Pulse oximetry is a test used to measure the oxygen level (oxygen saturation) of the blood. 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. For people with COPD, asthma, Congestive Heart Failure (CHF) and other conditions, pulse oximetry is a technology used to measure the oxygen level in your blood and your heart rate. A finger pulse oximeter is equipped with technology to rapidly detect changes in your blood oxygen level.