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

Almost everyone who has surgery has some atelectasis from anesthesia. Anesthesia changes your regular pattern of breathing and the absorption of gases and pressures, which may combine to cause some degree of collapse of the tiny air sacs (alveoli) in your lungs. Atelectasis is particularly prominent after heart bypass surgery.

Obstructive atelectasis may be caused by:

  • Mucus plug. Accumulation of mucus in your airways, often occurring during and after surgery because you can't cough, is a 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. Mucus plugs also are common in children, people with cystic fibrosis and during severe asthma attacks.
  • Foreign body. Atelectasis is common in children who have inhaled 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 infection of your lungs, may temporarily cause atelectasis.
  • 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.
June 11, 2015