Longitudinal change in ultrasound-derived rectus femoris cross-sectional area in COPD.

Background: Skeletal muscle dysfunction is common in COPD. Ultrasound-derived rectus femoris cross-sectional area (RFCSA) is a radiation free, non-invasive measure of muscle bulk that relates to quadriceps strength in people with COPD. However, there are limited longitudinal data for RFCSA, and it is not known whether longitudinal change in RFCSA reflects change in quadricep strength, exercise capacity, lower limb function or muscle mass. We aimed to quantify longitudinal change in ultrasound-derived RFCSA and assess its relationship with change in quadriceps maximal voluntary contraction (QMVC), incremental shuttle walk test (ISWT), five-repetition sit-to-stand (5STS) and fat-free mass (FFM) over 12 months in people with COPD.
Methods: We measured ultrasound-derived RFCSA, QMVC, ISWT, 5STS and FFM (measured by bioelectric impedance analysis) at baseline and 12 months in 169 people with stable COPD. Change was correlated using Pearson's or Spearman's coefficients.
Results: Baseline characteristics: mean±sd age 70.4±9.4 years; FEV ₁ 53.3±18.9% predicted. Over the course of 12 months mean RFCSA change was -33.7 mm ² (99% CI -62.6- -4.9 mm ² ; p=0.003) representing a mean±sd percentage change of -1.8±33.5%. There was a weak correlation between change in RFCSA and FFM (r=0.205, p=0.009), but not with change in QMVC, ISWT or 5STS.
Conclusion: There is a statistically significant decrease in ultrasound-derived RFCSA over 12 months in people with stable COPD, but this decrease does not correlate with change in quadriceps strength, exercise capacity, FFM or lower limb function.
Competing Interests: Conflict of interest: T.O. Jenkins reports grants from the Royal Brompton and Harefield Hospital Charity, outside of the submitted work. T.O. Jenkins received funding from the National Institute for Health Research to undertake the submitted work. C.M. Nolan reports grants from the National Institute for Health and Care Research, Royal Brompton and Harefield Hospital Charities, and Brunel University London, outside of the submitted work. M. Maddocks reports grants from the National Institute for Health Research, the European Commission and UKRI Innovate UK, outside of the submitted work. M. Maddocks received funding from the National Institute for Health Research to undertake the submitted work. W.D-C. Man reports grants from the National Institute for Health Research, outside of the submitted work. W.D-C. Man received funding from the Medical Research Council to undertake the submitted work. W-D.C. Man is an Associate Editor of this journal. The remaining authors report no grants outside of the submitted work, or to undertake the submitted work.
(Copyright ©The authors 2024.)