Introduction: We evaluated the reliability of measuring muscle thickness with ultrasound in limbs and diaphragms of critically ill children and determined the sensitivity of these measures to quantitate muscle atrophy over time. Methods: An expert and trained novice sonographers prospectively measured limb and diaphragm muscle thickness in 33 critically ill children. Results: Expert and novice intrarater and interrater reliability were similar. Intraclass correlations (ICC) and coefficients of variation (CoV) were better in limbs (ICC > 0.9; CoV 3.57%–5.40%) than in diaphragm (ICC > 0.8; CoV novice 11.88%, expert, 12.28%). Mean relative difference in all muscles was small (1%-8%). Limits of agreement of the relative difference were smaller in limb (<13%–18%) than in diaphragm (<38%) muscles. Discussion: Muscle thickness is reliably measured with ultrasound by trained examiners in critically ill children. Our approach detects atrophy >13% in limb and >38% in diaphragm muscles. The smaller detectable change in limb muscles is likely due to their greater thickness. Muscle Nerve 59:88–94, 2019.
- ICU-acquired weakness
- muscle thickness