Correlation of pulmonary function with the chest roentgenogram in chronic airway obstruction

To evaluate the correlation of various roentgenographic indices with airway obstruction, the chest roentgenograms of 189 patients were independently examined (without knowledge of their clinical status or measured pulmonary function) by a pulmonary physician and by a chest radiologist. For most indices, there was a close correlation in the measured results between the 2 observers; the exception was assessment of areas of hyperlucency. Airflow obstruction was best correlated with the level of the right dome of the diaphragm. When this level was at or below the anterior end of the seventh rib, airflow obstruction was almost invariably present (specificity greater than 97%); however, the sensitivity of this index was low (range, 31 to 42%). There was a significant correlation with other roentgenographic indices; however, curvature of the diaphragm and retrosternal space were not as good over-all indices of airflow obstruction as was the level of the right dome of the diaphragm. When the retrosternal space was greater 4.4 cm or the transverse diameter of the heart was less than 11.5 cm, airflow obstruction was almost invariably present; but the sensitivity of these indices was low. In contrast, the presence and extent of areas of hyperlucency were poorly correlated with airflow obstruction. Parahilar bronchi were visualized in less than 50% of the chest roentgenograms by either observer; the ratio of wall thickness to diameter of these bronchi was not well correlated with the degree of airflow obstruction. The results indicate that a good assessment of the presence or absence of airflow obstruction can be made from various features of the chest roentgenogram.