Atelectasis is a collapse of lung tissue affecting part or all of one lung. This condition prevents normal oxygen absorption by the blood as it passes through the lungs.

Atelectasis can result from an obstruction (blockage) of the airways. This causes the tiny air sacs in the lung, called alveoli, to collapse. These sacs are very thin-walled and contain a rich blood supply. Their function is to increase the surface area where the exchange of oxygen for carbon dioxide can take place as blood passes through the lungs. When the airways are blocked by amucus plug, a foreign object, or tumor, the alveoli are unable to fill withair, and the surface area for oxygen-carbon dioxide exchange is decreased. Collapse of the alveoli can occur in any area of the lung.

Atelectasis is a potential complication following surgery, especially in people who have undergone chest or abdominal operations. Congenital atelectasis can result from a failure of the lungs to expand at birth. This is a special concern in premature babies. The congenital condition may be localized or mayaffect all of both lungs.

Causes of atelectasis include insufficient attempts at respiration by the newborn, bronchial obstruction, and absence of surfactant (a substance secretedby alveoli that maintains the stability of lung tissue by reducing the surface tension of fluids that coat the lung). The lack of surfactant reduces the surface area available for effective gas exchange.

Pressure on the lung from fluid or air can cause atelectasis. So can obstruction of airways by thick mucus that develops with some infections and lung diseases. Tumors and inhaled objects can also cause obstruction of the airway, leading to atelectasis.

Anyone undergoing chest or abdominal surgery using general anesthesia is at risk to develop atelectasis, since breathing is often shallow after surgery toavoid pain from the surgical incision. Any significant decrease in airflow to the alveoli allows secretions to collect, which increases the chance of infection. Chest injuries causing shallow breathing, including fractured ribs, can also cause atelectasis.

Common symptoms of atelectasis include shortness of breath and decreased chest wall expansion. If atelectasis only affects a small area of the lung, symptoms are usually minimal. If the condition affects a large area of the lung and develops quickly, the individual may turn blue or pale, have trouble breathing, and feel a stabbing pain on the affected side. Fever and increased heartrate may occur if infection accompanies atelectasis.

Atelectasis can be diagnosed by a thorough physical examination. When the doctor listens to the lungs through a stethoscope, diminished or bronchial breath sounds may be heard. By tapping on the chest while listening through the stethoscope, the doctor can often tell if the lung is collapsed. A chest x raythat shows an airless area in the lung confirms the diagnosis. If an obstruction of the airways is suspected, a computed tomography scan (CT) or bronchoscopy may be performed. In a bronchoscopy, a device with a camera is inserted through the airways to detect a blockage.

If atelectasis is due to obstruction of the airway, the first step in treatment is to remove the cause of the blockage. This may be done by coughing, suctioning, or bronchoscopy. If a tumor causes the blockage, surgery may be necessary to remove it. Antibiotics are commonly used to fight the infection thatoften accompanies atelectasis. In cases where recurrent or long-lasting infection is disabling or where significant bleeding occurs, the affected sectionof the lung may be surgically removed.

If atelectasis is caused by a mucus plug or inhaled foreign object, the patient usually recovers completely when the blockage is removed. If it is causedby a tumor, the outcome depends on the nature of the tumor involved

When recovering from surgery, frequent repositioning in bed along with coughing and deep breathing exercises help keep the lungs clear. Breathing exercises and breathing devices, such as a spirometer that measures air flow, encourage the lungs to expand. Although smokers have a higher risk of developing atelectasis following surgery, stopping smoking six to eight weeks before surgery can help reduce the risk. Increasing fluid intake during respiratory illness or after surgery helps lung secretions to remain loose. Increasing humiditymay also be beneficial. Postural drainage techniques can be learned from a respiratory therapist or physical therapist and are a useful tool for anyone affected with a illness that could cause atelectasis.

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