Fig. 16.

Phase plots showing the relative speed of each variable during closed-loop bursting identify $P{a}_O{}_{{}_2}$ as a slow variable. x-Axis is x and vertical y-axis is the rate of change x′(t) normalized by the range of x, where x = n, V, α, h, vol_L, $P{A}_{O_2}$, $P{a}_O{}_{{}_2}$. Green dots indicate the maximal speed v_x of each variable (−v_x is shown for x = h). Note the significantly different timescales involved: $P{a}_O{}_{{}_2}$, $P{A}_{O_2}$, and vol_L are slower than h and α, which themselves are slower than V and n.