Atelectasis is when the airways or air sacs in the lungs collapse or do not fully expand. Symptoms can include shallow breathing, coughing, and wheezing. Treatment may involve medications, breathing exercises, or surgery.

Sometimes, atelectasis may also be called total or partial lung collapse. Atelectasis may affect both lungs or only part of them, with several causes and types.

Around 90% of people who are placed under general anesthetic during surgery experience atelectasis afterward. Atelectasis is usually reversible. However, without medical care, it can lead to potentially fatal complications

In this article, we look at the types, causes, symptoms, diagnosis, treatment, and outlook of atelectasis.

a doctor looks over a chest X-ray for signs of atelectasisShare on Pinterest
Image credit: AzmanL/Getty Images

The types of atelectasis sit within four categories based on the conditions that cause them.


Types of nonobstructive atelectasis include:

  • Compression: Due to increased pressure on the lungs.
  • Adhesive: Caused by dysfunction or deficiency of pulmonary surfactant. This is a soap-like substance that creates surface tension in the air sacs, helping them stay open.
  • Cicatrization: Occurs due to scarring, which causes the lungs to shrink.
  • Relaxation: The loss of contact between the membranes connecting to the chest wall, called the parietal pleura, and the membranes covering the lungs, known as the visceral pleura.
  • Replacement atelectasis: Occurs when tumors fill or replace the air sacs.


Obstructive atelectasis is also called resorptive atelectasis.

An obstruction triggers a partial or complete lack of ventilation to the impacted area, though gas uptake into the blood still occurs.

When all of the gas is absorbed, the air sacs eventually collapse as the obstruction prevents more gas from entering.


Postoperative atelectasis usually develops within 72 hours of receiving general anesthesia because of altered gas exchange during sedation.


Rounded atelectasis is less common than other forms.

It occurs due to the folding of the lung tissue to the membranes covering the lungs and connecting them to the chest wall, known as the external pleura.

People may refer to both atelectasis and pneumothorax as collapsed lung.

However, although pneumothorax can cause atelectasis, they are different conditions.

Pneumothorax occurs when air collects between the inner and outer membranes, or pleura, of the lungs. This triggers pressure that can cause the lungs to collapse.

The potential causes of atelectasis depend on whether it is a nonobstructive or obstructive type.


Causes of nonobstructive atelectasis include:


Sedating medications for surgery, such as general anesthetic, change the way the lungs work, as well as the flow of gas exchange and ventilation. This can cause lung tissues or airways to collapse.

Certain types of surgeries may also make it more difficult or painful to breathe deeply. This interferes with gas exchange and ventilation. About 90% of people who are given general anesthesia develop atelectasis.

Pleural effusion

Pleural effusion occurs when fluid accumulates between the lungs’ inner and outer membranes, which can cause a partial or total collapse. This condition is commonly caused by acquiring an infection, inflammatory diseases, and malignant (cancerous) tumors.

Lung damage

Lung damage or scarring can cause the lungs to shrink or become unable to expand fully. Conditions, such as tuberculosis, fibrosis, and other chronic destructive lung conditions, often lead to lung damage.

Chest tumors

Either cancerous or benign (non-cancerous) tumors can put pressure on airways and lung tissues, potentially causing them to collapse.

Surfactant conditions

A deficiency or dysfunction can reduce the surface tension in the air sacs, causing them to collapse. This is often due to conditions that arise from premature birth, including respiratory distress syndrome and acute respiratory distress syndrome.

Airways or lung tissue defects

Abnormalities in airways or lung tissues can interfere with gas exchange, ventilation, surface tension, and how the lungs connect to the chest wall or fit within the chest cavity.


Pleurisy occurs when the lung pleura become inflamed, rough, and sticky. They rub against one another instead of smoothly gliding during inhalation and exhalation.

This condition may occur due to inflammatory diseases, infection, tumors, or other conditions known to cause inflammation.


Obstructive types of atelectasis occur when an object or abnormal growth physically blocks an airway or increases pressure on lung tissues or airways.

Common causes of obstructive atelectasis include:

  • inhaling a foreign object or getting one lodged in the airways or lung tissues
  • tumors in the airways or lung tissues
  • growths or objects in lung tissues and airways
  • mucus buildup that causes a so-called mucus plug to block the airways

If a small portion of the lung or airways become affected, atelectasis may not cause any obvious symptoms.

However, when the condition impacts a significant portion of the lung or airways, common symptoms of atelectasis include:

  • shallow breathing
  • coughing
  • wheezing or trouble breathing
  • fever
  • reduced or absent breathing sounds
  • crackling when breathing
  • excess mucus or sputum
  • reduced chest expansion during inhalation

A doctor will normally diagnose atelectasis by asking someone about their symptoms, underlying conditions, medical history, and by performing a physical exam.

A doctor will also use the results from a chest X-ray or other imaging of the chest, such as computed tomography or ultrasound scan.

They may also diagnose the condition using bronchoscopy. This involves placing a small tube with a camera and light through the windpipe, bronchi, and bronchioles to see inside the lung airways.

Common treatments for atelectasis include:

  • inhaled medications
  • breathing and coughing exercises
  • assistive breathing machines
  • sitting upright
  • getting up and moving around soon after surgery

A doctor may also perform surgery for one or more of the following reasons:

  • removing fluid
  • removing obstructions
  • removing growths
  • correcting anatomical structures
  • reopening collapsed tissues

There are several factors that healthcare professionals believe increase the risk of developing atelectasis, especially following surgery. They include:

  • administration of general anesthesia, sedatives, or muscle relaxants
  • obesity
  • pregnancy
  • smoking
  • improper pain control
  • thoracic or cardiopulmonary procedures
  • sleep apnea
  • lung conditions such as asthma, cystic fibrosis, or chronic obstructive pulmonary disease

Some methods may also help prevent the risk of developing atelectasis, especially before surgery or medical procedures involving sedation.

Ways to prevent atelectasis include:

  • quitting smoking
  • maintaining a moderate weight
  • using assistive breathing or lung-pressure machines
  • practicing breathing exercises
  • treating lung conditions or those that interfere with airflow
  • ensuring proper pain management
  • sitting upright instead of laying down

Atelectasis usually resolves itself with time or treatment, while lung or airway collapse is reversible.

For example, most people who develop atelectasis due to surgery recover 24 hours afterward.

However, if atelectasis is left undiagnosed or untreated, serious complications can develop. These can be potentially fatal, including but not limited to:

  • fluid buildup in the lung, pleural space, or chest
  • respiratory infections such as pneumonia
  • respiratory failure

The outlook for someone with atelectasis depends on how serious their condition is, the root cause, and any additional underlying conditions.

Atelectasis occurs when the air sacs, or alveoli, collapse or cannot fully expand.

The condition typically develops after a person goes under general anesthetic, or if they have a condition that impacts the lungs or structures and organs surrounding them.

Most people recover from atelectasis with proper treatment within 24 hours. However, without medical intervention, atelectasis can lead to serious complications, including death.