Last Updated: October 04, 2017



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

Causes of non-obstructive atelectasis:

Risk factors for atelectasis


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:

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:

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:


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.


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Authored by: Tina Shahian, PhD