CHAPTER 3 John Harvey1, Andrew McDuff2 and Ian Hunt3 1 North Bristol NHS Trust, Bristol, UK 2 New Cross Hospital, Wolverhampton, UK 3 St. George’s Hospital, London, UK Pneumothorax describes the presence of air in the pleural space. Classification of pneumothorax depends on whether there is underlying lung disease or the presence of identifiable trauma (Box 3.1). Hospital admission rates for spontaneous pneumothorax in the UK have been reported as 16.7/100 000 for men and 5.8/100 000 for women, with corresponding mortality rates of 1.26/million and 0.62/million per annum between 1991 and 1995. The incidence of iatrogenic pneumothorax is not precisely known; however, the most common causes are subclavian vein cannulation, thoracentesis and positive pressure ventilation. Anatomical abnormalities have been demonstrated, even in patients without clinically apparent underlying lung disease. Sub‐pleural blebs and bullae (termed emphysema‐like changes) are found at the lung apices at thoracoscopy and on computed tomography (CT) scanning in up to 90% of cases of primary pneumothorax and are thought to be involved in the development of pneumothorax. Small airway obstruction, mediated by an influx of inflammatory cells, often characterises pneumothorax. Smoking has been implicated in this aetiological pathway. Smoking is associated with a 12% lifetime risk of developing pneumothorax in men who smoke heavily, compared to 0.1% in those who have never smoked. Patients with primary spontaneous pneumothorax tend to be taller than control patients. The gradient of negative pleural pressure increases from the lung base to the apex, so that alveoli at the lung apex in tall individuals are subject to significantly greater distending forces than those at the base of the lung, and this may in theory predispose to the development of apical sub‐pleural blebs. Unfortunately, despite the clear relationship between smoking and pneumothorax, over 80% of patients continue to smoke after a primary pneumothorax. The risk of recurrence is as high as 54% within the first 4 years. Risk factors for recurrence are smoking, height and age over 60 years, pulmonary fibrosis and emphysema. Determined efforts should be directed at smoking cessation after the development of a pneumothorax. Classically, patients present with an episode of pleuritic chest pain and dyspnoea. Clinical examination reveals the reduced movement of the chest wall, hyper‐resonance on percussion and absence of breath sounds on the affected side. However, the symptoms are often minor, particularly in primary pneumothorax, and in busy emergency and admission units the signs may be difficult to detect. A high clinical index of suspicion must therefore be maintained, especially in thin, young smokers. Symptoms and signs are often more obvious in secondary pneumothorax because of underlying lung disease. Tension pneumothorax is a medical emergency which requires immediate treatment prior to any further examination or imaging (Box 3.2). The standard imaging for diagnosis is the postero‐anterior chest X‐ray (PA‐CXR) (Figure 3.1). Expiratory films are no longer recommended as they have not been shown to improve detection. Management is guided by the X‐ray findings as the plain PA‐CXR has been used to quantify the pneumothorax size. However, it should be remembered that it tends to underestimate the size because a radiograph is a two‐dimensional image whilst the pleural cavity is a three‐dimensional structure. A 2 cm rim of air between chest wall and lung edge measured at the level of the hilum represents a 50% pneumothorax (Figure 3.2, line b). There are alternative strategies for estimating the size (e.g. Figure 3.2, line a), but these tend to overestimate size and are not recommended. A 2 cm (i.e. 50%) pneumothorax is classified as large and expert opinion typically favours active intervention in these patients. Figure 3.1 Tension pneumothorax with evidence of early tracheal shift. Figure 3.2 Standard methodology for measurement of pneumothorax size. In cases of uncertainty where underlying lung disease (e.g. bullous emphysema) or where previous thoracic surgery makes interpreting the CXR difficult, then CT scanning is the ‘gold’ standard (Figure 3.3) and should be undertaken prior to intervention. Figure 3.3 Secondary pneumothorax with evidence of interstitial lung disease. There is increasing interest in the role of ultrasound scanning in the diagnosis of pneumothorax especially in critical care environments where traditional imaging techniques may be more challenging. However, there are few data on the value of this modality and it requires specialist sonographic skills and its place in routine management pathways is unclear. The aim of managing patients with pneumothorax is to relieve symptoms using the minimal intervention necessary in order to allow a prompt return to their usual activities of daily living. The current British Thoracic Society guidelines for management are summarised in Figure 3.4. Figure 3.4 British Thoracic Society 2010 guideline algorithm for the management of pneumothorax. This is a medical emergency and intervention should not be delayed for any reason (including CXR). The affected side should undergo immediate needle decompression with an 18 G (i.e. green), or larger, cannula. A chest drain will be inserted afterwards. It is important to make the distinction between primary (i.e. no underlying lung disease) and secondary pneumothoraces as this is the key step in determining management of haemodynamically stable patients. The intervention options are needle aspiration or insertion of a chest drain. Some patients with pneumothorax have mild symptoms. Some patients, particularly those with primary pneumothorax and a small pneumothorax, do not require specific treatment. A pneumothorax will slowly resolve over time as the air is reabsorbed and some haemodynamically stable patients may be safely managed without an immediate procedure to remove the air. It is known that aspiration (Box 3.3) of primary spontaneous pneumothorax is safe, effective and allows early discharge from hospital. Needle aspiration works as the air leak causing the pneumothorax heals rapidly and there is frequently no ongoing air leak when the patient is seen. Needle aspiration is also less painful than chest drain insertion and requires less operator skill. This is therefore the recommended first intervention in primary pneumothoraces. It has a success rate of 50–70% in clinical trials. No more than 2.5 L of air should be aspirated as this is likely to signify the presence of a persistent air leak and suggests that further re‐expansion of the lung is unlikely at this point.
Pneumothorax
Definition, epidemiology, risk factors and aetiology
Presentation
Investigations
Management
Tension (i.e. haemodynamically unstable) pneumothoraces
Haemodynamically stable
Conservative management
Needle aspiration
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