Subcutaneous emphysema is a condition most often seen in hospital settings. It occurs because of diffusion of air into the subcutaneous tissues due to blunt or penetrating trauma to the chest. While in most cases, the disorder is benign, in some cases, it may signal something ominous like a tension pneumothorax.
Since air always travels to the top, subcutaneous emphysema is most common on the neck, face and chest. However, in severe cases, it may be found all over the body. When the skin is palpated, one may feel a crunch or crackling sensation like bubbles underneath the skin. Some people describe this sensation as touching rice krispies. On a ventilator especially if barotrauma occurs, the positive pressure causes a large amount of air to escape into the tissues, this can sometimes can cause swelling of the face, neck and eyelids.
It is important to note that the diagnosis of subcutaneous emphysema in most cases is done after palpation of the body. One may feel crepitus which signals presence of air underneath the skin. Blood work is usually not required to make a diagnosis of subcutaneous emphysema. However, in some cases in patients on ventilators who develop subcutaneous emphysema, one may order an arterial blood gas to assess for oxygenation.
In most other cases where the amount of gas in the tissues is not palpable, the plain X-ray is diagnostic. Pockets of air in the subcutaneous tissues will be obvious both on the plain X-ray and the CT scan. On a chest X-ray one can easily see the radiolucent striations. If there are many air pockets it can make detection of a pneumothorax very difficult on a chest X-ray. Ultrasonography is usually not a helpful technique as its sensitivity is decreased due to the presence of air. CT scan is perhaps the best test to detect subcutaneous emphysema as it can help detect minute amounts of air in the tissues.
Even though there is no universal classification, some experts classify the severity of subcutaneous emphysema based on number of organs and the degree of body surface involved  .
Once subcutaneous emphysema is detected, the common disorders that need to be ruled out include the following:
Once the above disorders have been ruled out, then other causes are less serious and can often be treated with supportive management   . The treatment of subcutaneous emphysema is not difficult but there is no overall consensus. The first thing to do is try and determine the cause. If the cause is an infection, then this is an indicative of a gas forming organism and urgent incision and debridement of the tissues is required.
If the subcutaneous emphysema occurs in a patient on a ventilator, then a pneumothorax must be suspected. Bilateral chest tubes are required even if no pneumothorax is seen on either side. In the past, some healthcare workers have inserted needles into the emphysematous pocket to release air but this has not been clinically proven to work, nor is it a widely accepted technique. Other doctors have inserted drains or made incisions to allow for the air to escape. Again, this is not based on any clinical studies but just personal experience. If the subcutaneous emphysema is in the chest and the patient is symptomatic, chest tubes will suffice. The decision to make infraclavicular incisions can help the air escape but this can also have an adverse cosmetic effect in the patient.
Only extremely large amounts of air will sometimes cause breathing problems. In most cases of small to moderate amounts of subcutaneous emphysema, observation is adequate. The aim of the treatment is to treat the condition causing the subcutaneous emphysema. Most patients given oxygen, bed rest and pain relief medication will recover without sequelae. It has been shown that breathing oxygen can help the body absorb the subcutaneous air quickly. In any case, the patient needs to be observed until the condition resolves. The majority of cases of subcutaneous emphysema resolve within 2-5 days. Most minor cases disappear within 48 hours. However the duration of time for the reabsorption of air is dependent on the condition causing it.
The prognosis of subcutaneous emphysema depends on the cause. In asthmatics it may be benign but in cases of infections, it may signal presence of gas forming bacteria, which can be lethal or limb threatening. For most patients the prognosis is good. For those who have suffered tracheal or bronchial injury, a chest tube and surgery to repair the airway injury is necessary. When treated promptly most patients do survive and do well. In the ICU the prognosis of patients with subcutaneous emphysema depends on other comorbid conditions. In patients with barotrauma on a mechanical ventilator, however, extensive subcutaneous emphysema can result in respiratory distress and failure to ventilate the patient. Alone subcutaneous emphysema is rarely life threatening. The air is usually reabsorbed by the body within a few days.
The chief causes of subcutaneous emphysema are conditions that can release air from the airways. This may be blunt or penetrating trauma to the trachea, bronchus or the lungs. Even rupture of alveoli can result in subcutaneous emphysema. Common cause of subcutaneous emphysema include the following:
Pneumothorax results in air in the chest cavity. If this free air is not drained then it can start to diffuse into the subcutaneous tissues. Tension pneumothorax or barotrauma are notorious for causing subcutaneous emphysema if the treatment is delayed.
Bronchial or tracheal injury
The bronchus or trachea can be injured from trauma or from intubation. This results in leakage of air into the mediastinum. There may be other associated symptoms like fever, hemoptysis and neck swelling .
The esophagus can rupture after forceful retching or vomiting or it may occur after a procedure like endoscopy. The leaked air often remains localized. Rupture of esophagus is a surgical emergency and needs to be fixed immediately.
There are some infections caused by gas forming bacteria. Gas gangrene is a limb and life threatening disorder which often presents with air underneath the skin. These individuals have crepitus and are very ill.
Dental procedures that utilize compressed air equipment can also cause subcutaneous emphysema.
Other causes of subcutaneous emphysema include:
The exact number of people who develop subcutaneous emphysema is not known but the numbers are not miniscule. The condition is frequently observed in the ICU in ventilated patients and in patients who suffer blunt and penetrating chest trauma. Subcutaneous emphysema can occur at all ages and in both genders. There are many causes of subcutaneous emphysema and often the disorder is identified on a plain X-ray or on a physical exam. Because of the varied conditions causing subcutaneous emphysema, the exact numbers remain unknown.
Once free air is present in the body, it cannot readily escape. Hence it tracks along the path of least resistance. When air escapes from the lungs or the trachea, it usually travels from the mediastinum into the retroperitoneum or into the soft tissues of the neck. These organs systems are lined by fascial planes which allow the air to pass through. Once inside the mediastinum, the air moves upward along the perivascular sheath and into the neck. If the patient is on a mechanical ventilator, the positive pressure further pushes this air into and out of the chest cavity into the abdomen, neck and face. In the chest cavity, the free air often collects inside the pericardium (pneumopericardium) or around the mediastinum (pneumomediastinum). However, it can also cause a pneumothorax.
There is no way to prevent subcutaneous emphysema. However, one must be aware of the conditions that can cause it and look for the signs and symptoms. Once the disorder is identified by noting air in subcutaneous tissues, steps should be taken to treat the cause. To prevent mortality, patients with tracheal, bronchial or esophageal injury need to be referred immediately to a thoracic surgeon. If the patient is on a mechanical ventilator with high positive end-expiratory pressure, prophylactic bilateral chest tubes are recommended.
Subcutaneous emphysema is a medical condition where accumulation of air occurs in the subcutaneous layer of skin. When air accumulates under the skin, the sensation felt during palpation is referred to as crepitus. Subcutaneous emphysema generally occurs from some type of pathology in the neck or chest, but the condition can occur anywhere in the body. Subcutaneous emphysema can be caused by many processes including trauma, pneumothorax, barotrauma, malignancy, infection or complication from a surgical procedure. In most cases, subcutaneous emphysema is felt as “crackles” under the skin. The swelling is often minor. Most patients have no symptoms but in some cases, it may signal something threatening like an infection or a tension pneumothorax    .
Subcutaneous emphysema is defined as the presence of air underneath the skin. The condition is most often seen in the chest and neck area. Subcutaneous emphysema has many causes including blunt and penetrating trauma to the neck and chest, infections, following surgery on the chest, poorly functioning chest tube and having asthma. The condition is easily diagnosed by feeling the skin but sometimes a plain X-ray may reveal air in the tissues. The treatment in most cases is observation but those cases caused by trauma or injury to the major airways usually require a chest tube.