Playing by Ear: the 47021A

Introduced by the Medical Products Group in late 1974, the new 47201A pulse oximeter could measure oxygen saturation in a patient’s blood continuously and non-intrusively. Instead of requiring that the blood be drawn from the body, the device could simply be clipped to a patient’s ear and would measure the passage of light through the ear to determine oxygen levels. For years, the 47021A was the criterion for oximetry and even tested the accuracy of the first pulse oximeters in clinical studies.