Correlation of Oxygenation and Radiographic Assessment of Lung Edema (RALE) Score to Lung Ultrasound Score (LUS) in Acute Respiratory Distress Syndrome (ARDS) Patients in the Intensive Care Unit

Abstract

Background Lung ultrasound score (LUS) as well as radiographic assessment of lung edema (RALE) score as calculated from chest radiography (CXR) have been applied to assess Acute Respiratory Distress Syndrome (ARDS) severity. CXRs, which are frequently performed in ARDS patients, pose a greater risk of radiation exposure to patients and health care staff. Aims and objectives The aim of the study was to evaluate if LUS had a better correlation to oxygenation (PaO~2~/FiO~2~) compared with the RALE score in ARDS patients. We also aimed to analyse if there was a correlation between RALE score and LUS. We wanted to determine the LUS and RALE score cut-off, which could predict a prolonged length of intensive care unit (ICU) stay (≥10 days) and survival. Methods Thirty-seven patients aged above 18 years with ARDS as per Berlin definition and admitted to the ICU were included in the study. It was a retrospective study done over a period of 11 months. On the day of admission to ICU, the global and basal LUS, global and basal RALE score, and PaO~2~ /FiO~2~ were recorded. Outcome and days of ICU stay were noted. Results Global LUS score and PaO~2~/FiO~2~ showed the best negative correlation (r = --0.491), which was significant (p = 0.002), followed by global RALE score and PaO~2~/FiO~2~ (r = --0.422, p = 0.009). Basal LUS and PaO~2~/FiO~2~ also had moderate negative correlation (r = --0.334, p = 0.043) followed by basal RALE score and PaO~2~/FiO~2~ (r = --0.34, p = 0.039). Global RALE score and global LUS did not show a significant correlation. Similarly, there was no significant correlation between basal RALE score and basal LUS. Global and basal LUS as well as global and basal RALE score were not beneficial in predicting either a prolonged length of ICU stay or survival as the area under curve was low. Conclusion In ARDS patients, global LUS had the best correlation to oxygenation (PaO~2~/FiO~2~), followed by global RALE score. Basal LUS and basal RALE score also had moderate correlation to oxygenation. However, there was no significant correlation between global LUS and global RALE score as well as between basal LUS and basal RALE score. Global and basal LUS as well as global and basal RALE scores were not able to predict a prolonged ICU stay or survival in ARDS patients.