DefinitionSubcutaneous emphysema occurs when air gets into tissues under the skin covering the chest wall or neck.Alternative NamesCrepitus; Subcutaneous air; Tissue emphysemaConsiderationsSubcutaneous emphysema can often be seen as a smooth bulging of the skin. When a health care provider feels (palpates) the skin, it produces an unusual crackling sensation as the gas is pushed through the tissue.Common CausesThis is a rare condition. When it does occur, possible causes include:Collapsed lung (pneumothorax), often occurring with a rib fractureFacial bone fractureRuptured bronchial tubeRuptured esophagusThis condition can happen due to:Blunt traumaGun shot woundsStabbingAir can also be found in between skin layers on the arms and legs or torso during certain infections, including gas gangr