What is the definition of extrapulmonary air?

The definition of extrapulmonary air refers to air that is found outside of the lungs. This usually pertains to air that is located in the thoracic cavity but is not within the lung tissue itself. Such air may be present in areas such as the pleural space or the mediastinum, and it's important in clinical assessments as its presence can indicate certain medical conditions like pneumothorax or other complications. Understanding this concept is crucial for healthcare providers, as it helps in diagnosing and managing respiratory issues.

In the context of the other options, air found within the lungs pertains specifically to intrapulmonary air, while air trapped in the pleural space refers to a specific condition affecting the thoracic cavity. Air entering the bloodstream is a completely different phenomenon known as "air embolism," which involves air bubbles entering systemic circulation and posing a risk for serious complications.