From the Guidelines
Tension pneumothorax is primarily a clinical diagnosis that may require immediate treatment before imaging, and on X-ray, it is characterized by complete lung collapse with mediastinal shift away from the affected side, among other key radiographic findings. Recognizing a tension pneumothorax on X-ray requires identifying several key radiographic findings. On chest X-ray, look for:
- Complete lung collapse with mediastinal shift away from the affected side, which is the most characteristic finding 1
- Depression of the ipsilateral hemidiaphragm
- Widening of intercostal spaces on the affected side
- Hyperexpansion of the hemithorax
- The trachea and heart will be displaced toward the unaffected side due to the increasing pressure in the pleural space. Unlike a simple pneumothorax, which shows a visible pleural line with absence of lung markings peripherally, tension pneumothorax demonstrates these findings plus mediastinal displacement due to the one-way valve effect that continuously increases intrapleural pressure 1. Remember that patients with tension pneumothorax are typically in severe respiratory distress with hypotension and may not be stable enough to obtain an X-ray; treatment with immediate needle decompression followed by chest tube placement should not be delayed for imaging if clinical suspicion is high 1.
From the Research
Recognizing Tension Pneumothorax on X-ray
To recognize a tension pneumothorax on X-ray, several key factors should be considered:
- Mediastinal shift: This is a significant indicator of tension pneumothorax, as it suggests that the pressure of intrapleural gas exceeds atmospheric pressure, producing adverse effects 2.
- Size of the pneumothorax: A large and rapidly expanding pneumothorax may require urgent intervention, although it is unlikely that the effects are mediated by high intrapleural pressures 2.
- Clinical presentation: Patients with tension pneumothorax often present with hypotension, reduced venous return, and kinking of the great vessels, leading to cardiovascular collapse 2, 3.
- Underlying lung disease: Risk factors for spontaneous pneumothorax, such as smoking, family history, and underlying lung disease (e.g., COPD, cystic fibrosis, tuberculosis), may increase the likelihood of developing tension physiology 3.
Radiological Evidence
Radiological evidence of mediastinal shift on chest X-ray is more common than true clinical tension pneumothorax 4. However, not all patients with mediastinal shift on X-ray require emergency needle decompression 4. In fact, most patients with mediastinal shift can be managed with intercostal catheter (ICC) insertion 4.
Key Findings
Key findings on X-ray that may indicate tension pneumothorax include:
- Mediastinal shift
- Large pneumothorax
- Evidence of cardiovascular collapse (e.g., decreased cardiac output) It is essential to consider the clinical presentation and underlying lung disease when interpreting X-ray findings, as radiological evidence of mediastinal shift does not always necessitate emergency intervention 4.