Etymology
Derived from the Greek words pneuma (air) and thorax (chest), pneumothorax refers to the presence of air within the pleural space.
AKA
Primary pneumothorax; Secondary pneumothorax
What is it?
A spontaneous pneumothorax is the accumulation of air in the pleural space without preceding trauma or iatrogenic causes. It disrupts the negative pressure within the pleural cavity, leading to partial or complete lung collapse.
Caused by
Primary Spontaneous Pneumothorax (PSP):
Occurs in individuals without known underlying lung disease.
Most commonly associated with young, thin men with narrow anteroposterior (AP) chest diameters, where mechanical forces in the lung apices predispose to rupture of subpleural bullae or blebs.
Secondary Spontaneous Pneumothorax (SSP):
Occurs in individuals with underlying lung diseases, including:
Collapse of the lung and loss of effective ventilation in the affected area.
Impaired gas exchange leading to hypoxemia.
Potential progression to tension pneumothorax if air continues to accumulate without exit, causing mediastinal shift and hemodynamic compromise.
Structural changes
Air within the pleural space separating the visceral and parietal pleura.
Collapse of the lung with loss of normal lung volume.
Pathophysiology
Rupture of subpleural blebs, bullae, or alveoli results in air escaping into the pleural cavity.
In PSP, the apical region is most affected due to higher transpulmonary pressure gradients and mechanical stress.
In SSP, compromised lung architecture due to underlying disease predisposes to alveolar rupture.
Pathology
Primary pneumothorax typically involves ruptured subpleural blebs or bullae, with no underlying disease evident on histology.
Secondary pneumothorax shows features of the underlying lung condition (e.g., emphysema, cystic lung disease, infection).
Diagnosis
Clinical
Symptoms: Sudden onset of pleuritic chest pain, dyspnea, or both.
Signs: Decreased breath sounds, hyperresonance to percussion, and reduced chest wall movement on the affected side.
Severe cases: Hypotension and signs of respiratory distress if tension pneumothorax develops.
Radiology
CXR: Visualization of the visceral pleural line, absence of lung markings beyond the line, and collapse of the affected lung.
CT: Most sensitive for detecting small pneumothoraces, characterizing underlying lung disease, and identifying bullae or blebs.
Radiology Detail
CXR
Findings
Thin visceral pleural line with no lung markings beyond it.
Lung collapse, with the extent often proportional to the amount of air in the pleural space.
Associated Findings
Subpleural bullae or blebs (more prominent in secondary pneumothorax).
Signs of tension pneumothorax: Mediastinal shift, depressed hemidiaphragm, or widened intercostal spaces.
CT
Parts
Identifies air in the pleural space, as well as associated bullae, blebs, or underlying pathology.
Size
Quantification of pneumothorax size, with large pneumothoraces often requiring intervention.
Shape
Crescentic collection of air outlining the lung margin.
Position
Predominantly apical location in primary spontaneous pneumothorax.
Character
Thin-walled bullae or blebs in PSP; thicker, irregular walls in SSP due to underlying disease.
Time
Can recur, particularly in PSP, with risk increased in smokers or untreated cases.
Associated Findings
Evidence of secondary conditions such as emphysema, interstitial lung disease, or infections.
Pulmonary Function Tests (PFTs)
Limited role during acute pneumothorax but may show obstructive or restrictive patterns in secondary cases.
Recommendations
In PSP: Observation is appropriate for small, asymptomatic pneumothoraces; supplemental oxygen may accelerate reabsorption of air.
In SSP or symptomatic PSP: Chest tube insertion or needle aspiration to evacuate air.
Preventive measures: Pleurodesis or surgical resection of bullae in recurrent cases.
Key Points and Pearls
Primary spontaneous pneumothorax is most common in young, thin men and typically involves the apices due to increased transpulmonary pressure gradients.
Secondary spontaneous pneumothorax often results from COPD, cystic lung diseases, or infections.
Tension pneumothorax is a life-threatening complication requiring immediate decompression.
CT is the gold standard for identifying small pneumothoraces and associated conditions.
Smoking cessation is crucial to reducing the risk of recurrence in PSP.
