A clinical evaluation of VO2 kinetics in kidney transplant recipients

Abstract

Purpose Aerobic exercise capacity is reduced in patients with chronic kidney disease, partly due to alterations at the muscular and microvascular level. This study evaluated oxygen uptake (VO2) kinetics as indicator of muscular oxidative metabolism in a population of Kidney Transplant Recipients (KTRs). Methods Two groups of KTRs enrolled 3 (n = 21) and 12 months (n = 14) after transplantation and a control group of healthy young adults (n = 16) underwent cardiopulmonary exercise testing on cycle-ergometer. The protocol consisted in two subsequent constant, moderate-load exercise phases with a final incremental test until exhaustion. Results The time constant of VO2 kinetics was slower in KTRs at 3 and 12 months after transplantation compared to controls (50.4 ± 13.1 s and 43.8 ± 11.6 s vs 28.9 ± 8.4 s, respectively; P < 0.01). Peak VO2 was lower in KTRs evaluated 3 months after transplantation compared to patients evaluated after 1 year (21.3 ± 4.3 and 26.4 ± 8.0 mL/kg/min; P = 0.04). Blood haemoglobin (Hb) concentration was higher in KTRs evaluated at 12 months (12.8 ± 1.7 vs 14.6 ± 1.7 g/dL; P < 0.01). Among KTRs, τ showed a moderate negative correlation with Peak VO2 (ρ = − 0.52) and Oxygen uptake efficiency slope (OUES) (r = − 0.57) while no significant correlation with Hb and peak heart rate. Conclusions KTRs show slower VO2 kinetics compared to healthy controls. Hb and peak VO2 seem to improve during the first year after transplantation. VO2 kinetics were significantly associated with indices of cardiorespiratory fitness, but less with central determinants of aerobic capacity, thus suggesting a potential usefulness of adding this index of muscular oxidative metabolism to functional evaluation in KTRs.

Changes in peak oxygen uptake (VO 2peak ) following renal transplant: Results after 3‐year follow‐up

“…It has recently been reported that patients with RTx on average have a higher VO 2 peak at 1‐year follow‐up as compared with 3 months post‐transplant 13 . The observed VO 2 peak in these populations at both the 3 months (1.4 L/min) and at 12 months (1.9 L/min) were significantly higher than those observed in our patients at baseline and 3‐year follow‐up.…”

Overshoot of the Respiratory Exchange Ratio during Recovery from Maximal Exercise Testing in Kidney Transplant Recipients

“…Cardiopulmonary exercise testing (CPET) is currently recognized as a useful clinical tool to assess the physical fitness and exercise limitations of patients with cardiac, pulmonary and musculoskeletal diseases [1][2][3]. Its value has been demonstrated in the prevention and prognostic monitoring of cardiovascular diseases, in the prescription and follow-up of exercise training interventions and in the evaluation of medical treatment measures [1,4].…”

“…Moreover, a CPET evaluation has an important role in driving clinical decisions in end-stage heart or lung disease, guiding the selection process of candidates for transplantation [4]. However, the current body of evidence about CPET is mainly focused on the exercise response [2,3]; fewer studies have investigated the behavior of respiratory gas indices during recovery after maximal exercise testing especially in clinical populations.…”

“…Considering the possible impact of peripheral (e.g., muscular and vascular) factors in the genesis and modulation of this phenomenon, the behavior of these respiratory gas indices during recovery should also be studied in a population of patients with peripheral limitations to exercise in the absence of major cardiac limitations [3,13,14]. In this context, kidney transplant recipients (KTRs) are patients with a generally reduced cardiovascular fitness also due to long-term uremia.…”

Cardiorespiratory kinetics in exercise physiology: estimates and predictions using randomized changes in work rate

“…In terms of control technology, the CRP responses to exercise can be described as a single-input/single-output system (i. e. WR-CRP). The description of these systems allows to identify the influence of factors such as type of exercise (Koschate et al 2019a , b ), ambient conditions (Drescher et al 2018 ) and individual characteristics, e. g. age (Koschate et al 2016a , b ; Ebine et al 2018 ; Patti et al 2021 ) or fitness (Beltrame et al 2020 ; Inglis et al 2021 ), on the regulation of the cardiorespiratory system. From the individual kinetics and other characteristics of regulation, interventions, e. g. exercise prescriptions for athletes and patients, can be defined.…”