An open-circuit liquid ventilation system includes a reservoir containing a breathable liquid, a patient interface receiving breathable liquid from the reservoir, a pump directing breathable liquid from the reservoir to the patient, a controller for the pump, and a tank for storing used breathable liquid. The system may be passive regarding expired liquid. Alternatively, the system may be active and include a bypass line connected to the pump such that used breathable liquid is drawn from the patient. The patient interface may be adapted to interface a gas ventilation system to facilitate a rapid conversion from gas to liquid ventilation. The system may include sensors monitoring pressure and volume parameters and may include an output displaying information including schematics and real time tracings regarding a ventilation procedure.