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Background Chronic kidney disease (CKD) involves a progressive, irreversible loss of kidney function. While early-stage CKD patients may show changes in pulmonary function and lowered exercise tolerance, the role of the estimated glomerular filtration rate (eGFR) in these patterns remains unknown. The aim of this study was to investigated pulmonary function and exercise tolerance in pre-dialytic CKD patients. Methods A cross-sectional study was carried out with 38 adult volunteers divided into a control group (CG), consisting of 9 healthy adults, and 29 pre-dialytic CKD patients in stages 3 (G3), 4 (G4), and 5 (G5). All participants underwent spirometric and manovacuometric tests, a cardiopulmonary exercise test (CPET), a 6-minute walk test (6MWT), and laboratory tests. Results The significant differences was observed in maximal exercise tolerance, measured as peak oxygen consumption percentage (VO2peak) (mL/kg/min) (CG = 28.9 ± 7.8, G3 = 23.3 ± 5.6, G4 = 21.4 ± 5.2, G5 = 20.2 ± 6.9; p = 0.03), and submaximal exercise tolerance, measured by 6MWT (m) (CG = 627.6 ± 37.8, G3 = 577.4 ± 66.1, G4 = 542.7 ± 57.3, G5 = 531.5 ± 84.2, p = 0.01). The eGFR was associated with pulmonary function-forced expiratory volume in the first second percentage (FEV1) (%) (r = 0.34, p = 0.02) and maximum inspiratory pressure (PImax) (r = 0.41, p = 0.02) - and exercise tolerance - VO2peak (mL/kg/min) (r = 0.43, p = 0.01) and 6MWT distance (m) (r = 0.55, p < 0.01). Conclusion Pre-dialytic CKD patients showed lower maximal and submaximal exercise tolerances than healthy individuals.

Background Frailty is a state of physiological vulnerability common in the elderly. It is more predominant in patients with Chronic Kidney Disease in comparison to healthy subjects, which can also be diagnosed in non-elderly individuals and be associated with innumerous causes such as muscle strength, body composition and inflammation. The association between frailty and endothelial function, as well as the association between frailty and the combined outcome of mortality multiple cause and start of renal replace therapy were assessed. Methods In the initial analysis, sixty-one predialysis patients with Chronic Kidney Disease stages were evaluated and included in this study. Due to patient drop-out during follow-up, fifty-seven patients were subsequently re-evaluated 12 months later. The diagnosis of frailty was based on the Johansen et al. (J Am Soc Nephrol 18(11):2960-67, 2007) criteria. The groups were divided into Non-frail and Frail. Sociodemographic, inflammatory markers (IL-6, TNF-?, CRP-us), endothelial dysfunction (flow-mediated vasodilatation - FMD), body composition (DXA) and the 25-hidroxi-vitamin D parameters were analyzed. Results The average age of the patients used in the study was 64.9 ± 10.3 years old. The predominance of frailty was 42.6 %, of which 46 % were non-elderly. After some adjustments, frailty was associated with gender (OR = 11.32; IC 95 % = 2.30 to 55.67), advanced age (OR = 4.07; IC 95 % = 1.02 to 16.20), obesity (OR = 6.63; IC 95 % = 0.82 to 11.44) and endothelial dysfunction (OR = 3.86; IC 95 % = 1.00 to 14.88). The ratio of the incidence of frail subjects to the variable outcome was 2.5 (CI 95 %, 1.04 to 6.50). Conclusions Although an observational study does not allow one to determine the casual relation between frailty and endothelial dysfunction, we conclude that frailty was predominant in our sample of Brazilian patients with chronic kidney disease on predialysis, even in elderly individuals. This was linked to either worse endothelial function or mortality.