Fig. 4. Results of the sensitivity analysis for the model parameters of the empirical carbon dioxide model of the ventilatory controller in one subject. The data are control data obtained using a multifrequency binary sequence input function (continuous lines). For comparative reasons, we added the sensitivity analysis on GPand GCobtained from a single step input function of the same subject (subject 936; broken lines). The x-axis gives the optimal parameter value (100%) ± 100%; the y-axis gives the increase in residual sum of squares (Δresidual SSQ) from the optimal value (residual SSQ set at 0).