Diagnostic accuracy of bedside ultrasound measurement of limb skeletal muscle thickness for intensive care unit-acquired weakness

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To explore the diagnostic accuracy of bedside ultrasound measurement of limb skeletal muscle thickness for intensive care unit-acquired weakness (ICU-AW) in patients receiving mechanical ventilation. A prospective observational study was conducted. Patients receiving mechanical ventilation admitted to the emergency ICU of Cangzhou Central Hospital from June 2018 to March 2020 were enrolled. The demographic data were collected. Medical Research Council (MRC) score was used to assess muscle strength and to determine the presence of ICU-AW once the patients were awake. The thicknesses of biceps brachii (BB), flexor carpi radialis (FCR), rectus femoris (RF) and tibialis anterior (TA) were measured by bedside ultrasound. The difference of each index was compared between the patients in ICU-AW group and in non-ICU-AW group. Receiver operator characteristic (ROC) curves were plotted to examine the values of the thicknesses of these four muscles in diagnosing ICU-AW. Forty-one patients receiving mechanical ventilation (15 patients with ICU-AW, 26 patients without ICU-AW) were recruited. Compared with the non-ICU-AW group, the MRC score, the thicknesses of FCR, RF and TA were lower in the ICU-AW group [MRC score: 36 (30, 40) vs. 60 (56, 60), FCR (cm): 1.09±0.19 vs. 1.30±0.28, RF (cm): 1.57±0.58 vs. 2.23±0.58, TA (cm): 1.76±0.33 vs. 2.21±0.43, all P < 0.05], and the length of ICU stay was longer [days: 15 (9, 26) vs. 10 (4, 12), P < 0.05]. Although the thickness of BB was also lower in the ICU-AW group, there was no statistical difference between the two groups (cm: 2.45±0.57 vs. 2.70±0.61, P = 0.205). ROC curve showed that the thicknesses of FCR, RF and TA had diagnostic values for ICU-AW [area under ROC curve (AUC) and 95% confidence interval (95%CI) was 0.742 (0.582-0.866), 0.787 (0.631-0.899), 0.817 (0.665-0.920), respectively, all P < 0.01]. The thicknesses of BB couldn't diagnose ICU-AW (AUC = 0.597, 95%CI was 0.433-0.747, P = 0.296). The thicknesses of FCR, RF and TA measured by bedside ultrasound in patients with mechanical ventilation had diagnostic values for ICU-AW, while the thickness of BB could not diagnose ICU-AW.