Pneumothorax

Spontaneous (no external insult)

• Primary: rupture of apical subpleural blebs/bullae in structurally "normal" lungs. The apex sees the most negative pleural pressure (gravity-dependent pressure gradient in an upright thorax), so distending stress is greatest there — the reason tall stature is mechanistically relevant.
• Secondary: rupture of diseased parenchyma — COPD/emphysema (most common cause overall in older adults), cystic fibrosis, necrotizing or cavitary infection (TB, Pneumocystis jirovecii), lung cancer, and cystic lung diseases such as lymphangioleiomyomatosis (young women, chylothorax) and Langerhans cell histiocytosis (smokers).
• Catamenial: thoracic endometriosis, right-sided and menses-associated.

Traumatic and iatrogenic

• Penetrating or blunt trauma: rib fracture laceration of visceral pleura; the setting in which tension physiology and hemopneumothorax are most likely.
• Iatrogenic: subclavian/internal jugular central line placement, thoracentesis, transbronchial or CT-guided lung biopsy, and barotrauma from positive-pressure ventilation (high plateau pressures, high PEEP) or CPR. Iatrogenic causes now rival spontaneous ones in frequency in hospitalized patients.

Non-modifiable risk factors

• Male sex, age 20–40, tall thin habitus: the tall thin young male stem.
• Heritable connective tissue disease: Marfan syndrome, vascular Ehlers-Danlos, and Birt-Hogg-Dubé (FLCN mutation — basilar lung cysts, fibrofolliculomas, renal tumors). A family history of pneumothorax should prompt consideration of these.
• Prior pneumothorax: the single strongest predictor of another.

Modifiable risk factors

• Cigarette smoking: the dominant modifiable factor, raising risk many-fold and driving small-airway inflammation and bleb formation; cannabis and vaping are also implicated. British Thoracic Society pleural disease guidance makes smoking cessation counselling a core part of management and cessation lowers recurrence risk.
• Ambient pressure change: scuba diving and unpressurized flight (Boyle's law expansion of trapped gas).
• Ventilator settings and procedural technique: lung-protective ventilation and ultrasound-guided line placement reduce iatrogenic events.

• Primary spontaneous pneumothorax: Results from rupture of subpleural blebs or bullae (small air-filled cavities) located at lung apices, typically in tall, thin individuals with abnormal connective tissue; the exact etiology of bleb formation remains incompletely understood but involves apical alveolar enlargement
• Secondary spontaneous pneumothorax: Arises from rupture of existing lung parenchymal lesions (emphysematous bullae in COPD, cavitary lesions in tuberculosis or fungal infections, or cystic spaces in cystic fibrosis, PCP pneumonia, or lymphangioleiomyomatosis)
• Mechanical effects of pneumothorax: Progressive air accumulation increases intrapleural pressure, causing elastic recoil of the lung and reduction in lung volume; mediastinal structures may shift with large pneumothoraces, potentially compromising venous return
• Tension pneumothorax formation: Occurs when air enters the pleural space but cannot escape (one-way valve mechanism), leading to progressive pressure increase, cardiopulmonary compromise, and hemodynamic instability
• Recurrence risk: Primary spontaneous pneumothorax recurs in 20-40% of cases (second ipsilateral recurrence ~60%, contralateral recurrence ~10%); secondary pneumothorax has higher recurrence rates (up to 50%) due to persistent underlying lung pathology

• Sudden-onset pleuritic chest pain: Typically sharp, unilateral, and worsened by deep inspiration or coughing; may radiate to ipsilateral shoulder; pain severity does not correlate with pneumothorax size
• Dyspnea: Range from absent (small pneumothorax) to severe and progressive; in secondary pneumothorax, dyspnea is often more pronounced due to limited respiratory reserve from underlying disease
• Tachycardia and tachypnea: Non-specific findings reflecting compensatory response; tachycardia may be prominent in tension pneumothorax
• Physical examination findings: Decreased breath sounds and hyperresonance to percussion on the affected side; absent tactile fremitus; tension pneumothorax presents with severe distress, hypotension, jugular venous distention (JVD), tracheal deviation away from the affected side, and potential loss of consciousness
• Clinical pearl—asymptomatic presentations: Small pneumothoraces (typically <2 cm at the hilum on imaging) may be completely asymptomatic and discovered incidentally on imaging obtained for other reasons; conversely, some patients with large pneumothoraces remain surprisingly asymptomatic
• Secondary pneumothorax considerations: Patients with COPD often present with more severe dyspnea and hemodynamic changes with smaller pneumothoraces due to compromised baseline lung function

• Chest X-ray (CXR)—gold standard initial imaging: Look for visceral pleural line (thin, white line representing the collapsed lung edge) separated from the parietal pleura with absent lung markings peripheral to this line; typically obtain both inspiratory and expiratory films (pneumothorax becomes more apparent on expiration); measure size as either largest distance between lung edge and chest wall at the level of the hilum (small if <2 cm) or percentage of hemithorax volume
• CT chest: More sensitive than CXR, particularly for detecting small or loculated pneumothoraces; useful when CXR is equivocal or to characterize underlying lung disease in secondary pneumothorax; can identify blebs, bullae, or other parenchymal abnormalities
• Ultrasound: Lung point sign (transition between visceral and parietal pleura visible at the lung edge) is highly specific for pneumothorax and has excellent sensitivity (~95%) in trained hands; increasingly used in critical care and emergency settings as it avoids radiation
• Arterial or venous blood gas: Not routinely needed for diagnosis; may show mild hypoxemia or hypercapnia depending on degree of collapse
• Diagnostic consideration—size classification: British Thoracic Society defines small as <2 cm at hilum or <20% of hemithorax volume; large pneumothoraces (≥2 cm or ≥20%) require more aggressive management

• Tension pneumothorax—immediate needle decompression: This is a clinical diagnosis requiring immediate intervention without awaiting imaging; perform immediate needle thoracostomy (insert 14-16 gauge needle into 2nd intercostal space, midclavicular line, or 4th-5th intercostal space, anterior axillary line) followed by chest tube placement (typically 28-32 French tube into 4th-5th intercostal space, anterior to midaxillary line); failure to immediately decompress leads to cardiovascular collapse and death
• Primary spontaneous pneumothorax—small and stable: Observation alone is appropriate; spontaneous reabsorption occurs at ~1-2% per day; patients may be discharged with close outpatient follow-up and repeat imaging in 2-4 weeks if asymptomatic; supplemental oxygen (high-flow O₂) accelerates reabsorption by creating nitrogen gradient favoring pleural absorption
• Primary spontaneous pneumothorax—large or symptomatic: Aspiration (needle or catheter aspiration of air) is first-line intervention in many centers, particularly in British practice; if aspiration fails, proceed to chest tube (tube thoracostomy) with suction (typically -20 cm H₂O) until lung re-expands and air leak ceases
• Secondary spontaneous pneumothorax: More aggressive approach warranted given high recurrence risk and baseline pulmonary compromise; even small pneumothoraces typically warrant aspiration or chest tube; supplemental oxygen strongly recommended
• Chest tube management: Maintain water-seal drainage or suction; monitor for persistent air leak (indicates ongoing air entry); apply positive pressure via one-way valve or water seal; remove once air leak has ceased for 24 hours and lung remains expanded; typical duration is 3-7 days
• Recurrent or persistent pneumothorax—definitive management: Chemical pleurodesis (talc, doxycycline, or other agents instilled into pleural space to create inflammation and fusion of visceral-parietal pleura) or surgical intervention (VATS with pleurectomy/abrasion or open thoracotomy); pleurodesis is preferred for first recurrence; surgery reserved for failure of pleurodesis, bilateral pneumothoraces, or hemopneumothorax
• Special situation—catamenial pneumothorax: Recurrent pneumothorax occurring in women in temporal relationship to menses; associated with thoracic endometriosis; managed with hormonal suppression (continuous oral contraceptives or GnRH agonists) or surgical treatment
• Special situation—primary spontaneous pneumothorax in pregnancy: Chest tube preferred over observation due to physiologic changes; pleurodesis and surgery deferred until after delivery if possible

• Recurrent pneumothorax: Occurs in up to 40% of primary and 50% of secondary cases; risk increases with multiple prior episodes; necessitates consideration of definitive intervention (pleurodesis or surgery)
• Persistent air leak: Air continues to enter pleural space despite chest tube, preventing lung re-expansion; suggests ongoing parenchymal damage; may require higher suction levels

• The stem archetype: tall, thin, young male smoker with abrupt pleuritic chest pain and dyspnea at rest — primary spontaneous pneumothorax from apical bleb rupture. Contrast with the older COPD patient whose "small" pneumothorax produces disproportionate distress because of absent reserve.
• Tension pneumothorax is a clinical diagnosis — decompress before imaging: hypotension, JVD, tracheal deviation away, unilateral absent breath sounds with hyperresonance. ATLS is explicit that ordering a chest X-ray first is the wrong answer; needle thoracostomy then tube thoracostomy is the sequence.
• The one association examiners test: sudden hypotension with a rising peak inspiratory pressure in a mechanically ventilated patient = tension pneumothorax from barotrauma until proven otherwise.
• Classic distractor — cardiac tamponade: both give hypotension plus JVD. Tamponade has muffled heart sounds, pulsus paradoxus, and bilaterally normal breath sounds with normal percussion; pneumothorax gives unilateral hyperresonance and absent breath sounds. Massive hemothorax gives dullness, not hyperresonance.
• Supine film buzzword: the deep sulcus sign — an abnormally deep, lucent costophrenic angle in a trauma or ICU patient whose air layers anteriorly rather than at the apex.
• Ultrasound: absent lung sliding and the barcode/stratosphere sign on M-mode support the diagnosis; only the lung point is essentially pathognomonic.
• Supplemental oxygen is therapeutic, not just supportive: high-FiO₂ washes out alveolar and blood nitrogen, steepening the nitrogen gradient out of the pleural space and multiplying the resorption rate.
• Counselling that shows up as a "next step": per British Thoracic Society guidance, air travel is deferred until radiographic resolution, and scuba diving is permanently avoided unless definitive bilateral surgical pleurectomy has been performed — Boyle's law makes ascent catastrophic.
• Do not attribute apical blebs to alpha-1 antitrypsin deficiency: that emphysema is basilar/lower-lobe, whereas smoking-related and bleb-related disease is apical.