Abstract: An electronic circuit included in a pacer detects the impedance between two electrodes connected to it and made up by the conducting part of the pacer case (B) and by an auxiliary subcutaneous lead placed in the chest or by an electrode placed on the insulating part (C) of the case itself. The changing geometry of the chest, due to pulmonary ventilation, determines the impedance variations. The electronic circuit, by processing the impedance signal is able to automatically adjust the stimulation rate of the ventricle and/or of the atrium between minimum and maximum preset values according to the activity levels of the patient.

Abstract: A low electric energy consumption circuit to detect parameters associated to the patient's respiration, suitable for the realization of implantable devices, such as implantable and physiologic pacemakers, is designed to detect, at the same sample rate of the impedance in a part of the patient's body, the voltage variations V (.DELTA.ZL) corresponding to said impedance with both negative and positive variations from the base line. According to a first scheme, these variations V' (.DELTA.ZL) are subsequently processed by means that produce a clean V.sub.OUT signal, e.g. a squared one, which shows a transition every time that the difference between minimum value and maximum value and maximum value and minimum value of the input signal exceeds a fixed a preferably programmable value. According to a second scheme, said variations V' (.DELTA.ZL) are processed by means producing a signal proportional to the variation speed of the body impedance and by means producing a signal Vm (.DELTA.

Abstract: An implantable cardiac pacemaker in which the stimulation rate is determined through a suitable programmable algorithm by the patient's ventilation rate which is taken by measuring the impedance variations throughout a distance within the human body; preferably a distance within the thoracic region that goes between the pacemaker box and the lead which is placed subcutaneously. The pacemaker is constructed to detect variations, even rapid ones, of the corporeal impedance and to discriminate substantial variations attributable in all probability to a respiratory act, as well as to limit the drain of electrical energy.