receive and process the output signals delivered by this second sensor, such that the first sensing circuit is switched back in service as a function of the output signals delivered by the second sensor.

Claims

1. An active implantable medical device comprising:

at least one control function enslaved to a measured parameter;

a first sensor measuring a parameter indicative of patient activity, the first sensor having an output signal corresponding to the measured parameter;

a first sensing circuit operable to process the first sensor output signals and determine a first level of patient activity to control said at least one control function; and

means for switching in and out of service the first sensing circuit according to the determined first level of patient activity;

wherein;

the first sensing circuit is operable to determine when said first level of patient activity corresponds to a state of rest of the patient; and

the switching means switches out of service the first sensing circuit in response to the first determined patient activity level corresponding to said state of rest.

2. The device of the claim 1, wherein the at least one control function further comprises a cardiac stimulation frequency, and the sensing circuit further comprises a first predetermined criteria corresponding to a calculated value of a state of rest of the patient, the device further comprising a means for determining when the first level of activity corresponds to a state of rest of a patent as a function of the first predetermined criteria and the first determined patient activity level.

3. The device of the claim 1, further comprising:

a second sensor measuring a parameter representative of the activity of the patient and having an output signal corresponding to the measured parameter; and

a second sensing circuit operable to process the second sensor output signals and determine a second level of patient activity,

wherein;

the second sensing circuit is operable to determine when the determined second level of patient activity corresponds to a state of non-rest of the patient; and

the switching means operates to switch back in service the first sensing circuit in response to the second determined patient activity level corresponding to said state of non-rest.

4. The device of the claim 1, further comprising a counter and a preselected count value, wherein the counter is incremented as a function of an elapsed time after the first sensing circuit is switched out of service, and the switching means switches back in service the first sensing circuit in response to the counter incrementing to said preselected count value.

5. The device of claim 1, in which the first sensor is a sensor of effort for measuring a parameter of physiological preponderance and delivering a signal that is a function of the effort developed by the patient.

6. The device of claim 1, wherein the first sensor further comprises a sensor for measuring an acceleration of the patient.

7. The device of claim 1, wherein the first sensor further comprises a sensor for measuring an effort of the patient.

8. The device of claim 1, wherein the first sensor further comprises a sensor for measuring a preponderantly physical parameter of the patient.

9. The device of claim 1, further comprising:

a second sensor measuring a parameter representative of the activity of the patient and having an output signal corresponding to the measured parameter; and

a second sensing circuit operable to process the second sensor output signals and determine a second level of patient activity,

wherein;

the switching means operates to switch back in service the first sensing circuit as a function of the output signals delivered by the second sensor; and

the first sensor is a sensor of effort measuring a preponderantly physiological parameter and delivering a signal that is a function of the metabolic state of the patient and the second sensor is a sensor of activity measuring a preponderantly physical parameter.

10. The device of claim 9 wherein the first sensor has a first response time, the second sensor has a second response time, and the first response time is longer than the second response time.

11. The device of claim 1, further comprising:

a sample period;

a second sensor measuring a parameter representative of the activity of the patient and having an output signal corresponding to the measured parameter;

a second sensing circuit operable to process the second sensor output signals over said sample period and determine a second level of patient activity selected from among at least a rest level and a non-rest level;

wherein;

the switching means operates to switch back in service the first sensing circuit in response to the determined second patient activity level corresponding to a non-rest state of the patient;

and further comprising;

means for switching in and out of service the second sensing circuit in response to the determined first patient activity level and the determined second activity level,

wherein;

i) in response to the determined second patient activity level corresponding to a non-rest state, the second sensing circuit is switched in service;

ii) in response to the determined second patient activity level corresponding to a rest state and the determined first patient activity level corresponding to a non-rest state, the second sensing circuit is switched out of service for a first duration and thereafter switched in service for at least one sample period; and

iii) in response to the determined second patient activity level corresponding to a rest state and the determined first patient activity level corresponding to a rest state, the second sensing circuit is switched out of service for a second duration and thereafter switched in service for at least one sample period, the second duration being longer than the first duration.

12. The device of claim 11 wherein the first duration comprises a first number of sample periods, the second duration comprises a second number of sample periods, and the second number of sample periods is greater than the first number of sample periods.

13. The device of claim 12 wherein the means for switching in and out of service the second sensing circuit further comprises a counter operable to count a first count value corresponding to said sample period, the second sensor further comprises an accelerometer sensor measuring patient motion wherein the second sensing processes the second sensor output signals periodically at a sampling interval, wherein the sample period corresponds to a first number of sampling intervals, the first number of sampling periods is a first multiple of the first number of sampling intervals, and the second number of sampling periods is a second multiple of the first number of sampling intervals.

14. The device of claim 12 wherein the means for switching in and out of service the second sensing circuit further comprises a first counter operable to count a first count value corresponding to said sample period and a second counter operable to count to a second count value corresponding to the first duration and to a third count value corresponding to the second duration, the third count value being greater than the second count value and wherein the sampling period comprises a first number of breathing cycles of the patient and the second sensor further comprises a sensor for measuring minute ventilation.

15. A method for operating a power consuming circuit of an implanted medical device having a control function enslaved to a measured parameter, comprising:

a. measuring a first parameter indicative of patient activity over a first sample period and determining therefrom a first patient activity level;

b. determining when the determined first patient activity level corresponds to a rest level of patient activity and a non-rest level of patent activity; and

c. in response to a determined first patient activity level corresponding to a rest level, interrupting the measuring of the first parameter, thereby reducing power consumption during said interrupted measuring.

16. The method of claim 15 further comprising:

d. timing a period of time in response to interrupting measuring the first parameter; and

e. resuming steps a-c in response to the period of time elapsing.

17. The method of claim 15 further comprising:

d. measuring a second parameter indicative of patient activity over a second sample period and determining therefrom a second patient activity level;

e. determining when said determined second patient activity corresponds to a rest level of activity and a non-rest level of activity;

f. resuming measuring of the first parameter in response to a determined second level of activity corresponding to a non-rest patient activity level.

18. The method of claim 17 wherein step a further comprises measuring a preponderantly physiological parameter and wherein step d further comprises measuring a preponderantly physical parameter.

19. The method of claim 17 wherein step a further comprises measuring a preponderantly physiological parameter indicative of the metabolic state of the patient and wherein step d further comprises measuring a preponderantly physical parameter.

20. The method of claim 17 wherein step a further comprises measuring a minute ventilation parameter and wherein step d further comprises measuring an acceleration parameter.

21. The method of claim 17 wherein step a further comprises measuring a preponderantly physical parameter and wherein step d further comprises measuring a preponderantly physiological parameter.

22. The method of claim 17 further comprising the step of counting an interval of time following each interruption of said measuring, wherein step f further comprises resuming measuring of the first parameter in response to either step e determining that the second patient activity level is non-rest or said counted interval of time, and resetting said counter in response to resuming measuring of the first parameter.

23. The method of claim 17 further comprising:

g. controlling the measuring of the second parameter by;

i) interrupting measuring the second parameter for a first duration in response to the determined first patient activity level corresponding to a non-rest level and the determined second patient activity level corresponding to a rest level, and resuming measuring the second parameter for at least one second sample period following the end of the first duration

ii) interrupting measuring the second parameter for a second duration in response to the determined first patient activity level corresponding to a rest level and the determined second patient activity level corresponding to a rest level, and resuming measuring the second parameter for at least one second sample period following the end of the second duration, the second duration being longer than the first duration, and

iii) maintaining measuring the second parameter in response to the determined second activity level corresponding to a non-rest level,

thereby reducing power consumption during each of said first durations and said second durations.

24. The method of claim 23 wherein step g.i) further comprises providing the first duration as a first multiple of the sample period and the second duration as a second multiple of the sample period.

25. The method of claim 15 wherein step a further comprises measuring a physiological parameter representative of a minute ventilation.