Agreement between Lung Ultrasound and Chest X-ray Scoring in Invasively Ventilated ICU Patients

Background: Lung ultrasound (LUS) is a non–invasive imaging technique useful for diagnosing and monitoring pulmonary edema. The Radiographic Assessment for Lung Edema (RALE) score was recently proposed for semi–quantification of pulmonary edema on chest X-rays (CXRs) (Thorax 2018; 73:840). We assessed the correlation between the global LUS score (CCM; 2010; 38:84) and the RALE score in a cohort of ICU patients expected to need invasive mechanical ventilation (MV) for >24 hours. Methods: Global LUS (range 0–36) and RALE scores (range 0–48) were calculated by independent observers from the first available LUS and CXR within the first 48 hours of MV. The Berlin Definition was used for diagnosing ARDS. Linear regression was used to quantify the proportion of variance in RALE (response variable) explained by LUS (explanatory variable). Results: LUS and CXR of 144 patients (33 with ARDS) were analyzed. The correlation between the global LUS and the RALE score was highly significant, with 89% of the variance in the RALE being explained by the global LUS score (Figure). The RALE score could be calculated from the global LUS score, as follows: RALE score = global LUS score * 1.3 – 0.7. Conclusions: The global LUS score explains most of the variance in the RALE score. This information adds to the available evidence that LUS is a potentially radiation–free alternative to the CXR in ventilated ICU patients.