Relation between abnormalities in the chest radiograph and changes in pulmonary function in chronic bronchitis and emphysema.

Chest radiographs of 101 patients with chronic airflow obstruction were assessed for evidence of over-inflation (increased retrosternal space, low diaphragm, and increased total lung capacity), pulmonary hypertension (increase in size of heart and major pulmonary vessels) and attenuation of medium-sized pulmonary vessels. The radiological abnormalities were related to the alterations in pulmonary function. When the position of the diaphragm was low or the retrosternal space was 4·5 cm or more the average FEV was below 1·0 litre, but severe impairment of the FEV could be present when the position and contour of the diaphragm were normal and the retrosternal space was 2·5 cm or less. The radiological method for estimating total lung capacity agreed well with the results obtained with body plethysmography, but there was not a close correlation between the standard radiological signs of over-inflation and a large total lung capacity. When the radiograph showed widespread vascular attenuation as well as over-inflation the impairment in FEV and other tests of pulmonary function was considerably more severe than when the radiograph showed over-inflation alone. Severe reduction in transfer factor was usually associated with changes in the pulmonary vessels. It is concluded that the radiological diagnosis of widespread emphysema can be made with confidence only when there is attenuation of pulmonary vessels as well as evidence of over-inflation. In attempting to diagnose emphysema in life all available clinical and functional data should be considered in conjunction with the radiographic appearances.