Relationship between lung functions and extent of emphysema as assessed by high-resolution computed tomography in patients with COPD

Background: To investigate whether the extent of emphysema, visually confirmed by high resolution computed tomography (HRCT) in patients with COPD were associated with different indices of lung functions. Methods: Eighty-two patients with COPD underwent HRCT scanning, visual assessment of HRCT scan was used in the calculation of extent of emphysematous destruction. The patients were clinically stable at the time of the evaluation. All subjects were smokers or past smokers who had smoked>10 pack-years. Results: The mean visual emphysema score in all patients was 2.21±1.11. While the mean emphysema score in patients with COPD GOLD (Global Initiative for Chronic Obstructive Lung Disease) stage 3 was 2.88 ±1.03, it was 1.54 ±1.16 in COPD GOLD stage 2 (p<0.001). There was a significant correlation between the emphysema score and the numbers of pack/years smoked (R=0.58, p<0.001). The visual emphysema score was inversely correlated with the FEV1(r = -0.56, p<0.0001), FVC ( r= -0.38, p=0.001), FEV1/FVC ( r=-0.43, p<0.001),PEF(r=-0.44, p<0,001) and with carbon monoxide diffusion capacity (DL CO )( r = -0.50, p<0.001). In our study population, patients had a limited expression of the disease as represented by low scores in Saint George Respiratory Questionnaire (SGRQ), and there was no correlation between emphysema score and SGRQ. Conclusions: HRCT visual scores correlated with functional indices of airflow obstruction and impaired lung diffusing capacity in patients with stable COPD of varying severity, the presence of pulmonary emphysema is best represented by the FEV1 and DL CO .