Atelectasis is a collapse of the air sacs in the lungs called alveoli. It may occur in a portion of the lung, or in the entire lung. Normally, oxygen enters the body through the lungs and is exchanged with carbon dioxide in the alveoli. The lungs expand and contract to create the exchange of these gases.

Atelectasis is not a disease, but a condition or sign that results from disease or abnormalities in the lungs.

The Lungs (Cut-away View)
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Atelectasis is caused by a:

  • Blockage of the airway
  • Reduced amount of surfactant, a liquid that keeps the lungs expanded

Blockage may be caused by:

  • Infection
  • Tumors, mucus, or a foreign object in the lungs
  • Compression, resulting from emphysema, an enlarged heart, or a tumor
  • Scarring that blocks the airway as a result of radiation therapy, frequent infections, or disease
  • Pneumothorax (leakage of air into the space surrounding the lungs)

Reduced amounts of surfactant may be caused by:

  • Lung immaturity in premature babies
  • Fluid accumulation
  • Failure to take deep breaths
  • Not coughing, which keeps the airway clear