Pulse oximetry in people with more pigmentation

Measurement error in pulse oximetry

Studies show that conventional pulse oximeters are prone to mismeasurements in people with more pigmented skin. In pulse oximetry, a sensor emits light to measure the pulse and oxygen saturation in the blood. The problem with this method is that the light can be “blocked” by stronger pigmentation in the skin. More specifically, the substance melatonin is responsible for this. The amount of melatonin is a determining factor in how much light is blocked.

What is the solution?

The solution is probably more banal than some might think. Even with strong skin pigmentation, the palms of the palms are usually very low pigmented. The same applies to the soles of the feet. It can therefore be assumed that at these parts of the body the amount of melatonin is also lower and that the light can radiate freely into the skin during a pulse oximetry.


The CIRCUL ring is a health tracker that measures oxygen saturation and pulse at a sampling rate of 100 Hz. The sensors are located on the underside of the hand or the finger, not on the underside of the hand or the finger, as with conventional pulse oximeters. As a result, the rate of incorrect measurements in people with stronger pigmentation should be much lower.

The first investigations and results

Initial investigations have already been carried out with the CIRCUL ring. These are available for free download here.