Pulmonary fibrosis in severe acute respiratory failure.

Diffuse interstitial fibrosis often follows severe acute lung injury of diverse causes. Total lung collagen (g per m2 of body surface area) was determined in 12 patients who died at various times after severe acute respiratory failure (ARF). The total collagen content of each lung was calculated from the mean concentration of collagen (hydroxyproline × 7.23) in numerous tissue samples taken from one to 3 lobes and the total weight of the lung. These results were compared to those obtained with 9 normal lungs. In 2 patients who succumbed during the first 10 days of ARF, total lung collagen was within the normal range, whereas it was abnormally high in patients who survived for longer periods (12 to 29 days). Morphologic evidence of fibrosis correlated with chemical results in the patients with ARF. After three to 4 weeks of ARF, the lungs of all patients had severe and diffuse interstitial fibrosis as evidenced by histologic assessment; in these lungs, the total collagen content was increased two- to 3-fol...