CAMRT Radiography Practice Exam

Why is an expiration PA chest radiograph included in evaluating a potential pneumothorax?

1. To assess diaphragm movement

2. To reduce lung volume

3. To increase lung volume of the unaffected area

4. To increase the area the pneumothorax occupies

The correct answer is: To reduce lung volume

Including an expiration PA chest radiograph in the evaluation of a potential pneumothorax is particularly useful for understanding the dynamics of lung volume during the expiratory phase. When a patient exhales, lung volume decreases, and any air that has accumulated in the pleural space (as in the case of a pneumothorax) will occupy a larger relative area, thereby making it easier to visualize on the radiograph. In this context, reducing lung volume during expiration helps highlight the presence of the pneumothorax by allowing a clearer view of the space where the pleural air is located. Instead of the lung obscuring the upper part of the thoracic cavity, the decrease in volume can result in a better contrast between the lung marking and the air in the pleural space. Understanding this physiological change is crucial, as it allows radiologists and medical professionals to accurately assess the presence and extent of a pneumothorax, improving diagnosis and subsequent treatment planning.