Medical Research Council Scale Predicts Spontaneous Breathing Trial Failure and Difficult or Prolonged Weaning of Critically Ill Individuals

Handgrip strength is an alternative measure to assess peripheral muscle strength and is correlated with the Medical Research Council (MRC) scale, with promising values for diagnosing ICU-acquired weakness (ICUAW). Because ICUAW has been associated with delayed weaning from mechanical ventilation, we hypothesized that ICUAW evaluated with both the MRC scale score and handgrip strength are associated with failure of a spontaneous breathing trial (SBT) and duration of mechanical ventilation weaning. We conducted a prospective observational study in 3 general ICUs with a total of 54 beds at 2 academic hospitals. Adult subjects with > 48 h of mechanical ventilation who were eligible for weaning were included in the study. In the evaluation before the first SBT, the MRC score ( < .001) and handgrip strength ( < .001) were significantly different between subjects extubated after a successful first SBT (simple weaning) and those extubated any time after a failed first SBT (difficult weaning). Only the MRC score discriminated between first SBT success or failure ( < .001); in multivariate analysis, the MRC score was significantly associated with first SBT failure (odds ratio 0.91, 95% CI 0.88-0.97, < .001) and difficult weaning (odds ratio 0.91, 95% CI 0.87-0.96, < .001). Handgrip strength exhibited good accuracy in identifying ICUAW. MRC score was independently associated with SBT failure and difficult or prolonged weaning.