What Maintains the Metabolic Cost at Peak Aerobic Exercise in End Stage Renal Disease Patients?

Background: End-stage renal disease (ESRD) reduces performance of cardiopulmonary function and peak oxygen uptake (VO2 peak). The possible roles of oxygen delivery and oxygen extraction as limiting factors of exercise tolerance in ESRD patients were assessed.Methods: A cross-sectional study was conducted with twenty-two ESRD patients who underwent a peak cardiopulmonary and echocardiograph exercise test via leg cycle ergometry.Results: During exercise, elevated lactic acid occurred at a mean workload of 68.6 ± 5.7 Watts, corresponding to 78% of their respective peak work capacity. At peak exercise, in all measured variables except for systolic blood pressure, ESRD patients did not achieve normally predicted values. Heart rate, left ventricular end diastolic and systolic volumes, stroke volume, cardiac output, VO2 peak, arteriovenous oxygen difference, and workload were below normal values, while diastolic blood pressure, mean blood pressure and total peripheral resistance were above normal values.Conclusions: In ESRD patients, values for both oxygen delivery and extraction were far below the recorded values in normal. This suggests diminished central cardiopulmonary responses as well as reduced peripheral capacity to extract oxygen at the muscle level. Findings support the concept and possible importance of exercise rehabilitation programs in the approach for treatment of ESRD patients.