Implantable pressure transducer

A system for measuring biological pressures, comprising:

• an elongated and biologically implantable housing having an axis of elongation;
• a capacitor assembly mounted in the housing;
• an inductor assembly mounted in the housing and connected across the capacitor to form a resonant L-C circuit;
• one of the assemblies being of coaxial form and including an axially movable element for varying the reactance thereof, the element being movable along the axis of elongation;
• pressure-sensing means mounted on the housing and effective to generate a displacement in response to applied pressure;
• means connecting the pressure-sensing means and the axially movable element whereby displacement of the pressure-sensing means is transmitted by the connecting means to move the element and thereby vary the resonant frequency of the L-C circuit in response to applied pressure;
• a flexible covering secured to the housing and extending over the pressure-sensing means to form a sealed clearance space between the covering and pressure-sensing means, and further including a body of liquid filling the clearance space whereby a biological fluid pressure to be sensed is exerted on the covering and transmitted through the covering and liquid to the pressure-sensing means;
• the implantable housing being free of external wired connections and having outer surfaces formed of materials suitable for human implantation, the inductor and capacitor assemblies being isolated within the housing against contact with biological material in which the transducer is implantable;
• and
• external means for wireless transmission of electromagnetic energy to the implantable L-C circuit, and for detecting the resonant frequency of the circuit.