A novel ultrasound approach in assessing IMAT in critically ill patients

Abstract

BackgroundMuscle wasting is a common finding in critically ill patients associated with increased days of mechanical ventilation in the ICU. Muscle wasting and associated morphological changes are hallmarks of ICU-acquired weakness. Muscle wasting can be diagnosed and quantified by muscle biopsy, but biopsies can cause multiple adverse effects. MuscleSound® has developed a non-invasive, real-time novel MusculoSkeletal (MSK) ultrasound approach to measure the ratio between percentage intramuscular adipose tissue (%IMAT) with muscle cross-section area (MCSA) (termed IMAT-Index). The present study aimed to assess the IMAT-Index in ICU patients longitudinally and compare it to age-matched healthy controls.MethodsTransverse (short-axis) ultrasound images of the rectus femoris muscle were obtained upon admission and discharge in 35 ICU patients and compared to age-matched healthy controls (n = 975). The echo intensity of the image taken from the muscle is used to automatically calculate the ratio between intramuscular adipose tissue by cm2 (IMAT-Index), the cross-sectional area of the muscle (MCSA), and muscle thickness (MT).ResultsIMAT-Index was successfully measured in all subjects. The mean IMAT-index (%IMAT/cm2) upon admission was significantly higher in critically ill patients compared to healthy controls (7.4 ± 4.3 vs. 3.1 ± 0.9, p < 0.001). At ICU discharge, the IMAT-index increased in the ICU group compared to admission (8.1 ± 3.5 vs. 7.4 ± 4.3, p < 0.05).ConclusionReal-time noninvasive MSK ultrasound IMAT-Index was higher in ICU patients than in healthy controls and increased during the ICU stay, both in male and female patients.