Self-actuated cylinder and oscillation spirometer

1. 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.

2. The self-actuated cylinder according to claim 1 , wherein the interface comprises holes and the external environment is an ambient environment.

3. The self-actuated cylinder according to claim 1 , wherein the interface comprises a rear port and the external environment is a ventilator circuit.

4. The self-actuated cylinder according to claim 1 , further comprising:

a second pressure transducer for measurement of a pressure difference between the front air chamber and atmosphere.

5. The self-actuated cylinder according to claim 1 , wherein the piston comprises a reflective surface on a rear surface thereof and the position sensing device comprises:

an off-center laser diode projecting a laser beam onto the reflective surface; and

an optical position sensor receiving the reflected laser beam.

6. The self-actuated cylinder according to claim 5 , further comprising:

electronic circuitry to servo-control the position of the piston by energizing the electro-magnetic force generating means based on readings from the position sensing device.

7. The self-actuated cylinder according to claim 1 , wherein the front port is fitted with an anti-bacterial filter.

8. The self-actuated cylinder according to claim 1 , further comprising attachment means for attaching the cylinder to an external structure.