Abstract: A medical diagnostic tool provides a fixture mounted on a cart, the fixture having an inspiratory conduit joined with an expiratory conduit, with both joined to a patient interface. An air inlet, and an inlet valve are interconnected in series by the inspiratory conduit; and a manometer is interconnected with the inspiratory conduit between the inlet valve and the patient interface. An air outlet, a spirometer, and an outlet valve are interconnected in series by the expiratory conduit, and a side-stream capnometer is interconnected with the expiratory conduit between the outlet valve and the patient interface. The inlet valve and the outlet valve each enable air flow in only one direction. The inlet valve further provides a shutoff, which when activated, prevents air flow through the inlet valve.