Ultrasound assessment of rectus femoris muscle in rehabilitation patients with chronic obstructive pulmonary disease screened for sarcopenia: correlation of muscle size with quadriceps strength and fat-free mass.

Abstract

To determine the relationship of the size of the rectus femoris muscle, assessed by ultrasonography, with parameters of muscle strength and body composition that are commonly used in the case-finding of sarcopenia in rehabilitation patients with chronic obstructive pulmonary disease (COPD). Cross-sectional pilot study of 18 men with severe COPD and 17 healthy controls. cross-sectional area, thickness, and width of the non-dominant rectus femoris muscle obtained by ultrasound, muscle strength determined by voluntary maximum isometric contraction of the quadriceps muscle, and fat-free mass assessed by bioimpedance analysis. Ultrasounds detected differences in the size of the rectus femoris muscle: cross-sectional area was 4.3 (SD 1.05) cm2 in patients, compared to 5.6 (SD 1.25) cm2 in controls; patients also presented lower quadriceps strength, and fat-free mass index. Cross-sectional area of the rectus femoris muscle showed a moderate correlation with quadriceps strength (R = 0.497, p = 0.036) and fat-free mass (R = 0.584, p = 0.011). In a multivariate linear model adjusted for age, body mass index,fat-free mass and muscle size, muscle strength was 7.44kg lower (p value = 0.014) in patients, compared to controls. A causal relationship was observed between the cross-sectional area of the rectus femoris muscle, assessed with ultrasonography, and maximum isometric strength of knee extension in COPD rehabilitation patients. Reduced cross-sectional area was also associated with loss of fat-free mass. Muscle ultrasound and bioimpedance analysis provide complementary and relevant information that could be useful in the case-finding of sarcopenia in COPD patients.