Cardiorespiratory fitness assessed by cardiopulmonary exercise testing between different stages of pre-dialysis chronic kidney disease: A systematic review and meta-analysis

Effect of heart failure and atrial fibrillation on cardiorespiratory fitness in hemodialysis patients

PURPOSE

Heart failure (HF) and atrial fibrillation (AF) are highly prevalent in hemodialysis. They are well-known significant modifiers of the disease associations with cardiovascular outcomes, but there is a lack of evidence regarding the effects of HF and AF on cardiorespiratory fitness. This study is the first to examine the possible association of the presence of HF and AF with exercise intolerance in patients undergoing hemodialysis.

METHODS

This analysis included 40 sex- and age-matched participants [10 hemodialysis patients with HF or AF, 10 hemodialysis patients without HF or AF, 10 patients with HF or AF without chronic kidney disease (CKD) and 10 healthy controls] that underwent CPET and spirometry examinations. The total of patients with HF had preserved ejection fraction.

RESULTS

VO2peak(ml/kg/min) showed a graded increase between hemodialysis patients with HF or AF, hemodialysis patients without HF or AF, non-CKD patients with HF or AF and controls (13.17 ± 2.45 vs 15.26 ± 3.29 vs 19.64 ± 5.84 vs 25.11 ± 6.94 ml/kg/min, p < 0.001); VO2peak(ml/min) followed the same pattern (1172 ± 197 vs 1269 ± 314 vs 1817 ± 583 vs 1952 ± 592 ml/min respectively, p = 0.001). VO2peak(%predicted), VO2AT(ml/kg/min), VO2AT(ml/min) and maximal work load significantly differed between the study groups, with a tendency for higher values from hemodialysis patients to non-CKD patients with HF or AF and to healthy controls. FEV1 and FVC levels were similar between the study groups. In the whole population, VO2peak(ml/kg/min) showed a positive correlation with hemoglobin (r = 0.663, p < 0.001) and negative correlations with high-sensitivity cardiac troponin I (r = - 0.493, p = 0.001) and BNP (r = - 0.479, p = 0.002).

CONCLUSION

Hemodialysis patients have low exercise tolerance, and the presence of HF or AF is associated with further decreased values of VO2peak, the most important determinant of cardiorespiratory fitness.

Review of Exercise Interventions to Improve Clinical Outcomes in Nondialysis CKD

Exercise interventions in chronic kidney disease (CKD) have received growing interest, with over 30 meta-analyses published in the past 5 years. The potential benefits of exercise training in CKD range from slowing disease progression to improving comorbidities and quality of life. Nevertheless, there is a lack of large, randomized control trials in diverse populations, particularly regarding exercise in nondialysis-dependent CKD (NDD). When exercise interventions are implemented, they often lack fundamental features of exercise training such as progressive overload, personalization, and specificity. Furthermore, the physiology of exercise and CKD-specific barriers appear poorly understood. This review explores the potential benefits of exercise training in NDD, draws lessons from previous interventions and other fields, and provides several basic tools that may help improve interventions in research and practice.

Effects of intradialytic bicycle ergometer exercise on transcription factors NF-ĸB and Nrf2 in patients with chronic kidney disease: A randomized crossover clinical trial

PURPOSE

To evaluate the effects of an intradialytic aerobic exercise training program on the expression of transcription factors nuclear factor κappa B (NF-κB) and nuclear factor erythroid 2-related factor 2 (Nrf2), related to inflammatory and antioxidant pathways, respectively, in patients with chronic kidney disease (CKD) on hemodialysis.

METHODS

This was a longitudinal, randomized clinical trial with a washout period and crossover performed with 33 patients randomized into two groups: Exercise (individualized intradialytic aerobic exercise on an adapted stationary exercise bike) three times per week for three months and control (without exercise). After the washout period (1 month), the exercise group became the control, and the other group performed the exercises for another three months. Blood sample collection, food intake, and anthropometry were evaluated at the beginning and end of each study phase. Nrf2, its target gene NAD(P)H quinone oxidoreductase 1 (NQO1), and NF-κB transcription factors were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and the inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) by ELISA assay.

RESULTS

Eighteen patients [11 men, 44.1 ± 8.4 years, 17.3 (6.6-124) months on HD] completed all the study. The obtained data revealed that the intervention did not affect Nrf2, NQO1, and NF-κB mRNA expression. Also, TNF-α levels were not changed. However, IL-6 showed a tendency to decrease after the exercise intervention (p = 0.054).

CONCLUSION

In hemodialysis patients, three months of intradialytic aerobic exercise did not modulate the transcription factors associated with inflammation (NF-κB) and antioxidant activity (Nrf2 and NQO1).

CLINICAL TRIALS REGISTRATION NUMBER

NCT04375553.

Whole body resistance training on functional outcomes of patients with Stage 4 or 5 chronic kidney disease: A systematic review

Chronic kidney disease (CKD) causes skeletal muscle wasting, resulting in reduced function and inability to live independently. This systematic review critically appraised the scientific literature regarding the effects of full-body resistance training on clinically-relevant functional capacity measures in CKD. The study population included studies of people with Stage 4 or 5 CKD and a mean age of 40+ years old. Eight databases were searched for eligible studies: Pubmed, Embase, Cochrane, CINAHL, Scopus, Web of Science, MEDLINE, and AGELINE. MeSH terms and keyword combinations were used for screening following the PRISMA conduct. Inclusion criteria were based on PICO principles and no date of publication filter was applied. The intervention was training 2 days/week of structured resistance exercises using major upper and lower muscle groups. Minimum intervention period was 7 weeks. Comparison groups maintained their habitual activity without structured exercise training. Outcome measures of interest were: 6-min walk test, grip strength, timed up-and-go test, and sit-to-stand. Eight randomized controlled trials and one nonequivalent comparison-group study fulfilled the inclusion criteria and underwent data extraction. All studies were of hemodialysis patients. The evidence indicates that full-body resistance exercise significantly improved grip strength, timed up and go and sit to stand tests; metrics associated with enhanced quality and quantity of life.

Different Interdialytic Intervals and Cardiorespiratory Fitness in Patients Undergoing Hemodialysis

Key Points

This is the first study exploring differences in cardiorespiratory fitness assessed with cardiopulmonary exercise testing between the 2-day and the 3-day interdialytic interval. The 3-day interdialytic interval was associated with further impaired cardiorespiratory fitness. This effect was predominantly driven by excess fluid accumulation during the extra interdialytic day.

Background

Long interdialytic interval in thrice-weekly hemodialysis is associated with excess cardiovascular and all-cause mortality risk. Impaired cardiorespiratory fitness is a strong predictor of mortality in hemodialysis. This study investigated differences in cardiorespiratory fitness assessed with cardiopulmonary exercise testing (CPET) between the end of the 2-day and the 3-day interdialytic interval.

Methods

A total of 28 hemodialysis patients, randomized in two different sequences of evaluation, underwent CPET and spirometry examination at the end of the 2-day and the 3-day intervals. The primary outcome was the difference in oxygen uptake at peak exercise (VO2peak [ml/kg per minute]) assessed with CPET. Volume status was assessed with interdialytic weight gain, lung ultrasound, bioimpedance spectroscopy, and inferior vena cava measurements. A total of 14 age-matched and sex-matched controls were also evaluated. Comparisons of changes in parameters of interest were performed with paired or independent t -tests or relevant nonparametric tests, as appropriate. Bivariate correlation analyses and generalized linear mixed models were used to examine associations between changes in CPET parameters and volume indices.

Results

Hemodialysis patients at the end of both 2-day and 3-day intervals presented lower values in all major CPET parameters than controls. VO2peak (ml/kg per minute) was significantly higher at the end of the 2-day than the 3-day interval (15.2±4.2 versus 13.6±2.8; P < 0.001); the results were similar for VO2peak (ml/min) (1188±257 versus 1074±224; P < 0.001) and VO2peak (% predicted) (58.9±9.2 versus 52.3±8.6; P < 0.001). Numerical but no statistically significant differences were detected in VO2 anaerobic threshold (ml/kg per minute) and VO2 anaerobic threshold (ml/min) between the two time points. Maximal work load (90.1±23.2 versus 79.3±25.1; P < 0.001), exercise duration, heart rate at peak exercise, and oxygen pulse also showed lower values at the end of the 3-day interval. Forced expiratory volume in 1-second levels were similar between the two evaluations. Generalized linear mixed model analysis, including interdialytic weight gain as random covariate, attenuated the observed differences in VO2peak (ml/kg per minute). Changes in bioimpedance spectroscopy–derived overhydration indexes were moderately correlated with changes of VO2peak (ml/kg per minute).

Conclusions

The 3-day interval was associated with further impairment of VO2 at peak exercise. This effect was predominantly driven by excess fluid accumulation during the extra interdialytic day.

Effects of whole-body vibration exercise on physical function in patients with chronic kidney disease: a systematic review and meta-analysis

BACKGROUND

The current state of knowledge regarding the efficacy of whole-body vibration (WBV) training for individuals with chronic kidney disease (CKD) is limited. To address this gap, the present study seeks to undertake a comprehensive systematic review and meta-analysis of clinical trials to evaluate the impact of WBV on physical function and quality of life outcomes in CKD patients.

METHODS

A systematic search was performed on the PubMed, Embase, Web of Science, and Scopus databases from inception to March 2023 and updated in June 2023. The inclusion criteria comprised randomized controlled studies, quasi-experimental studies, and single-arm trials that evaluated the impact of WBV on physical function, encompassing cardiopulmonary fitness, muscle strength, mobility, and balance, in CKD patients. Adverse events that were included in the study reports were recorded. The pooled evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) method.

RESULTS

Nine studies were identified, of which seven were included in the meta-analysis. The results of the meta-analysis indicated a statistically significant improvement in upper (mean difference: 3.45 kg; 95% confidence interval 1.61 to 5.29) and lower (standardized mean difference: 0.34, 95% confidence interval 0.08 to 0.59) extremity muscle strength in patients with CKD who underwent WBV training compared to baseline (low-level evidence). Furthermore, WBV training favored improved cardiorespiratory fitness, mobility, and balance function, but no statistical difference was observed. The impact of WBV training on quality of life in patients with CKD requires further validation. Notably, only one adverse event (nausea) was reported in the included studies.

CONCLUSIONS

WBV has demonstrated efficacy and feasibility in enhancing muscle strength among patients with CKD. However, further investigation is warranted to determine its potential for improving cardiorespiratory adaptations, mobility, balance function, and quality of life. Additionally, future research should prioritize comprehensive reporting of WBV protocols to establish an optimal training regimen for the CKD population.

COVID-19 reduces cardiorespiratory fitness even months after a mild to moderate acute phase: a retrospective cohort study

BACKGROUND

COVID-19 survivors may experience long-term health problems, including deterioration of cardiorespiratory fitness (CRF), as demonstrated by several cross-sectional studies that compared the results of cardiopulmonary exercise tests (CPET) performed only after COVID-19 with predicted values. This study aimed to analyze a change in CRF between repeated CPETs in response to suffered COVID-19.

METHODS

A total of 127 healthcare workers (HCWs; mean age 55.7 years) underwent two CPETs with a mean interval of 762 days. Forty HCWs suffered from COVID-19 (mild to moderate severity) in the interim (321 days before the second CPET), and 87 HCWs formed a control group. Mixed-effects regression with multiple adjustment and interaction terms was used for two response variables - maximum oxygen uptake (VO2 max) and power output.

RESULTS

Between both CPETs, mean VO2 max decreased statistically significantly in the COVID-19 subgroup (by 3.12 mL/kg/min, p = .034) and insignificantly in controls (by 0.56 mL/kg/min, p = .412). The proportion of HCWs achieving predicted VO2 max decreased from 75.9% to 59.5% (p = .161) in COVID-19 survivors, while it increased from 73.8% to 81% (p = .274) in controls. COVID-19 (β = -0.66, p = .014) and body mass index (β = -0.49, p < .001) were independent negative predictors of VO2 max change. COVID-19 was not associated with a change in power output.

CONCLUSIONS

On the basis of repeated CPETs, COVID-19 significantly, albeit rather modestly, reduces CRF almost one year after infection. The reduction persists even after the acute phase with mild or moderate severity.

Physical function in children/adolescents with chronic kidney disease and the impact of exercise intervention: a protocol for systematic review and meta-analysis

INTRODUCTION

Impaired physical function is relatively common in children/adolescents with chronic kidney disease (CKD), affecting not only patients' daily lives but also the efficiency of later treatment and rehabilitation. Exercise is a recognised intervention to improve physical function and quality of life in adult patients with CKD. However, implementing this strategy in paediatric/adolescent populations remains relatively limited. For exercise training to be widely delivered as part of paediatric public health policy, a better understanding of the physical function and the impact of exercise interventions in children/adolescents with CKD is needed.

METHODS AND ANALYSIS

A systematic review and meta-analysis will be conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to compare physical function in children/adolescents with CKD with healthy controls and the impact of exercise interventions on their outcomes. The systematic review will search the following databases: PubMed, Embase, Scopus and Web of Science. We will use the Risk Of Bias In Non-Randomised Studies-of Interventions and the second edition of the Cochrane Risk of Bias to assess the quality of the literature. Where feasible, we will conduct random effects meta-analyses where appropriate. If possible, we will conduct subgroup analyses to explore potential sources of heterogeneity.

ETHICS AND DISSEMINATION

Due to the nature of the protocol, ethical approval is not required. We will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to disseminate the study results through publication and conference presentations.

PROSPERO REGISTRATIONNUMBER

CRD42023416208.

Exercise and chronic kidney disease: potential mechanisms underlying the physiological benefits

Increasing evidence indicates that exercise has beneficial effects on chronic inflammation, cardiorespiratory function, muscle and bone strength and metabolic markers in adults with chronic kidney disease (CKD), kidney failure or kidney transplants. However, the mechanisms that underlie these benefits have received little attention, and the available clinical evidence is mainly from small, short-duration (<12 weeks) exercise intervention studies. The available data, mainly from patients with CKD or on dialysis, suggest that exercise-mediated shifts towards a less inflammatory immune cell profile, enhanced activity of the NRF2 pathway and reduced monocyte infiltration into adipose tissue may underlie improvements in inflammatory biomarkers. Exercise-mediated increases in nitric oxide release and bioavailability, reduced angiotensin II accumulation in the heart, left ventricular remodelling and reductions in myocardial fibrosis may contribute to improvements in left ventricular hypertrophy. Exercise stimulates an anabolic response in skeletal muscle in CKD, but increases in mitochondrial mass and satellite cell activation seem to be impaired in this population. Exercise-mediated activation of the canonical wnt pathway may lead to bone formation and improvements in the levels of the bone-derived hormones klotho and fibroblast growth factor 23 (FGF23). Longer duration studies with larger sample sizes are needed to confirm these mechanisms in CKD, kidney failure and kidney transplant populations and provide evidence for targeted exercise interventions.

Effect of kidney transplantation on indices of cardiorespiratory fitness assessed with cardiopulmonary exercise testing: a systematic review and meta-analysis

BACKGROUND

Patients with kidney failure often present with reduced cardiovascular reserve. Kidney transplantation (KT) is the optimal treatment for patients with end-stage kidney disease as it is associated with longer survival and improved quality of life compared to dialysis.

METHODS

This is a systematic review and meta-analysis of studies using cardiopulmonary-exercise-testing to examine the cardiorespiratory fitness of patients with kidney failure before and after KT. The primary outcome was difference in pre- and post-transplantation values of peak oxygen uptake (VO2peak). Literature search involved three databases (PubMed-Web of Science-Scopus), manual search, and grey literature.

RESULTS

From 379 records initially retrieved, six studies were included in final meta-analysis. A marginal, but not significant, improvement was observed in VO2peak after KT compared to pre-transplantation values (SMD: 0.32, 95%CI -0.02; 0.67). Oxygen consumption at anaerobic threshold was significantly improved after KT (WMD: 2.30 ml/kg/min, 95%CI 0.50; 4.09). Consistent results were shown between preemptive and after-dialysis-initiation transplantation and a trend for improvement in VO2peak was observed at least 3 months post-transplantation, but not earlier.

CONCLUSION

Several major indices of cardiorespiratory fitness tend to improve after KT. This finding may represent another modifiable factor contributing to better survival rates of kidney transplant recipients compared to patients undergoing dialysis.

Cardiorenal syndrome and the association with fitness: Data from a telerehabilitation randomized clinical trial

Aims

To investigate the associations of cardiorespiratory fitness with cardiac, vascular, renal and cardiorenal characteristics in chronic heart failure in a telerehabilitation randomized clinical trial. Secondly, to evaluate the associations of cardiorenal syndrome with the effects of exercise.

Methods and results

Sixty‐nine heart failure patients attended baseline examination, and 61 patients were randomly assigned 1:1 to 3‐month telerehabilitation or control. Data were collected at baseline and 3‐month post‐intervention, including echocardiography and vascular ultrasound, laboratory tests, exercise test with peak oxygen consumption (VO_2peak) measurement and 6‐min walk test (6MWT). Baseline VO_2peak and 6MWT distance was 0.85 mL*min⁻¹*kg⁻¹ lower and 20 m shorter per 10 mL/min/1.73m² lower estimated glomerular filtration rate (both P < 0.001). Heart failure patients with cardiorenal syndrome had 3.5 (1.1) mL*min⁻¹*kg⁻¹ lower VO_2peak and diastolic dysfunction grade 2–3, and elevated filling pressure was >50% more common compared with those without (all P < 0.05). At the 3‐month post‐intervention follow‐up, only the non‐CRS patients in the intervention group increased VO_2peak (0.73 (0.51) mL*min⁻¹*kg⁻¹), whereas VO_2peak in the CRS subpopulation of controls decreased (−1.34 (0.43) mL*min⁻¹*kg⁻¹). Cardiorenal syndrome was associated with a decrease in VO_2peak in CRS patients compared with non‐CRS patients, −0.91 (0.31) vs. 0.39 (0.35) mL*min⁻¹*kg⁻¹ respectively, P = 0.013.

Conclusions

Cardiorenal syndrome was negatively associated with VO_2peak and 6MWT distance in chronic HF, and the associations were stronger than for heart failure phenotypes and other characteristics. The effect of exercise was negatively associated with cardiorenal syndrome. Exercise seems to be as important in heart failure patients with cardiorenal syndrome, and future studies should include CRS patients to reveal the most beneficial type of exercise.