Reliability of standardized ultrasound measurements of quadriceps muscle thickness in neurological critically ill patients: a comparison to computed tomography measures.

OBJECTIVE: Muscle atrophy is frequent in critically ill patients and is associated with increased mortality and long-lasting alteration in quality of life. Muscle ultrasound has not been clearly validated in intensive care unit patients. The aim of this study was to compare the level of agreement between ultrasound and computed tomography scan for the measurement of quadriceps muscle thickness.
DESIGN: A prospective observational study. PATIENTS: Forty-two consecutive patients admitted to a neurological intensive care unit.
METHODS: Quadriceps thickness was measured 15 cm above the upper edge of the patella. Iterative brain computed tomography scans were associated with a quadriceps-centred acquisition sequence. Concomitantly, an ultrasound of the quadriceps was performed. The position of the studied leg was standardized for ultrasound and computed tomography.
RESULTS: A total of 73 measurements of ultrasound and computed tomography quadriceps thickness were compared. The correlation between both measures was 0.93 (95% confidence interval (95% CI) 0.84-1.02). Intra-rater reliability of ultrasound measurements and inter-rater reliability were excellent, with an ICC of 0.98 (95% CI 0.97-0.99) and 0.96 (95% CI 0.92-0.98), respectively.
CONCLUSION: A specific ultrasound set-up for measurement of quadriceps thickness is reliable and reproducible in an intensive care unit population.