SIM Tension Pneumothorax

Question 1

What is the pathophysiology of spontaneous pneumothorax?

Answer 1

• Likely due to rupture of subpleural bleb or bullae.
• Bullae likely form due to degradation of elastic fibers in lung.
  
  • Degradation exacerbated by smoking-related inflammation, influx of neutrophils & macrophages.
• Degradation of elastic fibers causes imbalance in protease-antiprotease and oxidant-antioxidant systems.
• After bullae have formed, small airway obstruction increases alveolar pressure, resulting in air leaking into pulmonary interstitium.
• Air moves to hilum where increased pressure causes reputure of mediastinal parietal pleura and resulting in pneumothorax formation.

Question 2

What are the risk factors for primary spontaneous pneumothorax?

Answer 2

• More common in males (~2-4:1 male:female)
• Most common in age 10 - 30
• More common in tall, thin people
• More common in smokers
• May be familial

Question 3

What is the relative sensitivity of bedside ultrasound compared to chest x-ray for identification of pneumothorax?

Answer 3

• CXR shows a visceral pleural line outlining the edge of lung, absence of lung markings beyond that line.
• Ultrasound findings of pneumothorax include loss of B-lines and loss of sliding pleura.
  
  • Bedside ultrasound is more sensitive than chest x-ray
• Both CXR & US are highly specific for pneumothorax.

Question 4

What components of the history and physical exam are suspicious for pneumothorax?

Answer 4

• Tachycardia is the most common exam finding.
• Larger pneumothorax may have
  
  • decreased chest wall motion
  • hyperresonnance on percussion
  • diminished fremitus
  • decreased or absent breath sounds on the affected side

Question 5

What are the signs & symptoms of a tension pneumothorax?

Answer 5

• Tachycardia > 135 bpm
• hypotension and/or cyanosis should increase suspicion for tension pneumothorax
• may see contralateral tracheal deviation and JVD with tension pneumothorax
• Vital signs are unstable

Question 6

What is the impact of a pneumothorax on acid-base status?

Answer 6

ABG will typically have an increased A-a gradient and findings of acute respiratory alkalosis.

Question 7

What are the management options for pneumothorax?

Answer 7

• Observation (for small or asymptomatic pneumothorax)
• Aspiration with catheter with immediate removal of catheter
• Insertion of chest tube
• Pleurodesis
  
  • Pleurodesis (using talc) via chest tube or thorascopy reduces recurrence rate
• Video-Assisted Thoracoscopic Surgery (VATS)
• Surgery may be indicated in primary spontaneous pneumothorax if persistent air leak, eg > 4 days or if recurrent pneumothorax
• Oxygen accelerates resporption of air by the pleura.
• Tension pneumothorax requires immediate aspiration

Question 8

Deep-sea diving, e.g. SCUBA, is contraindicated in patients with previous spontaneous pneumothorax, unless when procedures has been performed?

Answer 8

bilateral surgical pleurectomy