A 10% pneumothorax in a patient with moderate-to-severe COPD may present very dramatically with respiratory failure and hypotension, whereas a 15%-20% pneumothorax in a patient with normal lung physiology may cause relatively mild respiratory discomfort. Although COPD is the leading cause of SSP, many other lung diseases can predispose a patient to the development of SSP. These include asthma, cystic fibrosis, sarcoidosis, tuberculosis, histiocytosis X, and Pneumocystis jirovecii pneumonia (more commonly seen in patients with HIV/AIDS).
Traumatic pneumothorax may result from penetrating, blunt, or blast thoracic injury. Iatrogenic traumatic pneumothorax is most common after invasive procedures such as thoracentesis, transbronchial biopsy, or transthoracic aspiration, but it may also result from barotrauma in the mechanically ventilated patient. Tension pneumothorax, a particularly important type of pneumothorax, commonly occurs in the context of trauma. Tension pneumothorax occurs when air in the pleural space compresses mediastinal structures and limits central venous return. This decrease in central venous return induces hypotension and may lead to cardiac arrest, including pulseless electrical activity. A tension pneumothorax is a medical emergency; the diagnosis is made clinically by the presence of respiratory distress, diminished or absent breath sounds on the affected side, hypotension, and tracheal deviation. Immediate decompression by needle thoracostomy should be followed by insertion of a chest tube, without delaying to obtain chest films.
A pneumothorax often presents with acute unilateral pleuritic chest pain and/or dyspnea. In any patient with underlying lung disease, such as COPD or cystic fibrosis, the diagnosis should be considered for any sudden decline in respiratory function, especially when accompanied by chest pain. Hyperresonance, decreased tactile vocal fremitus, and decreased air entry are signs of pneumothorax. Of note, physical signs are not sensitive enough to rule out a pneumothorax, especially in patients with underlying emphysema, who tend to have hyperinflated lungs at baseline.
The diagnosis of pneumothorax is most commonly confirmed by x-rays (preferably upright) or CT scans of the chest. Chest x-rays can miss small pneumothoraces in patients with underlying lung disease, especially when multiple thin-walled bullae are present. Supine chest x-rays also frequently miss pneumothoraces. Classic chest x-ray findings include a lack of lung markings, lung asymmetry, pleural line, and, in a tension pneumothorax, mediastinal shift. Most patients with a first episode of spontaneous pneumothorax do not need CT scans; however, they are helpful in evaluating lung parenchyma, in differentiating primary from secondary disease, and in assessing the recurrence risk. Thoracic ultrasonography can identify a pneumothorax with excellent sensitivity.
Patients with a pneumothorax should be immediately placed on oxygen therapy. Observation is only appropriate for small primary pneumothoraces. Simple aspiration may also be sufficient in small primary pneumothoraces; however, most patients with SSP should have tube thoracostomy. If the patient develops respiratory failure requiring mechanical ventilation, definitive chest tube placement is preferable to simple aspiration because positive pressure ventilation will enlarge a pre-existing pneumothorax and may lead to rapid decline. In the case of a tension pneumothorax with signs and symptoms of shock, it is crucial to perform needle decompression emergently, followed by placement of a chest tube.
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