Definition and epidemiology
Pneumothorax refers to air entering the pleural space between the visceral and parietal pleura, leading to loss of the negative intrapleural pressure that keeps the lung expanded. This results in partial or complete lung collapse on the affected side.
It is classified as:
- Primary spontaneous pneumothorax (PSP): occurs without underlying lung disease, typically in tall, thin young men aged 10-30, often smokers, due to rupture of subpleural blebs/bullae at the apex
- Secondary spontaneous pneumothorax (SSP): occurs in patients with underlying lung disease (COPD, cystic fibrosis, Pneumocystis pneumonia, lung cancer), typically older patients, and carries higher morbidity
- Traumatic pneumothorax: from penetrating or blunt chest trauma, including iatrogenic causes (central line placement, thoracentesis, mechanical ventilation, lung biopsy)
- Tension pneumothorax: a life-threatening progression where accumulating air under pressure shifts the mediastinum and compromises venous return
PSP incidence is roughly 1-18 per 100,000 per year in men (lower in women). Smoking increases lifetime risk substantially (over 20-fold in heavy smokers). Recurrence rates after a first spontaneous pneumothorax approach 30-50% without intervention.
- Tension pneumothorax is a clinical diagnosis — treat with needle decompression before getting imaging
- PSP classically affects tall, thin young male smokers from ruptured apical blebs
- SSP is most commonly caused by COPD and carries worse prognosis due to limited reserve
- Needle decompression site: 2nd intercostal space midclavicular line (classic) or 4th/5th ICS anterior axillary line (updated ATLS)
- Ultrasound finding: absence of lung sliding plus 'barcode sign' on M-mode
- High-flow oxygen speeds pleural air reabsorption even in observed patients
- Recurrence risk is 30-50% after a first spontaneous pneumothorax
- Catamenial pneumothorax recurs with menstruation and is linked to thoracic endometriosis
Etiology and risk factors
Primary spontaneous
- Rupture of subpleural apical blebs or bullae
- Smoking (strongest modifiable risk factor)
- Tall, thin body habitus (increased apical transpleural pressure)
- Marfan syndrome, homocystinuria
- Family history (familial pneumothorax, often linked to FLCN gene mutations in Birt-Hogg-Dube syndrome)
Secondary spontaneous
- COPD/emphysema (most common cause overall)
- Cystic fibrosis
- Pneumocystis jirovecii pneumonia (classically in HIV/AIDS)
- Tuberculosis, necrotizing pneumonia
- Lung cancer, metastatic disease
- Catamenial pneumothorax (thoracic endometriosis, recurs with menses)
Traumatic/iatrogenic
- Penetrating or blunt trauma with rib fracture
- Central venous catheter placement (subclavian/internal jugular)
- Thoracentesis, transbronchial or transthoracic biopsy
- Positive pressure mechanical ventilation (barotrauma)
Tension pneumothorax triggers
- Positive pressure ventilation in a patient with an undetected pneumothorax
- Penetrating chest trauma with a one-way valve defect
Pathophysiology
Normally the pleural space has slightly negative pressure relative to atmospheric pressure, keeping the elastic lung expanded against the chest wall. When the pleura is breached (rupture of a bleb, trauma, or needle injury), air enters the pleural space, equalizing or exceeding atmospheric pressure, and the lung's elastic recoil causes it to collapse inward.
In tension pneumothorax, a one-way valve mechanism allows air to enter the pleural space during inspiration but prevents its escape during expiration. Pressure progressively rises, collapsing the ipsilateral lung and pushing the mediastinum toward the contralateral side. This kinks the great vessels and vena cava, reducing venous return to the heart, causing obstructive shock, hypotension, and ultimately cardiac arrest if untreated.
In secondary pneumothorax, diseased lung tissue (bullae, necrotic cavities, cystic changes) is more fragile and prone to rupture, and patients tolerate the resulting respiratory compromise far less well because they lack pulmonary reserve.
Clinical features
- Sudden onset pleuritic (sharp, unilateral) chest pain, often at rest
- Acute dyspnea, which can range from mild to severe depending on size and underlying lung function
- Dry cough (less common)
- Tachycardia and tachypnea
Physical examination
- Decreased or absent breath sounds on the affected side
- Hyperresonance to percussion
- Reduced chest wall movement/tactile fremitus on the affected side
- Subcutaneous emphysema may be present, more often with traumatic pneumothorax, but it is not a core or reliable finding
Tension pneumothorax (clinical emergency)
- Severe respiratory distress, hypotension, tachycardia
- Tracheal deviation away from the affected side
- Distended neck veins (jugular venous distension)
- Hypoxia and signs of obstructive shock
Tension pneumothorax must be diagnosed clinically and treated immediately; do not wait for a chest X-ray.
Diagnosis
Imaging
- Upright chest X-ray (expiratory films do not improve sensitivity and are not routinely recommended): shows a visceral pleural line with absence of lung markings peripheral to it
- CT chest: gold standard for size estimation, detecting small pneumothoraces, bullae, or underlying lung disease; used when diagnosis is uncertain or for surgical planning
- Bedside ultrasound (point-of-care, eFAST): increasingly used in trauma/ICU; findings include absence of lung sliding, absence of comet-tail artifacts, and the 'barcode sign' on M-mode
Sizing (guides management)
British Thoracic Society (BTS) uses the distance from the lung edge to the chest wall at the level of the hilum (greater than 2 cm = large). American College of Chest Physicians (ACCP) uses the distance from the apex to the cupola. This is one area where guidelines genuinely differ.
Tension pneumothorax
Diagnosed clinically based on respiratory distress plus hypotension, tracheal deviation, and JVD. Imaging should NOT delay treatment.
Differential diagnosis
| Condition | Distinguishing feature |
|---|---|
| Pulmonary embolism | Pleuritic pain + dyspnea but normal/clear breath sounds, risk factors for VTE |
| Acute coronary syndrome | Pain often exertional, ECG changes, elevated troponin |
| Pericarditis | Pain relieved by sitting forward, friction rub, diffuse ST elevation |
| Pleural effusion | Dullness to percussion rather than hyperresonance |
| Pneumonia | Fever, productive cough, consolidation on imaging |
| Aortic dissection | Tearing pain radiating to back, pulse/BP differential between limbs |
| Bullous emphysema (giant bulla mimic) | Can look like pneumothorax on CXR; CT helps differentiate |
Management
Management depends on size, symptoms, hemodynamic stability, and whether it is primary or secondary.
Tension pneumothorax
- Immediate needle decompression (large-bore needle, 2nd intercostal space midclavicular line, or 4th/5th intercostal space anterior axillary line per updated ATLS guidance), followed by chest tube (tube thoracostomy)
- This is a clinical emergency; treat before confirmatory imaging
Primary spontaneous pneumothorax
- Small, minimally symptomatic: observation and high-flow supplemental oxygen (speeds pleural air reabsorption); outpatient follow-up with repeat imaging
- Large or symptomatic: needle aspiration or small-bore chest tube/catheter; many patients can be managed without hospital admission if stable
- Guidelines increasingly favor conservative management (observation alone) for stable patients even with larger PSP, per recent randomized trial evidence informing BTS/ACCP updates
Secondary spontaneous pneumothorax
- Lower threshold for chest tube drainage given reduced pulmonary reserve
- Hospital admission generally recommended given higher risk of deterioration
Recurrent or persistent pneumothorax
- Pleurodesis (chemical, e.g., talc, or surgical) to obliterate the pleural space and prevent recurrence
- Video-assisted thoracoscopic surgery (VATS) with bullectomy/stapling of blebs, often combined with pleurodesis, indicated after first recurrence, persistent air leak (greater than 3-5 days), bilateral pneumothorax, or high-risk occupations (pilots, divers)
Supportive
- Supplemental oxygen for all patients regardless of strategy
- Analgesia for pleuritic pain
- Smoking cessation counseling (reduces recurrence risk)
- Avoid air travel and diving until full resolution and clearance
Complications and prognosis
- Recurrence: 30-50% after a first spontaneous pneumothorax without definitive intervention; risk increases with each subsequent episode
- Tension pneumothorax: can rapidly progress to cardiac arrest if untreated
- Re-expansion pulmonary edema: can occur after rapid lung re-expansion, especially with large or longstanding pneumothorax
- Persistent air leak/bronchopleural fistula: may require surgical intervention
- Respiratory failure: particularly in secondary pneumothorax with limited pulmonary reserve
- Empyema: rare, associated with chest tube drainage
Overall prognosis is excellent for primary spontaneous pneumothorax with appropriate treatment and follow-up. Secondary pneumothorax carries higher mortality (up to several percent) due to underlying lung disease and reduced reserve.
Tension pneumothorax signs — 'TRACHEA': Tracheal deviation, Resp distress, Absent breath sounds, Collapsed lung on affected side, Hypotension, Elevated JVP, Asymmetric chest expansion.
Practice questions
1. A 19-year-old tall, thin man presents with sudden onset right-sided pleuritic chest pain and mild dyspnea while at rest. He is a smoker. Vital signs are stable: BP 118/76 mmHg, HR 92/min, RR 18/min, SpO2 96%. Chest X-ray shows a small apical pneumothorax with less than 2 cm rim of air. Which of the following is the most appropriate next step?
2. A 34-year-old man is brought to the emergency department after a motor vehicle collision. He is in severe respiratory distress with BP 82/50 mmHg, HR 130/min, and SpO2 85%. Exam reveals absent breath sounds on the left, distended neck veins, and tracheal deviation to the right. What is the most appropriate immediate management?
3. A 58-year-old woman with longstanding COPD presents with acute dyspnea and right-sided chest pain. Chest X-ray confirms a secondary spontaneous pneumothorax occupying about 30% of the hemithorax. She is hemodynamically stable but hypoxic on room air. Compared to a healthy young adult with a similar-sized primary spontaneous pneumothorax, which statement is most accurate regarding her management?
Frequently asked questions
What causes a pneumothorax?
A pneumothorax occurs when air enters the pleural space, usually from rupture of a subpleural bleb (primary spontaneous type), underlying lung disease like COPD (secondary type), or trauma including medical procedures such as central line placement. Smoking is the strongest risk factor for the spontaneous form. The air disrupts the negative pressure that normally keeps the lung expanded, causing it to collapse.
What are the first symptoms of pneumothorax?
The earliest symptoms are sudden, sharp, one-sided chest pain and shortness of breath, often occurring at rest without any clear trigger. Some patients also notice a dry cough or a sense of chest tightness. Severity varies widely, from barely noticeable in small pneumothoraces to severe respiratory distress in large ones or in patients with underlying lung disease.
How is pneumothorax diagnosed?
Pneumothorax is diagnosed with an upright chest X-ray showing a visceral pleural line with no lung markings beyond it, or with CT chest for smaller or uncertain cases. Bedside ultrasound is increasingly used, especially in trauma and ICU settings, showing absent lung sliding. Tension pneumothorax, however, is diagnosed clinically from symptoms and exam findings and treated immediately without waiting for imaging.
Is pneumothorax curable?
Yes, most pneumothoraces resolve fully with appropriate treatment, whether observation, needle aspiration, or chest tube drainage, and the lung re-expands completely. However, recurrence is common, occurring in roughly 30-50% of patients after a first spontaneous episode. Procedures like pleurodesis or VATS surgery significantly reduce recurrence risk for patients with repeat episodes.
Pneumothorax vs pleural effusion — what is the difference?
Pneumothorax is air in the pleural space causing hyperresonance to percussion and absent breath sounds, while pleural effusion is fluid in the pleural space causing dullness to percussion and decreased breath sounds. Both cause reduced breath sounds, but the percussion note and underlying cause differ markedly. Imaging easily distinguishes the two, showing a pleural line with lucency in pneumothorax versus a meniscus sign with fluid density in effusion.
Key drugs
Related conditions and differentials
Sources and further reading
StatPearls (NCBI Bookshelf)MedlinePlusWHO ICD-10: J93
Educational content for medical students, prepared by the WhiteCoat Pro editorial team with AI assistance; every page is reviewed by a second AI model for factual errors. It is not medical advice and does not replace the product label, local guidelines or a clinician.