Subcutaneous 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 (crepitus) as the gas is pushed through the tissue.

This is a rare condition. When it does occur, possible causes include:

• Collapsed lung (pneumothorax), often occurring with a rib fracture
• Facial bone fracture
• Rupture or tear in the airway (larynx or trachea)
• Rupture or tear in the esophagus or gastrointestinal tract

This condition can happen due to:

• Blunt trauma.
• Blast injuries.
• Breathing in cocaine.
• Corrosives or chemical burns of the esophagus or airway.
• Diving injuries.
• Forceful vomiting (Boerhaave syndrome).
• Penetrating trauma, such as gunshot or stab wounds.
• Pertussis (whooping cough).
• Certain medical procedures that insert a tube into the body. These include endoscopy (tube into the esophagus and the stomach through the mouth), a central venous line (thin catheter into a vein close to the heart), endotracheal intubation (tube into the throat and trachea through the mouth or nose), and bronchoscopy (tube into the bronchial tubes through the mouth).

Air can also be found in between skin layers on the arms and legs or torso after certain infections, including gas gangrene, or after scuba diving. Scuba divers with asthma are more likely to have this problem than other scuba divers.

When caused by surgery, subcutaneous emphysema is sometimes referred to as "surgical emphysema."

Most of the conditions that cause subcutaneous emphysema are severe, and you are likely already being treated by a provider. Sometimes a hospital stay is needed. This is more likely if the problem is due to an infection.

When found after trauma or injury, the presence of subcutaneous emphysema can indicate serious underlying injuries that may require urgent treatment.

If you feel subcutaneous air in relation to any of the situations described above, particularly after trauma, call 911 or the local emergency services number immediately.

Do not administer any fluids by mouth. Do not move the person unless it is absolutely necessary to remove them from a hazardous environment. Protect the neck and back from further injury when doing so.

The provider will measure and monitor the person's vital signs, including:

• Oxygen saturation
• Temperature
• Pulse
• Breathing rate
• Blood pressure

Symptoms will be treated as needed. The person may receive:

• Airway and/or breathing support -- including oxygen via external delivery device or endotracheal intubation (placement of a breathing tube through the mouth or nose into the airway) with placement on a ventilator (life support breathing machine)
• Blood tests
• Chest tube -- tube through the skin and muscles between the ribs into the pleural space (space between the chest wall and the lung) if there is lung collapse
• CT scan (computerized tomography) of the chest and abdomen or area with the subcutaneous air
• Electrocardiogram or heart tracing (ECG)
• Fluids through a vein (IV)
• Medicines to treat symptoms
• X-rays of chest and abdomen and other body parts that may have been injured

The prognosis depends on the cause of the subcutaneous emphysema. If associated with major trauma, a procedure or infection, the severity of those conditions will determine the outcome.

Subcutaneous emphysema associated with scuba diving is most often less serious.

Crepitus; Subcutaneous air; Tissue emphysema; Surgical emphysema

Davis AS, Mohr NM. Pleural disease. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 63.

Lenz RJ, Loyd JE. Mediastinitis and fibrosing mediastinitis. In: Broaddus VC, Ernst JD, King TE, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 7th ed. Philadelphia, PA: Elsevier; 2022:chap 116.

Peak DA. Scuba diving and dysbarism. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 131.

Raja AS. Thoracic trauma. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 37.

Updated by: Jesse Borke, MD, CPE, FAAEM, FACEP, Attending Physician at Kaiser Permanente, Orange County, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.