The destructive index and early lung destruction in smokers

The destructive index (DI), a measure of alveolar septal damage and emphysema, has been proposed as a sensitive index of lung destruction that closely reflects functional abnormalities, especially loss of elastic recoil. To better understand the progression of lung destruction in smokers, we studied the contribution of its principal components: breaks in the alveolar septa (DIb) and the presence of emphysematous spaces (DIe), and compared them to the mean linear intercept (Lm) and DI as originally described. To do this we employed lungs obtained at autopsy from non-smokers and smokers. Lungs were selected by emphysema score (ES) so that all cases were emphysema free (nonsmokers and seven smokers) or had minimal emphysema (nine smokers; ES = 5). Of these indices, only DIb was significantly increased in the lungs of smokers: 17.8 +/- 1.2 versus 12.4 +/- 1.6, p less than 0.05. We also investigated the regional distribution of destruction by comparing results in upper and lower lobes. DIe, but not DIb, was significantly increased in upper lobes of smokers. These data support the notion that increases in DI in the lungs of smokers that occur before increases in Lm or ES reflect the presence of alveolar septal breaks and highlight the importance of alveolar septal destruction as a precursor to the development of airspace enlargement in the lungs of cigarette smokers.