Developing a reliable and convenient methodology for ultrasound muscle assessment in critically ill patients: A reliability study

This study proposed a reliable and convenient methodology to assess rectus femoris (RF) and gastrocnemius muscles using ultrasound in critically ill patients. The focus was on reliability and convenience, considering both intra- and inter-observer reliability in the ICU and outpatient clinical settings. The RF and gastrocnemius muscles of 23 patients in the ICU were assessed using ultrasound. Two assessors, an expert and a novice, performed measurements across 2 consecutive days. Muscle thickness (MT), cross-sectional area (CSA), and echogenicity were measured in the RF, while MT, echogenicity, and pennate angle were measured in the gastrocnemius. The intra-class correlation coefficient (ICC) was assessed for intra- and inter-rater reliability for all markers. Intra- and inter-observer reliability was almost perfect (ICC > 0.80) for all markers, irrespective of the assessor's expertise. The CSA of the RF muscle exhibited the highest reliability (ICC > 0.95). MT of the gastrocnemius also demonstrated high intra- and inter-observer reliability (ICC > 0.91). In echogenicity measurements, gastrocnemius showed the highest (ICC > 0.91) intra- and inter-observer reliability. Ultrasound measurement of RF and gastrocnemius muscles in critically ill patients using the proposed methods demonstrated almost perfect reliability in both muscle mass and quality measurements. These methodologies, prioritizing convenience and reliability, could be employed for evaluating muscle status and changes in ICU settings and outpatient follow-ups.