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

Abstract

A substantial proportion of patients with coronavirus disease 2019 (COVID-19) admitted to intensive care units (ICU) requires 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 few simple tools that might help personalize the level of PEEP in those patients at the bedside. Among them, lung ultrasound (LUS) aeration score and recruitment-to-inflation ratio (R/I) 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 PEEP-induced lung recruitment but does not reliably detect hyperinflation (4, 5). The R/I ratio is a recent tool that has been developed to evaluate both the potential for lung recruitment and the risk for hyperinflation, but does not provide regional information about lung recruitment (6-8). Therefore, these two tools, readily available at 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. Methods We conducted a prospective observational study between March 31 and October 29, 2020 in a 26-bed university-affiliated ICU in Lyon, France, which was approved by our institutional ethics committee.

Differential effects of prone position in COVID-19-related ARDS in low and high recruiters

“…The response to prone position, in terms of oxygenation and respiratory mechanics, would differ according to the potential for lung recruitment in supine position in COVID-19-ARDS [ 3 ]. Recruitment-to-inflation ratio (R/I), which is measurable with almost all modern respirators, allows, at bedside, the distinction between patients with a low or high potential for lung recruitment [ 4 ], including in those with COVID-19-ARDS [ 5 ]. This tool may henceforth help clinicians to set adequate positive end-expiratory pressure (PEEP) levels in ARDS [ 4 ].…”

The POCUS Consult: How Point of Care Ultrasound Helps Guide Medical Decision Making

“…Stevic et al simultaneously assessed lung recruitability using both recruitment-to-inflation (R/I) ratio and lung ultrasound aeration score in a prospective observational study of 24 patients with novel coronavirus disease-associated ARDS. 132 The R/I ratio was calculated by the compliance of recruited lung divided by the lung compliance at low PEEP, 133 while the lung ultrasound aeration score was determined according to the method described by Bouhemad et al 129 Investigators found that an R/I ratio of 0.7 correlated with lung ultrasound aeration score, further validating the use of ultrasound-guided lung recruitment. 132 …”

“… 132 The R/I ratio was calculated by the compliance of recruited lung divided by the lung compliance at low PEEP, 133 while the lung ultrasound aeration score was determined according to the method described by Bouhemad et al 129 Investigators found that an R/I ratio of 0.7 correlated with lung ultrasound aeration score, further validating the use of ultrasound-guided lung recruitment. 132 …”

Advanced respiratory monitoring in mechanically ventilated patients with coronavirus disease 2019-associated acute respiratory distress syndrome

“…To define optimal PEEP or guide recruitment by LUS there are different techniques: calculating the LUS score counting B-lines (an artifact), the change in lung sliding (anatomical) or looking for atelectasis at the posterior lateral lung point (anatomical). The first was tested in 24 invasively ventilated C-ARDS patients [ 38 ]. In high recruiters there was a significant decrease in LUS score especially in the lateral and posterior lung regions.…”