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

Alessandro Patti,Andrea Ermolao,Francesco Marchini,Marco Vecchiato,Lucrezia Furian,Marco Bergamin,Francesca Battista,Daniel Neunhaeuserer,Andrea Gasperetti,Veronica Baioccato

doi:10.3390/ijerph18179236

Abstract

The overshoot of the respiratory exchange ratio (RER) during recovery from exercise has been found to be reduced in magnitude among patients with heart failure. The aim of this study is to investigate whether this phenomenon could also be present in patients with peripheral, and not cardiac, limitations to exercise such as kidney transplant recipients (KTRs). In this retrospective cross-sectional study, KTRs were evaluated with maximal cardiopulmonary exercise testing (CPET) assessing the RER overshoot parameters during recovery: the RER at peak exercise, the maximum RER value reached during recovery, the magnitude of the RER overshoot (RER mag = (RER max-peak RER)/peak RER%) and the linear slope of the RER increase after the end of exercise. A total of 57 KTRs were included in the study (16 females), all of them showing a significant RER overshoot (RER mag: 28.4 ± 12.7%). Moreover, the RER mag showed significant correlations with the fitness of patients (peak VO2: ρ = 0.57, p < 0.01) and cardiorespiratory efficiency (VE/VCO2 slope: r = −0.32, p < 0.05; oxygen uptake efficiency slope (OUES): r = 0.48, p < 0.01). Indeed, the RER mag was significantly different between the subgroups stratified by Weber’s fitness class or a ventilatory efficiency class. Our study is the first to investigate recovery of the RER in a population of KTRs, which correlates well with known prognostic CPET markers of cardiorespiratory fitness, determining the RER mag as the most meaningful RER overshoot parameter. Thus, the RER recovery might be included in CPET evaluations to further improve prognostic risk stratifications in KTRs and other chronic diseases.

Highlights

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]
9 were excluded because a clear overshoot could not be defined in the recorded recovery interval; i.e., the respiratory exchange ratio (RER) descent after the maximum RER reached during recovery (RER max) was not observed
The recovery of the respiratory gas exchange parameters was studied in kidney transplant recipients (KTRs), evaluating the RER overshoot after maximal exercise testing

Summary

Introduction

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]. Several of the parameters determined during CPET, such as evaluating the physical fitness of patients (i.e., peak oxygen uptake: peak VO2 ) and cardiorespiratory efficiency (i.e., the ventilation to carbon dioxide production ratio: VE/VCO2 ) during exercise, have been shown to be well-consolidated prognostic markers in patients with heart failure. A CPET evaluation has an important role in driving clinical decisions.

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