Oxygen uptake efficiency slope as monitoring tool for physical training in chronic hemodialysis patients

Abstract

The purpose of this study was to clarify the utility of oxygen uptake efficiency slope (OUES) as a monitoring tool, and to investigate the effects of physical training in chronic hemodialysis (HD) patients. Seventeen patients (Trained Group) received physical training 2-3 times per week for 20 weeks at the intervals between exercise tests. Patients underwent a combination training of bicycle ergometry, walking and jogging for 30 min duration. The intensity of physical training was adjusted to maintain the exercising heart rate at between 50 and 60% of the peak heart rate. Twelve patients (Control Group) lived without physical training throughout the 20 weeks. Both the Groups received the symptom limited exercise tests before and after the 20 week physical training. Minute ventilation (VE), carbon dioxide output (VCO2) and oxygen uptake (VO2) were continuously measured during the exercise tests. Oxygen uptake efficiency slope was derived from the logarithmic relation between VO2 and VE during an incremental exercise test. In the Trained Group, OUES after physical training (30.1 +/- 5.8) was significantly (P < 0.01) higher than that before physical training (25.2 +/- 2.6), while in the Control Group, OUES did not change in this study period of 20 weeks. In the Trained Group, changes in OUES correlated with those in the maximum oxygen uptake (r = 0.78, P < 0.001) and the anaerobic threshold (r = 0.61, P < 0.01). It was suggested that OUES was applicable as a monitoring tool for cardiorespiratory functional reserve during physical training in HD patients.