Implantable pump with reservoir level detector
An implantable pump includes a base plate and a can that are parts of the pump housing. The base plate bottom divides the housing into a first electronics chamber and a second chamber. A bellows mechanism is connected to the base plate and is disposed within the second chamber. The bellow mechanism has an expandable sidewall and a bottom plate. The bellow mechanism divides the second chamber into a medicament receiving portion and a non-medicament-receiving portion. The bellow mechanism has an intermediate plate disposed within the medicament-receiving portion. A coil is disposed in a recess on the lower surface of the base plate, and the coil is spaced from an internal wall of the recess. The amount of fluid remaining in the implantable pump can be monitored by energizing the coil. A primary magnetic field is generated by the energized coil. A secondary magnetic field, which is dependant on the position of the bottom and intermediate plate of the bellow mechanism, couples back to the primary field affecting the electrical characteristics of the coil. The amount of fluid remaining in the reservoir is determined based on the resulting changes in the electrical characteristics of the coil.
1. A method of monitoring the amount of fluid remaining in an implantable pump, the pump having a housing; a base plate connected to said housing, said base plate dividing said housing into an electronics chamber and a second chamber; a bellow mechanism connected to said base plate and disposed within said second chamber, said bellow mechanism having an expandable side wall and a bottom plate, said bellow mechanism dividing said second chamber into a medicament receiving portion and a non-medicament receiving portion, said bellow mechanism having a intermediate plate disposed within said medicament receiving portion, the intermediate plate being directly connected to the expandable side wall portion of the bellow mechanism, the intermediate plate being movable within the medicament receiving portion depending upon the amount of medicament remaining in the medicament receiving portion; and a coil disposed on the lower surface of the base plate; the method comprising the steps of:
energizing the coil such that a magnetic field, that is affected by the location of the intermediate plate within the medicament receiving portion, is generated by the coil; and determining the amount of fluid remaining in the reservoir based on the electrical characteristics of the coil.
2. The method of claim 1 , further comprising the step of:
generating a frequency signal based on the value of the inductance; and
measuring the value of the frequency.