(See also Overview of Thoracic Trauma.)
Spontaneous pneumothorax is discussed elsewhere.
Pneumothorax can be caused by penetrating or blunt trauma; many patients also have a hemothorax (hemopneumothorax). In patients with penetrating wounds that traverse the mediastinum (eg, wounds medial to the nipples or to the scapulae), or with severe blunt trauma, pneumothorax may be caused by disruption of the tracheobronchial tree. Air from the pneumothorax may enter the soft tissues of the chest and/or neck (subcutaneous emphysema), or mediastinum (pneumomediastinum).
A simple unilateral pneumothorax, even when large, is well tolerated by most patients unless they have significant underlying pulmonary disease. However, tension pneumothorax can cause severe hypotension, and open pneumothorax can compromise ventilation.
Patients with traumatic pneumothorax commonly have pleuritic chest pain, dyspnea, tachypnea, and tachycardia.
Breath sounds may be diminished and the affected hemithorax hyperresonant to percussion—mainly with larger pneumothoraces. However, these findings are not always present and may be hard to detect in a noisy resuscitation setting. Subcutaneous emphysema causes a crackle or crunch when palpated; findings may be localized to a small area or involve a large portion of the chest wall and/or extend to the neck; extensive involvement suggests disruption of the tracheobronchial tree.
Air in the mediastinum may produce a characteristic crunching sound synchronous with the heartbeat (Hamman sign or Hamman crunch), but this finding is not always present and also is occasionally caused by injury to the esophagus.
Diagnosis is usually made by chest x-ray. Ultrasonography (done at the bedside during initial resuscitation) and CT are more sensitive for small pneumothoraces than chest x-ray.
The size of the pneumothorax, stated as percent of the hemithorax that is vacant, can be estimated by x-ray findings. The numerical size is valuable mainly for quantifying progression and resolution rather than for determining prognosis.
Treatment of most pneumothoraces is with insertion of a thoracostomy tube (eg, 28 Fr) into the 5th or 6th intercostal space anterior to the midaxillary line.
Patients with small pneumothoraces and no respiratory symptoms may simply be observed with serial chest x-rays until the lung re-expands. Alternatively, a small pigtail catheter drain can be placed. However, tube thoracostomy should be done in patients who will undergo general anesthesia, positive pressure ventilation, and/or air transport because these interventions can convert a small, simple (uncomplicated) pneumothorax to a tension pneumothorax.
If a large air leak persists after tube thoracostomy, tracheobronchial tree injury should be suspected and bronchoscopy or immediate surgical consultation should be arranged.
Physical findings can be subtle or normal, particularly if pneumothorax is small.
Although CT and ultrasonography are more sensitive, chest x-ray is usually considered sufficient for diagnosis.
Tube thoracostomy is indicated if pneumothorax causes respiratory symptoms or is moderate or large or if air transport, positive pressure ventilation, or general anesthesia is necessary.