Fig. 1

Strain (tidal volume divided by the functional residual capacity) and total lung capacity (y axis) are represented as a function of the applied transpulmonary pressure (x axis) [22]. In the resting position, the collagen fibers are folded within the elastic spring [23]. Increasing the transpulmonary pressure, the excessive strain may lead firstly to an inflammatory reaction and, when the collagen is completely unfolded, to stress at rupture. At ~ 12 cmH₂O transpulmonary pressure (i.e., the specific elastance), the initial lung volume is doubled [7]