The evolution of radiographic edema in ARDS and its association with clinical outcomes: A prospective cohort study in adult patients

Abstract

Purpose: To assess the longitudinal evolution of radiographic edema using chest X-rays (CXR) in patients with Acute Respiratory Distress Syndrome (ARDS) and to examine its association with prognostic biomarkers, ARDS subphenotypes and outcomes.

Materials and methods: We quantified radiographic edema on CXRs from patients with ARDS or cardiogenic pulmonary edema (controls) using the Radiographic Assessment of Lung Edema (RALE) score on day of intubation and up to 10 days after. We measured baseline plasma biomarkers and recorded clinical variables.

Results: The RALE score had good inter-rater agreement (r = 0.83, p < 0.0001) applied on 488 CXRs from 129 patients, with higher RALE scores in patients with ARDS (n = 108) compared to controls (n = 21, p = 0.01). Baseline RALE scores were positively correlated with levels of the receptor for end-glycation end products (RAGE) in ARDS patients (p < 0.05). Baseline RALE scores were not predictive of 30- or 90-day survival. Persistently elevated RALE scores were associated with prolonged need for mechanical ventilation (p = 0.002).

Conclusions: The RALE score is easily implementable with high inter-rater reliability. Longitudinal RALE scoring appears to be a reproducible approach to track the evolution of radiographic edema in patients with ARDS and can potentially predict prolonged need for mechanical ventilation.

Keywords: Chest X-ray; Extubation; Heterogeneity; Phenotype; Pulmonary Edema; Respiratory distress syndrome.

Fig. 1.

RALE score calculation from a chest radiograph (CXR) of an intubated patient with ARDS. First, the CXR is divided in four quadrants defined by drawing a horizontal line from the first branch of the left main bronchus with the spinal column separating the left and right lungs. The consolidation extent and density of each quadrant is scored separately, which are then multiplied for each quadrant and the total RALE score is obtained by simple addition of all quadrant scores (0–48).

Fig. 2.

Selection process of patients from the ALIR cohort. 129 patients of the 327 enrolled were diagnosed with ARDS or CHF and had both CXRs and data required for analysis. Of these, we were able to retrieve baseline (day of intubation) CXRs for 124 patients (104 ARDS and 20 CHF). ALIR: Acute Lung Injury Repository; ARDS: Acute respiratory distress syndrome; CHF: Congestive heart failure; CXR: Chest x-ray.

Fig. 3.

Kaplan-Meier estimates of 30-day survival in patients with ARDS stratified by baseline RALE score quartiles. There was no statistically significant difference in survival between the quartiles after adjusting for age and SOFA score (HR: 0.65, 95% CI: 0.24–1.76, p-value = 0.4). Q: Quartile.

Fig. 4.

Longitudinal evolution of the RALE score in patients with ARDS over the study period. When separated into groups based on need for prolonged mechanical ventilation (still intubated day 7 post-intubation), gradual decline in the RALE score was only observed in patients with early liberation from mechanical ventilation (p < 0.0001).