Muscle mass in critically ill patients: analysis using ultrasound, traditional bioelectrical impedance analysis, and wearable devices: a prospective observational study

BACKGROUND: Accurate muscle mass assessment is essential in critical care, but no consensus exists on the optimal method because of invasiveness and limited feasibility in immobile patients. We evaluated the effectiveness of non-invasive and easily applicable ultrasound, traditional bioelectrical impedance analysis (BIA), and wearable technology in this context. METHODS: We recruited patients who stayed in the intensive care unit (ICU) for at least 7 days. Muscle mass was assessed at three time points: within 48 h of admission and on days 7 and 14 after admission. RESULTS: We analyzed the data of 53 patients (age: 71.8 ± 11.3 years; length of ICU stay: 10 days). Their muscle mass significantly declined during their ICU stay. The rectus femoris (RF) muscle thickness declined by day 7 and declined further by day 14 (89.7% of initial value). The total anterior thigh muscle thickness and cross-sectional area (CSA) of the RF showed a similar trend. The traditional BIA device reflected a decrease in skeletal muscle mass to 96.2% and 91.8% on day 7 and 14, respectively, while wearable device assessment showed a modest decline to 95% and 89.2% on day 7 and 14, respectively. The groups experiencing weaning failure, death, or discharge to a facility other than home exhibited a higher percentage decline in muscle mass compared with the groups experiencing weaning success, survival, or discharge to home, respectively. CONCLUSIONS: Ultrasound is a reliable method for monitoring muscle atrophy in critically ill patients, demonstrating a consistent decrease in muscle mass. The outcomes of traditional BIA and wearable devices suggest that careful consideration of their interpretations is necessary. Utilizing these tools may be valuable for assessing patient prognosis and facilitating more proactive interventions for patients experiencing muscle loss.