Certified Respiratory Therapist Practice Exam

What is indicated by an elevated hemidiaphragm as seen on a radiograph?

1. Pleural effusion

2. Phrenic nerve paralysis

3. Rib fracture

4. Asthmatic attack

The correct answer is: Phrenic nerve paralysis

An elevated hemidiaphragm observed on a radiograph is commonly indicative of phrenic nerve paralysis. The diaphragm is a muscle that plays a critical role in respiration, and it is primarily innervated by the phrenic nerve. When there is paralysis of this nerve, the diaphragm on the affected side becomes ineffective during inhalation, leading to its upward shift. This elevation can be seen on a chest X-ray, where one side of the diaphragm appears higher than the other. In contrast, other conditions such as pleural effusion or rib fractures may also alter diaphragm position, but they do not specifically result in unilateral paralysis of the diaphragm. Pleural effusion can cause a downward shift of the diaphragm due to fluid accumulation, and rib fractures may affect the structural integrity of the thorax but do not directly cause diaphragm elevation due to nerve paralysis. An asthmatic attack typically involves airway obstruction rather than diaphragm displacement, so it is not associated with an elevated hemidiaphragm. Understanding the significance of diaphragm position is crucial, as it can help healthcare providers diagnose underlying conditions related to respiratory function.