Measurement of lung lobar volume of children with funnel chest by computed tomography

The aim of this study was to evaluate the influence of funnel chest on lung lobar volume and the correlation of lung lobar volume to the severity of funnel chest, which was measured by using computed tomographic (CT) images. Fifty-one patients with funnel chest (group 1) and 28 children without funnel chest (group 2) were selected for this study. The CT scans were obtained from the apex to the base of the lung at inspiratory phase. The outlines of the lung lobes were traced, and the area of the lung lobes in a cross-sectional plane was calculated. The lobar volume was determined by the thickness of scan space multiplied by the total area of all slices in each lobe. There was no difference between total lung capacity of group 1 and group 2. The left lower lobar volumes of group 1 was significantly smaller than group 2 (362±269 ml vs 539±361 ml). Both the ratios of the left lower lobar and left lung volume to the whole lung volume were significantly smaller group 1 than in group 2 (19.39±2.88% vs 24.01±1.98%, 42.87±2.99% vs 45.91±1.58%, respectively). On the other hand, ratios of the right lower lobar, left upper lobar and right lung volume to the whole lung volume were larger in group 1 (27.71±3.32% vs 25.97±2.03%, 23.47±2.20% vs 21.90±1.44%, 57.14±2.99% vs 54.09±1.58%, respectively). There were correlations between the pectus index (p=0.0109, r=-0.354) and the ratio of the left lower lobar volume to the whole lung volume to the depression rate (p=0.0174, r=-0.332) and between the pectus index (p=0.0053, |r|=0.385) and the ratio of each lung to the depression rate (p=0.0004, |r|=0.476). A new index, the ratio of the left to the right side of the heart, indicating the grade of heart displacement to the left was created and adapted for the study. The left-right ratio of the heart was significantly larger in group 1 than in group 2 (82.0±4.7 vs 67.8±3.0), and there were correlations of the left-right ratio of the heart to the ratio of the right upper lobar volume (p=0.0443, r=0.227), the right lower lobar (p=0.0043, r=0.318), the left upper lobar volume (p=0.0014, r=0.353), the left lower lobar volume (p<0.0001, r=-0.675) and each lung to the whole lung volume (p<0.0001, |r|=0.528). The left lower lobes of the children with funnel chest were indirectly compressed by the heart, which was displaced to the left side and had a reduced volume. (author)