Radiographic evaluation of regional pulmonary dimensions and volumes: effect of age

On chest radiographs performed at spirometrically controlled residual volume (RV), functional residual capacity (FRC) and total lung capacity (TLC), several distances were measured in 8 young and 7 elderly male subjects. Regional volumes above and below the minor fissure were calculated using Barnhard's method for thoracic gas volume determination. When the volumes above and below the fissure were expressed as a percentage of their volume at TLC, and related to overall lung volumes (in percent of TLC), graphs similar to the ones obtained in scintigraphic studies were obtained. This illustrates that the present radiographic method may provide information on regional pulmonary volumes. Regional TLC of the upper zone was larger in elderly subjects than in young ones, while the opposite was true for regional TLC of the lower zone, indicating that maximal regional expansion changes with age. For the upper zone, the changes in diameters between RV and TLC were largest in antero-posterior direction and smallest in cranio-caudal direction. For the lower zone, changes were largest in cranio-caudal direction. This suggests an anisotropic expansion of the upper and lower zone. This anisotropy was more pronounced in the young than in the elderly subjects.