The Effects of Age, Obesity and Smoking on the Lung Lobar Volume in Healthy Adult

In a recent Study, it was established that computed tomography (CT) was a useful and reliable method for the measurement of lung lobar volume. In order to assess the possibility of applying this method to clinical practice, we measured lobar volumes of normal human lung using CT in routine settings. The subjects were 60 men and women who were totally free of symptoms or history of pulmonary disease, ranging in age from 21 to 78 years. The CT scans were obtained from the apex to the base of the lung with the same technique as in clinical use (contiguous-1-cm sections). The outlines of the lung lobes were traced with a digitizer on CT film and the area of the lung lobes in the crossectional plane was calculated using a personal computer. The lobar volume was determined by the thickness of scan space being multiplied by the total area of all slices in each lobe. We investigated the relationship between the ratios of lobar volume to the whole lung volume by CT and three parameters (age, obesity index and smoking index). The ratio of the left upper lobe to the whole lung volume (LUL%) was greatest (25.4%), followed by those of the right lower lobe (RLL%), right upper lobe (RUL%), left lower lobe (LLL%) and right middle lobe (RML%). The ratios of bilateral upper lobes (RUL%, LUL%) increased significantly with age, obesity index, and smoking index. On the other hand, the ratios of bilateral lower lobes (RLL%, LLL%) decreased significantly with the same three parameters. The correlations between smoking index and the ratios of lobar volumes mentioned above, however, were not significant when the effect of age and obesity index were eliminated. We conclude that aging and obesity are important factors for quantitative assessment of lun