Abstract: A compact system that simulates a pair of human lungs. The lungs can be controlled to breathe spontaneously under a computer program, or the lungs can also be ventilated from a standard mechanical ventilator used in anesthesiology. Lung compliance and resistance can be varied during a simulation exercise to simulate various physiological disease conditions. The unit is compact and will fit into the chest cavity of a mannequin. The device is especially useful for the training of anesthesiologists, especially with respect to ventilating patients.

Abstract: An electronic compensation circuit for a pneumatic load bearing bellows system closed on position, in which a servo valve provides pressure to the bellows to actuate the top of the bellows to move to a predetermined position in response to a control signal. The compensation circuit (42) cancels at least one load-variable system characteristic which, if not cancelled would cause system instability at system gain levels which are necessary for desired system response. The compensation circuit electronically provides a replacement system characteristic which permits the system to be operated at a gain level substantially higher than the gain level at which the uncompensated system goes unstable.