To use a pulse oximeter, apply the probe to the victim’s finger or any other measuring site, such as the earlobe or foot, according to the manufacturer’s recommendation. Let the machine register the oxygen saturation level and verify the victim’s pulse rate on the oximeter with the actual pulse of the victim. Monitor and record the victim’s saturation levels while administering emergency oxygen. If the oxygen level reaches 100 percent and local protocols allow, you may decrease the flow rate of oxygen and change to a lower-flowing delivery device.