Biochemical changes in parenchymal lung tissue associated with posttraumatic respiratory failure.

We analysed the composition of parenchymal lung tissue from eleven multiply injured patients who died of protracted respiratory failure after an accident and six normal lungs. Lung wet and dry weights, protein, DNA, RNA and collagen amounts were determined in the lungs. Concentrations per dry weight of all parameters revealed only minor changes. Since there was a marked, time-dependent increase in both wet and dry weight, total lung contents of all components showed highly significant increases with survival time. Protein and RNA contents were elevated linearly in all patients, whereas DNA and collagen increased only in patients surviving more than 2 weeks. No correlation existed between biochemical data and a morphological fibrosis score, while morphometrically estimated cellularity and DNA concentration agreed well. Our results provide evidence that the reparative process for lung injury associated with traumatic shock is a tissue remodelling involving all tissue components in the long run.