[Relationship between thoracic cross-sectional area measured on CT and pulmonary function or dyspnea in patients with COPD].

We examined the relationship between the thoracic cross-sectional area (TCSA) and pulmonary function data or dyspnea grade in 24 patients with chronic obstructive pulmonary disease (COPD). The TCSA, i.e., the area surrounded by the rib cage, was measured on computed tomography (CT) images made 1 cm below the top of the aortic arch. Analysis of our data showed a good correlation between TCSA and total lung capacity (r = 0.65, p < 0.001), as well as functional residual capacity (r = 0.67, p < 0.0005) and residual volume (r = 0.62, p < 0.005). The patients were grouped according to their grade of dyspnea (Fletcher's five-degree scale), and the ratio of TCSA over square of height (TCSA/Ht2) was calculated for each patient. In the group with grade IV dyspnea, the TCSA/Ht2 ratios were significantly greater than those in the groups with grade II and III dyspnea, combined. In summary, in the patients with COPD, pulmonary function data indicative of lung hyperinflation correlated with the TCSA, and both parameters were increased in patients with severe dyspnea.