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Pneumothorax — Comprehensive Review

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1. Definition

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2. Classification

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3. Epidemiology

• PSP: Incidence ~7.4/100,000/year (men), ~1.2/100,000/year (women)
• Male:female ratio ~6:1 for PSP
• Peak age PSP: 20–30 years
• SSP: Higher morbidity/mortality due to underlying disease; affects older patients (mean age ~60 years)
• Smoking increases PSP risk 22-fold in men (Light's, p. 312)
• Recurrence rate: ~30% after first PSP; rises to ~60% after second untreated episode (Fishman's, p. 1520)

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4. Pathophysiology

Primary Spontaneous Pneumothorax

• Caused by rupture of subpleural blebs or bullae, most commonly at the apex
• These blebs arise from degradation of elastic fibers in the lung apex, possibly secondary to inflammation from smoking or infection
• Increased height → greater negative pressure gradient at the apex → bleb formation
• On CT, apical subpleural blebs are found in >80% of PSP patients even without clinical evidence (Fishman's, p. 1518)

Secondary Spontaneous Pneumothorax

• Mechanism varies by disease:
  • COPD/Emphysema: Rupture of emphysematous bullae
  • Tuberculosis: Rupture of subpleural caseous focus or cavity
  • PCP (Pneumocystis jirovecii pneumonia): Cyst rupture; high recurrence
  • Cystic fibrosis: Rupture of subpleural bullae; recurrence rate ~50%
  • LAM (Lymphangioleiomyomatosis): Cyst rupture; high recurrence
  • Marfan/Ehlers-Danlos syndromes: Connective tissue weakness
  • Lung cancer: Cavitation or pleural invasion

Tension Pneumothorax

• A one-way valve mechanism: air enters pleural space on inspiration but cannot exit
• Progressive accumulation raises intrapleural pressure above atmospheric
• Causes contralateral mediastinal shift, compression of the opposite lung, kinking of the SVC/IVC, reduced venous return → decreased cardiac output → cardiovascular collapse
• Can be rapidly fatal if untreated

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5. Clinical Features

Symptoms

• Small PSP may be asymptomatic in fit young patients
• SSP causes disproportionately severe symptoms even with small pneumothorax

Signs

• Decreased/absent breath sounds on affected side
• Hyperresonance (tympanic note) to percussion
• Reduced chest expansion on affected side
• Tracheal/mediastinal deviation to contralateral side (tension or large pneumothorax)
• Hypoxia, tachycardia
• Tension: Hypotension, tachycardia, distended neck veins, cyanosis, tracheal deviation, absent breath sounds → hemodynamic shock

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6. Imaging

Chest X-Ray (CXR)

• Upright PA CXR is the standard initial investigation
• Shows a thin white visceral pleural line (lung edge) with peripheral lucency devoid of vascular markings beyond it
• Always look for:
  • Mediastinal shift (tension)
  • Subcutaneous emphysema
  • Underlying lung disease (bullae, infiltrates)
  • Fluid level (hydropneumothorax)
• Expiratory CXR: May improve detection of small pneumothorax (debated)
• Supine CXR (ICU patients): Pneumothorax may manifest as a "deep sulcus sign" — abnormally deep costophrenic angle

Size Estimation

CT Chest

• More sensitive than CXR, particularly for:
  • Small/loculated pneumothorax
  • Distinguishing pneumothorax from bullae (critical before intervention)
  • Identifying underlying blebs, bullae, or lung disease
  • Guiding management decisions
• CT is not routine for first uncomplicated PSP but recommended for SSP, recurrent PSP, and before surgery

Ultrasound

• In ICU/trauma settings, lung ultrasound is highly sensitive
• Loss of lung sliding + absent comet-tail artifacts (B-lines) suggests pneumothorax
• "Lung point" sign = pathognomonic of pneumothorax (junction between collapsed and expanded lung)
• More sensitive than supine CXR for detecting occult pneumothorax

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7. Management

General Principles

1. Admit or observe as outpatient?
2. Supplemental oxygen?
3. Simple aspiration or intercostal tube drainage?
4. Definitive prevention of recurrence?

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Supplemental Oxygen

• Breathing 100% O₂ (high-flow) enhances nitrogen washout from the pleural space → accelerates reabsorption rate 4-fold (from ~1.25% per day to ~6% per day)
• Recommended for all hospitalized patients with pneumothorax

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Treatment by Type

A. Primary Spontaneous Pneumothorax (PSP)

• Conservative management with observation acceptable
• Outpatient management with early review possible in selected patients
• High-flow O₂ if admitted

1. Simple aspiration (manual aspiration with 16–18G cannula, 50 mL syringe + 3-way tap):
   • Success rate: ~70–80% for PSP
   • Preferred first-line for large PSP in BTS guidelines
   • If < 2.5 L aspirated and lung re-expands → discharge possible
2. Small-bore chest tube (8–14 Fr Seldinger technique):
   • For failed aspiration or recurrent PSP
   • Connected to water-seal drainage ± suction
   • Remove when lung re-expanded and air leak stopped for 24 hours

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B. Secondary Spontaneous Pneumothorax (SSP)

• All SSP should be admitted and treated
• Even small SSP causes significant compromise in patients with underlying lung disease
• Chest tube drainage is the preferred initial therapy (not simple aspiration)
• High-flow O₂ (unless hypercapnic/COPD — use controlled O₂)
• Surgical/pleurodesis consultation for recurrence prevention

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C. Tension Pneumothorax

• Do NOT wait for imaging if clinical diagnosis is clear — treat immediately
• Immediate needle decompression: 14–16G cannula into 2nd intercostal space, midclavicular line (or 4th/5th ICS, anterior axillary line)
• Rapid escape of air confirms diagnosis and provides temporary relief
• Follow immediately with large-bore chest tube (28–32 Fr) connected to underwater seal drain
• Leave needle in place until chest tube is inserted

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D. Iatrogenic Pneumothorax

• Post-thoracentesis: observation for small, asymptomatic cases; aspiration or tube for larger/symptomatic
• Post-subclavian CVL: as for PSP — aspiration or tube depending on size/symptoms
• Ventilator-associated: almost always requires tube drainage; high risk of tension

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E. Catamenial Pneumothorax

• Occurs within 72 hours of onset of menstruation, typically right-sided (>90%)
• Caused by diaphragmatic fenestrations or pleural/diaphragmatic endometriosis
• Treatment: chest tube for acute episode; hormonal suppression (GnRH agonists, OCP) to suppress menstruation; surgical repair of diaphragmatic defects + pleurodesis for recurrence

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Chest Tube Insertion — Key Points

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Pleurodesis

• Second ipsilateral PSP
• First contralateral PSP (bilateral disease)
• First SSP with ongoing air leak
• PSP in high-risk occupations (pilots, divers)
• Patient preference after first PSP

• Talc (poudrage via thoracoscopy or slurry via chest tube): most effective agent, success >90%
• Tetracycline/Doxycycline: second-line; success ~85%
• Bleomycin, silver nitrate: less commonly used

• Bullectomy/blebectomy + mechanical or chemical pleurodesis
• VATS: shorter hospital stay, less pain, equivalent recurrence rates to thoracotomy (~5%)
• Open thoracotomy: reserved for failed VATS, complex anatomy
• Recurrence after surgical pleurodesis: <5%

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8. Complications

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9. Special Situations

Pneumothorax in COPD

• Even small pneumothorax is life-threatening due to minimal respiratory reserve
• Chest tube drainage mandatory
• Avoid high-flow O₂ (risk of hypercapnic respiratory failure)
• VATS/pleurodesis recommended for any recurrence given high morbidity (Crofton & Douglas, p. 918)

Pneumothorax in HIV/PCP

• Bilateral involvement common (~25%)
• High recurrence rate (>50%) after first episode
• Bilateral simultaneous pleurodesis may be considered
• High mortality in mechanically ventilated PCP patients with pneumothorax (Light's, p. 333)

Pneumothorax in Cystic Fibrosis

• Lifetime incidence ~20%
• High recurrence (~50%)
• Bilateral occurrence possible
• Pleurodesis indicated but may complicate future lung transplantation (relative contraindication)
• Decision should involve CF specialist (Fishman's, p. 1519)

Pneumothorax during Pregnancy

• Rare; may worsen with advancing gestation
• Management similar to non-pregnant; chest tube if large/symptomatic
• Delivery by caesarean preferred near term to avoid Valsalva-related expansion (Light's, p. 334)

Pneumothorax in Mechanically Ventilated Patients

• High risk of tension pneumothorax due to positive pressure ventilation
• Any sudden deterioration (rising airway pressures, hypotension, desaturation) should prompt immediate diagnosis and treatment
• Prophylactic chest tube placement sometimes considered in high-risk situations (Fishman's, p. 1522; Harrison's, p. 8096)

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10. Recurrence Prevention — Summary Algorithm

First PSP, large, treated with aspiration/tube
         ↓
 Discharge + smoking cessation counselling
         ↓
 Recurrence (~30%)? → VATS blebectomy + pleurodesis
 
First SSP
         ↓
 Tube drainage → pleurodesis at same admission (or VATS)
 
High-risk occupations (pilot, diver)
         ↓
 Offer surgical pleurodesis after first episode

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11. Key Points from Each Reference

• Emphases on CT findings of apical blebs in >80% PSP; detailed pathophysiology of bleb formation; management of SSP in COPD and cystic fibrosis; surgical options

• Strong emphasis on clinical features, signs, radiographic findings; treatment algorithms for PSP and SSP; pleurodesis agents and outcomes

• Most detailed coverage of pneumothorax among pleural disease textbooks; Light's index for size estimation; catamenial pneumothorax pathophysiology; pleurodesis efficacy data; special populations (HIV, pregnancy, CF)

• Tension pneumothorax — clinical diagnosis (hyperresonance, absent breath sounds, mediastinal shift), immediate needle decompression with 14–16G cannula at 2nd ICS midclavicular line

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Clinical Pearl (Light's): A patient with SSP and a pneumothorax of only 10% should be treated as aggressively as a patient with PSP and a 50% pneumothorax — the physiological impact is determined by the underlying lung reserve, not just the size of the air collection.