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 it's untreated, it can lead to serious complications.

When atelectasis occurs, fresh air can't reach the alveoli, tiny balloon-shaped air sacs in the lungs where oxygen and carbon dioxide are exchanged. This results in hypoxia, which is when the organs and tissues of the body don't get enough oxygen.

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, it can be life-threatening and symptoms may be severe.

Atelectasis typically involves only one lung. However, it can also be bibasilar, which means that both lungs are affected, usually at the lowest sections 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 worsen as oxygen levels in the blood decrease. It can cause 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 mainly due 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 air sacs, increasing the chance that they will deflate and collapse.

During surgery, general anesthesia and muscle relaxants cause hypoventilation, increasing the risk of atelectasis. Postoperative pain involving the trunk or chest may also inhibit you from taking a deep breath, which can lead to atelectasis.

Obstructive Atelectasis

Obstructive atelectasis is caused by airway blockage. These blockages usually occur in the main airways, which are the trachea and bronchi. In obstructive atelectasis, the flow of air is either partly or completely prevented from reaching the alveoli.

The most common causes of obstructive atelectasis include:

• Inhaled objects
• Mucous plugs, which are thick and sticky
• Tumors that lead to partial or complete blockage of the airway

Nonobstructive Atelectasis

In nonobstructive atelectasis, pressure or a lung injury causes the alveoli to collapse.

Causes include:

• Compression: This is often caused by pleural effusion, which is a buildup of fluid in the space surrounding the lungs that can cause the lung to collapse due to pressure. It may also occur due to 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: 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 in the lungs.
• Adhesions: The internal tissues and organs have slippery surfaces due that allow the lung structures to glide past each other easily. Infection, cancer, or treatment for pleural effusion can cause adhesions within the lung's pleural layers, which may limit lung expansion and lead to atelectasis.

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, and the 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 shallow breathing
• Anesthesia, sedatives, and opioids, which can slow breathing

Diagnosis

If your healthcare provider 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 healthcare provider 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 healthcare provider might order additional tests, which can include:

• Chest X-ray: Can visualize abnormalities of the lungs and chest
• Computed tomography (CT scan): May detect obstruction
• Bronchoscopy: A flexible scope inserted into the windpipe to view the lungs may visualize an obstruction in an airway
• Blood gases (oximetry): Evaluates blood oxygen levels
• Positron-emission tomography (PET scan): Can spot hyperactive cell metabolism, which can occur with cancer

Complications

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 secretions in the affected area.
• 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 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 a lung, remove a tumor, 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 post-surgical atelectasis, your healthcare providers will advise you to stop smoking before your surgery if you are a smoker.

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

• Use an incentive spirometer: This is a simple medical device that you would use to measure the amount of air that you breathe in and out and to keep your lungs active. 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 your lungs.
• Move around: Change your position, sitting up or moving around as much as your healthcare provider allows.

Frequently Asked Questions

What is bibasilar atelectasis?

Bibasilar atelectasis is 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 a combination of 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 partial or complete collapse of the lungs and is usually treatable. If untreated, it can lead to serious complications.

What causes atelectasis?

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

A Word From Verywell

If you develop atelectasis—don't panic—it is an uncomfortable, yet treatable, condition. Treatments vary depending on the underlying cause and the severity of atelectasis. If you are at risk, there are ways to prevent atelectasis. Preventative strategies involve breathing exercises and sometimes may involve medication as well.