Figure 2. An Example of the Steady-State Ventilatory Response to an Increase in P_ET co₂ from 44 to 50 mm Hg.

The response is linear (continuous red line) over the given trajectory; the extrapolated P_ET co₂ (red circles) at which ventilation is zero is given (in this example it is 41.3 mm Hg, open symbol). Resting ventilation and resting P_ET co₂ are also shown (blue circle).