Pulse oximeters are devices that measure pulse rate and blood oxygen (SpO2) level. It is an easy, painless measure of how well oxygen is being sent to parts of your body furthest from your heart, such as the arms and legs. Pulse oximetry is also used to check the health of a person with any condition that affects blood oxygen levels, such as: heart attack, asthma, anemia, lung cancer, pneumonia and others.