Relation between small airways disease and parenchymal destruction in surgical lung specimens

The relation between small airways disease and parenchymal destruction was investigated in lungs and lobes removed at surgery from 27 patients aged 15-70 years. Eight of the 27 patients were life-long non-smokers. The degree of small airways disease was assessed by semi-quantitative grading (SAD score) and by measuring diameter and wall thickness of membranous bronchioles. Parenchymal destruction was measured in three ways. Firstly, the number of alveolar attachments on membranous bronchioles per millimetre of circumference (AA/mm) was counted; the number of broken attachments was subtracted from the total AA/mm to give the numbers of intact attachments (normal AA/mm). Secondly, a point counting technique was used to give a destructive index (DI). Thirdly, the mean linear intercept (Lm) was determined. Total and normal AA/mm correlated negatively with the SAD score of membranous bronchioles (rs = -0.48 and -0.51) and with wall thickness (rs = -0.37 and -0.45) and DI correlated with wall thickness (rs = 0.5) and with the SAD score of respiratory bronchioles (rs = 0.53). Lm did not correlate with indices of small airway disease and total and normal AA/mm did not correlate with diameter. Multiple regression analyses showed that the correlation of total AA/mm with the SAD score of membranous and respiratory bronchioles and with wall thickness were not confounded by age or smoking. It is concluded that small airways disease is related to destruction of peribronchiolar alveoli, and it is postulated that small airways disease has a direct role in the causation of centrilobular emphysema.