Risk Factors of Decreased Abdominal Expiratory Muscle Thickness in Mechanically Ventilated Critically Ill Patients – The mNUTRIC Score is an Independent Predictor

Background: The expiratory abdominal skeletal muscles are an important component of the respiratory muscle pump, and their reduced thickness has been associated with difficult weaning. There is no objective score that may help clinicians to predict expiratory abdominal muscle thinning. Patients and methods: This was a single-center retrospective study on 81 patients undergoing weaning from mechanical ventilation. The thickness of the four abdominal expiratory muscles – rectus abdominis (RA), internal oblique (IO), external oblique (EO), and transversus abdominis (TA) on the day of the first spontaneous breathing trial (SBT), were obtained. The various parameters of the patients with thinner RA, IO, EO, and TA below the determined thickness cut-off values, predicting difficult weaning was analyzed. Results: Modified nutritional risk in critically ill (mNUTRIC) score was found to be an independent predictor of thinner IO muscle after logistic regression analysis [p = 0.001, adjusted OR 2.33, 95% CI (1.394–3.892)]. The mNUTRIC score was also an independent predictor of thinner EO (p = 0.014, adjusted OR 1.57) and RA muscle (p = 0.002, adjusted OR 1.69). The mNUTRIC cutoff score ≥4 predicted thinner IO (AUC 0.813, p < 0.001 sensitivity 71%, specificity 77%) and thinner EO (AUC 0.738, p < 0.001, 71% sensitivity, 67% specificity). The mNUTRIC score ≥3 predicted that at least one out of the four abdominal expiratory muscles will be thin (AUC 0.849, p < 0.001, 95% CI [0.763–0.935], sensitivity 87.5%, specificity 59%). Conclusion: The mNUTRIC score is an independent predictor of thinner abdominal expiratory muscles in mechanically ventilated critically ill patients.