flowmeter

Flowmeter is a device that measures the flow rate of liquid or gas in a
closed tube. It is used to control rate of flow of gas and adjust the
proportion of gas delivered. The flow rate of gas through a tube will
depend on the pattern of flow, whether laminar or turbulent.
Flowmeters used in anesthesia machines help deliver anesthetic gases to
the patient. Flowmeters form the low pressure component of the
anesthesia machines and are known as rotameters as the “float” rotates
with the flow of gases. Rotameter is a variable orifice, constant pressure
flowmeter.
“Flow” is defined as the quantity of gas (or fluid) passing a point in unit
time. The units of flow are in mL/minute, L/minute, mL/ hour or L/hour.
In anesthesia, we talk of flow of gases in mL/ minute or L/minute.
Depending on the velocity of the flow, flow can be laminar (at lower
velocity) or turbulent (at higher velocity).