Fig. (10) The nonlinear PDM model response for subject #1 to step changes of MABP for fixed level of ETCO2 under hypercapnic conditions of +1 mmHg (left) and hypocapnic conditions of -1 mmHg (right) relative to baseline. An initial step increase of MABP to +2 mmHg for 20 sec is followed after by a return to the MABP baseline for 20 sec and a subsequent step decrease to -2 mmHg (note that the settling time of this system is <20 sec). As expected physiologically, the model autoregulates the MCBFV with respect to pressure changes (return to baseline after an initial transient) and the steady-state value of MCBFV is higher for hypercapnic conditions due to CO2 vasoreactivity.