‘Oximeters’ are small medical devices used to measure levels of oxygen in someone’s blood. The oximeter can be clipped over someones finger and uses specific frequences of light beamed through the skin to measure the saturation of oxygen in the blood.
These small and relatively inexpensive devices have played an important role in the COVID-19 pandemic, as oxygen saturation levels are one of the main indicators of whether someone suffering from COVID is in immediate need of medical help or can ride out the illness at home. One of the dangers of COVID is that oxygen levels drop without the patient noticing, so called ‘silent hypoxia’, which can mean that by the time the patient notices and becomes breathless, there is very little time to get help. Oximeters can detect dropping oxygen levels sooner, and make sure people get help in time.
The problem, however, is that these devices are developed on white skin and do not work as accurately on darker skin. The light beam that goes through the skin to measure the oxygen saturation is reflected back more in darker skin, which might make the device show higher oxygen levels than are actually present in the blood. This means people with darker skin go to the hospital later than people with white skin, which could be part of the explanation for the higher deathrates among people with darker skin.
What is wrong with these oximeters is the same blind spot that explains automated soap dispensers not working for darker skin: technologies are developed by and only tested on white people. However, in the case of the pandemic this racist technology compounded with other factors of systemic racism to result in higher rates of illness, long term effects and deaths for people of colour (here for Amsterdam, here for the UK and here for the US).