Correlation of lung functioning test and lung parenchymal changes on HRCT in patients with smokers and nonsmokers

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Experimental studyWe evaluated lung attenuation and attenuation changes and frequency of air trapping (AT) with respiration and body positions on high-resolution CT. The difference in lung attenuation was a little larger in the supine position than prone position. We believe that CT assessment in the supine position is suitable for evaluating for lung parenchymal changes. ATwas seen in 67% of subjects. It appeared in dependent lung regions and disappeared after changing body positions. The ratio of lung cross-sectional area on expiratory scan to inspiratory scan was 0.52 on the group with AT, and 0.69 on the group without AT (P<0.001). Body mass index was also higher in subjects with AT (P<0.05) than those without AT.Clinical studyWe examined lung attenuation changes and presence of AT and emphysematous lung change on HRCT In 36 smokers and 23 non-smokers AT was found in 19 smokers (53%) and 19 non-smokers (89%) (p<0.05). Emphysematous change was found in 16 smokers (44%). Mean of the percent of the forced expiratory volume in 1 second (FEV1.0%) was severely decreased in smoker group (68%). It was 84% in nonsmoker group (P<0.001). We compared the presence of AT with lung functioning test in smoker group. There was remarkable difference (P<0. 001) in FEV1.0% between group with AT (76%) and group without AT (60%). In patients without AT, lung attenuation was somewhat lower than those with AT and lung attenuation change was less. There was no statistical difference in the lung functioning test between the patients with and without emphysematous change. Furthermore, there was no remarkable difference in the lung attenuation and attenuation changes between two groups. We concluded that the presence of AT is not pathological changes related smoking and other respiratory diseases. Absence of AT is strongly related to lower lung. functioning test in smokers.