A differential pressure sensing device is fully implanted in the body of a patient to monitor internal pressure such as intracranial pressure. A movable element in the sensor communicates on one side with the internal pressure to be measured and on the other side with an external pressure which is applied...http://www.google.fr/patents/US4206761?utm_source=gb-gplus-shareBrevet US4206761 - Pressure-balanced telemetric pressure sensing method
