Development and reliability of an ultrasound protocol to evaluate quadriceps muscle mass and diaphragm structure: a pilot study

Abstract

Purpose: This study aimed to evaluate the intra and inter-operator reliability of an ultrasound (US) protocol, to assess quadriceps muscle mass and diaphragm structure in healthy people, for future monitoring of patients with respiratory disease. Methods and Materials: Twelve volunteers (6♀, 31.8±10.6 years; BMI=23.4±3.7 kg/m2) participated. An US equipment (Logiq P6 PRO, GE) with a multifrequency linear probe (11L) was used. Three measures of Quadriceps (QTK) and Rectus Femoris thickness (RFTK), RF cross sectional area (RFArea), bilateral diaphragmatic thickness at maximal inspiration (DTKI) and at end expiration (DTKE) were obtained by one operator. Six volunteers were randomly evaluated by two operators. Mann Whitney test was used to assess differences between inspiration and expiration and the right and left hemi-diaphragm. The Intraclass Correlation Coefficient (ICC2,1) was used to explore reliability. Results: Mean RFTK were 1.72cm, 8.19cm2 for RFArea and 3.23cm for QTK. Significant differences were found between DTKI and DTKE both at right (0.31±0,17cm vs 0.23±0.19cm, p=0.01) and left hemi-diaphragm (0.37±0.18cm vs 0.24±0.14cm, p=0.01). No significant differences between the right and left hemi-diaphragms were observed during inspiration or expiration. Intra and inter-operator reliability were all Excellent: DTKE (intra: ICC2,1=0.977; inter: ICC2,1=0.822), DTKI (intra: ICC2,1=,0.903; inter: ICC2,1=0.805), QTK (intra: ICC2,1=0.976; inter: ICC2,1=0,940), RFArea (intra: ICC2,1=0.973; inter: ICC2,1=0.981) and RFTK (intra: ICC2,1=0.998 ; inter: ICC2,1=0.762). Conclusion: Results showed the feasibility and reliability of this US protocol in healthy people. One single measurement by one operator seems to be adequate. Bilateral diaphragmatic measurements might not be necessary in respiratory patient's evaluation.