Abstract: A closed pressure monitoring system (20) is disclosed in which a pump (27) delivers gas on a supply line (22, 29) through a first accumulator chamber (30) to a load device (21) and returns the gas on a return line (23, 28) through a second accumulator chamber (34) to the pump (27). After pressures in the first and second chambers stabilize, the pressures are compared, and a leak warning signal is given if the compared pressures changed with respect to one another over time. The system is particularly adapted to use a pressure sensor as the load (21) which is implanted within a human patient. The pressure sensor receives air from a restrictor (32) in the supply line (22, 29) and is operative to maintain the pressure in the supply line substantially equal to the pressure surrounding the sensor.

Abstract: An apparatus (10) which measures and monitors the pressure within a human body includes a pressure sensor (11) having a housing (30) closed by a pressure sensitive diaphragm (34) to define a plenum (35), an exhaust tube (36) mounted within the plenum (35) which terminates adjacent the inner surface of the diaphragm (34), and tubes (13, 15) which transmit a substantially constant flow of gas into the plenum and which withdraw gas from the exhaust tube (36) to a location remote from the body. Changes in pressure within the body cause the diaphragm (34) to alternately close and open the end of the exhaust tube (36), thereby resulting in an increase or decrease in the pressure within the plenum until an equilibrium pressure is reached. A source (12) of gas pressure is provided, as well as a means for providing a substantially uniform flow rate (R) and means for measuring the pressure (14) within the tube (13) that transmits the gas flow to the sensor (11).