Energy efficient multiple sensor cardiac pacemaker

• US 5,441,524 A
• Filed: 08/30/1993
• Issued: 08/15/1995
• Est. Priority Date: 08/30/1993
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Rueter, John C., Wilkoff, Bruce L.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): Parker, Marianne
• Application Number:
  US08/113,950
• Time in Patent Office: 715 Days
• Field of Search: 607/7, 607/17, 607/18, 607/28, 607/19, 607/20
• US Class Current: 607/18
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence

Abstract

A multiple sensor cardiac pacemaker blends the outputs from a fast-reacting Activity sensor and a slower-reacting Minute Ventilation sensor to achieve an optimally desirable pacing rate. The pacemaker conserves battery energy by forcing the Minute Ventilation sensor output to be at its minimum value by disabling the Minute Ventilation algorithm for a predetermined time period when the Activity sensor is at its minimum observed value. Power is conserved because the Minute Ventilation sensor and associated algorithms which normally consume power to operate the circuitry, and to measure impedance are disabled temporarily only during selected periods where the Activity sensor is at its minimum observed value, thereby maintaining optimal blending of the pacemaker sensor outputs in achieving the desired pacing rates.

Claims

1. A method of pacing a patient'"'"'s heart, comprising the steps of:

(a) applying a respiration sensor which provides a respiration signal indicative of respiratory activity to said patient and activating said respiration sensor to produce said respiration signal;

(b) applying an activity sensor which provides an activity signal indicative of physical activity to said patient and activating said activity sensor to produce said activity signal;

(c) computing an average value of said respiration signal over a predetermined interval;

(d) comparing said activity signal and said average value with minimum values;

(e) delivering cardiac pacing pulses to said heart at a rate determined as a function of said activity signal and said respiration signal, when said activity signal and said average value are not at or below said minimum values simultaneously; and

(f) disabling said respiration sensor when said activity signal and said average value are at or below said minimum values, simultaneously.

2. A pacemaker, enclosed within a housing, comprising:

(a) a rate control circuit means for producing triggering signals at a rate varying between predetermined upper and lower pacing rates;

(b) a pulse generator means, coupled to said rate control circuit means, for generating a pacing pulse responsive to a triggering signal from said rate control circuit means;

(c) an activity sensor means for producing an activity signal indicative of patient activity;

(d) respiration sensor means for producing a respiration signal indicative of patient respiration, said rate control circuit means responsive to said activity signal and said respiration signal for varying said rate of said triggering signals and;

(e) processing means, coupled to said activity sensor means, said respiration sensor means, and said rate control circuit means, for comparing each of said activity signal and said respiration signal with a corresponding minimum values, and for producing a disable signal representative of a condition wherein said activity signal and said respiration signal are simultaneously equivalent to or less than said corresponding minimum values; and

means for disabling said respiration sensor in response to said disable signal.

3. A cardiac pacemaker, comprising:

first sensor means for measuring a first physiologic parameter of a patient;

second sensor means for measuring a second physiologic parameter of said patient, said second sensor means consuming less energy when activated than said first sensor means;

pulse generator means for generating pacing pulses at a pacing rate;

control means for determining said pacing rate as a function of said first measured physiologic parameter; and

means for inactivating said first sensor means in response to both said first and second measured physiologic parameters falling below predetermined minimum values.

4. A pacemaker according to claim 3 further comprising means for activating said first sensor means in response to said second measured physiologic parameter exceeding a predetermined value.

5. A pacemaker according to claim 3 or claim 4 wherein said control means comprises means for activating said first sensor means in response to said first sensor means being inactivated for an extended period.

6. A pacemaker according to claim 5 wherein said control means comprises means for activating said first sensor means in response to said first sensor means being inactivated for a predetermined period of time.

7. A pacemaker according to claim 3 wherein said first sensor means comprises means for measuring an average value of said first physiologic parameter over a predefined time period, and wherein said inactivating means comprises means for inactivating said first sensor means in response to both said measured average value and said second measured physiologic parameter falling below predetermined minimum values.

8. A pacemaker according to claim 3 wherein said first sensor means comprises a means for measuring respiratory activity of a patient and wherein said second sensor means comprises means for measuring physical activity of said patient.

9. A cardiac pacemaker, comprising:

a first sensor means for measuring a first physiologic parameter of a patient;

a second sensor means for measuring a second physiologic parameter of said patient, said second sensor means consuming less energy when activated than said first sensor means;

pulse generator means for generating pacing pulses at a pacing rate;

control means for determining said pacing rate as a function of said first measured physiologic parameter;

means coupled to said first sensor means for inactivating said first sensor means; and

means for activating said first sensor means in response to said first sensor means being inactivated for an extended period.

10. A pacemaker according to claim 9 wherein said activating means comprises means for activating said first sensor means in response to said first sensor means being inactivated for a predetermined period of time.

11. A pacemaker according to claim 9 wherein said inactivating means comprises means for inactivating said first sensor means in response to both said first and second measured physiologic parameters falling below predetermined minimum values.

12. A pacemaker according to claim 9 or claim 10 or claim 11 wherein said first sensor means comprises means for measuring respiratory activity of a patient and wherein said second sensor means comprises means for measuring physical activity of said patient.

13. A method of pacing a patient'"'"'s heart, comprising:

applying a first sensor which measures a first physiologic parameter to said patient and activating said first sensor to measure said first physiologic parameter;

applying a second sensor which measures a second physiologic parameter of said patient, said second sensor consuming less energy when activated than said first sensor, and activating said second sensor to measure said second physiologic parameter;

generating pacing pulses at a pacing rate;

determining said pacing rate as a function of said first measured physiologic parameter; and

inactivating said first sensor in response to both said first and second measured physiologic parameters falling below predetermined minimum values.

14. A method according to claim 13 further comprising activating said first sensor in response to said second measured physiologic parameter exceeding a predetermined value.

15. A method according to claim 13 or claim 14 further comprising activating said first sensor in response to said first sensor being inactivated for an extended period.

16. A method according to claim 15 wherein said activating step comprises activating said first sensor in response to said first sensor being inactivated for a predetermined period of time.

17. A method according to claim 13 wherein said step of measuring said first physiologic parameter comprises measuring an average value of said first physiologic parameter over a predefined time period, and wherein inactivating step comprises inactivating said first sensor in response to both said measured average value and said second measured physiologic parameter falling below predetermined minimum values.

18. A method according to claim 13 wherein said step of measuring said first physiologic parameter comprises measuring respiratory activity of a patient and wherein said step of measuring said second physiologic parameter comprises measuring physical activity of said patient.

19. A method of pacing a patient'"'"'s heart, comprising:

applying a first sensor which measures a first physiologic parameter, to said patient and activating said first sensor to measure said first physiologic parameter;

applying a second sensor which measures a second physiologic parameter, to said patient, said second sensor consuming less energy when activated than said first sensor and activating said second sensor to measure said second physiologic parameter;

generating pacing pulses at a pacing rate;

determining said pacing rate as a function of said first measured physiologic parameter;

after said determining step, inactivating said first sensor; and

thereafter activating said first sensor in response to said first sensor being inactivated for an extended period.

20. A method according to claim 19 wherein said activating step comprises activating said first sensor in response to said first sensor being inactivated for a predetermined period of time.

21. A method according to claim 19 wherein said inactivating step comprises inactivating said first sensor in response to both said first and second measured physiologic parameters falling below predetermined minimum values.

22. A method according to claim 19 or claim 20 or claim 21 wherein said step of measuring said first physiologic parameter comprises measuring respiratory activity of a patient and wherein said step of measuring said second physiologic parameter comprises measuring physical activity of said patient.