A Pulse Oximeter Showed a Calm Woman’s Heart Rate Swinging From 40 to Over 100, and White Nail Polish Was the Likely Culprit

The numbers on the fingertip monitor made no sense. Over a matter of seconds, the pulse oximeter clipped to an adult woman’s finger bounced among readings of roughly 40, 50, and more than 100 beats per minute. The woman felt fine, and her heart turned out to be beating normally.