Method and apparatus for implementing activity sensing in a pulse generator

Claim 2

A pacemaker, enclosed within a housing, comprising: rate control means for producing a triggering signal; a pulse generator adapted to be coupled to a patient's heart, and further coupled to said rate control means, said pulse generator responsive to said triggering signal from said rate control means to generate a pacing pulse; an activity sensor adapted to be coupled to said patient, said sensor producing an output signal having a signal level which varies as a function of patient activity; and an activity circuit, coupled to said activity sensor and to said rate control means, said activity circuit comprising a plurality of threshold detector means for detecting signal levels that exceed predetermined threshold levels, each of said detector means defining a different threshold level than others of said plurality of threshold detector means and each one of plurality of threshold detector means receiving said output signal; such that for a time-variant excursion of said output signal to a peak signal level, each one of said threshold detector means having a threshold lower than said peak signal level produces an output pulse in response to said signal excursion; said rate control means comprising: means for counting said output pulses; computing means responsive to said output pulses, said computing means assigning a weighted count value for each said output pulse, said computing means further calculating a running sum for said weighted count values; and adjustment means coupled to said computing means for varying a periodic rate for said triggering signal as a function of said running sum of weighted count values.

Claim 3

A pacemaker in accordance with claim 1, wherein said activity sensor comprises a piezoelectric crystal bonded to a wall of said housing so as to produce said output signal in response to deflections of said housing wall.

Claim 4

A pacemaker, comprising: rate control means for producing a triggering signal; a pulse generator adapted to be coupled to a patient's heart, and further coupled to said rate control means, said pulse generator responsive to said triggering signal from said rate control means to generate a pacing pulse; an activity sensor adapted to be coupled to said patient, said sensor producing an output signal indicative of patient activity; and an activity circuit, coupled to said activity sensor and to said rate control means, said activity circuit comprising a plurality of voltage threshold detector means for detecting signal levels that exceed predetermined threshold levels {T 1 . . .T N } each defining a threshold voltage {V l . . . V N } where V 1 <V 2 <. . . <V4N, each of said voltage threshold detector means {T 1 . . . T N } having a corresponding preassigned weight value {W l . . . W N } where W 1 <W 2 <. . . <W N , and each one of said threshold detector means {T l . . .T N } receiving said output signal, such that for a time-variant excursion of said output signal to a peak voltage level V P , each threshold detector means T X defining a threshold voltage V X <V P produces an output pulse in response to said given excursion; said rate control means comprising: means for counting said output pulses; computing means coupled to said output pulses, said computing means assigning a weighted count value for each said output pulse, said computing means further calculating a running sum for said weighted count values; and adjustment means coupled to said computing means for varying a periodic rate for said triggering signal as a function of said running sum of weighted count values.

Claim 5

A pacemaker, comprising: rate control means for producing a triggering signal; a pulse generator adapted to be coupled to a patient's heart, and further coupled to said rate control means, said pulse generator responsive to said triggering signal from said rate control means to generate a pacing pulse; an activity sensor adapted to be coupled to said patient, said sensor producing an output signal indicative of patient activity; and an activity circuit, coupled to said activity sensor and to said rate control means, said activity circuit comprising a plurality of voltage threshold detector means for detecting signal levels that exceed predetermined threshold levels {T 1 . . .T N } each defining a threshold voltage {V l . . . V N } where V 1 <V 2 <. . . <V4N, each of said voltage threshold detector means {T 1 . . . T N } having a corresponding preassigned weight value {W l . . . W N } where W 1 <W 2 <. . . <W N , and each one of said threshold detector means {T l . . .T N } receiving said output signal, such that for a time-variant excursion of said output signal to a peak voltage level V P , each threshold detector means T X defining a threshold voltage V X <V P produces an output pulse in response to said given excursion; said rate control means comprising: means for counting said output pulses; computing means coupled to said output pulses, said computing means assigning a weighted count value for each said output pulse, said computing means further calculating a running sum for said weighted count values; and adjustment means coupled to said computing means for varying a periodic rate for said triggering signal as a function of said running sum of weighted count values.

Claim 6

A pacemaker in accordance with claim 3, wherein said activity sensor comprises a piezoelectric crystal bonded to a wall of said housing so as to produce an output signal in response to deflections of said wall.

Claim 11

A pacemaker, enclosed within a housing, comprising: rate control means for producing a triggering signal; a pulse generator adapted to be coupled to a patient's heart, and further coupled to said rate control means, said pulse generator responsive to said triggering signal from said rate control means to generate a pacing pulse; an activity sensor adapted to be coupled to said patient, said sensor producing a pulsatile output signal indicative of patient activity; and an activity circuit, coupled to said activity sensor and to said rate control means, said activity circuit comprising a plurality of voltage threshold detector means for detecting signal levels that exceed predetermined threshold levels {T l . . .T N } each defining a threshold voltage {V l . . .V N } where V 1 <V 2 <. . .V N , each of said voltage threshold detector means {T l . . .T N } having a corresponding preassigned weight value {W l . . .W N 56 where W 1 <W 2 <. . .W N , and each one of said threshold detector means {T l . . .T N } receiving said pulsatile output signal, such that for a time-variant excursion of said activity signal to a peak voltage level V P , each threshold detector means T X defining a threshold voltage V X <V P produces an output pulse in response to said excursion; said rate control means comprising: means for counting said output pulses; said computing means adding said weight value for said corresponding threshold detector means to a running sum of weighted count values; adjustment means coupled to said computing means for varying a periodic rate for said triggering signal, said variable periodic rate corresponding to an Activity Rate Function, where ##EQU8## where K is a scaling factor which varies according to a maximum peak voltage level of an excursion of said pulsatile signal during a prior, predetermined time period; and where ##EQU9## and e is selectable in the range three to twelve, and where ##EQU10## with L.sub.τ and U.sub.τ corresponding to selected lower and upper rate limits, respectively, where possible values of L.sub.τ and U.sub.τ and respectively corresponding lower and upper rates are: ______________________________________ LOWER RATE L.sub.τ ______________________________________ 40 PPM 139 50 PPM 119 60 PPM 96 70 PPM 85 80 PPM 74 90 PPM 66 ______________________________________ UPPER RATE U.sub.τ ______________________________________ 100 PPM 59 125 PPM 47 150 PPM 39 175 PPM 22. ______________________________________

Claim 12

A pacemaker, enclosed within a housing, comprising: rate control means for producing a triggering signal; a pulse generator adapted to be coupled to a patient's heart, and further coupled to said rate control means, said pulse generator responsive to said triggering signal from said rate control means to generate a pacing pulse; an activity sensor adapted to be coupled to said patient, said sensor producing a pulsatile output signal indicative of patient activity; and an activity circuit, coupled to said activity sensor and to said rate control means, said activity circuit comprising a plurality of voltage threshold detector means for detecting signal levels that exceed predetermined threshold levels {T l . . .T N } each defining a threshold voltage {V l . . .V N } where V 1 <V 2 <. . .V N , each of said voltage threshold detector means {T l . . .T N } having a corresponding preassigned weight value {W l . . .W N 56 where W 1 <W 2 <. . .W N , and each one of said threshold detector means {T l . . .T N } receiving said pulsatile output signal, such that for a time-variant excursion of said activity signal to a peak voltage level V P , each threshold detector means T X defining a threshold voltage V X <V P produces an output pulse in response to said excursion; said rate control means comprising: means for counting said output pulses; said computing means adding said weight value for said corresponding threshold detector means to a running sum of weighted count values; adjustment means coupled to said computing means for varying a periodic rate for said triggering signal, said variable periodic rate corresponding to an Activity Rate Function, where ##EQU8## where K is a scaling factor which varies according to a maximum peak voltage level of an excursion of said pulsatile signal during a prior, predetermined time period; and where ##EQU9## and e is selectable in the range three to twelve, and where ##EQU10## with L.sub.τ and U.sub.τ corresponding to selected lower and upper rate limits, respectively, where possible values of L.sub.τ and U.sub.τ and respectively corresponding lower and upper rates are: ______________________________________ LOWER RATE L.sub.τ ______________________________________ 40 PPM 139 50 PPM 119 60 PPM 96 70 PPM 85 80 PPM 74 90 PPM 66 ______________________________________ UPPER RATE U.sub.τ ______________________________________ 100 PPM 59 125 PPM 47 150 PPM 39 175 PPM 22. ______________________________________