posted on 2018-08-15, 11:11authored byThomas J. Wilkinson, Alice E. M. White, Daniel G. D. Nixon, Douglas W. Gould, Emma L. Watson, Alice C. Smith
BACKGROUND: Chronic kidney disease (CKD) patients have reduced exercise capacity. Possible contributing factors may include impaired muscle O2 utilisation through reduced mitochondria number and/or function slowing the restoration of muscle ATP concentrations via oxidative phosphorylation. Using near-infrared spectroscopy (NIRS), we explored changes in skeletal muscle haemoglobin/myoglobin O2 saturation (SMO2%) during exercise. METHODS: 24 CKD patients [58.3 (± 16.5) years, eGFR 56.4 (± 22.3) ml/min/1.73 m2] completed the incremental shuttle walk test (ISWT) as a marker of exercise capacity. Using NIRS, SMO2% was measured continuously before, during, and after (recovery) exercise. Exploratory differences were investigated between exercise capacity tertiles in CKD, and compared with six healthy controls. RESULTS: We identified two discrete phases; a decline in SMO2% during incremental exercise, followed by rapid increase upon cessation (recovery). Compared to patients with low exercise capacity [distance walked during ISWT, 269.0 (± 35.9) m], patients with a higher exercise capacity [727.1 (± 38.1) m] took 45% longer to reach their minimum SMO2% (P = .038) and recovered (half-time recovery) 79% faster (P = .046). Compared to controls, CKD patients took significantly 56% longer to recover (i.e., restore SMO2% to baseline, full recovery) (P = .014). CONCLUSIONS: Using NIRS, we have determined for the first time in CKD, that favourable SMO2% kinetics (slower deoxygenation rate, quicker recovery) are associated with greater exercise capacity. These dysfunctional kinetics may indicate reduced mitochondria capacity to perform oxidative phosphorylation-a process essential for carrying out even simple activities of daily living. Accordingly, NIRS may provide a simple, low cost, and non-invasive means to evaluate muscle O2 kinetics in CKD.
Funding
This work was gratefully part funded by the Stoneygate Trust. The group also acknowledges the Leicester Kidney Care Appeal charity for funding awarded to Dr. Wilkinson to allow the purchase of the NIRS device. The research was supported by the National Institute for Health Research (NIHR) Leicester Biomedical Research Centre (BRC).
History
Citation
Clinical and Experimental Nephrology, 2018
Author affiliation
/Organisation/COLLEGE OF LIFE SCIENCES/School of Medicine/Department of Infection, Immunity and Inflammation
Version
VoR (Version of Record)
Published in
Clinical and Experimental Nephrology
Publisher
Springer Verlag (Germany) for Japanese Society of Nephrology (JSN)