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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Pneumothorax presents with sudden pleuritic chest pain, dyspnea, and unilateral decreased breath sounds
- Primary spontaneous pneumothorax occurs in tall thin young men; secondary occurs with underlying lung disease such as COPD
- Tension pneumothorax is a clinical diagnosis: hypotension, JVD, tracheal deviation, severe respiratory distress, and absent breath sounds
- Tension pneumothorax requires immediate needle decompression followed by chest tube; do not wait for chest X-ray
- Small stable primary pneumothorax may be observed; large, symptomatic, secondary, traumatic, or unstable cases usually need drainage
Overview
Pneumothorax occurs when air enters the pleural space and separates visceral from parietal pleura, reducing negative intrapleural pressure and collapsing the lung. Secondary pneumothorax is more dangerous because patients have limited pulmonary reserve. Tension pneumothorax causes mediastinal shift, reduced venous return, obstructive shock, and death if untreated.
Epidemiology
Primary spontaneous pneumothorax is most common in tall, thin young males and is strongly associated with smoking. Secondary spontaneous pneumothorax is seen in COPD, cystic fibrosis, interstitial lung disease, Pneumocystis pneumonia, lung cancer, and severe asthma. Iatrogenic pneumothorax can follow central venous catheter placement, thoracentesis, lung biopsy, or positive-pressure ventilation.
Clinical Features
Symptoms
Sudden unilateral pleuritic chest pain
Acute dyspnea, sometimes mild in primary pneumothorax
Severe dyspnea in COPD or other secondary pneumothorax
Chest trauma or recent procedure such as central line placement
Syncope, severe distress, or rapidly worsening dyspnea
Signs
Unilateral decreased or absent breath sounds
Hyperresonance to percussion on affected side
Tachycardia and tachypnea
Tracheal deviation away from affected side, hypotension, and JVD in tension pneumothorax
Hypoxemia or cyanosis
Investigations
First-line
Chest X-rayVisible pleural line with absent peripheral lung markings; expiratory films are usually not required
Bedside ultrasoundAbsence of lung sliding and lung point can rapidly identify pneumothorax, especially in trauma or ICU
Clinical diagnosisTension pneumothorax is diagnosed clinically and treated immediately without waiting for imaging
Second-line
CT chestMost sensitive test; use for occult pneumothorax, uncertain diagnosis, bullous disease, or persistent air leak
ABGAssess severe hypoxemia or respiratory failure in unstable or secondary pneumothorax
Specialist
Pleural manometry or surgical evaluationConsider for persistent air leak, recurrent pneumothorax, or bronchopleural fistula
Management
American College of Chest Physicians Delphi Consensus Statement on Spontaneous Pneumothorax1
Tension pneumothorax
- Immediate needle decompression, typically at the 4th or 5th intercostal space anterior/mid-axillary line or 2nd intercostal space midclavicular line depending on protocol
- Follow immediately with tube thoracostomy
- Give oxygen and hemodynamic support; do not delay for chest imaging
2
Stable primary spontaneous pneumothorax
- Small and minimally symptomatic: observation with repeat chest X-ray and close follow-up
- Large or symptomatic: needle aspiration or chest tube depending on local practice and recurrence risk
- High-flow oxygen may accelerate pleural air resorption in selected hospitalized patients
- Smoking cessation reduces recurrence risk
3
Secondary, traumatic, or iatrogenic pneumothorax
- Lower threshold for chest tube because underlying lung disease reduces reserve
- Traumatic pneumothorax generally requires tube thoracostomy, especially if positive-pressure ventilation is needed
- Small iatrogenic pneumothorax may be observed if stable and not enlarging
4
Recurrence and persistent air leak
- VATS bleb resection and pleurodesis for recurrent spontaneous pneumothorax, bilateral pneumothorax, persistent air leak, or high-risk occupation such as pilot or diver
- Avoid air travel until radiographic resolution; avoid scuba diving unless definitive pleurodesis and specialist clearance
Complications
- Tension pneumothorax: Obstructive shock from impaired venous return
- Respiratory failure: Especially secondary pneumothorax or bilateral disease
- Persistent air leak: Air leak lasting several days may indicate bronchopleural fistula
- Recurrence: Common after primary spontaneous pneumothorax, especially with smoking
- Re-expansion pulmonary edema: Rare complication after rapid re-expansion of a large chronic pneumothorax
USMLE Step 2 CK Exam Tips
- 1Tension pneumothorax = hypotension + JVD + tracheal deviation + absent breath sounds; treat before X-ray
- 2Primary spontaneous pneumothorax = tall thin young male smoker with sudden pleuritic pain
- 3Secondary pneumothorax in COPD is more dangerous and needs a lower threshold for chest tube
- 4Needle decompression is followed by chest tube; needle alone is not definitive
- 5Positive-pressure ventilation can convert a simple pneumothorax into tension physiology
- 6Sudden deterioration after central venous catheter placement = iatrogenic pneumothorax
practicetest your knowledge on pneumothoraxApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — respiratory and beyond.
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