Pneumothorax

Accumulation of air in the pleural space, between lung and chest wall. This causes partial or complete collapse of the lung.

Epidemiology

• Two peaks - 20-30 years (primary) and 60-70 years (secondary)
• M:F 4:1
• Cigarette smoking OR 20

Aetiological classification

Spontaneous

• • Primary spontaneous
    • Definition
      • Spontaneous pneumothorax in a patient without an immediately obvious underlying lung disease
    • Risk factors
      • Occurs between 20-30yo, mostly men
      • Smoking
      • Ectomorphic habitus
      • Genetics
      • Nitrous oxide canisters - inhaled under pressure
    • Pathophysiology
      • Rupture of small subpleural blebs (<2cm collections of air contained within visceral pleura), mostly found at apex of upper or lower lobes
      • Blebs result from ruptured alveoli - well-demarcated from normal lung, being located between elastic interna and externa of the visceral pleura
      • May be associated with apical fibrosis
      • PSP can also occur in the absence of blebs
  • Secondary spontaneous PTX
    • Aetiology
      • COPD (marker of severe disease with poor prognosis)
      • Bullous disease
      • Cystic fibrosis (marker of advanced disease)
      • Pneumocystis-related
      • Congenital cysts
      • IPF
      • Pulmonary embolism
      • Asthma
      • TB and other mycobacterial infections
      • Other infections
      • AIDS
      • Bronchogenic carcinoma
      • Metastatic lung disease (especially metastatic sarcoma)
      • Radiotherapy
      • Marfan syndrome
      • EDS
      • Histiocytosis X
      • Sarcoidosis
      • Scleroderma
      • Lymphangiomyomatosis
      • Pregnancy - usually around 26 weeks
    • Management
      • Refer to respiratory physician if not already known
  • Catamenial (occurs with 48-72 hours of onset of menstruation; part of thoracic endometriosis syndrome (TES) and in fact the most common presentation of that syndrome)
    • TES - haemothorax, haemoptysis, lung nodules. Growth of endometrial glands and stroma in the lungs, pleura, diaphragm and tracheobronchial tree. Mostly unilateral right PTX.
  • Neonatal

Traumatic

• • Generally sharp stumps of fractured ribs directed inwards, which can also cause HTX.
  • Barotrauma from diving

Iatrogenic

• • Mechanical ventilation
  • Needle puncture (thoracentesis, FNA lung nodule, central line insertion
  • Post-surgical

Pathophysiological classification

• Closed PTX - no communication between pleural space and outside of thorax. Amount of air is usually small, and it is usually reabsorbed in a short period of time.
• Open PTX - presence of open communication between pleural cavity and outside of the chest. Air enters during inspiration and exits during expiration. Most commonly the hole is in chest wall, but can also occur with rupture of the airway or parenchymal lesions. Repeated shifts of mediastinum during the respiratory cycle can cause refractory bradycardia or even cardiac arrest.
• Tension PTX - air freely enters chest cavity but does not exit. The lesion through which air enters acts as a unidirectional valve. See below.

Pathophysiology

• Introduction of air causes partial or complete collapse of the lung with consequent modifications in respiratory mechanics potentially affecting ventilation and gas exchange

Presentation

• Chest pain, dry cough, dyspnoea
• Pain predominant in younger patients, dyspnoea in older
• Decrease chest wall movement, tympanic resonance, reduced air entry
• Tachycardia almost always present
• Tension physiology: respiratory distress, anxiety, cyanosis, hypotension, fixed hyperexpanded hemithorax.

Imaging

• Standard erect CXR in inspiration. Expiration films can help to diagnose a small PTX (decreases lung volume, but doesn't decrease the volume of air, so relative increase in size of PTX)
• Signs of PTX on supine films
  • Air collects anteriorly, in front of the lungs
  • Relative lucency of ipsilateral lung
  • Deep sulcus sign
  • Increased sharpness of adjacent mediastinal margin and diaphragm
  • Double diaphragm sign, from visualisation of the anterior costophrenic sulcus
  • Depression of ipsilateral hemidiaphragm
• CT for uncertain cases, to assess aetiology
• Quantifying PTX
  • Size is less important than degree of clinical compromise
  • Complicated formulas are available, but impractical, requiring CT
  • Best is to describe 'small PTX' as one with the surface of the lung <3cm from the chest wall
  • Large PTX >3cm to chest wall

Complications

• 'Early tension'
  • Any evidence of volume gain, including increased rib spaces on ipsilateral side, tracheal deviation, depression of diaphragm, deep sulcus sign
• Tension
  • When air continues to enter the pleural space without decompression, resulting in positive intra-thoracic pressure causing compression of the lung and mediastinum, shift of the mediastinum into the contralateral chest, and decrease in ventilation and venous return
  • Produces a shunt with reduced oxygenation and cardiac output.
  • Cardiopulmonary collapse and death ensue, primarily from low preload due to kinked IVC
  • Must decompress immediately with needle or chest tube
• Haemopneumothorax
  • Usually rupture of a vascularised pleural adhesion or vascularised bleb or bulla
• Rarely
  • Pneumomediastinum
  • Pneumoperitoneum
  • Subcutaneous emphysema
  • Need to rule out airway/oesophageal/abdo visceral injury when these are present.

Management

• Options: bed rest and observation; aspiration; small-bore catheter; tube thoracostomy; VATS; open thoracotomy.
• Simple, small, uncomplicated, clinically stable, asymptomatic PTX: more conservative treatment, perhaps even just bed rest and observation, with oxygen (oxygen favours healing by increasing the gradient for nitrogen absorption from the pleural space). Should hospitalise for at least 24 hours.
  • Needle aspiration may be appropriate in this population (don't repeat if it doesn't work)
  • Especially applies to small PTX from biopsy needle
  • Progression in size requires drainage with small-bore chest tube such as Rocket 14Fr
• Symptomatic: tube thoracostomy with UWSD is mandatory
  • Tailor the size of the tube to the risk of substantial air leak
  • Direct tube towards apex
  • Reasonable to leave off suction initially (risk of re-expansion oedema), check re-expansion, then apply -10 to -20 cm H2O if needed. Use minimum suction to re-inflate lung.
  • Remove chest tube when air leak has stopped for at least 48-72 hours
• Persistent air leak - defined as >48 hours
  • Much more common with SSP as opposed to PSP (40% at 7 days compared to 5% at 7 days)
  • ACCP guidelines suggest surgical intervention at 4 days for PSP and 5 days for SSP, since a longer waiting time does not seem to substantially modify outcome
• Indications for surgery in primary spontaneous pneumothorax
  • Rationale
    • Prevent recurrence (30% without intervention, 2-3% with intervention)
  • First episode
    • Prolonged air leak (4 days)
    • Non-re-expansion of the lung
    • Bilateral pneumothorax
    • Haemothorax
    • Tension pneumothorax
    • Complete pneumothorax
    • Occupational hazard
    • Absence of medical facilities in isolated areas
    • Associated single large bulla
  • Second episode
    • Ipsilateral recurrence
    • Contralateral recurrence
• Lifestyle modifications if not had surgery
  • No scuba diving, piloting planes

Surgery - resect the cause and obliterate the pleural space

• Mostly need recurrent primary spontaneous PTX before considering VATS
• If blebs or bullae >1cm are seen, wedge resection is necessary
• Controversial as to whether VATS or limited thoracotomy are better. In bilateral disease, VATS is also reasonable.
• Mechanical abrasion of the parietal pleura
• Pleural space should be obliterated with apical parietal pleurectomy, pleural abrasion or chemical irritation
  • Apical parietal pleurectomy - surgical fixation of the lung to the endothoracic fascia - good long-term results
  • Pleural abrasion preferred for patients likely to need further thoracic surgery as it preserves the extra-pleural plane of dissection. Recurrence rate 2.3%
  • Chemical pleurodesis - mostly talc (powder of hydrous magnesium silicate. Commercially available talc is free of asbestos.
• Pleurodesis with talc is good in older patients or patients with malignancy, but surgery would be preferred in most patients.

Talc pleurodesis: maximum of 5g introduced as a slurry through chest tube

• Common reactions:
  • Low-grade fever
  • Local pain
  • Local infection - very hard/impossible to cure
  • Respiratory distress

Discharge advice:

• Consider respiratory physician follow-up
• Air travel should be avoided until full resolution
• Diving should be permanently avoided unless the patient has undergone bilateral surgical pleurectomy and has normal lung function and CT scan post-operatively