Atelectasis can occur when there is an airway blockage, when pressure outside the lung prevents it from expanding, or when there is not enough surfactant for the lung to expand normally. If your lungs don't fully expand and fill with air, they may not be able to supply enough oxygen to your blood.

Atelectasis can occur at any age and for a variety of reasons. For example, newborns whose lungs are not fully developed may have atelectasis as a result of respiratory distress syndrome. Atelectasis can also occur when a tumor, excess mucus, or a piece of food blocks an airway, or from a pneumothorax or pleural effusion.

You may be at higher risk for atelectasis if you smoke or have other conditions, including obesity, sleep apnea, or lung conditions such as asthma, COPD, or cystic fibrosis. You're also at higher risk if you've recently had surgery. The drugs used to make you sleep during surgery can affect the way your lungs work, or the surgery itself can make it painful to take a deep breath. To help prevent atelectasis during and after surgery, your medical team may ask you to stop smoking and give you breathing exercises, medications, or a breathing device such as a CPAP machine.

Atelectasis may not cause signs or symptoms if it affects only a small area of the lungs. If it affects a larger area of the lung, it can cause a fever, shallow breathing, wheezing, or cough. The most common test used to diagnose atelectasis is a chest X-ray. Bronchoscopy or imaging tests can confirm a diagnosis.

Atelectasis treatment may include breathing or coughing exercises, inhaled medications, breathing equipment, or surgery. Atelectasis usually gets better with time or treatment. However, if undiagnosed or untreated, serious complications can develop, including fluid retention, pneumonia and respiratory failure.