PROCEDE ET APPAREIL DE MESURE DE LA RESISTANCE OHMIQUE DU CONTACT ENTRE UNE ELECTRODE ET UN TISSU CORPOREL AUQUEL ELLE EST FIXEE

L'INVENTION CONCERNE UN PROCEDE ET UN APPAREIL DE MESURE DE LA RESISTANCE OHMIQUE DU CONTACT ENTRE UNE ELECTRODE ET UN TISSU CORPOREL AUQUEL ELLE EST FIXEE.CET APPAREIL COMPORTE UN GENERATEUR 10 D'IMPULSIONS RELIE A UNE ELECTRODE QUI EST FIXEE A UN TISSU CORPOREL, PAR EXEMPLE LE COEUR D'UN PATIENT. LE GENERATEUR 10 PEUT FAIRE PARTIE D'UN STIMULATEUR CARDIAQUE. UN DISPOSITIF, CONNECTE AU TISSU CORPOREL ET A L'ELECTRODE, DETERMINE LA TENSION INSTANTANEE ENTRE LE TISSU CORPOREL ET L'ELECTRODE A L'ATTAQUE D'UNE IMPULSION PRODUITE PAR LE GENERATEUR 10. UN CIRCUIT DE TRAITEMENT DE SIGNAUX ANALOGIQUES, RELIE AU DISPOSITIF PRECEDENT, DETERMINE LA RESISTANCE OHMIQUE DE CONTACT A PARTIR DE L'AMPLITUDE DONNEE DU GENERATEUR ET DE LA TENSION INSTANTANEE. UN ELEMENT, RELIE A CE CIRCUIT DE TRAITEMENT, REALISE UN AFFICHAGE NUMERIQUE DE LA RESISTANCE OHMIQUE DU CONTACT DE L'ELECTRODE.DOMAINE D'APPLICATION: IMPLANTATION DE L'ELECTRODE D'UN STIMULATEUR CARDIAQUE. A method and apparatus are disclosed for measuring the ohmic, that is, purely d-c, resistance at the area of contact between cardiac tissue and a pacemaker electrode surgically implanted in the heart of a patient requiring a pacemaker. The contact resistance is measured by apparatus connected across the electrical circuit formed by the electrode and heart. The apparatus includes circuitry for sampling and holding the instantaneous voltage across the electrical circuit formed by the electrode and heart at the onset of a pulse generated by the pacemaker pulse generator, at which time the effect of a parallel capacitance in the electrical circuit formed by the pulse generator, electrode wire, electrode, heart, and return path through the body to the pulse generator is such that the current initially produced is determined only by the voltage and equivalent output impedance of the pulse generator, the resistance of the electrode wire, and the resistance at the area of contact between cardiac tissue and the electrode. The apparatus further includes analog signal processing circuitry for deriving the contact resistance from the instantaneous voltage based on an equivalent circuit model for the electrical circuit formed by the pacemaker and the heart taking into account the effect of the parallel capacitance at the onset of a pulse. The apparatus also includes a device for displaying the measured contact resistance. The disclosed method and apparatus are also applicable for measuring the ohmic contact resistance of an elec