Dynamic loops during three modes of ventilation inscribed into the quasistatic pressure–volume curve of the respiratory system of an animal after lung washes. Loop A: tidal insuflation with a positive end-expiratory pressure (PEEP) below the lower inflection point before a sustained inflation. Loop B: tidal insuflation with a PEEP below the lower inflection point after a sustained inflation. Loop C: PEEP higher than the lower inflection point after a sustained inflation. Sustained inflation promoted alveolar recruitment at low PEEP levels (loop B). Sustained inflation superimposed on high PEEP favored alveolar overdistension in this model of surfactant depletion (loop C). Reproduced with permission from Rimensberger and coworkers .