Fig 5.
Realistic distributions of opening and closing pressures of lung units in ARDS. Arrows illustrate the range PEEPTOT to PPLAT under different ventilation regimes. Arrow 1 refers to obsolete high VT/low PEEP ventilation at which most lung units undergo RECOREX, while high PPLAT causes barotrauma. Arrow 2 represents moderate VT/high PEEP ventilation. Only units with high closing pressure undergo RECOREX, but barotrauma remains important. Arrow 3 illustrates moderate VT/low PEEPTOT. Low PPLAT prevents barotrauma, but many lung units collapsing during expiration undergo RECOREX. Arrow 4 illustrates very low VT/high PEEP ventilation. Low PPLAT prevents barotrauma. Only those units with particularly high closing pressures represented by the pink area will close. If these units also have high opening pressures (pink area), they will remain collapsed throughout the breath so as to fully prevent RECOREX.