The Association of the Medical Research Council Scale and Quantitative Computerized Dynamometry in Patients After Critical Illness: An Exploratory Study

Purpose: The purpose of this study was to determine the association between isometric peak torque obtained using the Biodex dynamometer (gold standard) to the Medical Research Council (MRC) scale for knee extension (KE), ankle dorsiflexion (DF), and shoulder flexion (SF) in patients after intensive care unit (ICU) discharge. Methods: A cross-sectional observational substudy was conducted. Adults with at least 7 days of mechanical ventilation were recruited from a parent study of outcomes after critical illness. Muscle strength of KE, DF, and SF was measured using the MRC scale (grades 0–5) and the Biodex dynamometer (peak torque, % predicted) at 3 months post-ICU discharge. Results: Twenty participants were included in the study. The median and interquartile ranges for MRC scores for KE, DF, and SF were 4.5 (IQR = 1), 4.5 (IQR = 1), 4.0 (IQR = 1), respectively. No significant correlations were found between isometric peak torque and MRC scores for any muscle group at 3 months post-ICU discharge. Conclusion: Medical Research Council scale may be limited in the ability to detect muscle weakness post-ICU discharge. Quantitative dynamometry is recommended in the post-ICU period to identify individuals with muscle weakness who may benefit from physical rehabilitation.