Manual flow regulator

This figure illustrates the level of fluid in the bag when it is almost empty. The flow (Q) is determined by the pressure gradient (ΔP) divided by the resistance of the roller clamp (R) as illustrated. The pressure gradient is the difference between the fluid level in the bag and the venous pressure at the level of the heart (Pv). Increasing the fluid flow during the procedure can be accomplished by increasing the pressure gradient by hanging a full bag of IV fluid, raising the height of the IV pole, or by decreasing the resistance of the roller clamp.