Pneumothorax

Detailed Overview

Pneumothoraces are classified as spontaneous (primary or secondary) or traumatic (including iatrogenic). Primary spontaneous pneumothorax (PSP) typically occurs in tall, thin young men without underlying lung disease due to the rupture of subpleural apical blebs. Secondary spontaneous pneumothorax (SSP) occurs in patients with underlying lung pathology, most commonly COPD. A tension pneumothorax is a life-threatening medical emergency where a 'one-way valve' effect causes progressively increasing intrapleural pressure, leading to mediastinal shift, compression of the contralateral lung, and collapse of venous return to the heart.

Epidemiology & Demographics

Incidence of PSP is ~20 per 100,000 per year in men, and ~6 per 100,000 in women. Peak age for PSP is 20-30 years. SSP peaks in patients >60 years old.

Etiological Mechanism

Rupture of apical blebs (PSP). Rupture of emphysematous bullae, cystic fibrosis, or necrotizing pneumonia (SSP). Blunt/penetrating chest trauma, central line placement, or mechanical ventilation barotrauma (Traumatic).

Primary Causes

Spontaneous bleb rupture, penetrating trauma (stab wounds), iatrogenic (thoracentesis, subclavian vein catheterization, transbronchial biopsy), positive pressure ventilation.

• Smoking: Increases the risk of primary spontaneous pneumothorax by up to 20-fold due to bronchiolar inflammation.
• Tall, thin body habitus: Increased negative pleural pressure gradient at the lung apex promotes bleb formation.
• COPD/Emphysema: Destruction of alveolar walls creates fragile bullae prone to rupture.
• Marfan Syndrome: Connective tissue weakness predisposing to apical bleb rupture.

The intrapleural pressure is normally negative (-5 cm H2O) relative to alveolar pressure, which keeps the lung expanded against the chest wall. When a defect occurs in the visceral pleura (e.g., ruptured bleb) or parietal pleura (e.g., stab wound), air flows down the pressure gradient into the pleural space. This equalizes pleural and alveolar pressure, eliminating the distending force and causing the elastic lung to collapse toward the hilum. This causes a V/Q mismatch and hypoxemia. In tension pneumothorax, the pleural defect acts as a one-way valve: air enters during inspiration but cannot exit during expiration. Intrapleural pressure rises rapidly above atmospheric pressure, compressing the superior and inferior vena cava, severely reducing venous return and cardiac output, leading to obstructive shock.

Characteristic Clinical Presentation

• Sudden Pleuritic Chest Pain: Sharp, severe, unilateral chest pain that starts abruptly, often while at rest.
• Dyspnea: Sudden onset shortness of breath, severity proportional to the size of the pneumothorax and underlying lung reserve.
• Tachypnea: Rapid breathing as a compensatory response to hypoxemia.

Physical Examination Signs

• Hyperresonance to percussion on the affected side.
• Decreased or absent breath sounds on the affected side.
• Decreased tactile fremitus.
• In Tension PTX: Tracheal deviation to the CONTRALATERAL side, distended neck veins (JVD), and severe hypotension.

• Tension Pneumothorax: Progression to obstructive shock and cardiac arrest.
• Re-expansion Pulmonary Edema: Alveolar flooding occurring after rapid evacuation of a large, long-standing pneumothorax.
• Recurrence: Up to 30% risk of recurrence after a first PSP, rising to 60% after a second.

Diagnostic Criteria & Guidelines

Diagnosis is based on the visualization of a visceral pleural line lacking lung markings distally on chest imaging. Tension pneumothorax is a CLINICAL diagnosis and must be treated before obtaining imaging.

Differential Diagnosis

• Pulmonary Embolism
• Myocardial Infarction
• Acute Exacerbation of COPD/Asthma
• Costochondritis

Laboratory Tests & Biomarkers

• Arterial Blood Gas (ABG): May show hypoxemia (PaO2 < 80 mmHg) and acute respiratory alkalosis (low PaCO2) due to hyperventilation.
• ECG: Usually normal, but massive left-sided pneumothorax can mimic anterior MI or show electrical alternans.

Imaging Modalities & Findings

• Upright Chest X-ray (PA): Visible thin white visceral pleural line with no pulmonary vascular markings peripheral to this line. Deep sulcus sign may be seen on supine films.
• Bedside Thoracic Ultrasound: Absence of lung sliding ('seashore sign' replaced by 'barcode/stratosphere sign' in M-mode) and presence of a 'lung point'.
• CT Chest: Most sensitive; identifies exact size, detects small blebs/bullae, and guides surgical planning for recurrent cases.

• Small (<2 cm)
  Distance from lung margin to chest wall at the hilum is <2 cm; often well-tolerated.
• Large (≥2 cm)
  Distance ≥2 cm; requires intervention due to significant lung collapse.
• Tension Pneumothorax
  Hemodynamic instability; immediate life-threatening emergency.

Second-Line & Adjunctive Therapy

For SSP, failed aspiration, or trauma: Standard tube thoracostomy (20-28F chest tube) placed in the 4th/5th ICS mid-axillary line, connected to wall suction.

Surgical & Procedural Management

VATS (Video-Assisted Thoracoscopic Surgery) with blebectomy/bullectomy and mechanical pleurodesis (pleural abrasion) is indicated for recurrent PSP, bilateral pneumothorax, or incomplete lung expansion after 3-5 days of chest tube drainage.

Recommended Lifestyle Changes

• Absolute smoking cessation to reduce recurrence risk.
• Avoid air travel for at least 2-4 weeks post-resolution due to pressure changes.
• Permanent avoidance of SCUBA diving unless definitive surgical pleurodesis has been performed.

Patient Counseling & Advice

Warn the patient about the high risk of recurrence (1 in 3 chance) and to immediately seek emergency care if sudden chest pain or shortness of breath returns. Emphasize that smoking is the largest modifiable risk factor.

Follow-Up & Monitoring Schedule

Outpatient follow-up with repeat chest X-ray in 2-4 weeks to ensure full lung re-expansion and no recurrence.

Preventive Strategies

Smoking cessation. Surgical pleurodesis for high-risk patients (e.g., airline pilots, deep-sea divers) even after a first episode.

Excellent with appropriate management. The primary issue is recurrence. Mortality from primary spontaneous pneumothorax is virtually zero, but secondary spontaneous pneumothorax carries a mortality of up to 10% due to poor baseline lung function.