Pneumothorax

Note: Davidson's Principles and Practice of Medicine is not in this textbook library. The following is a comprehensive clinical overview drawn from Murray & Nadel's Textbook of Respiratory Medicine and Harrison's Principles of Internal Medicine 22E (2025) - both cover the same content as Davidson's on this topic.

Definition

Classification

1. Spontaneous Pneumothorax

• Occurs without underlying lung disease or antecedent trauma
• Typical patient: tall, thin young male, often a smoker
• Due to rupture of apical pleural blebs - small cystic spaces (outpouchings of visceral pleura, <1 cm) that lie within or immediately under the visceral pleura
• Blebs vs. Bullae: A bleb (<1 cm) is an outpouching between the lamina elastica interna and externa; a bulla (>1 cm) is an airspace demarcated by a thin wall (Reid classified bullae into 3 types)
• Microscopic abnormalities include respiratory bronchiolitis and pleural fibroelastosis
• Smoking is a major risk factor (airway inflammation weakens the visceral pleura)
• ~50% of patients will have a recurrence after the first episode

• Occurs in the context of underlying lung disease
• More dangerous because of reduced pulmonary reserve
• Causes (Murray & Nadel's):

• Catamenial pneumothorax: Recurrent pneumothorax in women of childbearing age - consider thoracic endometriosis
• LAM: Spontaneous pneumothorax in younger women (30-40 years) may be the first manifestation

2. Traumatic Pneumothorax

• Results from penetrating or nonpenetrating chest injuries
• Present in 40% of blunt and 20% of penetrating thoracic trauma cases
• Iatrogenic causes: transthoracic needle aspiration, thoracentesis, central venous catheter insertion (most common iatrogenic causes)
• Open pneumothorax ("sucking chest wound"): chest wall defect allows air entry through the wound; if wound approaches the size of the trachea, ventilation is severely compromised
  • Management: cover with a one-way flutter (Heimlich) valve or occlusive dressing with one side open before operative repair

3. Tension Pneumothorax

• A medical emergency
• One-way valve mechanism: air enters but cannot escape - progressive intrapleural pressure rise
• Compresses the right ventricle, kinks the SVC/IVC, reduces venous return and cardiac output
• Causes obstructive shock: hypotension + hypoxia
• Hypoxemia is nearly universal (92%) in ventilated patients; present in only 50% breathing unassisted
• Treatment must not wait for radiologic confirmation - immediate thoracic decompression

Clinical Features

• Symptoms: Sudden onset ipsilateral pleuritic chest pain and breathlessness; may be minimal in small PSP
• Signs:
  • Reduced chest expansion on affected side
  • Hyperresonant percussion note
  • Diminished/absent breath sounds
  • Tracheal deviation away (in tension - a late sign)
• In tension: hypotension, tachycardia, raised JVP, cyanosis

Diagnosis

Chest X-Ray

• Gold standard for diagnosis
• Visible lung edge with absent lung markings peripherally
• BTS size classification: small (<2 cm rim of air at the hilum), large (≥2 cm)
• Note: Three different guidelines classify size differently with agreement in only 47% of cases

CT Chest

• More accurate for size estimation
• Identifies underlying lung disease, blebs, bullae
• Useful before surgical intervention

Ultrasound (POCUS)

• Pleural sliding (sea-shore sign on M-mode): when present, effectively excludes pneumothorax at that location
• Absence of sliding is not specific (also seen in apnea, pleural adhesions)
• "Lung point" (transition from sliding to no sliding at the edge of the pneumothorax): highly specific for pneumothorax
• B-lines: if present, excludes pneumothorax at that site
• "Bar code" / "stratosphere" sign (M-mode): linear pattern throughout depth - seen when sliding is absent
• More sensitive than CXR for occult pneumothorax, particularly in trauma

Management

Primary Spontaneous Pneumothorax

• Supplemental O₂ accelerates resolution of pneumothorax
• Needle aspiration vs. chest tube: Multiple RCTs show comparable initial success rates (aspiration 48-80%; chest tube 64-100%)
• Ambulatory management: One-way (Heimlich/flutter) valve attached to chest drain; effective in 85.8% - reduces hospital stay vs. standard chest drain (median 8 days hospitalized vs. outpatient)

Secondary Spontaneous Pneumothorax

• Nearly all patients require tube drainage
• Many will need thoracoscopy/thoracotomy with stapling + surgical pleurodesis
• If not a good operative candidate: chemical pleurodesis

Tension Pneumothorax

• Immediate decompression: needle thoracostomy or tube thoracostomy
• ATLS recommendations: insert needle at 4th-5th intercostal space, midaxillary line (higher success rate than traditional 2nd ICS midclavicular line due to thinner chest wall, avoids internal mammary/subclavian artery injury)
• A 5-cm angiocatheter at the anterior axillary line 4th-5th ICS has significantly lower failure rate (13% vs. 38% at midclavicular 2nd ICS)
• Follow immediately with chest tube

Traumatic Pneumothorax

• Usually treated with tube drainage unless very small
• Hemopneumothorax: one tube superiorly (air) + one inferiorly (blood)
• Iatrogenic: often managed with supplemental O₂ or aspiration; tube drainage if these fail

Prevention of Recurrence / Pleurodesis

• Talc poudrage: 2-4 g sufficient; no long-term sequelae (lung function near-normal 22-35 years later); relative contraindication if future lung transplant is anticipated (but not absolute)
• VATS: Important disadvantage - long-term postoperative pain (>30% patients, lasting 3-18 months)
• Mechanical pleurodesis: abrasion or partial parietal pleurectomy
• Bulectomy alone has unacceptably high recurrence (27.5% at 10 years) - must add pleurodesis

Complications

• Re-expansion pulmonary edema (RPE): Unilateral pulmonary edema after rapid lung reinflation; incidence ~1-3% symptomatic; treat with supplemental O₂ and diuretics
• Haemopneumothorax: Blood + air in pleural space (from torn adhesions or vascularized bullae rupture)
• Persistent air leak (bronchopleural fistula)
• Tension pneumothorax (if untreated)

Special Situations

• Air travel: Pneumothorax may expand at altitude (reduced cabin pressure) - patients should not fly until fully resolved
• Diving: Absolute contraindication until definitive treatment (surgical pleurodesis) given risk of rapid expansion at depth