Pneumothorax

Size of pneumothorax[17]Roberts ME, Rahman NM, Maskell NA, et al; BTS Pleural Guideline Development Group. British Thoracic Society guideline for pleural disease. Thorax. 2023 Jul;78(suppl 3):s1-s42. https://www.brit-thoracic.org.uk/quality-improvement/guidelines/pleural-disease http://www.ncbi.nlm.nih.gov/pubmed/37433578?tool=bestpractice.com

The British Thoracic Society (BTS) now advises that the size of a pneumothorax is no longer an indication for invasive management; however, it does dictate the safety of conducting an intervention.[17]Roberts ME, Rahman NM, Maskell NA, et al; BTS Pleural Guideline Development Group. British Thoracic Society guideline for pleural disease. Thorax. 2023 Jul;78(suppl 3):s1-s42. https://www.brit-thoracic.org.uk/quality-improvement/guidelines/pleural-disease http://www.ncbi.nlm.nih.gov/pubmed/37433578?tool=bestpractice.com ​

Often, the postero-anterior (PA) chest x-ray 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 by volume. Historically, the following has been recommended as a gauge to the size of a pneumothorax:

• 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 x-ray.

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

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 localised pneumothoraces. While CT scanning can be utilised as a means to estimate the size of a pneumothorax, not all facilities purchase the software necessary to make this assessment.