Reliability of ultrasound measurements of quadriceps muscle thickness in critically ill patients

Abstract

BackgroundMuscle wasting in critically ill patients is associated with negative clinical outcomes. Ultrasound quadriceps femoris muscle assessment may constitute a convenient tool to evaluate muscle wasting. Nevertheless, its reliability remains uncertain. Our primary aim was to study the intra- and inter-observer reliability of this technique. Our secondary aim was to assess the evolution of the quadriceps muscle during the first 3 weeks after ICU admission and its possible association with nutritional intake.MethodsThis observational study included patients expected to stay more than 7 days in the ICU. Ultrasound quadriceps muscle thickness was measured with a 12 MHz linear transducer, by two trained physicians, on D1, D3, D5, D7 and D21. Two measurements sites were evaluated: on the midpoint or on the two-thirds of the length between the anterior superior iliac spine and the upper border of the patella. Intra and inter-observer reliability was assessed by calculating the intra-class correlation coefficient (ICC).ResultsA total of 280 ultrasound quadriceps thickness measurements were performed on 29 critically ill patients. Intra-observer reliability’s ICC was 0.74 [95% CI 0.63; 0.84] at the “midpoint” site and 0.83 [95% CI 0.75; 0.9] at the “two-thirds” site. Inter-observer reliability’s ICC was 0.76 [95% CI, 0.66; 0.86] at the “midpoint” site and 0.81 [95% CI, 0.7; 0.9] at the “two-thirds” site. Quadriceps femoris muscle thickness decreased over 16% within the first week after ICU admission. No correlation was found between muscle loss and caloric (p = 0.96) or protein (p = 0.80) debt over the first week.ConclusionThe assessment by ultrasonography of the quadriceps muscle thickness reveals good intra- and inter-observer reliability and may constitute a promising tool to evaluate the effect of nutritional-based interventions on muscle wasting in critically ill patients.Trial registration“Committee for the Protection of Human Subjects in Biomedical Research” - Paris Ile de France VI Pitié-Salpêtrière – 10/07/2014.French Data Protection Committee (“Commission Nationale Informatique et Libertés”) - #1771144.