Choosing a Medical Gas Flow Meter for Oxygen and Air

What is an oxygen flow meter?

An oxygen flow meter is a device that controls and indicates the flow of oxygen from a pipeline outlet or cylinder to a delivery accessory such as a nasal cannula, mask or humidifier. It does not reduce supply pressure; pipeline pressure is already regulated, and a cylinder needs a regulator in front of the flow meter.

The same principle applies to medical air, but a flow meter is calibrated for a specific gas and supply pressure. Using it with the wrong gas gives a wrong reading, which is why connectors and labels are gas-specific.

Medical gas flowmeter Thorpe tube design

The Thorpe tube is a variable-area flowmeter: gas lifts a small float inside a tapered transparent tube and the nurse reads the float position against a scale. It is simple, visible from a distance and easy to repair, but it must be held vertical, and the reading is affected by the pressure downstream if it is not back-pressure compensated.

Some Thorpe-tube units are used with a humidifier bottle, and the type of compensation should be checked when resistance in the circuit is high. Ask whether the scale is in L/min and what the manufacturer specifies for accuracy.

Bourdon and dial flow meters

A Bourdon-type flow meter uses a pressure gauge calibrated in flow units across a fixed orifice. It works in any position, which is useful during transport, but the reading depends on back-pressure and should not be used with a restricted outlet. A dial type has a selector with calibrated fixed orifices and click stops, so the nurse sets a value and hears or feels the setting, and it is compact and robust.

Each design has a place. Thorpe tubes give direct visual feedback, Bourdon units suit mobile use, and dial units suit busy wards where fixed settings are common.

• Thorpe tube: clear reading, must be vertical
• Bourdon type: any position, sensitive to back-pressure
• Dial type: fixed settings, compact and robust
• All types: calibrated for a specific gas

Medical air versus oxygen flow meter and ranges

Medical air versus oxygen flow meter: the two are not interchangeable. Each is calibrated to its gas, and the connectors are keyed so that an oxygen unit cannot be plugged into an air outlet. Colour codes differ between countries, so rely on gas name labels and the connector. A typical oxygen therapy range is in the order of 0 to 15 L/min, with other ranges available for higher-flow or low-flow uses.

Choose a range that makes the usual settings sit in the middle of the scale, where reading accuracy is best, and check if a humidifier connection is required.

What to ask a supplier in the UAE

Confirm the connector standard of your outlets, the gas, the flow range, the calibration reference, the orientation limits and cleaning instructions. A gas flow meter in the UAE should come with documentation and clear regulatory status, which you should verify with the relevant authority because requirements change. See also our guides on oxygen regulator vs flowmeter and how to use an oxygen flowmeter.

For matching accessories to your medical gas outlets, Beckfinity's specialists can help. Contact us with your outlet standard.