Radiographic measures of hyperinflation in clinical emphysema. Discrimination of patients from controls and relationship to physiologic and mechanical lung function.

In a retrospective study we investigated the accuracy of radiographic measurements of hyperinflation in distinguishing a sample of patients with a clinical diagnosis of pulmonary emphysema (n = 44) from a sample of age- and sex-matched control subjects (n = 39). The relationship of the hyperinflation parameters to pulmonary function test results (PFTs) and arterial blood gas measurements (ABGs) in the emphysema patients was also examined. The radiographic measurements were diaphragmatic angle of depression, lung height, lung width, heart size, diaphragm level, radiographic total lung capacity (TLC), and size of the retrosternal air space. By discriminant function analysis, the best contributors to the function were lung height and diaphragmatic angle of depression, followed by radiographic TLC and heart size. The derived classification rule had a diagnostic accuracy of 88 percent. The radiographic measures, largely independent of one another, showed moderate correlations with percentage PFTs, ABGs, portable percentage spirometric studies, height, and weight. High correlations were found between several of the radiographic measurements and the PFTs that represent actual static lung volumes. The correlation between radiographically measured TLC and PFT TLC measured by the helium dilution technique was .90.