Mapping Bullous Emphysema With Lung Ultrasound: A Prospective Multicentre Study

Lung ultrasound holds high diagnostic performance for pleural diseases, notably pneumothorax. Bullous emphysema is a potential differential diagnosis of pneumothorax on ultrasound, but its precise semiology is poorly known. This study aimed to delineate the sonographic presentation of bullous emphysema and assess the diagnostic performance of common ultrasound features in identifying bullae.

From June 2019 to June 2021, patients with CT scanner-confirmed bullous emphysema were prospectively included. Investigators performed a standardised 14-region lung ultrasound. Sonographic features of bullous and non-bullous regions were compared. Diagnostic performances for bullae were calculated for each sign, and an additive score was constructed using signs with specificity > 85%. Pearson's correlation was used to examine the relationship between this score, bulla size, and respiratory functional parameters.

Thirty-six patients were included, mostly male (n = 33 patients, 91.7%), with an average age of 62 ± 11 years. Bullae mostly affected apical regions (n = 24 patients, 67%). Bullous regions displayed a more frequent absence of lung sliding (34% vs. 11% in non-bullous regions, p < 0.01), barcode sign (15% vs. 3%, p < 0.01), increased A-line visibility (16% vs. 8%, p = 0.048), and absence of Z lines (62% vs. 44%, p = 0.018). A bulla-point sign was visualised in 4% of bullous regions. Absent lung sliding was more frequent in patients with pulmonary distension and in apical regions. Patient bulla score (3 [2-6]) correlated with bulla size (r = 0.53 [0.25;0.73], p < 0.001), FEV₁ (r = -0.38 [-0.60;-0.03], p = 0.022), and forced vital capacity (r = -0.38 [-0.64;-0.08], p = 0.021).

Our findings challenge previous data about the specificity of ultrasound signs of pneumothorax in patients with bullous emphysema, highlighting the need for cautious interpretation in clinical practice.

NCT04012359.