BackroundThe CAST Grid has been developed to evaluate the use of closed-loop communication (CLC) in the trauma bay. MethodsThe CAST Grid and two validated non-technical team performance assessment tools (the TEAM and T-NOTECHS grids) were completed by 2 independent reviewers based on trauma care simulation videos from a French Level 1 trauma center. Intra- and inter-rater agreements were evaluated for CLC parameters and non-technical performance, and correlations between these parameters were analyzed. ResultsThe study analyzed 11 videos. The intra- and inter-rater agreement for the number of CLC per minute (CLC/min) was moderate and good, respectively, based on Lin's concordance correlation coefficient [95%CI] (0.57 [−0.40;0.94] and 0.77 [0.33;0.94]). However, the agreement was poor for the percentage of CLC (0.37 [−0.58;0.89] and -0.36 [−0.71;0.14], respectively). The study found that a lower number of CLC/min was correlated with an increased duration of the simulation (r = −0.75 [−0.93; −0.25]). ConclusionThe CAST Grid showed a relatively good inter-rater agreement to quantify the number of CLC/min which was inversely correlated with the duration of care. This tool opens up the possibility of quantifying CLC and allows for new analyses of team functioning and interactions.