Quantification of the size of primary spontaneous pneumothorax: accuracy of the Light index

Background: The size of a pneumothorax (PTX) is usually estimated by the Light index. Treatment strategies of (primary, spontaneous) PTX partially depend upon the size of the PTX. To our knowledge, the Light index has not yet been correlated with the actual volume of the PTX.

Objectives: To correlate the estimated size of a primary spontaneous PTX by means of the Light index, with the actual amount of air present in the pleural space.

Methods: Actual PTX volumes were measured by means of manual aspiration of air present in the pleural space in 18 patients with primary spontaneous PTX and correlated with the size estimation obtained by the Light index.

Results: Light index and volume measurements were strongly correlated (r = 0.84, p < 0.0001).

Conclusions: The Light index is a good estimate of the actual size of a (primary spontaneous) PTX.