Lung ultrasound aeration assessment: comparison of two techniques

Introduction

Lung ultrasound (LUS) allows semiquantification of lung aeration in PEEP trials [1], pneumonia [2] and weaning [3]. LUS score is based on number/coalescence of vertical artifacts (B-lines) in longitudinal scan (LONG) [4]: the pleura is identified between two ribs and its visualization limited by intercostal space (ICS) width. We hypothesized that a transversal scan (TRANSV) aligned with ICS would visualize longer pleura and a higher number of artifacts, with better assessment of loss of aeration (LoA).

Methods

LONG and TRANSV were performed in six areas per lung (anterior, lateral and posterior, each divided into superior and inferior). Once LONG was performed, TRANSV was obtained by a probe rotation until the ribs disappeared. We considered pleural length, B-line number/coalescence, and subpleural/lobar consolidations. LUS score was assigned: 0 normal lung, 1 moderate LoA (≥3 well-spaced B-lines), 2 severe LoA (coalescent B-lines), 3 complete LoA (tissue-like pattern).

Results

We enrolled 38 patients (21 males, age 60 ± 16 years, BMI 24.7 ± 4.7 kg/m²) corresponding to 456 ICSs. In 63 ICSs, a tissue-like pattern was visualized in both techniques. In the other 393, LONG versus TRANSV pleural length was 2.0 ± 0.6 cm (range 0.8 to 3.8; variance 0.31) versus 3.9 ± 0.1 cm (range 3.0 to 4.3; variance 0.1) (P < 0.0001), B-lines per scan were 1.1 ± 1.6 versus 1.8 ± 2.5 (P < 0.0001), coalescent B-lines were detected in 24 versus 30% (P < 0.05) and subpleural consolidations in 16 versus 22% (P < 0.05), respectively. LUS scores' prevalence significantly differed in LONG versus TRANSV (Figure 1).

Figure 1

LUS scores. *P <0.01 TRANSV versus LONG.

Conclusion

TRANSV visualizes significantly longer pleura and greater number of artifacts useful for lung disease assessment.