Implantable capacitive absolute pressure and temperature sensor

An implantable capacitive implantable lead for providing signals representative of the magnitude of body fluid pressure at a selected site and ambient operating conditions, including body temperature, at the site comprising:

• an elongated implantable lead body having proximal and distal end sections and having first and second electrical conductors extending from the proximal end section to the distal end section, said proximal end adapted to be coupled to a biasing signal source, and said distal end section adapted to be implanted in a body position for measuring a varying body fluid pressure;
• and a implantable module formed in the distal end section of the lead body and coupled to said first and second electrical conductors, the implantable module further comprising:
• a module housing attached to said lead body adapted to be positioned in a body cavity and enclosing a hermetically sealed chamber;
• pressure deformable pickoff capacitor means for varying in capacitance in response to variations in fluid pressure having a first plate formed of a pressure deformable diaphragm of said module housing and a second plate spaced apart therefrom;
• reference capacitor means having a first plate formed of a non-deformable portion of said module housing and a second plate spaced apart therefrom;
• and
• pressure and temperature signal modulating circuit means within said hermetically sealed chamber and electrically coupled to said first and second electrical conductors.

A pressure sensor module having a housing enclosing a hermetically sealed chamber for implantation into a living body, said housing for attachment to an implantable device such that the housing is adapted to be positioned in a body so as to sense pressure therein and;

• pressure deformable pickoff capacitor means for varying in capacitance in response to variations in pressure exterior to said chamber having a first pressure deformable, substantially flat, diaphragm element with an interior surface and an exterior surface, said diaphragm element disposed on said housing so as to have said exterior surface thereof exposed to said body and the interior surface thereof facing interior to said chamber, said interior surface disposed to substantially parallel alignment with a second plate member spaced apart from the interior surface of said diaphragm and within said chamber, and having a conductive pickoff capacitor member lining or formed of a portion of said interior surface of said diaphragm element and having a second capacitor conductive member lining or formed of a portion of said second plate member spaced from said first conductive member;
• reference capacitor pressure sensing means having a first conductive capacitor member lining a relatively non-deformable portion of said diaphragm element of said interior surface and being electrically isolated from and non coincident with said pickoff capacitor first conductive member, and a second conductive capacitor member on said second plate spaced apart from said reference capacitor conductive member;
• pressure and temperature signal modulating circuit electrically coupled to said first and second electrical conductors.