Lung Recruitability Evaluated by Recruitment-to-Inflation Ratio and Lung Ultrasound in COVID-19 Acute Respiratory Distress Syndrome

A substantial proportion of patients with coronavirus disease (COVID-19) admitted to the ICU require invasive mechanical ventilation for acute respiratory distress syndrome (ARDS), which is still associated with a high mortality rate (1). Applying the optimal positive end-expiratory pressure (PEEP) to ensure lung recruitment while limiting lung hyperinflation remains challenging in ARDS (2, 3). Yet, there are a few simple tools that might help personalize the level of PEEP in those patients at the bedside. Among them, the lung ultrasound (LUS) aeration score and the recruitment-toinflation (R/I) ratio have the potential to identify patients who are more likely to benefit from PEEP (2). Previous studies indeed suggested that LUS could assess spatial distribution of PEEPinduced lung recruitment but does not reliably detect hyperinflation (4, 5). The R/I ratio is a tool that has recently been developed to evaluate both the potential for lung recruitment and the risk for hyperinflation, but it does not provide regional information about lung recruitment (6–8). Therefore, these two tools, readily available at the bedside in most ICUs, could provide additive and complementary information on lung recruitment. In the present study, we aimed to assess lung recruitability simultaneously by the R/I ratio and the LUS in patients with COVID-19–related ARDS.