Figure 1: Example of pressure and flow rate traces for 2-level constant pressure perfusion.

(Ai) pressure (y-axis; scale: 0.5 mmHg per square) vs. time (x-axis; scale 1 minute per square); (Aii) flow rate (y-axis; scale: 0.05 μL/min per square) vs. time (x-axis; scale 1 minute per square); (B,C) detail of pressure (i, y-axis; scale: 0.5 mmHg per square) and flow rate (ii, y-axis; scale: 0.1 μL/min per square) traces on a time scale (x-axis; scale 5 sec per square). Spikes in the flow trace reflect a momentary increase in flow rate as the pump speed increased to meet a new set-point pressure. Flow rate then automatically readjusted to a lower steady rate commensurate with the new set-point pressure.