How can a hospital measure how much oxygen it actually uses?

Open Critical Care says a hospital's oxygen use may be measured most accurately at the source, from logs of cylinders delivered, liquid oxygen deliveries or tank contents, or a PSA plant's output, for example with a mass flow meter, and from the demand side with bedside records of devices and flow settings.

Why can current consumption mislead?

When the data are used to forecast needs or plan for surges, Open Critical Care warns that current consumption may grossly underestimate optimal consumption, and Global Fund guidance says need should not be estimated by current demand.

What should a PSA plant operator record?

Global Fund guidance asks for daily production to be recorded, separating oxygen sent to the pipeline from oxygen used to refill cylinders.

How do you measure a hospital's actual oxygen use?

Supply side: what the sources deliver

Cylinders: logs of the number, pressure and size of cylinders delivered to the facility or to wards.
Liquid oxygen: logs of cryogenic cylinders filled and emptied, or the supplier's delivery logs; changes in the mass of the storage tank contents may also be available.
PSA plants: if the plant fills cylinders, a cylinder log may be most useful; some plants continuously display their hourly output flow, which can be logged; for a plant supplying the pipeline directly, a mass flow meter can display, save or send the data and detect flow problems.
Portable concentrators: hours of operation from the built-in hour meter, with a known or estimated flow.

Open Critical Care notes that measuring at the source may not always be feasible, depending on the equipment and staff available to log the data.

What the guidance asks plants to record

Global Fund sustainability guidance (2024) asks PSA operators to record daily production, separating oxygen sent directly to the pipeline from oxygen used to refill cylinders, and to compare production with consumption every year. WHO's Foundations of medical oxygen systems (2023) recommends periodically monitoring and registering oxygen consumption to detect critical changes in time. HTM 02-01, the NHS England guidance (2026), includes two oxygen flow monitors and a concentration and flow recorder in a PSA plant's monitoring system, and asks for a valved bypass around inline equipment such as flow measuring devices, so that they can be serviced or calibrated without shutting down the supply.

Demand side: patients and devices

Where supply data are missing, or for a single area or patient group, Open Critical Care describes demand-side methods: crude modelling with consumption tools, which gives imprecise results; recording each patient's delivery device and settings, sampled once a day or less as a snapshot; or comprehensive collection daily or more often, which needs considerable resources or comprehensive electronic records.

Common pitfalls

Leaks in the oxygen infrastructure, from flow meters left on, oxygen titrated to too high a saturation target, poorly fitted regulators, or cracked tubing and pipes.
Misjudged device consumption, such as CPAP or BiPAP leak and ventilator bias flow.
Low oxygen concentration: a poorly maintained or overloaded PSA plant may deliver less oxygen than expected, staff may raise the flow, and flow consumption may then overestimate true demand.
Relying on current consumption: when the data are used to forecast needs, plan for surges or expand capacity, Open Critical Care warns that current consumption may grossly underestimate optimal consumption, and Global Fund guidance says need should not be estimated by current demand.

ULTRAOX

According to the ULTRAOX 2022 datasheet, an oxygen flow control system installed on every ULTRACON concentrator measures the instantaneous oxygen flow to the network and shows total oxygen consumption on the digital screen.