Correlation of regional densitometry patterns, radiological appearances, and pulmonary function tests in chronic bronchitis and emphysema.

In 20 male patients suffering from chronic bronchitis and emphysema investigated by pulmonary -ray densitometry, five different types of densitometer trace pattern were observed during the FEV manoeuvre, which appeared to be related to the degree of zonal airway obstruction and the radiological severity of emphysema. We thought some of the features of the traces were caused by displacement of blood from the area of the lung being examined by trapped alveolar air at a pressure exceeding those in the surrounding blood vessels. A close correlation (P<0·001) was found between the conventional FEV and the pulmonary densitometer score derived from summated regional observations made during the FEV manoeuvre. A similar high degree of correlation was observed between the FEV and a score based on regional radiological appearances. Correlations between Pao and Paco and the densitometer and -ray scores were of doubtful significance. The findings indicate that critical evaluation of the radiological features of the pulmonary vessels in patients with emphysema is useful in assessing the overall degree of airway obstruction. Regional densitometer pattern analysis is a valuable contributory method of investigating these patients and the results of a comparison of these two methods suggest that it may be possible to distinguish between larger and smaller airway obstruction.