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 x-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<0001) was found between the conventional FEV1 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 FEV1 and a score based on regional radiological appearances. Correlations between Pao2 and Paco2 and the densitometer and x-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. At the present time, methods of investigating regional ventilation include bronchospirometry, bronchial catheterization with mass spectrometry, and isotope scanning and counting techniques. Pulmonary x-ray densitometry may also be used have described the use of the method in various lung disorders. In several of these reports reference has been made to changes in the densitometry traces in patients with airway obstruction which have been attributed to air trapping and have taken the form of a displacement of the densitometer trace indicating increased x-ray translucency of the lung during expiration. It is the purpose of the present study to investigate these changes more fully in a group of patients suffering from chronic bronchitis and emphysema and to correlate the findings with abnormalities in the radiological appearances and blood gas determinations. SUBJECTS AND METHODS Twenty male patients aged 37-65 (mean 54) years diagnosed as suffering from chronic bronchitis and emphysema by the usual clinical criteria were studied (M.R.C., 1965). The presence of emphysema was deduced on the basis of clinical and radiological observations. The disease was of various degrees of severity and this was documented by forced expiratory volume in 1 second (FEV1) and forced vital capacity …