Can high resolution computed tomography predict lung function in patients with chronic obstructive pulmonary disease?

Abstract

High-resolution computed tomography (HRCT) is a useful method for quantifying the extent of emphysema. Few reports have mentioned the relationships between HRCT scans and pulmonary function tests in chronic obstructive pulmonary disease (COPD). For diagnosis, COPD requires chronic airflow limitation and emphysema and/or chronic bronchitis. We examined 20 who were previous smokers with middle to moderate COPD. All were normocapnic with mean arterial oxygen pressure (PaO2) 77,52 +/- 16,789 mmHg. Forced spirometry, somatic plethysmography and cardiopulmonary exercise test were performed in each patient. HRCT was performed in both full inspiration and full expiration at three levels through the upper (at the aortic arch), lower (2 cm above the diaphragm), and middle lung (midpoint between upper and lower) levels. During expiration all pulmonary function parameters correlated with the HRCT grade in the middle right and left part of the lungs. The middle right part of the lung during expiration correlated statistically significant with MVV (r = -0.681, p = 0.001), forced vital capacity (FVC) (r = -0.477, p = 0.027), forced expiratory volumein 1 sec (FEV1) (r = -0.632, p = 0.002), resistance (r = 0.674, p = 0.001), residual volume (RV) (r = 0.733, p = 0.001), total lung capacity (TLC) (r = 0.696, p = 0.001), functional residual capacity (FRC) (r = 0.752, p = 0.001) and peak oxygen consumption during exercise (VO2) (r = -0.493, p = 0.023). The middle left part of the lung during expiration correlated statistically significant with MVV (r = -0.673, p = 0.001), FVC (r = -0.493, p = 0.027), FEV1 (r = -0.629, p = 0.003), resistance (r = 0.593,p = 0.005), RV (r = 0.601, p = 0.005), TLC (r = 0.546, p = 0.012), FRC (r = 0.594, p = 0.006) and peak VO2 (r = -0.525, p = 0.015). Forced expiratory volume in 1 sec (FEV1), which is a well-established measure of airflow obstruction, correlated with the HRCT grade (1) in the middle left part of the lung during inspiration (r = -0.468, p = 0.035) and during expiration (r = - 0.629, p = 0.003) (2) in the lower right lung during inspiration (r = -0.567, p = 0.007) and during expiration (r = -0.558, p = 0.008) (3) in the lower left lung during inspiration (r = -0.542, p = 0.011) and during expiration (r = -0.558, p = 0.008) (4) in the upper right lung during expiration (r = -0.469, p = 0.037) (5) in the upper left lung during expiration (r = -0.463, p = 0.035) and (6) in the middle right lung during expiration (r = -0.632, p = 0.002). According to our results HRCT was a valuable tool for evaluating the severity of COPD--especially the middle right and left part of the lungs, during expiration--and correlated well with pulmonary function tests.