Abstract: In a preferred embodiment, there is provided a substantially rigid and self-supporting housing divided into two separate chambers and chamber spaces thereof each having mounted therein a separate lung-simulating flexible non-resilient enclosure structure and enclosure space thereof isolated from fluid flow communication with the chamber spaces, with the respective enclosure spaces being in flow communication with each other through an interconnecting conduit having mounted within conduit space a tube having an inflatable balloon mounted therearound adapted for inflation and deflation from an exterior location exterior to the interconnecting conduit, and each of the chamber spaces having a bellows mounted in flow communication with chamber space thereof with the bellows mounted above the flexible non-resilient enclosure structure within that chamber space, and a portion of each wall of the respective two separate chambers being flexible and in flow contact with exterior bellow and space thereof adapted to join