What is pneumomediastinum

Pneumomediastinum also known as mediastinal emphysema is an uncommon and usually a self-limited condition where there is air in the mediastinum ¹, ², ³, ⁴, ⁵, ⁶, ⁷. The mediastinum is the space in the middle of your chest, between your lungs and around your heart. The air or gas may originate from your lungs, trachea, central bronchi, esophagus, and peritoneal cavity and track from the mediastinum to your neck or abdomen.

Spontaneous pneumomediastinum is an uncommon condition presenting in approximately one in 1,000 to one in 40,000 emergency department referrals ⁸, ⁹, ¹⁰. Young patients with spontaneous pneumomediastinum typically present with a history of asthma or recent inhalation of cocaine, methamphetamine, ecstasy, marijuana or hydrocarbons ¹¹, ¹², ¹³, ¹⁴, ¹⁵, ¹⁶, ¹⁷, ¹⁸. Other causes include barotrauma in asthmatics and chronic obstructive pulmonary disease (COPD) patients, rapid ascent in scuba divers, valsalva maneuvers, vomiting, infections, blast injuries and iatrogenic injuries from endoscopy or surgery ¹⁹, but can also happen with no known cause (idiopathic).

Pneumomediastinum can either be spontaneous or secondary. Spontaneous pneumomediastinum (SPM) isn’t caused by injury or illness, or the cause is unknown (idiopathic). Secondary pneumomediastinum develops because of an injury, illness or surgery. While pneumomediastinum itself is usually harmless, the underlying causes can be serious. Potential life-threatening causes include esophageal rupture (Boerhaave syndrome) and tension pneumothorax, but these are historically evident at presentation ²⁰.

Some people with pneumomediastinum don’t have any symptoms. Pneumomediastinum usually causes chest pain behind the breastbone (nonspecific pleuritic chest pain) with shortness of breath, which may spread to the neck or arms. The pain may be worse when you take a breath or swallow.

Seek immediate medical attention or go to the nearest emergency room immediately if you’re experiencing:

• Chest pain.
• Shortness of breath.
• Severe face or neck swelling.
• Lightheadedness.

Because a subset of patients with pneumomediastinum have serious underlying condition, extensive workups are often necessary. During a physical exam, your doctor may feel small bubbles of air under the skin of your chest, arms, or neck called subcutaneous emphysema. When examined, sometimes the person can look very puffy (swollen) in the face and eyes. This can look worse than it actually is. Hearing a crunching sound in time with your heartbeat (Hamman’s sign) is a sign that you might have air in your mediastinum.

A chest x-ray or CT scan of the chest may be done. This is to confirm that air is in the mediastinum, and to help diagnose a hole in the trachea or esophagus.

A barium swallow may be indicated if Boerhaave syndrome (esophageal rupture following vomiting) is suspected from the history. If the pneumomediastinum has not resolved after 1 week, a CT of the chest is indicated to look for a source of persistent air leak.

There’s no specific treatment for pneumomediastinum. Often, no treatment is needed because your body will gradually absorb the air on its own over a period of one to two weeks without intervention and rarely recur ²¹. Breathing high concentrations of oxygen may speed this process. If you have an underlying health condition, like an infection or injury to an internal organ, your doctor will treat you for that condition.

Your doctor may admit you to the hospital for 24 hours or longer for observation or treatment. While there, your doctor might treat you with:

• Oxygen therapy. Breathing in additional oxygen can help the air absorb into your body faster.
• Medication. Medication like pain relievers or cough suppressants can ease your symptoms until your body absorbs the extra air.
• Needle aspiration. If you have a lot of air that’s pressing on structures inside of your body, a doctor may remove some of the air with a needle or put a drain in. This is rare.
• Your doctor may put in a chest tube if you also have a collapsed lung (pneumothorax). You may also need treatment for the cause of the pneumomediastinum. A hole in the trachea or esophagus needs to be repaired with surgery.

Your outlook (prognosis) depends on the disease or events that caused the pneumomediastinum. People with spontaneous pneumomediastinum can make a full recovery and rarely have it happen again. People with spontaneous pneumomediastinum spend an average of three days in the hospital, but are sometimes there for a week or more. People with underlying causes of pneumomediastinum can be hospitalized for several weeks. If you have secondary pneumomediastinum, recovery will depend on the severity of your underlying condition. Some conditions that cause pneumomediastinum can be fatal.

Figure 1. Pneumomediastinum

Footnotes: A 16 year old boy without asthma or smoking history presented with the sudden onset of behind the sternum chest pain for two days after performing a 4 hour push-up exercise. Chest X-ray shows gross subcutaneous emphysema over the neck and pneumomediastinum with a continuous diaphragm sign (black arrows). The gas outlining the mediastinum, aorta (red arrowheads), and heart (yellow arrowheads) extends into the neck.

Figure 2. Mediastinum

Is pneumomediastinum an emergency?

Spontaneous pneumomediastinum is not an emergency. But if you have air in your mediastinum due to an injury or illness, you should be treated right away. Go to the nearest emergency room or seek medical care immediately if you have chest pain and shortness of breath. These could be signs of life-threatening illnesses or conditions.

Can pneumomediastinum be fatal?

Pneumomediastinum isn’t fatal on its own. But sometimes, serious, life-threatening health conditions can cause it. Your doctor will look for causes of the air leak and treat them if necessary.

Can pneumomediastinum be prevented?

Pneumomediastinum is rare and scientists don’t understand all the causes or risk factors. There aren’t any recommended ways to prevent it. Not smoking and not using inhaled recreational drugs might lower your risk.

What is the difference between pneumomediastinum and pneumothorax?

Figure 4. Thoracic cavity

Footnote: The black dashed lines indicate the borders of the mediastinum.

Pneumomediastinum causes

Pneumomediastinum is usually caused by air moving into your mediastinum from an injury or disease to an internal organ or structure. This includes your airways (trachea or bronchi), air sacs in your lungs (alveoli), tube from your throat to your stomach (esophagus) or intestines. Anything that increases pressure in your chest can cause spontaneous pneumomediastinum, though this is rare. Sometimes, doctors can’t find the cause (idiopathic).

Increased pressure in the lungs or airways may be caused by:

• Too much coughing
• Repeated bearing down to increase abdominal pressure (such as pushing during childbirth, a bowel movement or weight lifting)
• Sneezing
• Vomiting
• Idiopathic

Pneumomediastinum may also happen after:

• An infection in the neck or center of the chest (bacterial, fungal or viral infection)
• Severe injury (trauma) to your chest
• Rapid rises in altitude, or scuba diving
• Tearing of the esophagus (the tube that connects the mouth and stomach)
• Tearing of the trachea (windpipe)
• Rupture of the small sacs of your lungs (alveoli)
• Use of a breathing machine (positive pressure ventilation)
• Use of inhaled recreational drugs, such as marijuana or crack cocaine
• Surgery such as tooth extraction or digestive tract surgery
• Extensive voice exercise
• Excessive blowing
• Lung diseases such as asthma, bronchitis and pneumonia
• Valsalva maneuver (a procedure that involves forcefully exhaling against a closed airway that is used to quickly return an abnormal heart rhythm called paroxysmal supraventricular tachycardia (PSVT) to normal) ²²

Pneumomediastinum also can occur with collapsed lung (pneumothorax) or other diseases.

Although it is rare, pneumomediastinum can occur spontaneously. This is considered benign and generally affects young adult males ²³.

Risk factors for pneumomediastinum

You might be at higher risk for pneumomediastinum if you:

• Smoke.
• Have asthma, COPD or other lung conditions.
• Use inhaled recreational drugs.
• Recently had surgery on your abdomen, neck or chest.
• Recently gave birth.

Pneumomediastinum symptoms

Some people with pneumomediastinum don’t have any symptoms. Symptoms of pneumomediastinum include ²⁴, ²⁵, ²⁶:

• Severe pain in the middle of your chest or breastbone. It may radiate to your arms or neck. The pain may be worse with breathing or swallowing.
• Shortness of breath.
• Air pockets under your skin on your face, neck or chest (subcutaneous emphysema).
• Neck or face swelling.
• High-pitched voice or other voice distortion.
• Throat pain.
• Neck pain.
• Painful swallowing (odynophagia).
• Difficulty swallowing (dysphagia).

Pneumomediastinum possible complications

Some rare complications of pneumomediastinum are life-threatening and need to be treated right away. They include:

• Air may build up and enter the space around your lungs (pleural space), causing your lung to collapse (pneumothorax).
• In rare cases, air may enter the area between your heart and the thin sac that surrounds the heart (pericardium). This condition is called a pneumopericardium.
• In other rare cases, so much air builds up in the middle of your chest that it pushes on your heart and the great blood vessels, so they cannot work properly.

All of these complications require urgent attention because they can be life threatening.

Pneumomediastinum diagnosis

During a physical examination, your doctor may feel small bubbles of air under the skin of your chest, arms, or neck called subcutaneous emphysema. Hearing a crunching sound in time with your heartbeat (Hamman’s sign) is a sign that you might have air in your mediastinum.

A chest X-ray or CT scan of your chest may be done. These are tests that take pictures of the inside of your chest. This is to confirm that air is in the mediastinum, and to help diagnose a hole in the trachea or esophagus.

A barium swallow may be indicated if Boerhaave syndrome (esophageal rupture following vomiting) is suspected from the history. If the pneumomediastinum has not resolved after 1 week, a CT of the chest is indicated to look for a source of persistent air leak.

Pneumomediastinum treatment

There’s no specific treatment for pneumomediastinum. Often, no treatment is needed because your body will gradually absorb the air on its own over a period of one to two weeks without intervention and rarely recur ²¹. Breathing high concentrations of oxygen may speed this process. If you have an underlying health condition, like an infection or injury to an internal organ, your doctor will treat you for that condition.

Your doctor may admit you to the hospital for 24 hours or longer for observation or treatment. While there, your doctor might treat you with:

• Oxygen therapy. Breathing in additional oxygen can help the air absorb into your body faster.
• Medication. Medication like pain relievers or cough suppressants can ease your symptoms until your body absorbs the extra air.
• Needle aspiration. If you have a lot of air that’s pressing on structures inside of your body, a doctor may remove some of the air with a needle or put a drain in. This is rare.
• Your doctor may put in a chest tube if you also have a collapsed lung (pneumothorax). You may also need treatment for the cause of the pneumomediastinum. A hole in the trachea or esophagus needs to be repaired with surgery.

Pneumomediastinum prognosis

Your outlook (prognosis) depends on the disease or events that caused the pneumomediastinum. People with spontaneous pneumomediastinum can make a full recovery and rarely have it happen again. If you have secondary pneumomediastinum, recovery will depend on the severity of your underlying condition. Some conditions that cause pneumomediastinum can be fatal.

The mortality rate associated with pneumomediastinum may be as high as 50-70% as seen in Boerhaave syndrome (esophageal rupture following vomiting) ²⁷. The development of air leak, according to Weg et al ²⁸, is not associated with an increased mortality rate in patients with sepsis-induced acute respiratory distress syndrome (ARDS). Other predisposing conditions associated with high mortality rates include trauma (blunt and penetrating, especially high velocity injury), asthma, and tracheobronchial perforation.

The most common morbidities attributable to pneumomediastinum are symptoms such as chest pain, voice change, and cough. Rarely, tension pneumomediastinum may result in decreased cardiac output. Laryngeal compression leading to stridor has been reported. Gas embolism has rarely been reported.

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