Association of Respiratory Functional Indices and Smoking with Pleural Movement and Mean Lung Density Assessed Using Four-Dimensional Dynamic-Ventilation Computed Tomography in Smokers and Patients with COPD

PURPOSE: To correlate the ratio of the non-dependent to dependent aspects of the maximal pleural movement vector (MPMV(ND/D)) and gravity-oriented collapse ratio (GCR(ND/D)), and the mean lung field density (MLD) obtained using four-dimensional (4D) dynamic-ventilation computed tomography (DVCT) with airflow limitation parameters and the Brinkman index. MATERIALS AND METHODS: Forty-seven patients, including 22 patients with COPD, 13 non-COPD smokers, and 12 non-smokers, with no/slight pleural adhesion confirmed using a thoracoscope, underwent 4D-DVCT with 16 cm coverage. Coordinates for the lung field center, as well as ventral and dorsal pleural points, set on the central trans-axial levels in the median and para-median sagittal planes at end-inspiration, were automatically measured (13–17 frame images, 0.35 seconds/frame). MPMV(ND/D) and GCR(ND/D) were calculated based on MPMV and GCR values for all the included points and the lung field center. MLD was automatically measured in each of the time frames, and the maximal change ratio of MLD (MLD(CR)) was calculated. These measured values were compared among COPD patients, non-COPD smokers, and non-smokers, and were correlated with the Brinkman index, FEV(1)/FVC, FEV(1) predicted, RV/TLC, and FEF(25–75%) using Spearman’s rank coefficients. RESULTS: MPMV(ND/D) was highest in non-smokers (0.819±0.464), followed by non-COPD smokers (0.405±0.131) and patients with COPD (−0.219±0.900). GCR(ND/D) in non-smokers (1.003±1.384) was higher than that in patients with COPD (−0.164±1.199). MLD(CR) in non-COPD smokers (0.105±0.028) was higher than that in patients with COPD (0.078±0.027). MPMV(ND/D) showed positive correlations with FEV(1) predicted (r=0.397, p=0.006), FEV(1)/FVC (r=0.501, p<0.001), and FEF(25–75%) (r=0.368, p=0.012). GCR(ND/D) also demonstrated positive correlations with FEV(1) (r=0.397, p=0.006), FEV(1)/FVC (r=0.445, p=0.002), and FEF(25–75%) (r=0.371, p=0.011). MPMV(ND/D) showed a negative correlation with the Brinkman index (r=−0.398, p=0.006). CONCLUSION: We demonstrated that reduced MPMV(ND/D) and GCR(ND/D) were associated with respiratory functional indices, in addition to a negative association of MPMV(ND/D) with the Brinkman index, which should be recognized when assessing local pleural adhesion on DVCT, especially for ventral pleural aspects.