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How it works ?

 

The cycle is divided into four distinct phases: 1) inspiration phase: valves 2 and 3 are closed, valve 1 is opened, and the inspiratory pump moves up to insert the inspiratory volume of PFC, Vi, into the lungs; 2) endinspiration pause: valves 1 and 3 are closed; the positive end-inspiratory pressure, PEIP, is measured during this pause with the use of a pressure sensor positioned in the endotracheal tube, 12 mm proximal to its ending; 3) expiration phase: valves 1 and 4 are closed, valve 3 is opened, and the expiratory pump moves down to withdraw the expiratory volume of PFC, Ve, from the lungs; 4) end-expiration pause: valves 1 and 3 are closed; the positive end-expiratory pressure, PEEP, is measured during this pause through the use of the endotracheal pressure sensor. The expiratory pump and the inspiratory pump are the same but are controlled individually. Pump independence is used to 1) optimize PFC residing time in the gas exchangers by pushing the expired liquid as soon as possible in the oxygenators; this is done at the onset of the inspiration phase by opening valve 4 (valve 3 is closed) and by pushing the liquid present in the expiratory pump as fast as possible; 2) improve pressure measurement in the buffer reservoir by waiting until the latest possible moment to fill the inspiratory pump with oxygenated PFC; at the end of the expiration phase, the PFC is pumped from the buffer reservoir by opening valve 2 (valve 1 is closed); 3) modify FRC during ventilation according to the clinician’s request; the requested correction of FRC, V, is the PFC volume to retrieve from (if negative) or to add into (if positive) the lungs during one cycle; 4) compensate for small pumping errors and to deal with an eventual exceptional stoppage of the cycle, caused when reaching either an upper or lower pressure limit detected by pressure measurement in the endotracheal tube.