Despite its importance in making major clinical decisions, several studies since its invention in 1974 have suggested a major drawback in how it measures oxygen levels in people of color. But the pandemic brought the problem to the forefront. The pulse oximeter showed inaccurate readings in people with dark skin tones.
Pulse oximeters have become a household device since COVID-19, as commonly available now as a thermometer. Used in routine medical practice, the pulse oximeter readings are considered “the fifth vital sign.” The device beams wavelengths of light onto the skin to provide immediate estimates of oxygen saturation levels in the blood, helping diagnose a range of common health conditions including respiratory and heart problems, non-invasively.
Though the topic demands research, it is believed that darker skin tones affect how a pulse oximeter absorbs light. The device shines two wavelengths of light into the finger. One wavelength gets absorbed by oxygenated blood, and the other by deoxygenated blood. But this light is also absorbed by melanin. The pulse oximeter was originally designed and calibrated using lighter skin tones. The melanin in people with darker skin causes the oximeter to overestimate how much oxygenated blood they have, underestimating the severity of the COVID-19 infection.
Kimani Toussaint, a physicist at Brown University, has now taken up this challenge to update the pulse oximeter design which has not changed for decades. Instead of calibrating the same infrared technology on a diverse population, Toussaint is focusing on using the polarization or electric field properties of light to come up with a new design independent of skin tones.
Besides COVID-19, an improved pulse oximeter can be useful for several diseases like pneumonia, asthma, COPD, emphysema, cystic fibrosis, heart failure, and others for which oxygen level monitoring is critical.
