The dynamic air bronchogram; a new parameter of thoracic ultrasound in predicting non-expandable lung

<bold>Background:</bold> Non-expandable lung (NEL) refers to the inability of the lung to fully re-expand after thoracentesis. Currently, pleural pressure measurements are used in the diagnosis of NEL. However, pleural monometry is an invasive procedure. Some thoracic ultrasound findings such as “absent sinusoid sign" have been reported to be useful diagnostic tools for NEL. The aim of this study is to evaluate the dynamic air bronchogram, a thoracic ultrasound finding, to determine the presence of a non-expandable lung. <bold>Methods:</bold> Ultrasonic evaluation was performed while the patient was in a sitting position On thoracic ultrasound, dynamic air bronchograms were observed as white columns within the atelectatic lung. Then, 1000 ml of pleural fluid was drained from all patients. NEL was defined based on a combination of clinical observation and post-thoracentesis radiology. Chest radiographs were evaluated 4 hours and 24 hours following the removal of the pleural fluid to identify NEL. <bold>Results:</bold> The study population consisted of 45 patients (27 male, 18 female) with a mean age of 65.4 years (range; 37-91 years). Of the 45 participants, 28 had malignant pleural effusion and 17 had benign pleural effusion. Of the included patients, 18/45 (40%) were categorized as NEL. The presence of a dynamic air bronchogram in thoracic ultrasound had a sensitivity of 92.5%, a specificity of 83.3% and diagnostic accuracy of 88.8% in detecting NEL, with a positive predictive value of 89.2% and a negative predictive value of 88.2%. <bold>Conclusion:</bold> In summary, our study shows that the presence of a dynamic air bronchogram observed on thoracic ultrasound is a simple and effective method for detecting NEL