How to clear up a common misunderstanding about the difference between gas pressure regulation and gas flow regulation?

Pressure is the measure of force (exerted by a liquid or gas) applied to a unit of “area”. The gas source (a cylinder or bulk delivery system) is at a high pressure. For example oxygen cylinders have usually service pressure of 200 bar (note they may be filled up to 300 psi). A pressure regulator reduces the high service pressure to a much lower delivery pressure. A standard medical oxygen delivery pressure is about 4 bar.

Flow is a measure of output in terms of volume per unit of time. In medical applications, oxygen flow is the dosage delivered to the patient and is expressed in liters per minute (l/m).
Thus, flow meters and regulators serve distinct purposes!