Liquid ventilator  A liquid ventilator is similar to a medical ventilator except that it should be able to ensure reliable total liquid ventilation with a breatheable liquid (a perfluorocarbon). Liquid ventilators are prototypes that may have been used for animal experimentations but experts recommend continued development of a liquid ventilator toward clinical applications. In total liquid ventilation (TLV), the lungs are completely filled with a perfluorocarbon (PFC) liquid while the liquid ventilator renews the tidal volume of PFC. The liquid ventilator operates in mandatory mode: it must force the PFC in and out of the lungs with a pumping system. The pumping system is either a peristaltic pump (in the simplest liquid ventilators) or two piston pumps (in the most advanced liquid ventilators). Because of the PFC viscosity, the head loss in the airways requires a low negative driving pressure during the expiration phase that can collapse the airways. This is the choked flow phenomenon in TLV which compromises the minute ventilation and consequently the gas exchanges. To address this limitation, liquid ventilator integrates a control of the pumping system. The introduction of computers in liquid ventilators to control the pumping system provides different control modes, monitoring and valuable data for decision making. The liquid ventilator is always volume-controlled because the specified tidal volume of PFC must be accurately delivered and retrieved. It is also pressure-limited because it must stop the expiratory or inspiratory phase when a too low, or a too large, driving pressure is detected. However, during the expiratory phase, the expiratory flow can be commanded by an open-loop controller or a closed-loop controller:  Also, during the inspiratory phase, the volume-controlled mode is realized by open-loop or closed loop control of the PFC flow. The liquid ventilator removes Carbon dioxide (CO2) from the PFC by saturating it with oxygen (O2) and medical air. This procedure can be performed with either a membrane oxygenator (a technology used in extracorporeal oxygenators) or a bubble oxygenator. The liquid ventilator heats the PFC to body temperature. This is performed with a heat exchanger connected to the oxygenator or with dedicated heaters integrated in the oxygenator. The oxygenator and the heater produce PFC vapor which is recuperated with a condenser in order to limit the evaporation loss (the PFC is a greenhouse gas).