Figure 5
Pressure-volume curves obtained in ZEEP conditions and at PEEPvalues of 5, 10 and 15 cmH2O in two patients with ARDS. In thepatientwho had a convex curve in ZEEP conditions (top left panel), PEEP did notinduce any alveolar recruitment. When the different PEEP levels were appliedthe pressure-volume curves appeared superimposed on the curve obtained in ZEEPconditions, indicating an over-distension of the lung (bottom left panel). Inthe patient who had a concave curve in ZEEP conditions (top right panel) PEEPdisplaced the curve upwards, indicating alveolar recruitment (bottom right). The increase in lung volume between ZEEP and PEEP for a given alveolar pressure(20 cmH2O) is the recruited lung volume. From Ranieri et al[17].