Simple pneumothorax is air in the pleural space without significant mediastinal shift or hemodynamic compromise. The air in the pleural space may originate from the external environment from a penetrating injury or may come from damage directly to the lung or tracheobronchial tree. Symptoms include chest pain from the causative injury and sometimes dyspnea. Diagnosis is made with chest radiograph. Treatment is usually with tube thoracostomy.
Pneumothorax can be classified by either physiology or by etiology.
Classification by physiology includes:
Simple pneumothorax: air accumulation in the pleural space without significant mediastinal shift or hemodynamic compromise
Open pneumothorax: chest wall defect allowing direct communication with the external environment; this type of pneumothorax is also called a "sucking chest wound"
Tension pneumothorax: a chest wound forms a one-way valve mechanism, resulting in progressive air accumulation, mediastinal shift, and decreased venous return to the heart
Occult pneumothorax: not visible on supine radiograph but detected on CT or ultrasound
A unilateral simple 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.
Classification by etiology includes:
Primary spontaneous pneumothorax: not accompanied by clinically apparent pulmonary injury or disease
Secondary spontaneous pneumothorax: a complication of preexisting lung disease (eg, chronic obstructive pulmonary disease)
Traumatic pneumothorax: result of penetrating or blunt chest trauma
Iatrogenic pneumothorax: a complication of diagnostic or therapeutic interventions (eg, thoracentesis, central venous catheter placement, mechanical ventilation, cardiopulmonary resuscitation)
This topic discusses simple traumatic pneumothorax, spontaneous pneumothorax is discussed elsewhere.
This video shows the development of a pneumothorax caused by injury to the lung. Air leaks from the injury into the ple
MohammedElAmine/stock.adobe.com
This video shows the development of a pneumothorax caused by injury to the lung. Air leaks from the injury into the pleural space, eliminating the negative pressure that normally keeps the lung expanded. As air accumulates, the affected lung partially or completely collapses, reducing the ability to bring oxygen into the body.
(Video has no audio.)
MohammedElAmine/stock.adobe.com
In pneumothorax 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).
Symptoms and Signs of Simple Pneumothorax
Patients with simple 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 of Simple Pneumothorax
Chest radiograph
Sometimes ultrasound or CT
Diagnosis is usually made by chest radiograph. Ultrasound (performed at the bedside during initial resuscitation, Extended Focused Assessment With Sonography in Trauma [E-FAST]) and CT are more sensitive for small pneumothoraces than chest radiograph (1).
The size of the pneumothorax, stated as percent of the hemithorax that is vacant, can be estimated by radiographic findings. The numerical size is valuable mainly for quantifying progression and resolution rather than for determining prognosis.
Diagnosis reference
1. Expert Panel on Polytrauma Imaging, Lee JT, Camacho MA, et al. ACR Appropriateness Criteria® Major Blunt Trauma: Update 2025. J Am Coll Radiol. Published online February 27, 2026. doi:10.1016/j.jacr.2026.01.030
Treatment of Simple Pneumothorax
Usually tube thoracostomy
Sometimes observation alone
Treatment of most pneumothoraces is with insertion of a thoracostomy tube into the 5th or 6th intercostal space anterior to the midaxillary line. Small-bore pigtail catheters (14 French) are effective for many pneumothoraces, especially in stable patients; larger tubes (28 to 32 French) are preferred in hemodynamically unstable patients or when rapid evacuation is required (1).
Patients with small pneumothoraces (≤ 35 mm in diameter based on CT) (2) and no respiratory symptoms may simply be observed with serial chest radiographs until the lung re-expands. However, a pigtail catheter or tube thoracostomy should be considered 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.
Treatment references
1. Lyons NB, Abdelhamid MO, Collie BL, et al. Small versus large-bore thoracostomy for traumatic hemothorax: A systematic review and meta-analysis. J Trauma Acute Care Surg. 2024;97(4):631-638. doi:10.1097/TA.0000000000004412
2. Bou Zein Eddine S, Boyle KA, Dodgion CM, et al. Observing pneumothoraces: The 35-millimeter rule is safe for both blunt and penetrating chest trauma. J Trauma Acute Care Surg. 2019;86(4):557-564. doi:10.1097/TA.0000000000002192
Key Points
Physical findings can be subtle or normal, particularly if pneumothorax is small.
Although CT and ultrasound are more sensitive, chest radiographs are usually obtained as part of initial evaluation.
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.
