From the Guidelines
Pneumothorax should be measured by calculating the distance from the lung edge to the chest wall at the level of the hilum, with a small pneumothorax defined as having a rim of air less than 2 cm and a large pneumothorax defined as having a rim of air 2 cm or greater, as per the British Thoracic Society guidelines. This measurement method is preferred over calculating percentage collapse because it's more practical and reproducible in clinical settings 1. When measuring, it's essential to use the posteroanterior (PA) chest radiograph when available, as this provides the most accurate assessment. If the patient cannot be positioned upright, a supine or semi-recumbent film may be used, though pneumothorax can be more difficult to detect in these positions as air may collect anteriorly rather than at the apex.
Some key points to consider when measuring pneumothorax include:
- The size of the pneumothorax is divided into “small” or “large” depending on the presence of a visible rim of <2 cm or >2 cm between the lung margin and the chest wall 1.
- The plain PA radiograph is a poor method of quantifying the size of a pneumothorax as it usually underestimates it, and CT scanning is the most robust approach for exact size estimates 1.
- The BTS measurement approach helps standardize pneumothorax assessment and guides appropriate management decisions, as treatment options differ significantly between small and large pneumothoraces 1.
It's also important to note that breathless patients should not be left without intervention regardless of the size of the pneumothorax on a chest radiograph, and high flow oxygen should be administered to patients with pneumothorax who are admitted overnight for observation, with appropriate caution in patients with COPD 1.
From the Research
Measuring Pneumothorax based on British Thoracic Society (BTS) Guidelines
To measure pneumothorax based on BTS guidelines, the following points should be considered:
- The BTS guidelines recommend classifying pneumothorax into size groups for treatment, but the exact method of measurement is not specified in the provided studies 2, 3.
- A study comparing BTS guidelines with other international guidelines found that the BTS guideline classified 10% of primary spontaneous pneumothorax (PSP) as large, compared to 47% by the Belgian Society of Pulmonology guideline and 49% by the American College of Chest Physicians guideline 3.
- Another study developed a formula to estimate the size of a pneumothorax on a supine anteroposterior chest radiograph, but this is not specifically mentioned in the BTS guidelines 4.
- The size of a pneumothorax can be quantified by measuring its maximal width in millimeters and the number of 10 millimeter CT sections on which it appears, as described in a study on occult pneumothorax 5.
- A more recent study found that a pneumothorax measuring 35 mm or less on chest CT can be safely observed in both blunt and penetrating trauma mechanisms, but this is not directly related to the BTS guidelines 6.
Key Points to Consider
- The BTS guidelines do not provide a specific method for measuring pneumothorax size.
- Different guidelines may classify pneumothorax size differently.
- Pneumothorax size can be quantified using various methods, including measurement of maximal width and number of CT sections.
- A cutoff of 35 mm on chest CT may be used to determine whether a pneumothorax can be safely observed, but this is not directly related to the BTS guidelines.