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

Abstract

Background: Muscle 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.

Methods: This 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).

Results: A 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.

Conclusion: The 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.

Keywords: Intensive care unit; Muscle wasting; Protein; Quadriceps muscle; Ultrasonography.

Conflict of interest statement

Ethics approval and consent to participate

The access to health information was approved by an ethics committee (“Committee for the Protection of Human Subjects in Biomedical Research” - Paris Ile de France VI Pitié-Salpêtrière – 10/07/2014) and by the French Data Protection Committee (“Commission Nationale Informatique et Libertés” - #1771144) who waived the need for individual consent according to the French law at the time of the study.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1

Ultrasound assessment of the quadriceps femoris muscle thickness. a Anatomical diagram locating the “midpoint” and the “two-thirds” measurement sites. From Wikimedia Commons. b Transverse ultrasound section made by linear probe at the midpoint site. RF: rectus femoris; VL: vastus lateralis; VM: vastus medialis; VI: vastus intermedius

Fig. 2

Intra-observer and inter-observer reliability independently of laterality at the two measurement sites. Bland Altman representation with mean differences (green solid line) and 1.96SD limits (blue dashed lines)

Fig. 3

Evolution of Quadriceps femoris muscle thickness between D1 and D21. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001 (comparison with D1 assessment). Values are represented by medians and 95% confidence interval

Fig. 4

Correlation between muscle loss and nutritional debt during the first week of ICU. a Muscle loss and caloric debt expressed in calories. b Muscle loss and protein debt. r: Spearman correlation coefficient