Atelectasis

In atelectasis, alveolar clusters (lobules) or lung segments that expand incompletely may produce a partial or complete lung collapse. This phenomenon effectively removes certain regions of the lung from gas exchange. This allows unoxygenated blood to pass unchanged through these regions and produces hypoxia.

Atelectasis may be chronic or acute. The disorder occurs to some degree in many patients undergoing upper abdominal or thoracic surgery. The prognosis depends on prompt removal of any airway obstruction, relief of hypoxia, and reexpansion of the collapsed lung.

Causes

• Fluid in or around the lungs
• Infection
• Blockage of airways in the lungs due to tumors, mucus, or a foreign object
• Compression, resulting from emphysema, an enlarged heart, or a tumor
• Restricted chest movement, due to bone or muscle problems
• Scarring, as a result of radiation therapy, frequent infections, or disease
• Injuries
• Pneumothorax

Signs and Symptoms

In acute atelectasis in which there is sudden obstruction of the bronchus, there may be dyspnea and cyanosis, elevation of temperature, a drop in blood pressure, or shock.

In the chronic form, the patient may experience no symptoms other than gradually developing dyspnea and weakness.

Other characteristics include diminished breath sounds, fever, and increasing dyspnea (shortness of breath).

Diagnostic tests

Chest X-rays are the primary diagnostic tool, although extensive areas of "microatelectasis" can exist without abnormalities appearing on the films. In wide­spread atelectasis, X-ray findings define characteristic horizontal lines in the lower lung zones. With segmental or lobar collapse, the films reveal characteristic dense shadows (commonly associated with hyperinflation of neighboring lung zones).

Bronchoscopy may be used to rule out an obstructing neoplasm or a foreign body if the cause of atelectasis can't be determined.

Arterial blood gas analysis may reveal respiratory acidosis and hypoxemia resulting from atelectasis.
Pulse oximetry may show deteriorating levels of arterial oxygen saturation.

Treatment

Incentive spirometry, chest percussion, postural drainage, and frequent coughing and deep-breathing exercises may improve oxygenation in the patient with atelectasis. If these measures fail, bronchoscopy may help remove secretions. Humidity and bronchodilator medications can improve mucociliary clearance and dilate airways. These drugs may be administered by nebulizer or by a face mask device that establishes continuous positive airway pressure. Alternatively, intermittent positive-pressure breathing therapy may be prescribed.

If the patient has atelectasis secondary to an obstructing neoplasm, he may need surgery or radiation therapy. To minimize the risk for atelectasis after thoracic and abdominal surgery, the patient requires analgesics to facilitate deep breathing.

Prevention

Deep breathing, aided by the use of inspiration breathing apparatus following surgery, is helpful in preventing complications of atelectasis.