Quantifying altered oxygen kinetics and reducing metabolic test times for children with cerebral palsy: a dual-exponential Bayesian modeling approach

Prior research using indirect calorimetry has shown that children with cerebral palsy (CP) exhibit significantly increased energetic costs during walking. However, metabolic testing to obtain oxygen cost is challenging. As a result, differences in oxygen uptake kinetics (V^_ o₂) in CP compared with their typically developing peers remain unexplored. Step changes in work rate have been shown to result in an exponential V^_ o₂ response with three distinct phases 1) cardiodynamic, 2) primary, and 3) steady-state. Here, we applied a dual-exponential Bayesian model to assess the time constant of the primary phase V^_ o₂ response from resting to walking in children with CP. In addition, we evaluated the model’s ability to estimate steady-state V^_ o₂ using shorter test durations. From a sample of 263 children with CP, the median V^_ o₂ time constant was 33.1 s (5th–95th percentile range: 14.5–69.8 s), significantly longer than reported values for typically developing children (range of means: 10.2–31.6 s). Furthermore, the model accurately estimated steady-state V^_ o₂ using only the first 3 min of metabolic data compared with the typical 6 min used in current clinical practice. The 3-min estimate explained >95% of the 6-min estimate variance, with <5% mean absolute error. Slower oxygen kinetics in children with CP suggest impairments in metabolic control, potentially contributing to their higher energy demands. Although the exact mechanisms remain unclear, this study provides valuable insights into the walking energetics of children with CP and presents a more efficient method for analyzing V^_ o₂ for this population.