Abstract: A wireless, surgically implantable pressure transducer for measuring pressure of fluid or tissue in a body chamber such as a brain ventricle of a patient suffering hydrocephalus or a head injury. The transducer includes an inductor and a capacitor connected in parallel to form a resonant L-C circuit. One of these reactive components is variable, and a bellows (or similar pressure-sensitive force-summing device) is mechanically connected to the variable component to vary the value of capacitance or inductance and hence the resonant frequency of the L-C circuit in response to pressure changes of the fluid in which the bellows is immersed. The transducer is electromagnetically coupled to an external source of variable-frequency energy such as a grid-dip oscillator, enabling external detection of the transducer resonant frequency which is a measure of the fluid pressure being sensed.

Abstract: A wireless, surgically implantable pressure transducer for measuring pressure of fluid or tissue in a body chamber such as brain ventricle of a patient suffering hydrocephalus or a severe head injury. The transducer includes a coaxial variable capacitor electrically connected across an inductor to form a parallel resonant L-C circuit. Alternatively, a coaxially variable inductor may be connected across a capacitor to form the L-C circuit. A bellows is mechanically connected to the variable component to vary the value of capacitance or inductance and hence the resonant frequency of the L-C circuit in response to pressure changes of the fluid in which the bellows is immersed. The transducer is electromagnetically coupled to an external source of variable-frequency oscillatory energy such as a grid-dip oscillator which enables external detection of the transducer resonant frequency which is in turn indicative of the level of fluid pressure being sensed.