Pneumothorax

 

• Background

  Pathophysiology

  • A defect in the visceral pleura causes air to enter the pleural space from the lungs. The elastic recoil of the lungs then causes them to deflate/collapse.
  • A simple pneumothorax is a non-expanding collection of air. In a tension pneumothorax, the communication acts like a valve, causing continued inflation.
  • Typically unilateral, but can be bilateral.
  • Once the communication is obliterated, air is gradually reabsorbed into the lung from the pleural space.

  Causes and classification

  • Primary spontaneous: no underlying cause.
  • Secondary spontaneous (due to lung disease): asthma, COPD, TB, pneumonia, lung cancer, cystic fibrosis, ILD. Also seen in connective tissue disorders like Marfan's.
  • Traumatic: iatrogenic or accidental (e.g. rib fracture).

• Signs and symptoms

  Symptoms:

  • Acute-onset SOB.
  • Pleuritic chest pain.
  • Sudden deterioration in asthma or COPD.
  • Can be asymptomatic.
  • Tension pneumothorax → respiratory distress.

  Signs:

  • ↓Chest expansion leading to asymmetrical expansion.
  • Hyper-resonant percussion.
  • ↓Breath sounds.
  • Trachea deviated away from affected side in severe tension pneumothorax.

• Investigations

  • Erect CXR, but skip it in tension pneumothorax.
  • CT only if diagnostic uncertainty.
  • USS can be used in supine trauma patients.

• Management

  Primary pneumothorax:

  • Conservative treatment if small and no SOB, as they usually self resolve. 'Small' is a margin of <2 cm on CXR between lung margin and chest wall at level of hilum.
  • Otherwise, needle aspiration, then chest drain if unsuccessful.

  Secondary pneumothorax:

  • Conservative treatment if <1 cm and no SOB.
  • Needle aspiration if 1-2 cm and no SOB. Chest drain if unsuccessful.
  • Chest drain if >2 cm or SOB.

  Tension pneumothorax:

  • 100% O2.
  • Needle aspiration for instant relief, then proceed to chest drain.

  Procedures

  Needle aspiration (aka thoracentesis):

  • Large bore cannula (16-18G, 14G if tension) into the lower 2nd intercostal space at the mid-clavicular line.
  • In simple pneumothorax, attach a tap and syringe for aspiration.
  • In tension pneumothorax, just remove the stylet for instant relief.
  • Not used in traumatic pneumothorax.

  Chest drain:

  • Inserted in the triangle of safety, in the 4th or 5th intercostal space, anterior to the mid-axillary line.
  • First infiltrate lidocaine 1% all the way through to the pleural space.
  • Small-bore drain via Seldinger technique is first choice. Large-bore drain via blunt dissection is only for very large air leaks.
  • Unlike for pleural effusions, ultrasound-guidance is not a requirement.

• Atelectasis and lung collapse

  Atelectasis, literally incomplete (ateles) expansion (ektasis), refers to collapse or incomplete expansion of the lung parenchyma.

  Passive (aka relaxation) atelectasis

  • Loss of contact between the visceral and parietal pleurae.
  • Causes: pneumothorax, pleural effusion.
  • Can lead to the collapse of an entire lung.

  Obstructive atelectasis

  Collapse secondary to the occlusion of a bronchus, as the air beyond the obstruction is gradually absorbed and the airways collapse.

  Causes:

  • Tumour
  • Aspirated foreign body, commonly right main bronchus.
  • Mucous plug e.g. in asthma.
  • Post-operative retention of secretions.
  • Tracheobronchial lymphadenopathy.

  Leads to lobar or segmental collapse.

  Linear atelectasis

  Small amount of incomplete expansion resulting from restricted breathing ('respiratory splinting').

  Causes:

  • Post-op pain.
  • Rib fracture.
  • Pleuritic chest pain.

  Compressive atelectasis

  Space occupying lesion compresses the lung.

  Causes:

  • Chest wall tumour.
  • Pleural effusion.
  • Elevated hemidiaphragm.