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.

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.

去年，面对 COVID-19 大流行，全世界的医院都面临着多重挑战。这包括本地 [ 1 ] 和全国 [ 2 ] 的氧气短缺。药品和保健产品监管机构提供了管理这种高需氧量的指导 [ 3 ]。我们以 5、10 和 15 l.min ^{-1测试了几台连接到我们医院 400 kPa 管道氧气供应的标准氧气流量计}使用 1 m 长标准绿色气泡氧气管的电子流量计（Certifier FA Plus 4080，TSI Incorporated，MN，USA）和最大流速。我们发现测试的流量在指示值的 5% 以内，考虑到完美对齐浮子的难度，这在合理的范围内。然而，当流量计完全打开并且浮子移动到校准标记之外时，测得的最大流量在 65 到 75 l.min ^-1之间（表 1）。之前有报道称标准氧气流量计可以提供高达 40 l.min ^-1 [ 4 ]，但我们的测量结果表明这可能是一个很大的低估。

对我们急诊科复苏室和手术室恢复区进行的点流行率调查表明，在一天内，21 名戴着带储气袋或 Mapleson C 回路的氧气面罩的患者中有 17 名在接受氧气流动。超过 15 l.min ^-1。这可能代表在规定 15 l.min ^-1的患者中过量使用氧气 400% 。

假设医院中只有两名患者在给定时间接受这种过量的氧气流量，这可能会浪费多达 7200 lh ^-1或 172,800 l.day ^-1（约占我们总氧气使用量的 10%）。在一年内推断，这将代表一家医院的 6300 万升，或英国国家卫生服务 (NHS) 的 200 家急症医院的 126 亿升。这会带来重大的环境和财务影响 [ 5 ]。此外，还可能对患者安全产生直接影响。在不知不觉中给予氧气超过 15 l.min ^-1，尤其是半封闭式呼吸系统，可能会掩盖患者病情的真实严重程度，并延迟他们向更合适的呼吸支持模式发展。

医护人员需要意识到按规定给予氧气很重要，如果有意使用更高流量的氧气，则应使用高流量转子流量计，以便准确测量氧气使用量，而不是简单地测量将标准流量计调高到校准刻度之外。