Pneumothorax

Definition/diagnostic criteria A pneumothorax is characterised by the accumulation of air in the pleural space, which can lead to partial or complete collapse of the lung. Clinically, it is suspected when a patient presents with acute onset of unilateral chest pain and breathlessness. Radiologically, the presence of a visible pleural line with no vascular markings extending to the edge of the lung field on a chest X-ray confirms the diagnosis.

Primary pneumothorax, also known as spontaneous pneumothorax, occurs without an obvious underlying lung disease or a clear precipitating event. It most commonly affects young, healthy individuals without a history of lung disease. The exact cause is not always known, but it may be related to the rupture of small air-filled sacs in the lung (blebs) or air pockets at the apex of the lung (bullae).

Secondary pneumothorax, on the other hand, occurs in the presence of pre-existing lung pathology. Diseases that may lead to secondary pneumothorax include chronic obstructive pulmonary disease (COPD), cystic fibrosis, lung cancer, asthma, tuberculosis and pneumonia, among others. In these cases, the lung disease can weaken the pleura, making it more susceptible to rupture.

Epidemiology The incidence of primary spontaneous pneumothorax is estimated at 18-28 per 100,000 annually for males and 1.2-6 per 100,000 for females in the UK. Certain lifestyle factors, such as smoking, can increase the risk of a primary pneumothorax. Secondary spontaneous pneumothorax occurs less frequently but has more significant health implications. High-risk populations include smokers and individuals with underlying lung disease.

Diagnosis
Clinical features: Typical presentations include sudden chest pain and dyspnoea, with physical examination findings of diminished breath sounds, reduced chest expansion and hyper-resonance to percussion on the affected side. Tachycardia and hypoxia may also be present, indicating more severe pneumothorax.

Investigations: The first-line investigation is a chest X-ray, which reveals the lung’s edge as a thin white line with no lung markings beyond it, indicating the presence of air in the pleural space. A CT chest may be utilised for complex cases or to determine the presence of underlying lung pathology. Ultrasound of the chest can also be effective, particularly in a trauma setting, as it can rapidly diagnose pneumothorax without radiation exposure.

Treatment The management of pneumothorax depends on its size and the patient’s clinical state. For small, asymptomatic pneumothoraces, conservative management with oxygen and observation may be sufficient. Larger or symptomatic pneumothoraces may require aspiration or a chest drain. Secondary pneumothorax, or those associated with significant symptoms, typically require chest drainage. In cases of recurrent pneumothorax, surgical intervention, such as video-assisted thoracoscopic surgery (VATS) or chemical pleurodesis, may be necessary.

Prognosis The prognosis for a primary spontaneous pneumothorax is generally good, with low rates of mortality. However, recurrence is common, with rates reported at between 16-52%. Secondary pneumothorax has a poorer prognosis, particularly in the presence of underlying lung disease, and requires more aggressive management. Early recognition and appropriate treatment are crucial to reduce the risk of complications and recurrence.