Delivery of oxygen by standard oxygen flowmeters.

The last year has seen hospitals worldwide face multiple challenges in the face of the COVID‐19 pandemic. This has included oxygen shortages, both locally [1] and nationally [2]. Guidance was offered by the Medicines and Healthcare products Regulatory Agency to manage this high oxygen demand [3]. We tested several standard oxygen flowmeters connected to our hospital’s 400 kPa pipeline oxygen supply at 5, 10 and 15 l.min‐1 and maximum flow rate using an electronic flowmeter (Certifier FA Plus 4080, TSI Incorporated, MN, USA) using a 1 m length of standard green bubble oxygen tubing. We found that the tested flow was within 5% of the indicated value, which is within reasonable limits given the difficulty in perfectly aligning the float. When the flowmeters were fully opened, however, and the float moved beyond the calibrated markers, the maximum flow rates measured were between 65 and 75 l.min‐1 (Table 1). It has been previously reported that standard oxygen flowmeters can deliver up to 40 l.min‐1 [4], but our measurements suggest this could be a large underestimate.

Table 1

Indicated and measured flow rates with oxygen flowmeters.

Indicated rate	Measured rate l.min‐1
	Therapy equipment Ltd 9505 a	Oxylitre F1601 b	Penlon O2 Flowmeter c	Medishield O2 Flowmeter d
5 l.min‐1	5.06	5.12	5.08	5.13
10 l.min‐1	10.32	10.26	10.11	10.47
15 l.min‐1	15.69	15.38	15.63	15.51
Fully open	75.53	66.98	65.62	71.86

Therapy Equipment Ltd, Potters Bar, UK.

OxyLitre Ltd, Manchester, UK.

Penlon Limited, Abingdon, UK.

Medishield, Guildford, UK.

F1601

A point prevalence survey of our emergency department resuscitation room and operating theatres' recovery areas demonstrated that, during one day, 17 out of 21 patients who were wearing an oxygen mask with a reservoir bag or a Mapleson C circuit were receiving oxygen at a flow in excess of 15 l.min‐1. This could potentially represent a 400% excess use of oxygen in patients who are prescribed 15 l.min‐1.

Assuming only two patients in a hospital are receiving this excess flow of oxygen at a given time, this could waste up to 7200 l.h‐1 or 172,800 l.day‐1 (representing approximately 10% of our total oxygen use). Extrapolated across a year, this would represent 63 million litres in one hospital, or 12.6 billion litres across the 200 acute hospitals in the UK National Health Service (NHS). This carries significant environmental and financial impact [5]. Furthermore, there may also be direct implications for patient safety. Unknowingly administering oxygen well in excess of 15 l.min‐1, especially with a semi‐closed breathing system, may mask the true severity of a patient’s condition and delay their progression to a more appropriate mode of respiratory support.

There needs to be awareness among healthcare workers that it is important to administer oxygen as prescribed, and that if higher flows of oxygen are used intentionally, a high‐flow rotameter should be used in order that oxygen use can be measured accurately, rather than simply turning a standard flowmeter up beyond the calibrated graduations.

An example of the measured flow rate when a flowmeter is fully opened.