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

Pressure is the measure of force applied on an area in pounds per square inch (psi). The gas source (a cylinder or bulk delivery system) is at a high pressure. For example, E size cylinders have service pressure of 1900 – 2,000 psi (note they may be filled up to 2,200 psi). A pressure regulator reduces the high service pressure to a much lower delivery pressure. In the US, 50 psi is a standard medical oxygen delivery pressure.

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!