What is one purpose of an end expiratory x-ray?

An end-expiratory x-ray is primarily utilized to assess the presence of small pneumothorax. During the end-expiratory phase, the lungs are less expanded, which helps in visualizing subtle changes or air collections within the pleural space. This phase enhances the contrast between the air in the pleural cavity and the surrounding tissues, making it easier to detect small amounts of air that may indicate a pneumothorax.

The other options focus on different clinical assessments. Measuring heart size typically relies on cardiac imaging techniques such as echocardiography or chest x-rays taken at different lung capacities. Evaluating stroke risk involves neurological assessments and imaging techniques primarily concerned with the brain, while measuring blood flow typically uses methods like Doppler ultrasonography or angiography to examine circulation rather than a standard chest x-ray.