Determining Physical Function Measures for Estimating VO₂Peak in Patients Receiving Hemodialysis

Cardiopulmonary exercise testing is the gold standard for evaluating cardiovascular functional capacity, as assessed by oxygen uptake at peak exercise (VO₂Peak). Traditional physical function tests have been proposed as predictive of VO₂Peak, although their associations remain inconclusive in individuals with kidney failure. This study aimed to assess whether comprehensive physical function metrics are associated with VO₂Peak in patients receiving hemodialysis.

Cross-sectional analysis from the "Effects of Long Interdialytic Intervals on Cardiovascular Functional Capacity (ECON)" study.

Thirty patients with kidney failure receiving maintenance thrice-weekly hemodialysis.

Physical function tests.

VO₂Peak (mL·min^-1·kg^-1) measured by cardiopulmonary exercise testing, with participants dichotomized into Low (n=14) and High (n=16) VO₂Peak groups.

Group comparisons for demographics and physical function measures were performed. Multivariable linear regression was used to assess associations.

The Low and High groups were well matched by age, sex, and race (all P ≥ 0.05). However, body mass index (32.7 ± 6.7 kg/m² vs 26.9 ± 6.5 kg/m²; 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 physical function computerized adaptive testing, Patient-Reported Outcomes Measurement Information System physical mobility computerized adaptive testing, handgrip strength, and 6-minute walk test were all significantly associated with VO₂Peak (all P < 0.05). However, after adjusting for age, sex, and fat mass composition, only 30sec-STS was significantly associated with VO₂Peak (P = 0.04).

The study's small sample size and cross-sectional design limit statistical power and causal inference.

Metrics of basic physical function demonstrate limited association with VO₂Peak in patients on hemodialysis, except for the 30sec-STS test.