Variation in cardiac chamber volume or pressure as a controlling parameter

Claim 1

A rate adaptive pacer comprising: implantable pulse generator means for normally producing cardiac stimulating pulses at a predetermined lower rate; sensing means for sensing impedance in the blood in a selected cardiac chamber; means for producing a time varying impedance signal proportional to the intracardiac impedance sensed in the selected cardiac chamber due to the beating action of the heart; means for extracting from the time varying impedance signal a modulation signal due to volume changes; means for relating the modulation signal to the respiratory activity of the patient and processing the modulation signal to extract quantitative information therefrom with respect to the respiratory activity of the patient in whom the pulse generator means is implanted, the respiratory activity information including that relating both to the respiration interval (I RESP ) and the respiration depth (D RESP ) wherein the means for relating the modulation signal to I RESP comprises a zero-crossing detector and wherein the means for relating the modulation signal to D RESP comprises a peak to peak amplitude detector; and means for producing a rate control signal from the processed modulation signal which, when applied to the pulse generator means, changes the rate at which the stimulating pulses are produced from the predetermined lower rate to a higher rate in accordance with a known relationship between I RESP and D RESP expressed as an empirical algebraic function.

Claim 5

A method for controlling a rate adaptive pacer comprising an implantable pulse generator means for normally producing cardiac stimulating pulses at a predetermined lower rate comprising the steps of: sensing an intracardiac parameter selected from the group consisting of impedance and pressure in the blood in a selected cardiac chamber; producing a time varying signal related to the magnitude of the intracardiac parameter sensed in the selected cardiac chamber due to the beating action of the heart; extracting from the time varying signal from the sensed parameter a modulation signal due to the selected one of impedance volume changes or pressure changes; relating the modulation signal to and extracting quantitative information from the modulation signal with respect to the respiratory activity of the patient in whom the pulse generator means is implanted, the respiratory activity information including that relating both to the respiration interval (I RESP ) and the respiration depth (D RESP ) wherein the modulation signal is related to I RESP by subjecting it to a zero-crossing detector and wherein the modulation signal is related to D RESP by processing it utilizing a peak to peak amplitude detector; producing a rate control signal from the modulation signal which, when applied to the pulse generator means, changes the rate at which the stimulating pulses are produced from the predetermined lower rate to a higher rate in accordance with a known relationship among the selected parameter, I RESP and D RESP in which the modulation signal is used to generate the rate control signal to control the interval between the cardiac stimulating pulses according to an empirical algebraic relationship; and applying the rate control signal to the pulse generator.

Claim 6

A method for controlling a rate adaptive pacer comprising an implantable pulse generator means for normally producing cardiac stimulating pulses at a predetermined lower rate comprising the steps of: sensing an intracardiac parameter selected from the group consisting of impedance and pressure in the blood in a selected cardiac chamber; producing a time varying signal related to the magnitude of the intracardiac parameter sensed in the selected cardiac chamber due to the beating action of the heart; extracting from the time varying signal from the sensed parameter a modulation signal due to the selected one of impedance volume changes or pressure changes; relating the modulation signal to and extracting quantitative information from the modulation signal with respect to the respiratory activity of the patient in whom the pulse generator means is implanted, the respiratory activity information including that relating both to the respiration interval (I RESP ) and the respiration depth (D RESP ) wherein the modulation signal is related to I RESP by subjecting it to a zero-crossing detector and wherein the modulation signal is related to D RESP by processing it utilizing a peak to peak amplitude detector; producing a rate control signal from the modulation signal which, when applied to the pulse generator means, changes the rate at which the stimulating pulses are produced from the predetermined lower rate to a higher rate in accordance with a known relationship among the selected parameter, I RESP and D RESP in which the modulation signal is used to generate the rate control signal to control the interval between the cardiac stimulating pulses according to an empirical algebraic relationship; and applying the rate control signal to the pulse generator.