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 mean a condition called pneumothorax. Atelectasis is usually reversible and not life-threatening. However, if left untreated, it can lead to serious complications.

When atelectasis occurs, fresh air can't reach the alveoli, tiny balloon-shaped structures in the lungs where oxygen and carbon dioxide are exchanged. This results in hypoxia, which is when not enough oxygen is delivered 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. It can be caused by a number of different medical conditions, ranging from lung injury to lung cancer.

Atelectasis Symptoms

The symptoms of atelectasis can vary, depending on how much of the lung is collapsed and how quickly it develops. 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 much of the lung, symptoms may be severe and life-threatening.

Atelectasis typically involves only one lung. However, it can also be bibasilar, which means that both lungs are affected, usually at the lowest parts or lobes of the lungs.

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, symptoms can get worse as oxygen 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 main categories of atelectasis: postoperative, obstructive, nonobstructive, and rounded. Each of these is associated with certain medical conditions.

Postoperative Atelectasis

Hypoventilation is one of the most common causes 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.

During surgery, the use of general anesthesia and muscle relaxants can inhibit coughing. This can then lead to hypoventilation and atelectasis.

Obstructive Atelectasis

Obstructive atelectasis is caused by airway obstruction or blockage. These blockages usually occur in the main airways, more specifically known as the trachea and bronchi. In obstructive atelectasis, the flow of air is either partly or completely blocked from reaching the alveoli.

The most common causes of obstructive atelectasis include:

• Inhaled foreign objects
• Mucous plugs, which are thick and sticky in consistency
• Tumors that lead to narrowing or blockage of the airway

Nonobstructive Atelectasis

In nonobstructive atelectasis, pressure or a lung injury causes the alveoli of the lungs to collapse. Causes include:

• Compression: This is often caused by pleural effusion, a buildup of fluid in the space surrounding the lungs leading to pressure that causes the lung to collapse. 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).
• Trauma: A chest injury, such as a car accident, can put pressure on the lungs or cause a pneumothorax, in which air leaks out of the lung making it difficult to inflate.
• Tumors: Alveoli can have the space of their balloon-like structures replaced by a tumor. Bronchioloalveolar carcinoma is a type of lung cancer (now renamed as a subtype of lung adenocarcinoma) known to cause tumors in the alveoli.
• Scar tissue: Lung diseases such as tuberculosis or inhalation of harmful chemicals can lead to scar tissue and contraction of the lung.
• Adhesions: The internal tissues and organs have slippery surfaces due to a substance called surfactant. This substance allows the lung structures to glide past each other easily. A defect in the production of surfactant interferes with lung movement, causing the alveoli to collapse.

Rounded Atelectasis

Rounded atelectasis is rare, but often seen in asbestosis. In this type of atelectasis, there is an infolding, or inward bulging, of a part of the lung, which can sometimes give the false appearance of a tumor or cancer on x-rays.

Risk Factors

Atelectasis is equally common in men and women. However, risk can increase with age.

Other factors that commonly contribute to atelectasis include:

• Obesity or pregnancy, which can press on the diaphragm
• Smoking
• Prolonged bed rest/immobility
• Rib fractures, which can result in shallower breathing
• Anesthesia, sedatives, and opioids, which can slow breathing

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 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 blood oxygen levels
• Positron-emission tomography (PET scan): Can spot hyperactive cell metabolism, which can occur with cancer

Complications

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

• Infections, caused by bacteria trapped in the area of collapse, which can lead to pneumonia or sepsis
• Bronchiectasis, an abnormal widening of the airways, which results in a pooling of fluid in the lungs
• Hypoxemia, a condition in which the blood carries low levels of oxygen
• Respiratory failure, a life-threatening condition in which the lungs cannot get enough oxygen into the blood

Treatment

Treatment of atelectasis is focused on re-expanding the lung to its normal size. The approaches can vary, depending on the cause. In most cases, a combination of therapeutic approaches will be needed.

The general treatments that relieve atelectasis include:

• Coughing and deep breathing exercises
• Airway suctioning to clear secretions
• Chest percussion to break up thick secretions so they can be coughed out
• Postural drainage, which involves sitting or lying in different positions to help move mucus and secretions out the lungs
• Positive-pressure breathing therapy, in which supplemental oxygen is given via a mask or breathing tube and air pressure is used to reopen the alveoli 

Other interventions performed by medical providers include:

• Drainage of the pleural cavity may be required to treat a pleural effusion.
• Bronchoscopy may be used to remove a foreign object that is causing an internal obstruction.
• Surgery may be done to remove the damaged portion of lungs, remove space-occupying tumors, or relieve pressure in the airways.

Medications can also be used to treat atelectasis and include:

• Bronchodilator medications may help open airway passages.
• Mucolytic agents, such as acetylcysteine, may break up mucus plugs in the airways.

Prevention

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

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.

Frequently Asked Questions

What is bibasilar atelectasis?

Bibasilar atelectasis is a partial or complete collapse of the small airways in the lower sections of both lungs.

How do you treat atelectasis?

Atelectasis treatment is aimed at the underlying cause and can include supplemental oxygen therapy, deep breathing and coughing exercises, medications, respiratory therapy, and medical or surgical interventions.

What is atelectasis?

The term atelectasis literally translated from its Greek origin means “imperfect expansion.” It refers to the partial or complete collapse of the lungs and is usually reversible. However, if left untreated, it can lead to serious complications.

What causes atelectasis?

The main causes of atelectasis are shallow breathing (hypoventilation), airway obstruction, a pressure that compresses the lung or airways, and lung damage.

A Word From Verywell

Prevention and treatment of atelectasis are important for reducing the risk of complications. Treatments vary depending on the underlying condition. Be sure to speak with your medical provider about what treatments are appropriate for your condition and ask any questions that you may have.