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Pneumothorax

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Overview

A pneumothorax is an abnormal collection of air in the pleural space (the potential space between the lungs and the chest wall) resulting in the collapse of the lung on the affected side.

This is not to be confused with atelectasis, which is usually due to blockage of the air passages and can be caused by a pneumothorax (due to pressure being exerted on the outside of the lung). This leads to deflation of the alveoli and subsequent lung collapse in a single region or multiple parts of the lungs.

A tension pneumothorax is a medical emergency and must initially be ruled out, see Tension Pneumothorax.

Pneumothoraces can be primary or secondary.

Types and Risk Factors

Primary spontaneous pneumothorax

These occur in people without lung disease, however, there are risk factors:

  • Smoking
  • Male sex
  • Family history
  • Tall and slender build, especially people with Marfan’s syndrome

Secondary spontaneous pneumothorax

These occur in people who have lung disease. Risk factors are:

Other causes

  • Traumatic pneumothorax:
    • Often following penetrating chest trauma (e.g. stabbing, gunshots, fractured ribs)
  • Iatrogenic pneumothorax:
    • Common causes are mechanical ventilation, central line placement, and lung biopsy
  • Catamenial pneumothorax – pneumothorax at the time of menstruation
    • Due to thoracic endometriosis

Epidemiology

  • Incidence is higher in men (24/100,000 in men, 10/100,000 in women)
  • Men in their 20s and 60s are at higher risk

Presentation

The symptoms are usually sudden in onset. Patients may have:

  • Dyspnoea
  • Pleuritic chest pain:
    • This is chest pain that is worse when breathing in
    • Some patients may have shoulder tip pain instead
  • Tachypnoea
  • Examination may show:
    • Ipsilateral reduced breath sounds
    • Ipsilateral hyper-resonance on percussion

Severe symptoms and signs of respiratory distress suggest the presence of a tension pneumothorax.

Differential Diagnoses

Pulmonary embolism

  • There may be venous thromboembolism risk factors present (e.g. prolonged immobility, pregnancy, recent surgery)
  • Examination may show a swollen calf
  • Sinus tachycardia is present

Tension pneumothorax

  • Tracheal deviation is present – deviates away from the affected side as thoracic pressure increases
  • Signs of haemodynamic compromise are present as blood vessels are kinked:

Investigations

All patients

  • Chest x-ray (posteroanterior):
    • Done initially and shows a visible rim between the lung margin and chest wall and absent lung markings between the lung margin and chest wall
  • Chest CT:
    • Considered if the diagnosis is uncertain or there is a complex case
  • Arterial blood gases:
    • Should only be done if oxygen saturations are <92%
    • Usually shows hypoxia depending on the severity

Diagnosis

British Thoracic Society

The size of the pneumothorax affects the rate of resolution and is used to guide whether management is carried out. The distance between the pleural surface and the lung edge is measured at the level of the hilum:

  • If ≤2cm – small pneumothorax
  • If >2cm – large pneumothorax

Management

Primary pneumothorax

Always remember to rule out a tension pneumothorax.

  • If <2cm and patient is not short of breath: discharge and review as an outpatient
  • If >2cm and/or patient is short of breath: attempt aspiration
    • If aspiration fails, insert a chest drain

Secondary pneumothorax

  • If >50 years old + >2cm and/or patient is short of breath: insert a chest drain
  • If 1-2cm: attempt aspiration
    • If aspiration fails, insert a chest drain
  • If <1cm: give oxygen and admit for 24 hours and review

Other situations

  • Iatrogenic pneumothorax: generally does not require chest drain – most patients resolve with observation alone
  • Persistent/recurrent pneumothorax: consider video-assisted thoracoscopic surgery (VATS) 

Monitoring

  • Patients with primary pneumothoraces that have been discharged for review are usually followed up after 2-4 weeks with a chest x-ray to monitor the resolution of the pneumothorax

Patient Advice

  • Patients should avoid smoking to reduce the risk of developing a pneumothorax
  • Air travel generally should be avoided until chest X-rays demonstrate resolution
  • Diving should be permanently avoided unless surgical interventions are carried out and testing and radiography demonstrate normal lung function post-operatively

Prognosis

  • Rates of recurrence are relatively high
  • Secondary pneumothoraces have a worse prognosis than primary pneumothoraces
  • Smoking cessation reduces the absolute risk significantly

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