For an ideal incompressible inviscid fluid, the Bernoulli equation tells us that the pressure drop in a tube of constant diameter is zero, irrespective of the fluid velocity. Changing the absolute level of the pressure has no effect on this.
For a real (viscous) fluid, the pressure at the inlet to the tube must be higher than the pressure at the outlet, in order to overcome viscous friction. There is a direct relationship between the volumetric throughput rate of the fluid (and the fluid velocity) and the pressure drop along the tube. The higher the pressure drop, the higher the volumetric flow rate. If the fluid is essentially incompressible, changing the absolute levels of the pressures at the inlet and outlet by the same amount has no effect. The pressure drop-flow rate behavior of real viscous fluids can be predicted using the Darcy-Weisbach correlation.