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Last Updated: Mar 1, 2019


Atelectasis is a condition where some or all of the air-filled sacs (alveoli) inside the lungs collapse, thereby reducing the lungs’ capacity to deliver oxygen to the body. Alveoli are surrounded by small capillaries that exchange carbon dioxide with oxygen from inhaled air. This oxygenated blood is then carried to the brain and other organs via the circulatory system. A coating of surfactant liquid inside the alveoli walls normally ensures they remain inflated for efficient gas exchange. However, mucus buildup, respiratory illness and surgery can hinder this process, causing atelectasis.

illustration of bronchi inside of lungs

In minor form, atelectasis may not produce noticeable symptoms. Adults with atelectasis generally recover quickly using respiratory exercises that re-inflate the affected alveoli. Persistent atelectasis can lead to infection of the lungs (pneumonia) and requires timely treatment, especially in infants, small children and adults with existing respiratory illness.

In obstructive atelectasis, alveoli become collapsed due to a physical blockage of airflow. Non-obstructive atelectasis is the term used when alveoli collapse due to factors acting via other mechanisms.

Causes and Risk Factors

Conditions that hinder deep breathing and coughing cause atelectasis.

Causes of obstructive atelectasis

  • Mucus buildup: Surgery and some respiratory conditions prevent the lungs from efficiently clearing fluids. Anesthesia drugs given during surgery disrupt the body’s normal breathing patterns, causing secretions to collect in the airways. Additionally, the pain following surgery of the chest/abdomen reduces the urge to cough and take deep breaths, exacerbating the problem. Such a “mucus plug” is also associated with cystic fibrosis and asthma attacks.
  • Infection: Chronic fungal, bacterial and other infections of the lungs can leave behind scars that affect airflow.
  • Foreign object: Accidental inhaling of small items (e.g., nuts and small toys) can block airflow to the lungs.
  • Tumor: An abnormal growth inside the lungs can impede airflow and collapse the alveoli.
  • Blood clot: Excessive bleeding inside the lungs can form obstructive clots.

Causes of non-obstructive atelectasis:

  • Trauma: Pain resulting from injury to the chest area can make it difficult to inhale and cough.
  • Pleural effusion: Accumulation of fluid in the space outside the lungs but inside the chest cavity (pleural space) can press on the airways, causing collapse.
  • Pneumothorax: Certain lung procedures or injuries to the chest cause air to leak into pleural space. This buildup of pressure exerts force and collapses the lungs.
  • Tumor: Large tumors within the vicinity of the lungs can push and deflate the alveoli.

Risk factors for atelectasis

  • General anesthesia
  • Lung or chest surgery
  • Lung or chest injury
  • Lung infection
  • Premature birth
  • Children under the age of three and adults over age 60
  • Neuromuscular diseases that impair deep breathing
  • Lung diseases such as asthma, bronchiectasis or cystic fibrosis
  • Being on a ventilator.


Mild atelectasis with only a few collapsed alveoli may not produce symptoms. However, symptoms develop quickly when larger areas of the lungs are affected. The symptoms of atelectasis include:

  • Difficulty breathing
  • Rapid breathing
  • Chest pain
  • Coughing.

Diagnosis and Treatment

Atelectasis is routinely diagnosed using a chest X-ray to visualize the lungs and surrounding areas. This imaging technique can identify most physical obstructions inside the airways, or factors exerting pressure on the lungs. Other techniques used to inspect the airways include:

  • Computed tomography (CT): A CT scan produces images that are more detailed than a routine X-ray.
  • Bronchoscopy: In this procedure, a lighted camera on a thin tube is guided down the bronchi, the main passageways that deliver air to the left and right lobes of the lungs. It allows for visualizing, and sometimes removing, physical obstructions.

Minor atelectasis does not require medical intervention and can subside on its own. Treatment for more severe disease is focused on re-expanding the alveoli and addressing the underlying cause, as described below:

  • Surgery: Atelectasis following surgery is treated by deep breathing and coughing exercises. Movement and changing positions in the hospital bed also facilitate recovery. Devices that increase the air pressure inside the lungs may also be used.
  • External pressure: Atelectasis caused by external pressure from a tumor or fluid is addressed by removing the tumor, or suctioning/draining the fluid.
  • Blockage: A physical obstruction of the airway can be removed surgically or via bronchoscopy. A mucus plug is loosened using medication or chest percussions.
  • Illness: Infections and other lung disorders are treated with appropriate therapies.


The risk of developing atelectasis can be reduced with persistent deep breathing and coughing following anesthesia or lung/chest surgery. In children, it is important to use age-appropriate toys without small parts.


  • “Atelectasis”. Mayo Clinic. Retrieved Dec. 10, 2015.
  • “Atelectasis”. Merck Manual. Retrieved Dec. 10, 2015.
  • “Atelectasis”. Medline Plus; NIH. Retrieved Dec. 10, 2015.
  • “What is Atelectasis”. National Heart, Lung and Blood Institute; NIH. Retrieved Dec. 10, 2015.

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Tina Shahian, PhD

Tina is a writer for Innerbody Research, where she has written a large body of informative guides about health conditions.


A communication specialist in life science and biotech subjects, Tina’s successful career is rooted in her ability to convey complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. Tina Shahian’s Linkedin profile.


In her spare time, Tina enjoys drawing science-related cartoons.