Motion sensor for implanted medical device

An implantable digital motion sensor for use with a pacemaker, said pacemaker electrically coupled to said sensor for receiving a digital signal therefrom, said sensor generating a digital signal as a function of the physical motion to which said motion sensor is subjected, said digital signal being used by said pacemaker to indicate the amount of physical motion to which said pacemaker is subjected, said sensor comprising:

• housing means for implantation in a body, said housing means comprising a housing affixed to said pacemaker, said housing having a plurality of electrodes therein;
• means for making and breaking electrical contact with said plurality of electrodes as a function of external forces applied to said pacemaker;
• and
• means for coupling a voltage potential between said plurality of electrodes, said voltage potential having first and second voltage levels associated therewith, the voltage present at a given electrode thereby varying between said first and second voltage levels as a function of whether electrical contact has been made or broken between said given electrode and at least one other of said plurality of electrodes, said voltage at said given electrode comprising said digital signal.

A method of sensing the physical motion of a patient having a pacemaker comprising the steps of:

• (a) placing a conductive element in a sealed housing, said housing having a plurality of electrodes spaced therein, said conductive element having a size that allows it to freely move within said housing when subjected to external forces, and to make simultaneous and momentary electrical contact with at least two of said electrodes as it moves within said housing;
• (b) implanting said housing, conductive element, and electrodes within said patient;
• (c) monitoring selected pairs of said electrodes to determine when electrical contact is made therebetween;
• (d) measuring the time interval or frequency between the making of electrical contact between the electrodes of step (c);
• and
• (e) determining the change of the measurement of step (d), which change is indicative of the change in physical motion of the patient.