Pneumothorax

Size of pneumothorax

The British Thoracic Society (BTS) now advise that the size of a pneumothorax is no longer an indication for invasive management; however, it does dictate the safety of conducting an intervention. In general they advise that ≥2 cm laterally or apically on chest x radiograph, or any size on computed tomography (CT) scan which can be safely accessed with radiologic support, is sufficient size to intervene.[24]British Thoracic Society. Guidelines: pleural disease​. Jul 2023 [internet publication]. https://www.brit-thoracic.org.uk/quality-improvement/guidelines/pleural-disease

Often, the posteroanterior (PA) chest radiograph is used to quantify the size of the pneumothorax. A pneumothorax with a visible rim of 2 cm between the lung margin and the chest wall, when measured at the level of the hilum, approximates a 50% pneumothorax. Historically, the following has been recommended as a gauge to the size of a pneumothorax:[49]MacDuff A, Arnold A, Harvey J, et al. Management of spontaneous pneumothorax: British Thoracic Society pleural disease guideline 2010. Thorax. 2010 Aug;65(suppl 2):ii18-31. https://thorax.bmj.com/content/65/Suppl_2/ii18.long

• Small pneumothorax - a visible rim of <2 cm between the lung margin and the chest wall at the level of the hilum on PA chest radiographs

• Large pneumothorax - a visible rim at least 2 cm between the lung margin and the chest wall at the level of the hilum on PA chest radiographs.

The choice of a 2 cm pneumothorax as the determinant of a small versus a large pneumothorax is a compromise between the theoretical risk of needle puncture of the lung with a smaller pneumothorax and the significant volume and length of time for spontaneous resolution of a larger pneumothorax.

Unfortunately lung collapse is not always uniform, particularly in patients with diseased lungs. Thus, it is more difficult to estimate the size of these localized pneumothoraces. While computed tomography scanning can be utilized as a means to estimate the size of a pneumothorax, not all facilities purchase the software program necessary to make this assessment. Additionally, in the clinical experience of the contributor of this topic, in patients who are minimally symptomatic and clinically stable, the size of the pneumothorax takes on less significance and patients can still be monitored conservatively even with a large collapse.