Atelectasis (at-uh-LEK-tuh-sis) is the collapse of a lung or part of a lung, also known as a lobe. It happens when tiny air sacs within the lung, called alveoli, lose air.

Atelectasis is one of the most common breathing complications after surgery. It's also a possible complication of other respiratory problems, including cystic fibrosis, lung tumors, chest injuries, fluid in the lung and respiratory weakness. You may develop atelectasis if you breathe in a foreign object.

This condition can make breathing hard, particularly if you already have lung disease. Treatment depends on what's causing the collapse and how severe it is.

The definition of atelectasis is broader than pneumothorax (noo-moe-THOR-aks). Pneumothorax is when air leaks into the space between your lungs and chest wall, causing part or all of a lung to collapse. Pneumothorax is one of several causes of atelectasis.


There may be no clear signs of atelectasis. If you have any signs, they may include:

  • Having a hard time breathing.
  • Rapid, weak breathing.
  • Wheezing.
  • Coughing.

When to see a doctor

Always get medical attention right away if you have a hard time breathing. Other conditions besides atelectasis can make it hard to breathe, so it's important to get the right diagnosis and treatment. If your breathing suddenly becomes difficult, get emergency medical help.


A blocked airway can cause atelectasis. This is called obstructive atelectasis. Pressure from outside the lung also can cause atelectasis. This is called nonobstructive atelectasis.

General anesthesia — which brings on a sleeplike state with the use of medicines before a procedure or surgery — is a common cause of atelectasis. It changes your regular pattern of breathing and affects the exchange of lung gases. This can cause the air sacs in your lungs to lose air. Nearly everyone who has major surgery has some amount of atelectasis. It often occurs after heart bypass surgery.

When a blocked airway causes atelectasis, it may be due to:

  • Mucus plug. A mucus plug is a buildup of sputum or phlegm in your airways. It commonly occurs during and after surgery because you can't cough. Drugs given during surgery make you breathe less deeply. So mucus that usually would move out of your lungs may build up in your airways. Suctioning the lungs during surgery helps clear them. But sometimes mucus still builds up. Mucus plugs also are common in children, people with cystic fibrosis and during severe asthma attacks.
  • Foreign body. Atelectasis is common in children who have inhaled an object into their lungs, such as a peanut or part of a small toy.
  • Tumor inside the airway. A growth, which may or may not be cancer, can narrow or block the airway.

Possible causes of atelectasis due to pressure from outside the lung include:

  • Injury. Chest trauma, such as from a fall or car accident, can cause you to avoid taking deep breaths due to pain. This can lead to the squeezing of your lungs.
  • Pleural effusion. This condition involves the buildup of fluid in the space between the lining of your lungs and the inside of your chest wall.
  • Pneumonia. Various types of pneumonia, which is a lung infection, can cause atelectasis.
  • Pneumothorax. This is when air leaks into the space between your lungs and chest wall, causing some or all of a lung to collapse.
  • Scarring of lung tissue. Injury, lung disease or surgery could cause scarring.
  • Tumor. A large tumor can press against the lung and force air out of it.

Risk factors

Factors that make you more likely to get atelectasis include:

  • Any condition that makes it hard to swallow.
  • Needing to stay in bed over a long time and not having enough changes of position.
  • Lung disease, such as asthma, bronchiectasis or cystic fibrosis.
  • Recent surgery in the stomach area or chest.
  • Recent general anesthesia.
  • Weak breathing muscles due to muscular dystrophy, spinal cord injury or another neuromuscular condition.
  • Medicines that may cause weak breathing.
  • Pain or injury that may make it painful to cough or cause weak breathing, including stomach pain or a broken rib.
  • Smoking.


A small area of atelectasis, especially in adults, usually can be treated. These complications may come from atelectasis:

  • Low blood oxygen (hypoxemia). Atelectasis makes it harder for your lungs to get oxygen to the air sacs.
  • Pneumonia. Your risk of pneumonia continues until the atelectasis goes away. Mucus in a collapsed lung may lead to infection.
  • Respiratory failure. Loss of a lobe or a whole lung, especially in an infant or someone with lung disease, can be life-threatening.


Atelectasis in children is often caused by a blockage in the airway. To lower the risk of atelectasis, keep small objects out of the reach of children.

In adults, atelectasis most commonly occurs after major surgery. If you're scheduled for surgery, talk with your doctor about ways to lower your risk. Some research shows that certain breathing exercises and muscle training may lower the risk of atelectasis after some surgeries.