Diaphragmatic dysfunction in patients with ICU-acquired weakness and its impact on extubation failure

Diaphragm function is rarely studied in intensive care patients with unit-acquired weakness (ICUAW) in whom weaning from mechanical ventilation is challenging. The aim of the present study was to evaluate the diaphragm function and the outcome using a multimodal approach in ICUAW patients. Patients were eligible if they were diagnosed for ICUAW [Medical Research Council (MRC) Score < 48], mechanically ventilated for at least 48 h and were undergoing a spontaneous breathing trial. Diaphragm function was assessed using magnetic stimulation of the phrenic nerves (change in endotracheal tube pressure), maximal inspiratory pressure and ultrasonographically (thickening fraction). Diaphragmatic dysfunction was defined by a change in endotracheal tube pressure below 11 cmH(2)O. The endpoints were to describe the correlation between diaphragm function and ICUAW and its impact on extubation. Among 185 consecutive patients ventilated for more than 48 h, 40 (22 %) with a MRC score of 31 [20-36] were included. Diaphragm dysfunction was observed with ICUAW in 32 patients (80 %). Change in endotracheal tube pressure and MRC score were not correlated. Maximal inspiratory pressure was correlated with change in endotracheal tube pressure after magnetic stimulation of the phrenic nerves (r = 0.43; p = 0.005) and MRC score (r = 0.34; p = 0.02). Thickening fraction was less than 20 % in 70 % of the patients and was statistically correlated with change in endotracheal tube pressure (r = 0.4; p = 0.02) but not with MRC score. Half of the patients could be extubated without needing reintubation within 72 h. Diaphragm dysfunction is frequent in patients with ICU-acquired weakness (80 %) but poorly correlated with the ICU-acquired weakness MRC score. Half of the patients with ICU-acquired weakness were successfully extubated. Half of the patients who failed the weaning process died during the ICU stay.