Visit any health-care facility, and one of the first things they'll do is clip a pulse oximeter to your finger. These devices, which track heart rate and blood oxygen, offer vital information about a person's health. For people with dark skin, pulse oximeters can overestimate just how much oxygen their blood is carrying. That means that a person with dangerously low oxygen levels might seem, according to the pulse oximeter, fine. The US Food and Drug Administration is still trying to figure out what to do about this problem. Last week, an FDA advisory committee met to mull over better ways to evaluate the performance of these devices in people with a variety of skin tones.