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Relatively few studies have addressed the specific issue of pneumothorax and its diagnosis, and these have tended to focus on expert diagnosis (by consultant radiologists) and the more discriminating departmental (rather than ward-based) workstations.Even so, some difficulties were found in the diagnosis of pneumothorax in early studies.41 42 Since then there have been technological advances, such that digital imaging may now be as reliable as more conventional chest x-rays in pneumothorax diagnosis, but there have been no more recent studies to confirm this.The physical signs of a pneumothorax can be subtle but, characteristically, include reduced lung expansion, hyper-resonance and diminished breath sounds on the side of the pneumothorax.Added sounds such as ‘clicking’ can occasionally be audible at the cardiac apex.23 The presence of observable breathlessness has influenced subsequent management in previous guidelines.17 23 In association with these signs, cyanosis, sweating, severe tachypnoea, tachycardia and hypotension may indicate the presence of tension pneumothorax (see later section).Arterial blood gas measurements are frequently abnormal in patients with pneumothorax, with the arterial oxygen tension (Pa This has been the mainstay of clinical management of primary and secondary pneumothorax for many years, although it is acknowledged to have limitations such as the difficulty in accurately quantifying pneumothorax size.
Commonly, the plain PA chest x-ray has been used to quantify the size of the pneumothorax.
Small airways obstruction, mediated by an influx of inflammatory cells, often characterises pneumothorax and may become manifest in the smaller airways at an earlier stage with ‘emphysema-like changes’ (ELCs).8Smoking has been implicated in this aetiological pathway, the smoking habit being associated with a 12% risk of developing pneumothorax in healthy smoking men compared with 0.1% in non-smokers.9 Patients with PSP tend to be taller than control patients.10 11 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 pressure than those at the base of the lung, and the vectors in theory predispose to the development of apical subpleural blebs.12Although it is to some extent counterintuitive, there is no evidence that a relationship exists between the onset of pneumothorax and physical activity, the onset being as likely to occur during sedentary activity.13Despite the apparent relationship between smoking and pneumothorax, 80–86% of young patients continue to smoke after their first episode of PSP.14 The risk of recurrence of PSP is as high as 54% within the first 4 years, with isolated risk factors including smoking, height and age 60 years.12 15 Risk factors for recurrence of SSP include age, pulmonary fibrosis and emphysema.15 16 Thus, efforts should be directed at smoking cessation after the development of a pneumothorax.
The initial British Thoracic Society (BTS) guidelines for the treatment of pneumothoraces were published in 1993.17 Later studies suggested that compliance with these guidelines was improving but remained suboptimal at only 20–40% among non-respiratory and A&E staff.
However, it tends to underestimate the size because it is a two-dimensional image while the pleural cavity is a three-dimensional structure.
The 2003 BTS guidelines22 advocated a more accurate means of size calculation than its predecessor in 1993,15 using the cube function of two simple measurements, and the fact that a 2 cm radiographic pneumothorax approximates to a 50% pneumothorax by volume.
The term ‘pneumothorax’ was first coined by Itard and then Laennec in 18 respectively,1 and refers to air in the pleural cavity (ie, interspersed between the lung and the chest wall).