Data from the Office for National Statistics show that Black people were four times more likely to die from COVID-19 than their White counterparts [1]. These might have been explained away as a consequence of socio-economic disparities, but once these differences are accounted for Black people are still twice as likely to die from COVID-19 infection [1].

In November 2021, the then-Health Secretary, Sajid Javid ordered a review of medical devices in relation to any racial bias, saying "It's unintentional but it exists… and the reason is that a lot of these medical devices, even some of the drugs, some of the procedures, some of the textbooks, most of them are put together in majority-white countries and I think this is a systemic issue around this." The results of this, ‘The Whitehead review’ are still awaited.

The pulse oximeter is an essential device used across healthcare from assessment in primary care to hospital wards. It is also a vital monitor in anaesthetic rooms, operating theatres and intensive care. Medical students and anaesthetists are usually taught that poor peripheral perfusion, cold peripheries, fingernail polish, dyshaemoglobinaemias, intravenous dyes and misplacement may be the cause for inaccuracies in pulse oximeter traces and readings. Skin colour is rarely raised as an issue.

The evidence however seems clear; occult or ‘hidden’ hypoxaemia, defined as SaO2 < 88% with SpO2 ≥ 92% recorded at the same time, is significantly increased in non-White skin. First identified as an issue in 1990, Jubran and Tobin found that “A pulse oximeter target of 92% ensured a safe arterial oxygen tension (PaO2) greater than 8 kPa in 91.7% of White patients, but in only 50% of our Black patients” [2]. The literature has exploded since the pandemic. Black patients have consistently been found to have significantly higher rates of occult hypoxaemia compared to White counterparts [3] and the risk of occult hypoxemia is most significant in Black patients with SpO2 93-96% [4]. A retrospective review of the Extracorporeal Life Support Organization registry demonstrated that in patients about to be initiated onto ECMO, the prevalence of occult hypoxaemia was higher in Black patients (21.5%) compared with White (10.2%) [5]. Similarly, the rates of intra-operative occult hypoxaemia are significantly increased in patients self-reporting as Black (2.1%) or Hispanic (1.8%) compared with patients selfreporting as White (1.1%) [6].

This is a not-inconsequential measurement error. Patients with occult hypoxaemia have higher rates of organ dysfunction 24-hrs later and higher in-hospital mortality [4]. This measurement bias has been associated with a delay in recognising patients’ eligibility for COVID-19 treatment, with minority racial and ethnic groups being most affected [7].

Part of the problem appears to be the calibration and validation of pulse oximeters. Since 2013, the US FDA has required the study population to include at least 15% people with diverse skin pigmentation, or two individuals with darkly pigmented skin. This sampling does not reflect the US 2010 population census that recorded Asian (5.9%), Black (13.4%), Hispanic (18.5%) and White (60.1%). If an FDA-approved pulse oximeter reads 90%, the true oxygen saturation could be anywhere between 86-94% [8].

Pulse oximetry however, is not the only variable under scrutiny. The NHS Race and Health Observatory (RHO), an independent body founded in April 2021 that examines ethnic health inequalities with the aim of eradication, reported a 4-times higher maternal death rate in Black women and a 40% higher death rate from coronary heart disease in South Asian Britons. The list goes on; we can no longer afford to duck this issue.

Structural racism results in poorer health outcomes. The intersection of the pandemic and social justice movements has created a new and impassioned endeavour for the abolishment of ethnic health inequalities. We need to recognise the systemic and historical foundations upon which modern medicine, research and medical education are built and the wider inequalities to which these lead. Without this we cannot embark upon positive change for all. We cannot be to blame for the system that we have inherited, but it is our responsibility to reflect upon our privileges, be more anti-racist and demand change. What else in clinical practice are we unconscious of? How can we reduce the known inequalities that exist? Organisations such as the NHS RHO are vital in driving positive change, and the findings of the Whitehead review into medical devices and pulse oximetry are eagerly awaited.

Ben Hylton
ST6 Intensive Care Medicine
Severn Deanery