Respiratory system PV curve from ARDSp is shifted down and right with respect to ARDSe. When fractional volumes are considered these differences are also significative. The lung PV curve of ARDSp is shifted in a similar way. However, when considering fractional volumes, the differences are only significative in the low pressure range (0–10cmH2O). The chest wall PV curve in the ARDSp group is, as expected, shifted to the left.