Determining Physical Function Measures for Estimating VO2Peak in Patients Receiving Hemodialysis

Rationale & Objective Cardiopulmonary exercise testing (CPET) is the gold standard for evaluating cardiovascular functional capacity, as assessed by oxygen uptake at peak exercise (VO 2 Peak). Traditional physical function tests have been proposed as predictive of VO 2 Peak, though their associations remain inconclusive in individuals with kidney failure. This study aimed to assess whether comprehensive physical function metrics are associated with VO 2 Peak in patients on hemodialysis. Study Design Cross-sectional analysis from the "Effects of Long Interdialytic Intervals on Cardiovascular Functional Capacity (ECON)" study. Setting & Participants Thirty patients with kidney failure on maintenance thrice-weekly hemodialysis. Predictors Physical function tests. Outcomes VO 2 Peak (mL·min –1 ·kg -1 ) measured by CPET, with participants dichotomized into Low (n=14) and High (n=16) VO 2 Peak groups. Analytical Approach Group comparisons for demographics and physical function measures were performed. Multivariable linear regression was used to assess associations. Results The Low and High groups were well matched by age, sex, and race ( all P's ≥ 0.05). However, body mass index (32.7±6.7 kg/m 2 vs. 26.9±6.5 kg/m 2 ; P = 0.02) and fat mass composition (41.8±7.3 % vs. 28.9±12.0 %; P = 0.002) were significantly higher in the Low group. The Short Form-36-Physical Function Scale total score, standing static balance test score, number of sit-to-stands in 30 seconds (30sec-STS), total short physical performance battery score, Patient-Reported Outcomes Measurement Information System (PROMIS) physical function computerized adaptive testing, PROMIS physical mobility computerized adaptive testing, handgrip strength, and 6-Minute-Walk-Test were all significantly associated with VO 2 Peak ( all P's < 0.05). However, after adjusting for age, sex, and fat mass composition, only 30sec-STS was significantly associated with VO 2 Peak ( P = 0.04). Limitations The study's small sample size and cross-sectional design limit statistical power and causal inference. Conclusions Metrics of basic physical function demonstrate limited association with VO 2 Peak in patients on hemodialysis, except for the 30sec-STS test.