Pneumothorax

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:



image 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.


image 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.



Box 67-1 Common causes of iatrogenic pneumothorax




image Positive Pressure Ventilation


image Central venous catheter placement


image Thoracentesis


image Tracheostomy


image Nasogastric tube placement*


image Bronchoscopy†


image Pericardiocentesis


image Transthoracic needle aspiration


image Cardiopulmonary resuscitation



* Because of inadvertent insertion of the nasogastric tube into the tracheobronchial tree.


† Especially if transbronchial biopsy is performed.



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:



image Smaller tidal volumes in patients with underlying lung disease


image Permissive hypercapnia when high minute ventilation is required


image 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.



5 What subtle signs or symptoms should prompt consideration of pneumothorax in patients receiving mechanical ventilation?


The sudden onset of any of the following should raise the possibility of a pneumothorax in patients receiving mechanical ventilation:



image Decline in oxygen saturation


image Agitation


image Respiratory distress


image Patient-ventilator dyssynchrony


image Sudden increase in peak inspiratory and/or static airway pressure


image Hypotension


image Cardiovascular collapse


image Pulseless electrical activity



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?


Ultrasonography has several important advantages in the diagnosis of pneumothoraces in critically ill patients. Pneumothoraces can be detected by ultrasound with certainty at the bedside, without the need for conventional radiography, thus potentially saving time and sparing patients radiation exposure. Other advantages include portability and real-time imaging. These features are especially important when a diagnosis must be made emergently. Large dressings, agitation, significant subcutaneous emphysema, and posterior or mediastinal air collections may decrease the sensitivity of ultrasonography. Several studies have shown that the sensitivity and specificity of ultrasonography for the detection of pneumothorax is greater than 90% in the initial management of trauma patients.

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Jul 7, 2016 | Posted by in CRITICAL CARE | Comments Off on Pneumothorax

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