Response of the oxygen uptake efficiency slope to exercise training in patients with chronic kidney disease

Background

Chronic kidney disease (CKD) patients have poor cardiorespiratory fitness. Although cardiopulmonary exercise testing (CPET) is the universal assessment of cardiorespiratory fitness, values taken at ‘peak’ effort are strongly influenced by motivation and choice of test end point. The ‘oxygen uptake efficiency slope’ (OUES) integrates cardiovascular, musculoskeletal, and respiratory function into a single index, and may provide a pragmatic and safer alternative to maximal testing. No research has explored whether exercise training can improve OUES in CKD.

Methods

31 patients with non-dialysis CKD were recruited into a 12-week exercise programme consisting of mixed aerobic and resistance training 3x/week. CPET was conducted at baseline, and then, following a 6-week control period, pre- and post-exercise intervention. Direct measurements of oxygen consumption and ventilatory parameters were collected. The OUES was calculated as the relationship between V̇O2 and the log10 of minute ventilation (V̇E).

Results

No changes were observed in any variable during the control period, although modest increases in V̇O2peak were observed. No meaningful changes were observed as a result of exercise in any cardiorespiratory value obtained. The OUES calculated at 100%, 90%, 75%, and 50% of exercise duration did not significantly change after 12-weeks of exercise.

Conclusions

Our results show that 12-weeks of exercise training had no beneficial effects on OUES. The lack of change in OUES supports the modest change in V̇O2peak observed. The lack of change in OUES and other parameters possibly indicate a dysfunctional cardiorespiratory response to exercise in patients with CKD, likely mediated by dysfunctional peripheral metabolic mechanisms.