Pacemaker with automatic calibration of the response of multiple sensors

• US 5,755,740 A
• Filed: 10/22/1997
• Issued: 05/26/1998
• Est. Priority Date: 08/22/1996
• Status: Expired due to Term

• Current Assignee: Nappholz, Tibor
• Original Assignee: Nappholz, Tibor
• Inventors: Nappholz, Tibor
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US08/956,764
• Time in Patent Office: 216 Days
• Field of Search: 607/17-24
• US Class Current: 607/18
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters

Abstract

In a dual sensor pacer/defibrillator the output of a metabolic sensor is used to calibrate the output a second sensor over a long time period. In this manner the two sensor outputs track accurately the metabolic demand of the patient and no recalibration by a clinician is necessary.

Claims

1. A multiple sensor pacemaker/defibrillator for insertion in a patient, comprising:

a first sensor generating a first parameter correlated with a metabolic demand of said patient;

a first converter converting said first parameter into a first indicated rate in accordance with a first gain;

a second sensor for generating a second parameter related to a physical activity of said patient;

a second converter for converting said second parameter into a second indicated rate in accordance with a second gain;

a comparator comparing said first and second rates between an upper and a lower limit to determine which is larger;

an adjustment circuit adjusting over an extended time period said second gain using said first parameter as a calibration target for calibrating said second parameter to automatically adjust to the biological needs of the patient;

a selector for selecting a dual rate by selecting the larger of said metabolic and activity rates as determined by said comparator; and

a pace generator for generating pacing pulses at said combined rate;

whereby the gains of the converters are automatically calibrated.

2. A dual sensor implantable pacemaker for implantation in a patient, said pacemaker comprising:

a metabolic sensor sensing a metabolic demand of said patient and generating in response a metabolic demand parameter;

a first converter converting said metabolic demand parameter into a corresponding demand pacing rate, said demand pacing rate having a demand peak rate level;

an activity sensor sensing a physical activity of said patient and generating in response a physical activity parameter, said activity sensor having a sensitivity;

a second converter converting said physical activity parameter into a corresponding activity pacing rate, said activity pacing rate having an activity peak rate level dependent on said sensitivity;

a combining circuit for combining said activity pacing rate and said demand pacing rate into a dual pacing rate by selecting the larger of said activity pacing rate and said demand pacing rate between a predetermined lower and a predetermined upper pacing limit;

a pacing generator generating pacing pulses in response to said dual pacing rate;

a comparator comparing said activity peak rate level and said demand peak rate level; and

a sensitivity adjusting circuit adjusting said sensitivity if said activity peak rate level is outside a preselected range of said demand peak rate level as determined by said comparator.

3. The pacemaker of claim 2 further comprising a first and a second accumulator for accumulating said demand and said activity peak rate levels respectively to determine corresponding long term activity and demand peak levels, and wherein comparator compares said long term peak levels.

4. The pacemaker of claim 3 wherein said accumulators accumulate said peak levels over several days.

5. An implantable pacemaker comprising:

a metabolic sensor for generating a metabolic parameter indicative of metabolic demand of a patient;

a first convertor generating a metabolic pacing rate from said metabolic parameter;

a first peak detector detecting a metabolic peak rate for said metabolic pacing rate;

a first accumulator accumulating said metabolic peak rate to generate a long term metabolic peak rate level;

an activity sensor having a sensitivity and generating an activity parameter indicative of a physical activity of said patient;

a second convertor generating an activity pacing rate corresponding to said activity parameter;

a second peak detector detecting an activity peak rate for said activity pacing rate;

a second accumulator generating a long term peak activity rate level;

a comparator comparing said metabolic and activity long term peak rate levels;

an adjustor circuit adjusting said sensitivity if said comparator indicates a difference between said long term peak rate levels until said peak activity rate level is within a preselected range of said peak metabolic rate;

a combiner circuit for combining said metabolic and said activity pacing rates to define a dual pacing rate by selecting the larger of said metabolic and said activity pacing rates over a predetermined pacing range; and

a pacing generator generating pacing pulses in accordance with said dual pacing rate.

6. The pacemaker of claim 5 wherein said combiner circuit ignores said activity pacing rate if said peak activity level is outside said range.