Certified Respiratory Therapist Practice Exam

Which specialized imaging test is most useful in diagnosing a pulmonary embolism?

1. Chest X-ray

2. ABG

3. Ventilation-perfusion scan (V/Q scan)

4. Pulmonary function tests (PFTs)

The correct answer is: Ventilation-perfusion scan (V/Q scan)

The ventilation-perfusion scan, or V/Q scan, is a specialized imaging test that is particularly useful in diagnosing pulmonary embolism (PE) because it assesses the circulation of air and blood within the lungs. A V/Q scan involves two components: ventilation imaging, which shows how well air is distributed in the lungs, and perfusion imaging, which indicates how well blood flows through the lung's blood vessels. In cases of pulmonary embolism, blood flow to certain areas of the lung is obstructed, typically due to a blood clot. The V/Q scan highlights areas with normal ventilation but low or absent perfusion, which is characteristic of a PE. This mismatch is a clear indicator of a potential pulmonary embolism, making the V/Q scan a valuable diagnostic tool. Other imaging tests may not provide the same level of specificity for diagnosing pulmonary embolism. A chest X-ray, while useful in ruling out other conditions, typically cannot visualize blood flow and may appear normal even in the presence of a PE. Arterial blood gases (ABG) can offer information on oxygenation and acid-base balance, but they do not identify clots in the pulmonary circulation. Pulmonary function tests (PFTs) assess lung mechanics and function but are not designed