Fibrosing Alveolitis in the Adult Respiratory Distress Syndrome

In this issue, Clark and coworkers [1] make a valuable contribution to our understanding of the adult respiratory distress syndrome. They measure a biological marker of collagen synthesis, type III procollagen (procollagen III), in bronchoalveolar lavage fluid from patients with the adult respiratory distress syndrome. Their study indicates that elevated levels of procollagen III identify those patients at increased risk for death.

The rationale for their study was based on several previous observations. First, fibrosing alveolitis is a well-recognized morphologic finding in most patients dying with the adult respiratory distress syndrome [2, 3]. Second, increased levels of collagen have been found in the lungs of patients with the adult respiratory distress syndrome who die after the acute phase of lung injury [4, 5]. Third, because the N-terminal peptide of procollagen III is cleaved from the precursor procollagen molecule during collagen synthesis, elevated serum levels of procollagen III have been used as biochemical markers of collagen synthesis in surgical patients after major trauma and orthopedic surgeries [6, 7]. Fourth, increased levels of procollagen III in the serum or bronchoalveolar lavage fluid have been reported in pulmonary sarcoidosis and idiopathic pulmonary fibrosis [8, 9]. Fifth, in one study [10], a correlation was noted between histologic evidence of intra-alveolar fibrosis and elevated levels of procollagen III in bronchoalveolar lavage fluid from five patients with the adult respiratory distress syndrome, but the relation to survival was not examined.

The results of Clark and colleagues' study [1] indicated that the mean procollagen III levels in bronchoalveolar lavage fluid were threefold to fourfold higher at 3 and 7 days after the onset of the adult respiratory distress syndrome in patients who died …