Fig. 1
A. Comparison of the chemical controller characteristic for the Cheyne-Stokes and the current continuous model. The chemical controller characteristic in the Cheyne-Stokes model goes to zero ventilation at PCO2 values that vary with PO2 while in the continuous controller model the chemical controller has no zero ventilation thresholds.
B. The effect of alertness factors on ventilation. As alertness factors decrease, the ventilation threshold for the chemical controller characteristic is lowered so that the possibility for apneas increases and the controller characteristic becomes that of the Cheyne-Stokes model.