Pneumothorax - 20 Marks (MBBS Final Year Surgery Theory)

Definition

Classification

A. Spontaneous Pneumothorax

• Occurs in apparently healthy individuals with no clinically apparent lung disease.
• Classic profile: young (15-35 years), tall, thin male, smoker.
• Incidence: ~10 per 100,000 in men, ~3 per 100,000 in women.
• Underlying mechanism: rupture of subpleural blebs/bullae (found in ~80% at CT or surgery).
• Smoking increases risk 10-20 fold.
• Recurrence rate: ~25% after first episode; rises to 50-60% after second episode.

• Occurs in patients with pre-existing lung disease (COPD/emphysema most common, also TB, asthma, cystic fibrosis, malignancy, Pneumocystis pneumonia).
• Patients are typically 15-20 years older than PSP patients.
• More physiologically dangerous because underlying lung reserve is already compromised.
• Higher recurrence rate than PSP.

B. Traumatic Pneumothorax

• Due to blunt or penetrating chest trauma.
• Rib fractures lacerate the lung parenchyma.
• Includes iatrogenic causes: central line insertion (subclavian route), mechanical ventilation with high pressures, thoracentesis, lung biopsy, pacemaker insertion.

C. Tension Pneumothorax

• Air enters the pleural space via a one-way valve mechanism; air enters with inspiration but cannot exit on expiration.
• Intrapleural pressure becomes positive, causing lung collapse on affected side.
• Progressive mediastinal shift to the contralateral side compresses SVC and IVC, severely reducing venous return and cardiac output.
• Life-threatening emergency.

D. Open Pneumothorax (Sucking Chest Wound)

• Large chest wall defect (e.g., gunshot wound) exceeding the laryngeal cross-sectional area.
• Atmospheric air enters the pleural space freely with each breath.
• Rapid equilibration of intrapleural with atmospheric pressure causes lung collapse.

Pathophysiology

• Normally, intrapleural pressure is negative (-5 to -8 cm H₂O), which keeps the lung expanded.
• Entry of air into the pleural space neutralizes this negative pressure, causing lung collapse.
• Degree of collapse depends on the volume of air and speed of accumulation.
• In tension pneumothorax, positive intrapleural pressure develops, compressing the mediastinum, great veins, and contralateral lung.
• Physiological consequences: decreased vital capacity, ventilation-perfusion mismatch, decreased PaO₂, decreased venous return (in tension type).

Clinical Features

Symptoms

• Sudden-onset sharp, pleuritic chest pain (worse on breathing).
• Dyspnea (can be severe in tension or SSP).
• Classically begins at rest or with mild exertion.

Signs (on affected side)

Note on Tension Pneumothorax: The triad of absent breath sounds, hyper-resonance, and tracheal deviation with hypotension and JVD is the hallmark. Tracheal deviation is a late sign. JVD may be absent if the patient is also hypovolemic.

Diagnosis

Chest X-Ray (Gold Standard)

• Visible lung edge (white visceral pleural line) separated from the chest wall with absent lung markings peripheral to it.
• Contralateral mediastinal shift and ipsilateral diaphragmatic depression in tension pneumothorax.
• BTS criteria:
  • Small pneumothorax: lung edge <2 cm from chest wall at hilum level.
  • Large pneumothorax: lung edge >2 cm from chest wall.

CT Chest

• Most sensitive; detects even small pneumothoraces.
• Identifies underlying blebs, bullae, and co-existing lung disease.
• Image guidance useful for loculated pneumothoraces.

Ultrasound (POCUS/eFAST)

• "Sliding sign" - movement of visceral over parietal pleura with breathing. Presence of sliding effectively excludes pneumothorax at that location.
• Absent sliding + "barcode/stratosphere sign" on M-mode suggests pneumothorax.
• "Lung point" - transition from sliding to absent sliding - highly specific for pneumothorax.
• B-lines, when present, exclude pneumothorax at that location.

Tension pneumothorax is a clinical diagnosis - do NOT delay treatment to obtain imaging.

Needle Aspiration Test (Bedside)

• Insert a fine-bore needle into the 2nd intercostal space, 2 cm from the sternal edge in the midclavicular line. Free aspiration of air confirms the diagnosis.

Differential Diagnosis

• Large bulla mimicking pneumothorax on CXR.
• Pulmonary embolism (pleuritic pain + dyspnea).
• Myocardial infarction.
• Cardiac tamponade (for tension pneumothorax).
• Aortic dissection.
• Spontaneous esophageal rupture (Boerhaave syndrome).

Treatment

1. Observation (Conservative)

• Small, asymptomatic primary spontaneous pneumothorax with <2 cm rim.
• Supplemental oxygen (accelerates nitrogen reabsorption by ~60x - oxygen is absorbed 60 times faster than nitrogen).
• Bed rest; repeat CXR in 4-6 hours.
• Outpatient observation acceptable only in reliable, well-supported patients close to emergency care.

2. Simple Aspiration (Needle Aspiration)

• First-line for small, symptomatic PSP or first-episode moderate PSP (BTS guidelines).
• 16G or 18G IV catheter inserted at 2nd ICS in midclavicular line anteriorly after local anesthesia.
• Three-way stopcock and large syringe used; metal needle removed once air aspirated, aspiration continued through plastic cannula.
• Observation for several hours with repeat CXR before discharge.
• Failure of aspiration is an indication for tube drainage.
• Not appropriate for secondary pneumothorax.

3. Tube Thoracostomy (Chest Drain / Intercostal Drain)

• Large or symptomatic pneumothorax.
• Failed needle aspiration.
• Secondary (traumatic or SSP) pneumothorax.
• Tension pneumothorax (after initial needle decompression).
• Bilateral pneumothorax.
• Pneumothorax in ventilated patients.
• Hemopneumothorax.
• Patient requiring general anesthesia.
• Recurrent pneumothorax after removal of initial chest tube.

• Site: 4th or 5th ICS, anterior axillary line (safe triangle: lateral border of pectoralis major, lateral border of latissimus dorsi, above the 5th rib/nipple level).
• Alternatively: 2nd ICS, midclavicular line (Monaldi position, less preferred due to cosmesis).
• Tube sizes: 16-22 Fr (small bore) or 20-28 Fr (large bore).
• Connected to underwater seal drainage ± suction (-10 to -20 cm H₂O).
• Confirm position with CXR.
• Tube removed when lung is fully re-expanded and air leak has stopped (cessation of bubbling for 24 hours).

4. Needle Decompression (Tension Pneumothorax - Emergency)

• Immediate insertion of large-bore IV catheter (14-16G) at 2nd ICS, midclavicular line.
• Converts tension pneumothorax to simple pneumothorax: rush of air + immediate improvement in vitals.
• This is a temporizing measure - must be followed by formal tube thoracostomy.
• In obese patients: 5th ICS, anterior axillary line may be more reliable.

5. Open Pneumothorax Management

• Apply three-sided occlusive dressing (flutter valve effect) to prevent air entry but allow trapped air to escape.
• Chest tube insertion before closing the defect (to prevent creating a tension pneumothorax).
• Surgical repair of the chest wall defect once patient is stabilized.

6. Surgical Management

• Persistent air leak > 5-7 days despite chest tube drainage.
• Recurrent pneumothorax (2nd ipsilateral or 1st contralateral episode).
• Bilateral simultaneous pneumothorax.
• Failure of lung re-expansion.
• High-risk occupation (pilots, divers).
• Patient preference (after first episode).

• Bullectomy/bleb resection.
• Pleurodesis (mechanical abrasion, talc insufflation, or partial pleurectomy).
• Less invasive, shorter hospital stay, faster recovery, equivalent recurrence rates.

• For failed VATS, complex cases, or when VATS is unavailable.
• Bullectomy + pleurectomy (stripping of parietal pleura) provides the lowest recurrence rate (<1%).

• Talc slurry via chest tube or medical thoracoscopy.
• Talc poudrage (during thoracoscopy) - preferred in patients unsuitable for surgery.
• Autologous blood patch: 50 mL blood injected through drain to seal air leak.

Complications

Summary Table