Patent ID: 8449474

Claim:
A self-actuated cylinder comprising: a cylinder housing comprising electro-magnetic force generating means to generate electro-magnetic forces; a piston within the cylinder housing; a position sensing device for measurement of a position of the piston with respect to the cylinder housing; front and rear air chambers within the cylinder housing on opposite sides of the piston; a flow pathway to permit airflow between the front and rear air chambers; a front cover plate covering the front air chamber, and comprising a front port to allow an exchange of air between the front air chamber and a respiratory system; a rear cover plate covering the rear air chamber comprising an interface to allow an exchange of air between the rear air chamber and an external environment; and a pressure transducer to measure a pressure drop across the flow pathway, wherein the electro-magnetic forces act directly on said piston to displace said piston within said cylinder housing, and the pressure measurement is used to determine air flow from the front port when the piston is held in a forward position, and the pressure and position measurements are used to determine an input impedance of the respiratory system attached to the front port when the piston oscillates according to a predefined waveform.