Figure 2.

Scatter plots of CPET variables predicted to be relatively body size-dependent (A, B) and body size-independent (C, D) versus peak $\stackrel{•}{\mathrm{V}}{\mathrm{O}}_2$. Females are shown as open circles, males as closed circles. The correlation and corresponding 95% CI are shown for each plot. The body size-dependent CPET variables, $\mathrm{\Delta }\stackrel{•}{\mathrm{V}}{\mathrm{O}}_2/\mathrm{\Delta }\mathrm{H}\mathrm{R}$ and ΔWR/ΔHR, were highly correlated with peak $\stackrel{•}{\mathrm{V}}{\mathrm{O}}_2$. Since these variables do not require achievement of a maximal or near maximal effort, they may be useful as surrogates for peak $\stackrel{•}{\mathrm{V}}{\mathrm{O}}_2$ (or $\stackrel{•}{\mathrm{V}}{\mathrm{O}}_2\text{max}$) for subjects who are unable to achieve an acceptable peak or maximal $\stackrel{•}{\mathrm{V}}{\mathrm{O}}_2$. In contrast, the body size-independent variables, $\mathrm{\Delta }\stackrel{•}{\mathrm{V}}{\mathrm{O}}_2/\mathrm{\Delta }\mathrm{W}\mathrm{R}$ and $\mathrm{\Delta }{\stackrel{•}{\mathrm{V}}}_{\mathrm{E}}/\mathrm{\Delta }\stackrel{•}{\mathrm{V}}\mathrm{C}{\mathrm{O}}_2$, were mildly correlated with peak $\stackrel{•}{\mathrm{V}}{\mathrm{O}}_2$. The value of these slopes is not as a surrogate for peak $\stackrel{•}{\mathrm{V}}\mathrm{O}2$, but rather a useful additional biomarker for abnormal respiratory or cardiovascular function that may only be detected with exercise.