Atelectasis may be the result of a blocked airway (obstructive) or of pressure from outside the lung (nonobstructive).

Almost everyone who undergoes surgery has some atelectasis from anesthesia. Anesthesia changes the dynamics of airflow within the lungs, the absorption of gases and pressures, all of which combine to cause some degree of collapse of the tiny air sacs (alveoli) in your lungs. It is particularly prominent after heart bypass surgery.

A blockage in your air passages (bronchial tubes) can cause obstructive atelectasis. Possible causes of blockage include:

  • Mucus plug. Accumulation of mucus in your airways, often occurring during and after surgery because you can't cough, is the most common cause of atelectasis. Drugs given during surgery make the lungs inflate less fully than usual, so normal secretions collect in the airways. Suctioning the lungs during surgery helps clear away these secretions, but they may continue to build up afterward. This is why it's important to breathe and cough deeply during your recovery. Expanding the lungs gets air around the mucus plugs and makes them easier to cough out. Mucus plugs also are common in people with cystic fibrosis and during severe asthma attacks.
  • Foreign body. Children are most likely to inhale an object, such as a peanut or small toy part, into their lungs.
  • Narrowing of major airways from disease. Chronic infections, including fungal infections, tuberculosis and other diseases can scar and constrict major airways.
  • Tumor in a major airway. An abnormal growth can narrow the airway.
  • Blood clot. This occurs only if there's significant bleeding into the lungs that can't be coughed out.

Possible causes of nonobstructive atelectasis include:

  • Injury. Chest trauma — from a fall or car accident, for example — can cause you to avoid taking deep breaths (due to the pain), which can result in compression of your lungs.
  • Pleural effusion. This is a buildup of fluid between the tissues (pleura) that line the lungs and the inside of the chest wall.
  • Pneumonia. Different types of pneumonia, an inflammation of your lungs, temporarily can cause atelectasis. An atelectatic lung that remains collapsed for a few weeks or more can result in bronchiectasis (brong-key-EK-tuh-sis), a condition in which damage to the airways causes them to widen and become flabby and scarred.
  • Pneumothorax. Air leaks into the space between your lungs and chest wall, indirectly causing some or all of a lung to collapse.
  • Scarring of lung tissue. Scarring could be caused by injury, lung disease or surgery. In these rare cases, the atelectasis is minor compared with the damage to the lung tissue from the scarring.
  • Tumor. A large tumor can press against and deflate the lung, as opposed to blocking the air passages.
Jul. 14, 2012