EXPIRATORY CHEST RADIOGRAPHS DO NOT IMPROVE VISIBILITY OF SMALL APICAL PNEUMOTHORACES BY ENHANCED CONTRAST

Demonstration of small apical pneumothoraces is supposed to be facilit ated by expiratory chest radiographs. This study aimed to analyse the assumed enhancement of visual contrast on expiratory chest radiographs in patients with small apical pneumothoraces. Optical densities (OD) were obtained with a densitometer (X-rite 3001) on 54 paired inspirato ry and expiratory chest radiographs of 22 consecutive patients with sm all apical pneumothoraces. The ODs were measured: at the intervertebra l space between the first and second thoracic vertebrae (Area 1); at t he peripheral part of the affected lung parenchyma (Area 2); and at th e adjacent intrapleural space (Area 3). Excellent correlations of OD o f each area were obtained between paired inspiratory and expiratory ch est radiographs. The ODs of all areas on expiratory chest radiographs were significantly higher than on inspiratory chest radiographs, Contr ast between pulmonary parenchyma and intrapleural air in inspiratory a nd expiratory films did not differ significantly. Expiratory chest rad iographs do not improve visibility of small apical pneumothoraces by e nhanced contrast between pulmonary parenchyma and intrapleural air, Ex piratory chest radiographs show equally increased OD in the area of lu ng tissue and intrapleural air, caused by increased extrapulmonary tis sue density during expiration, resulting in increased radiation exposu re monitored by the ionization chambers of standard radiological equip ment. If expiratory chest radiographs are really improving the visibil ity of apical pneumothoraces, there must be other reasons than contras t enhancement to explain this. (C)ERs Journals Ltd 1996.