Correlation Of Mean Lung Density And Air Trapping With Smoking At HRCT Of The Lung In 114 Asymptomatic Subjects

PURPOSE: To assess the value of mean lung density and the frequency and degree of air trapping at HRCT in relation to smoking history in asymptomatic subjects. MATERIALS AND METHODS: HRCT of the lung was performed prospectively at end inspiration and end expiration in 114 subjects (57 smokers, 57 nonsmokers) without any history of pulmonary diseases and without present pulmonary symptoms. The MLD' (average of the mean lung density of six spots) of the upper, middle and lower lung and characteristics of air trapping were evaluated according to age and smoking status.RESULTS: (1) The overall frequency of air trapping was 55.396(63 of 114 subjects) and manifested as a mosaic pattern with lower lobe predominance. (2) The EMLD' had a significant correlation with age in nonsmokers (p<0.05). (3) The UIMLD' of smokers was lower than that of nonsmokers in 61 years~ group (p<0.05). There was no significant difference of the IMLD' between smokers and nonsmokers in other groups according to their age. The MEMLD' of smokers in 51-60years group and the MEMLD' and LEMLD' of smokers in 41-50years were lower than that of nonsmokers (p<0.05). There was no significant difference of EMLD between smokers and nonsmokers in other groups according to their age. (4) The EMLD' and the grading of air trapping of smokers had a significant correlation with smoking history. The LEMLD' of heavy smokers was lower than that of smokers with a smoking history of less than 50 pack-years (p<0.05). The MEMLD' of heavy smokers was lower than that of smokers with a smoking history of less than 25 pack-years (p<0.05). The grading of air trapping of heavy smokers in upper and middle lung were higher than that of smokers with a smoking history of less than 50 pack-years (p<0.05); and in lower lung was higher than that of smokers with a smoking history of less than 25 pack-years (p<0.05).CONCLUSION: HRCT is a useful tool to analysis CT imaging quantitatively. The mean lung density of smokers is a dynamic course as a result of respiratorybronchiolitis and air trapping. Smoking makes the old more affectable to emphysema.Heavy smokers tend to have heavier air trapping and emphysema.Abbreviations:EMLD' : MLD' at expiratoryIMLD' : MLD' at inspiratoryL/M/UEMLD' : MLD' of lower/middle/upper lung at expiratoryL/M/UIMLD' : MLD' of lower/middle/upper lung at inspiratoryPostgraduate: Wei Zhou(Radiographic Diagnosis) Directed by: Xiao Dong Lu...