Lung tissue mechanics and extracellular matrix remodeling in acute lung injury

This study was undertaken to test whether there is structural remodeling of lung parenchyma that could lead to tissue mechanical changes at an early p hase of varying degrees of acute lung injury (ALI). Tissue resistance (R), dynamic elastance (E), and hysteresivity (eta) were analyzed during sinusoi dal oscillations of rat lung parenchymal strips 24 h after intraperitoneal injection of saline (C) or paraquat (P [10, 15, 25, and 30 mg/kg]). These s trips were also stained in order to quantify the amount of collagen and of three types of elastic fibers (elaunin, oxytalan, and fully developed elast ic fibers) in the alveolar septa. E augmented progressively from C to P25, but the data from the P25 and P30 groups were not different (p < 0.0001). R and <eta> increased from C to P10 and from P15 to P25 (p < 0.001). Collage n fiber content increased exponentially with the severity of the injury. El aunin and fully developed elastic fibers remained unchanged in the five gro ups, while oxytalan fibers increased only in the P25 and P30 groups. In con clusion, the pronounced mechanical changes at the tissue level and fibroela stogenesis happened at an early phase of the disease and even in mildly abn ormal lung parenchyma.