A 35-year-old man with known COPD presents with sudden-onset severe dyspnea, hypotension (BP 85/50 mmHg), and tachycardia (HR 125/min). Breath sounds are absent on the left. A portable chest X-ray (anteroposterior, supine) is obtained urgently in the ICU. The radiograph shows a hyperlucent left hemithorax with a sharp white line at the left lung margin, mediastinal shift to the right, and a prominent lucency at the left costophrenic angle extending across the diaphragm. What is the most likely diagnosis?

Explanation

## Tension Pneumothorax: Diagnosis and Imaging **Key Point:** Tension pneumothorax is a **life-threatening emergency** characterized by progressive air accumulation in the pleural space that compresses the ipsilateral lung, shifts the mediastinum, and compromises venous return. Clinical signs (hypotension, tachycardia, JVD, absent breath sounds) combined with imaging findings (mediastinal shift, pleural line, hyperlucency) confirm the diagnosis. ### Distinguishing Simple vs. Tension Pneumothorax | Feature | Simple Pneumothorax | Tension Pneumothorax | |---------|-------------------|---------------------| | **Pleural line** | Present | Present | | **Lung collapse** | Partial (< 50%) | Often > 50% | | **Mediastinal shift** | Absent or minimal | **Marked shift away** | | **Hemodynamic status** | Stable | **Hypotensive, tachycardic** | | **JVD** | Absent | **Present** | | **Tracheal deviation** | Absent | **Present** | | **Deep sulcus sign** | Mild | **Exaggerated** | | **Treatment** | Observation ± needle aspiration | **Immediate needle decompression** | **High-Yield:** The **deep sulcus sign** (prominent lucency at the costophrenic angle on supine film) is an early sign of tension pneumothorax. In this case, the lucency extends across the diaphragm, indicating air under pressure. ### Radiological Signs of Tension Pneumothorax ```mermaid flowchart TD A[Pneumothorax on CXR]:::outcome --> B{Mediastinal shift present?}:::decision B -->|No shift| C[Simple pneumothorax]:::outcome B -->|Shift away from side| D{Hemodynamically stable?}:::decision D -->|Yes| E[Tension pneumothorax - imaging sign only]:::action D -->|No - hypotensive, tachycardic| F[Tension pneumothorax - EMERGENCY]:::urgent F --> G[Immediate needle decompression 2nd ICS midclavicular]:::action G --> H[Chest tube placement]:::action ``` **Clinical Pearl:** Tension pneumothorax is a **clinical diagnosis** — do NOT wait for imaging confirmation if the patient is hemodynamically unstable. Immediate needle decompression (2nd intercostal space, midclavicular line) is lifesaving. Imaging (mediastinal shift, pleural line, hyperlucency) provides confirmatory support. ### Why This Case is Tension Pneumothorax 1. **Hemodynamic instability:** BP 85/50, HR 125 → indicates impaired venous return 2. **Mediastinal shift to right:** Confirms mass effect from left-sided air accumulation 3. **Deep sulcus sign:** Exaggerated lucency at costophrenic angle = air under pressure 4. **Absent breath sounds + hyperlucency:** Confirms complete lung collapse 5. **Clinical context:** COPD patient at high risk for secondary spontaneous pneumothorax with air trapping → tension **Warning:** Do not confuse tension pneumothorax with simple pneumothorax. The presence of **mediastinal shift + hemodynamic compromise** is the key distinction. Simple pneumothorax may have a pleural line but NO shift and patient is hemodynamically stable. [cite:Harrison 21e Ch 254; Felson's Principles of Chest Roentgenology 3e Ch 10]