Factors Affecting Exercise Capacity in Renal Transplantation Candidates on Continuous Ambulatory Peritoneal Dialysis Therapy

It is well known that reduced peak oxygen uptake (peak VO2) is a predictor for mortality in several chronic diseases and during the preoperative period. The aim of this study was to investigate the factors that influence peak VO2 in renal transplant candidates receiving continuous ambulatory peritoneal dialysis (CAPD) therapy. We included 22 chronic renal failure patients (12 men, 10 women; ages 29.64 ± 8.29 years; CAPD duration, 37.35 ± 7.15 months) in this study. Pulmonary function tests and symptom-limited cardiopulmonary exercise tests were administered to all patients. Cardiopulmonary exercise tests were performed on a cycle ergometry at the same time of day for all patients. We analyzed the exercise duration, maximum work rate, and peak VO2 level during cycle ergometry. Serum hemoglobin, hematocrit, total cholesterol, triglyceride, blood urea nitrogen, creatinine, albumin, prealbumin, C-reactive protein, sedimentation rate, ferritin, sodium, potassium, parathyroid hormone, calcium, and phosphorus levels were analyzed from samples. Mean values of exercise duration (6.86 ± 1.56 minutes), peak VO2 (17.20 ± 4.91 mL/min/kg), and maximum work rate (77.09 ± 26.09 watts) were lower when we compared them with predicted values for a healthy population. Peak VO2 was well correlated with serum phosphorus levels (4.51 ± 1.28 mg/dL, r = .592, P = .004). Test duration was correlated with peak VO2 ( r = .489, P = .025) and serum phosphorus levels ( r = .530, P = .024). There were no significant correlations with other factors. As a component of ATP, phosphorus is at the hub of the energy-related mechanisms operative in muscles of the respiratory and musculoskeletal systems. Therefore, we suggest that low exercise capacity might be related to low serum phosphorus levels, and that optimal control of serum phosphorus therapy would increase exercise capacity, exercise duration, and oxygen consumption resulting in a decrease of postoperative mortality in renal transplantation candidates.