Pulmonary function and exercise tolerance are related to disease severity in pre-dialytic patients with chronic kidney disease: a cross-sectional study

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 (VO(2)peak) (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 - VO(2)peak (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.