Objective: To estimate the morphologic characteristics of chronic obstructive pulmonary disease (COPD) induced pulmonary fibrosis.
Methods: 41 autopsy cases of COPD were chosen as the study group and other 10 autopsy cases died from non-respiratory diseases as control group. Histochemical stain and image quantitative analysis were used to identify the type of collagen.
Results: In 36 cases (88%) of study group, fibrosis proliferation could be seen in peri-bronchial area, especially in the bronchi under grade VI. Respiratory bronchiole and alveoli were also involved in 11 cases. The main component of collagen in fibrosis area was identified as type III collagen by sirius red stain, reticular fiber could also be seen by Gomori stain. The type III collagen in alveoli distributed interruptedly. Image quantitative analysis showed: the integral optical density (A) of type III collagen was much higher than that of type I collagen in peri-bronchial area (P < 0.01); Both A of type III and type I collagen in peri-bronchial area were higher than that in alveolar area (P < 0.01). Mucous purulent plugs, interrupted elastic fibers in bronchial wall and chronic inflammation accompanied with lymphocytes infiltration in fibrosis area could also be seen.
Conclusions: COPD induced pulmonary fibrosis distributed mainly in peri-bronchial area, especially in the bronchi under grade VI. The main component of proliferative collagen was type III collagen. The genesis of pulmonary fibrosis might be associated with chronic inflammation accompanied with lymphocytes. Peri-bronchial fibrosis, interrupt of elastic fibers in bronchial wall caused the bronchial lumen narrowed or collapsed making both airway obstruction and ventilation insufficiency deteriorated.