An Overview of Atelectasis

Atelectasis is a medical term used to describe the complete or partial collapse of a lung. It is sometimes referred to as a "collapsed lung," although the term can also be applied to a condition called pneumothorax.

When atelectasis occurs, fresh air is unable to reach the tiny structures of lungs, called the alveoli, where oxygen and carbon dioxide are exchanged. This results in decreased levels of oxygen being delivered to the organs and tissues of the body (hypoxia).

Atelectasis may be acute, occurring suddenly over the matter of minutes, or chronic, developing over a period of days to weeks. There are four main causes of atelectasis, which in turn may be caused by a number of different medical conditions, ranging from lung cancer, to an enlarged heart.

Atelectasis often has few symptoms if it develops slowly or involves only a small portion of the lung. Conversely, if the condition develops rapidly or affects a larger portion of shock, symptoms may be dramatic and even lead to shock. Atelectasis typically occurs unilaterally, meaning in either one lung or the other.

Common symptoms include:

• Shortness of breath (dyspnea)
• Wheezing
• Rapid shallow breathing
• A persistent, hacking cough
• A sharp chest pain that worsens with a deep breath, typically on one side of the chest

As the condition progresses, the symptoms can become more profound as oxygen saturation levels in the blood begin to decrease. This can lead to a sudden, severe drop in blood pressure, rapid heart rate (tachycardia), and shock.

There are four primary causes of atelectasis: hypoventilation, airway obstruction, airway compression, and adhesions. Understanding these mechanisms makes it a little easier to understand some of the common medical conditions that may result in this condition.

Hypoventilation

Hypoventilation, or breathing at an abnormally slow rate, is common during surgery, especially with general anesthesia, or when a person is placed on a respirator. The very act of shallow breathing prevents air from getting to the alveoli, causing the air sacs to deflate and collapse. Hypoventilation is the most common cause of atelectasis, especially after chest surgery.

Airway Obstruction

Airway obstruction may be caused when something blocks a passage either inside the lung (like a mucus plug or a foreign object) or outside of the lungs (like a tumor which presses on the airway and causes obstruction). Bronchioloalveolar carcinoma is one type of cancer (now renamed as a subtype of lung adenocarcinoma) known to cause tumors in the alveoli and allied passages.

Airway Compression

Compression of the airways is often caused by the buildup of fluid in the space surrounding the lungs (pleural effusion). It may also be the result of an enlarged heart, an aneurysm, a tumor, enlarged lymph nodes, or accumulation of fluids in the abdominal cavity (ascites).

Adhesions

Adhesions are an abnormal condition where tissues begin to stick together. Normally, internal tissues and organs have slippery surfaces, so they can shift easily as the body moves.

Other Factors

Other factors contributing to atelectasis include obesity, smoking, prolonged bed rest/immobility, rib fractures (which can result in shallower breathing), narcotics or sedatives (which can slow respiration), and respiratory distress syndrome (RDS) in newborns.

If your doctor suspects you have atelectasis, he or she will perform a physical exam by tapping on (percussing) the chest to listen for tell-tale sounds. If there is a partial or complete lung collapse, breathing sounds may be quiet or noticeably absent.

Following this, the doctor will order a number of investigations which may include:

• Chest X-ray, which may reveal that the trachea and heart have shifted position
• Computed tomography (CT scan) to look for visual evidence of obstruction
• Magnetic resonance imaging (MRI), using magnetic waves to produce images
• Bronchoscopy, a flexible scope inserted into the windpipe to view the lungs that may reveal a tumor or foreign body in an airway that has led to the collapse
• Blood gases (oximetry) to evaluate the level of oxygen deprivation
• Positron-emission tomography (PET scan), which can spot hyperactive cell metabolism as can occur with cancer

Treatment of atelectasis depends on the underlying cause, with the aim of re-expanding the lung to its normal size. The approaches can vary. If a tumor is the cause of the collapse, surgery may be involved.

With small degrees of atelectasis that are found while an infection or tumor is being actively treated, physicians may simply observe the area of atelectasis to see if it resolves with appropriate treatment of the underlying problem. In this case, breathing exercises, chest percussion, or postural drainage may help accelerate improvement and relieve some of the symptoms.

For pleural effusion, drainage of the pleural cavity may be required. For internal obstructions, bronchoscopy may be used to remove a foreign object, while bronchodilation medications may assist with the opening of airway passages. In most cases, a combination of therapeutic approaches will be needed.

When symptoms are pronounced, positive end-expiratory pressure (PEEP) may be used. This is a treatment in which a mixture of oxygen is given via endotracheal tube, preventing the lungs from collapsing completely during exhalation. If symptoms are severe, intubation and ventilation (placing a person on a respirator) may be needed until the underlying condition is fully under control.

When atelectasis is chronic, it can often be difficult to get the lungs to re-expand. Removal of the damaged portion of the lung (via a lobectomy or segmental resection) may be indicated.

Complications

Complications may result when bacteria become trapped in the area of the collapse. This can lead to the development of an infection, including pneumonia and sepsis. Bronchiectasis, an abnormal widening of the airways which results in a pooling of fluid the lungs, can also sometimes occur. When a large portion of the lungs is affected by these things, respiratory failure may result.

Chest surgery remains the predominant cause of atelectasis. To prevent it from occurring after a surgical procedure, doctors will typically advise you to stop smoking first and foremost.

After surgery, there are four things you should do ensure your lungs remain fully inflated:

• Use an incentive spirometer, a simple medical device to keep your lungs healthy. It's the most used device that prevents atelectasis.
• Perform deep breathing exercises, focusing on long inhales and controlled exhales. Pain medication may also be prescribed if breathing is especially uncomfortable.
• Make an effort to cough to clear any mucus or sputum from the lungs.
• Change your position, sitting up or moving around as much as your doctor allows.