Figure 3

Changes in extracellular matrix. Illutrated are changes in the extracellular matrix that occur during hydraulic and lesional oedemas in spontaneous breathing (SB) and physiological and injurious mechanical ventilation (MV) early and late in the course of lung injury. Bold lines represent the new synthesis of heparan sulphate (HS)-proteoglycan (PG) or chondroitin sulphate (CS)-PG. During hydraulic oedema and in the early phase, the prevalent lesion is fragmentation of CS, whereas in the lesional oedema HS is damaged. In physiological MV, mainly CS-PG was fragmented, but the ongoing MV yields the fragmentation of both glycosaminoglycans. During injurious MV, although HS-PG and CS-PG are injured, collagen fibre content increases early and late in the course of lung injury. Thus, we hypothesize that in the early phase of lung injury collagen fibre synthesis could be beneficial in avoiding the rupture of glycosaminoglycans, minimizing interstitial oedema formation. Pi, interstitial pressure; W/D, wet weight:dry weight ratio.