Lung attenuation measurements in healthy young adults

Background: High-resolution computed tomography (HRCT) attenuation measurements may be more sensitive in finding early emphysematous changes in relatively young subjects than lung function measurements. Objectives: To define lung attenuation parameters in smokers and never-smokers. Methods: A prospective comparative study in a university hospital setting was designed with 20 healthy smoking and 20 nonsmoking volunteers. Attenuation measurements on spirometrically controlled HRCT at three levels in the upper half of the lungs at 10% and 90% of vital capacity (VC10% and VD90%) were done, and lung function measurements were performed. Results: Mean lung attenuation (MLD) and pixel index (PI) were correlated with lung function and smoking history. Small attenuation differences in the left and right lung were found but no sex-related differences. At main carina (MC) level, the PI was higher at VC90% (p < 0.0001) but lower at VC10% (p < 0.01) compared to the apex. Age correlated with attenuation parameters at VC10%, whereas for pack-years no correlation was found. There were attenuation correlations with VC (PI: R = 0.31, p < 0.05 at VC10%/90%), residual volume (MLD: R = -0.31, p < 0.05 at VC10%), and total lung capacity (PI: R = 0.31, p < 0.05 at VC10%/VC90%). Conclusions: Lung attenuation during inspiration was lower at the MC level than at the top, but higher on expiratory scans. No sex-related differences were found. Lung attenuation decreases with age on expiratory scans. This seemed to be of more importance than the amount of pack-years of smoking. A relationship with lung function parameters is not uniformly proven.