CAMRT Radiography Practice Exam

In performing a decubitus chest x-ray, which position is recommended if free air is suspected?

1. Upright

2. Down

3. Up

4. Supine

The correct answer is: Up

When performing a decubitus chest x-ray for suspected free air, placing the affected side "up" is the recommended position. This approach allows any free air to rise to the non-dependent side of the thoracic cavity. If free air is present, it will accumulate at the highest point, which will be the site opposite the position of the patient when they are lying down. In this context, the rationale for choosing this position is based on the behavior of free air within the body—a principle understood in radiographic imaging. This technique enhances the visibility of free air in the pleural space, as it allows radiologists to distinctly observe air-fluid levels. In contrast, placing the affected side down would not be effective for diagnosing free air since the air would remain obscured by the lung or other tissues. An upright position might be suitable for viewing air but does not provide the detailed imaging benefits that a decubitus position offers for this specific situation. The supine position, while common in some imaging scenarios, would also not adequately demonstrate the presence of free air as it would not allow gravity to assist in dispersing the air to a position where it can be visualized clearly on the x-ray.