Filling Methods and Apparatus for Implanted Medical Therapy Delivery Devices

A filling apparatus for use by an operator in delivering a liquid therapeutic agent into a refill chamber of a therapy delivery device through a non-conductive septum of the refill chamber wherein the septum, refill chamber and therapy delivery device are implanted subcutaneously in a patient, the apparatus comprising:

• a needle comprising a proximal end, a distal portion, a distal-most end having a piercing distal tip, a conduit extending along the needle, from a proximal opening at the proximal end to a distal opening located in proximity to the distal-most end, and a connector at the proximal end configured to connect to a syringe containing the liquid therapeutic agent, first, second and third electrodes located on the distal portion of the needle so that when the distal-most end of the needle is inserted through the septum and in the refill chamber the second electrode is located within the septum and wherein each of the first electrode is spaced distally or proximally from the septum and the third electrode is spaced proximally from the septum;
• a detection circuit attached to the proximal end of the needle and electrically coupled to the first, second and third electrodes of the needle, the circuit configured to measure a first impedance between the first and second electrodes, a second impedance between the second and third electrodes, and a third impedance between the first and third electrodes, and to compare each of the measured impedances to a threshold impedance as the needle is being guided through the patient's tissue to the refill chamber, and the circuit is further configured to generate a confirmation signal when the first and second measured impedances are greater than the threshold impedance and the third measured impedance is less than the threshold impedance, the signal indicating to the operator that the second electrode is within the septum and the distal-most end of the needle is in the refill chamber and the liquid therapeutic agent can be delivered.