Pneumothorax

Published on 07/03/2015 by admin

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Chapter 67 Pneumothorax

Madison Macht, MD , Michael E. Hanley, MD

1 What are the major etiologic classifications of pneumothoraces?

Pneumothoraces are classified as spontaneous or traumatic:

Spontaneous: Spontaneous pneumothoraces occur without antecedent trauma or other obvious cause. A primary spontaneous pneumothorax occurs in a person without underlying lung disease. Secondary spontaneous pneumothoraces occur as a complication of underlying lung disease.

Traumatic: Traumatic pneumothoraces result from direct or indirect trauma to the chest and are further classified as iatrogenic or noniatrogenic.

2 What are the common causes of pneumothorax in critically ill patients?

Secondary spontaneous pneumothoraces occasionally require admission to the intensive care unit because of acute respiratory failure resulting from the combination of the pneumothorax and underlying lung disease. In addition, secondary spontaneous pneumothoraces may develop in patients with lung disease who are already in the intensive care unit. This occurs more commonly in patients with chronic obstructive lung disease, asthma, interstitial lung disease, necrotizing lung infections, and Pneumocystis jiroveci pneumonia. However, most pneumothoraces that develop in the intensive care unit are due to either antecedent noniatrogenic chest trauma or iatrogenic causes. Box 67-1 lists the common causes of iatrogenic pneumothorax.

3 What measures reduce the risk of iatrogenic pneumothorax in patients receiving positive pressure ventilation?

End-inspiratory plateau pressure should be kept < 35 cm H₂O, and both positive end-expiratory pressure (PEEP) and auto-PEEP levels should be minimized. Approaches that may help achieve these goals include using the following:

Smaller tidal volumes in patients with underlying lung disease

Permissive hypercapnia when high minute ventilation is required

High inspiratory flow rates

In addition, thoracentesis and subclavian or internal jugular venous line insertion should be performed with utmost care (including under ultrasound guidance) in high-risk patients.

4 Describe the clinical manifestations of pneumothoraces

Dyspnea and unilateral chest pain are the most common manifestations of primary spontaneous pneumothorax. Physical examination findings include tachycardia, ipsilateral chest expansion, hyperresonance to percussion, decreased tactile fremitus, and decreased breath sounds on the affected side. The trachea may also be deviated toward the contralateral side. On rare occasions patients with primary pneumothoraces may have no symptoms.

In contrast, most patients in whom secondary spontaneous pneumothoraces develop have preexisting lung pathologic conditions and resultant decreased pulmonary reserve. Therefore their symptoms are often more severe than in those with primary pneumothoraces. Dyspnea occurs in virtually all patients with secondary pneumothoraces and is commonly out of proportion to the size of the pneumothorax. Cyanosis and hypotension are common. Side-to-side differences in the examination of the chest may not be so apparent because many of the physical signs associated with the underlying lung disease are similar to those associated with pneumothoraces.

6 How is the diagnosis of pneumothorax established in critically ill patients?

Chest radiography is the most common tool used to confirm the presence of a pneumothorax. A thin pleural line and the absence of lung parenchymal markings between the pleural line and chest wall adequately support the diagnosis. Upright radiographs are most helpful, as the supine position commonly allows free pleural air to collect anteriorly and avoid detection. Evidence of an increase in the size of the ipsilateral hemithorax, including contralateral shift of the mediastinum and heart, as well as depression of the ipsilateral hemidiaphragm, may be the only radiographic clues to the presence of a pneumothorax in such cases. A wide, deep radiolucency along the costophrenic angle is referred to as the deep sulcus sign and may be the only clue to the presence of a pneumothorax on supine chest radiography. Chest roentgenograms obtained at expiration are often requested, although some data suggest that inspiratory and expiratory films are equally sensitive for the diagnosis. Radiographs taken with the patient in the lateral decubitus position or from the cross-table lateral view may be useful in confirming the diagnosis in select cases. If chest radiographs are nondiagnostic and the patient’s condition is sufficiently stable for transport, computed tomography of the chest may be required to prove the diagnosis.

7 What is the role of ultrasonography in the diagnosis of pneumothorax in critically ill patients?

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