A Method for Normalization of Oxygen Cost and Consumption in Normal Children While Walking

Measurement of oxygen use is helpful in determining energy consumption in children with walking abnormalities; however, no statistically valid measurements of nondisabled children have been established using a telemetric system. Data from 94 nondisabled children, ages 5-15 years, were collected using the Cosmed K2 oxygen analysis system. Oxygen cost, measured in milliliters O2/kg/m walked, and oxygen consumption, measured in milliliters O2/kg/min, were correlated to inverse body surface area (IBSA) measured in meters. Linear relationships between oxygen cost and IBSA and between oxygen consumption and IBSA were best described by the following equationsoxygen cost = 0.256 (IBSA) + 0.052 (r = 0.806) and oxygen consumption = 17.635 (IBSA) + 4.956 (r = 0.758). From these data, equations were derived to calculate predicted oxygen cost and predicted oxygen consumption for each child. Indices were developed to express the difference between a measurement and the predicted mean in reference to the normal variation. These equations and indices can help quantify the variation of energy use of children with walking abnormalities when compared with their nondisabled peers. Additionally, the indices enable multiple tests from one subject to be compared, regardless of a change in age, height, and weight between measurements.