The nature, severity and distribution of obstructive airway lesions in COPD studied by morphometry and computer-assisted 3-D reconstruction

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The severity of obstructive bronchial lesions and their distribution in the airway tree were studied in autopsy lungs from ten patients with various types of chronic obstructive pulmonary disease (COPD), where the changes of bronchial dimension were studied by morphometry and the 3-D distribution of obstructive lesions by computer-assisted 3-D reconstruction. A case of paraquat intoxication was added in order to study the airway changes in lungs with early fibrotic changes. In each case, morphometry was performed on microscopic lung sections where the initial diameter of bronchi was estimated from that of the accompanying pulmonary arteries. The varyingly constricted airways and arteries were standardized into a circular state by measuring the perimeter length L of the epithelial basement membrane (BM) and the internal elastic membrane (IEM) with a digital image analyzer; D(br), the anatomical diameter of an airway, and D(pa), that of an artery, were calculated at this state of completely stretched BM or IEM. Rs, the ratio of luminal stenosis by thickened epithelia, was also determined from the area of epithelium simultaneously measured. Three-D reconstruction of airway was performed in cases typically representing different types of obstruction; from microscopic, sometimes macroscopic serial sections, where the 2-D images were inputted into a computer which integrated in its display a 3-D picture. It was shown that in lungs with chronic bronchitis, the bronchial dimension did not significantly differ from that of ordinary lungs. Overt shrinkage of bronchial dimension was demonstrated in chronic obstructive bronchiolitis; in both diffuse panbronchiolitis (DPB) and broncho-bronchiolitis obliterans (BBO), narrowing of the peripheral airways combined with ectasis of the proximal bronchi proved to be a common feature. However, reconstruction disclosed an essential difference between these in the distribution of occlusive lesions, which mainly involved the respiratory bronchioles in DPB, while in BBO, the site of obstruction was from the terminal to slightly upper bronchioles. Also in pulmonary emphysema, the pattern of bronchial dimension was a narrowing in the periphery, both in the centrilobular and panlobular types. Especially worth of attention was that the study disclosed the presence of a type of COPD hitherto poorly defined. In a patient who had a 25-year history of COPD and died of respiratory failure, the lungs, only mildly emphysematous, were shown to have uniformly narrowed bronchioles; also mucus hypersecretion and elevated Rs appeared to have contributed to the obstruction.(ABSTRACT TRUNCATED AT 400 WORDS)