What is subcutaneous emphysema characterized by?

Subcutaneous emphysema is characterized by a crackling sensation felt on palpation, known as crepitus. This phenomenon occurs when air becomes trapped in the subcutaneous tissue, often as a result of trauma, surgery, or lung injury. When pressure is applied to the affected area, the trapped air shifts under the skin, producing a distinct crackling sound and sensation.

While other options like a burning sensation on the skin, extreme pain and redness, or visible air bubbles might be associated with various skin or tissue conditions, they do not represent the defining feature of subcutaneous emphysema. The key identifying characteristic is the tangible sensation of air in the tissue, which provides important diagnostic information in a clinical setting.