Semi-quantification of pneumothorax volume by lung ultrasound.

BACKGROUND: Lung ultrasound (LUS) may accurately diagnose pneumothorax. However, there is uncertainty about its usefulness in the quantification of pneumothorax size. To determine the ability of LUS in the semi-quantification of pneumothorax volume, we compared the projection of the lung point (LP) with the pneumothorax volume measured by computerized tomography (CT) and the interpleural distance on chest radiography (CXR).

METHODS: We performed LUS in patients with pneumothorax and all the LP located on the chest wall were compared to CXR and CT studies. The primary outcome of the study was the ability of LP to grade pneumothorax volumes measured by CT. The secondary outcome was the accuracy of LP to predict small and large pneumothorax according to the societal guidelines based on CXR reading.

RESULTS: A total of 124 patients with pneumothorax were enrolled (76 spontaneous, 20 traumatic and 28 post-procedural). Ninety-four CXR and 58 CT were available for the analysis. An LP posterior to the mid axillary line corresponded to three different CXR criteria for large pneumothorax with sensitivity from 81.4 to 88.2 % and specificity from 64.7 to 72.6 %. The mid axillary line also represented the limit for predicting greater than 15 % of lung collapse when volume is measured at CT, with sensitivity 83.3 % and specificity 82.4 %.

CONCLUSIONS: LUS-targeted assessment of LP was a useful predictor of pneumothorax volume in this research study setting. LUS reliably classified pneumothorax size when compared to criteria based on CXR reading, particularly the small sized pneumothorax. However, LUS greatly outperformed conventional CXR reading for a graded quantification of the percentage of lung collapse.