What Is Atelectasis?

Atelectasis is the complete or partial collapse of a lung. It is sometimes referred to as a "collapsed lung," although a collapsed lung can also be applied to a condition called pneumothorax.

When atelectasis occurs, fresh air can't reach the alveoli, tiny structures in the lungs where oxygen and carbon dioxide are exchanged. This results in hypoxia, which is insufficient oxygen delivery to the organs and tissues of the body.

Atelectasis may be acute, occurring suddenly over minutes, or chronic, developing over a period of days to weeks. Atelectasis can be caused by a number of different medical conditions—ranging from lung cancer to an enlarged heart.

Atelectasis Symptoms

The symptoms of atelectasis can vary, depending on the size of lung collapse and the progression of the condition. Atelectasis might produce minimal symptoms if it develops slowly or involves only a small portion of the lung. If the condition develops rapidly or affects a large portion of the lungs, symptoms may be severe and life-threatening.

Atelectasis typically occurs unilaterally, affecting only one lung.

Common symptoms include:

• Dyspnea (shortness of breath)
• Wheezing
• Rapid, shallow breathing
• A persistent, hacking cough
• Sharp chest pain that worsens with a deep breath, typically on one side of the chest

As the condition progresses, the symptoms can become more profound as oxygen saturation levels in the blood begin to decrease. This can lead to a sudden, severe drop in blood pressure, tachycardia (rapid heart rate), and shock.

Causes

There are four primary mechanisms of atelectasis: hypoventilation, airway obstruction, airway compression, and adhesions. Each of these is associated with certain medical conditions.

Hypoventilation

Hypoventilation is the most common cause of atelectasis, especially after chest surgery.

Hypoventilation is very slow or shallow breathing. When hypoventilation causes atelectasis, it is due mainly to breathing an abnormally low volume (i.e. shallow breaths), rather than an abnormally slow rate. The very act of shallow breathing prevents air from getting to the alveoli, causing the air sacs to deflate and collapse.

Airway Obstruction

Airway obstruction may occur when something blocks a passage either inside the lung (like a mucus plug or an inhaled foreign object) or outside of the lungs (like a tumor pressing on the airway).

Bronchioloalveolar carcinoma is a type of lung cancer (now renamed as a subtype of lung adenocarcinoma) known to cause tumors in the alveoli and allied passages that can block the airway.

Airway Compression

Compression of the airways is often caused by pleural effusion, a buildup of fluid in the space surrounding the lungs. It may also be the result of an enlarged heart, an aneurysm, a tumor, enlarged lymph nodes, or ascites (accumulation of fluids in the abdominal cavity).

Adhesions

Adhesions can be the underlying cause of atelectasis. Internal tissues and organs have slippery surfaces, so they can shift easily as the body moves. Adhesions are thick, irregular scars that can interfere with lung movement, obstruct airflow, or compress tissue.

Other Factors

Other factors contributing to atelectasis include obesity, smoking, prolonged bed rest/immobility, rib fractures (which can result in shallower breathing), narcotics or sedatives (which can slow respiration), and respiratory distress syndrome (RDS) in newborns.

Diagnosis

If your doctor suspects you have atelectasis, they will perform a physical exam. If you have a partial or complete lung collapse, your breathing sounds may be quiet or they may be absent in the affected areas of your lung.

Your doctor will also perform percussion by tapping on your chest. The sound of the fingers tapping will be different over areas of atelectasis than over healthy areas of your lung.

Your doctor might order additional tests, which can include:

• Chest X-ray: Can visualize abnormalities of the lungs and chest
• Computed tomography (CT scan): Can detect obstruction
• Magnetic resonance imaging (MRI): Can identify tumors and subtle abnormalities
• Bronchoscopy: A flexible scope inserted into the windpipe to view the lungs and may reveal a tumor or foreign body in an airway that has led to the collapse
• Blood gases (oximetry): Evaluates the blood oxygen concentration
• Positron-emission tomography (PET scan): Can spot hyperactive cell metabolism, which can occur with cancer

Treatment

Treatment of atelectasis is focused on re-expanding the lung to its normal size. The approaches can vary, depending on the cause.

With small degrees of atelectasis that occur due to an infection or a tumor that is being actively treated, your doctor may observe the area of atelectasis to see if it resolves with appropriate treatment of the underlying problem. In this case, breathing exercises, chest percussion, or postural drainage may help accelerate improvement and relieve some of the symptoms.

Other interventions can include:

• For treatment of a pleural effusion, drainage of the pleural cavity may be required.
• Bronchoscopy may be used to remove a foreign object that's causing an internal obstruction.
• Bronchodilator medications may assist with the opening of airway passages.

In most cases, a combination of therapeutic approaches will be needed.

When symptoms are pronounced, positive end-expiratory pressure (PEEP) may be used. This is a treatment in which a mixture of oxygen is given via endotracheal tube to prevent the lungs from collapsing completely during exhalation. If symptoms are severe, intubation and ventilation may be needed until the underlying condition is fully under control.

When atelectasis is chronic, the lungs might not re-expand, even after the cause is resolved. Removal of the damaged portion of the lung via a lobectomy or segmental resection may be indicated.

Complications

When a large portion of the lungs is affected by atelectasis, respiratory failure may result. Additionally, several complications can occur due to atelectasis.

• Bacteria trapped in the area of collapse can lead to an infection, including pneumonia and sepsis.
• Bronchiectasis, an abnormal widening of the airways which results in a pooling of fluid in the lungs, can also sometimes occur.

Prevention

Chest surgery is the most common cause of atelectasis. To prevent it from occurring after a surgical procedure, your doctors will advise you to stop smoking if you smoke.

After surgery, there are four things you should do to prevent atelectasis:

• Use an incentive spirometer: This is a simple medical device to keep your lungs healthy. It's the most used device that prevents atelectasis.
• Deep breathing: Perform deep breathing exercises, focusing on long inhales and controlled exhales. Pain medication may also be prescribed if breathing is especially uncomfortable.
• Clear particles or phlegm: Make an effort to cough to clear any mucus or sputum from the lungs.
• Move around: Change your position, sitting up or moving around as much as your doctor allows.