It might have, at one time; doctors in the ER would check the level of oxygen in a patient’s blood by pressing on their nails. If a purple hue appears in the nail bed, it means the person has low oxygen (or hypoxia), says Dr. Andrew Affleck, an ER doctor at Thunder Bay Regional Health Sciences Centre in Thunder Bay, Ont., and co-chair of public affairs and health policy leadership for the Canadian Association of Emergency Physicians. An oxygen measure helps evaluate whether a patient needs supplemental oxygen’crucial knowledge, since getting too little oxygen could kill you. If you’re wearing nail polish, it’s not possible to check this by looking at the nail bed.
But these days, ER doctors measure oxygen with a pulse oximeter. The machine’s clip-on device attaches to your fingertip or earlobe. With the device, nail polish shouldn’t pose a problem. Several studies done on the topic have concluded that most polish colours have little to no effect on the reading.
More research is needed to determine what effect, if any, acrylic and gel nails could have. But Affleck clarifies an important fact: ‘A pulse oximeter isn’t going to give a false high. If anything, it’ll read low and we’d give you oxygen. We’d err on the side of caution.’