MODEL RELEASED. Pulse oximeter and fast heart rate. Close-up of a pulse oximeter on the finger of a patient being assessed at a general practice (GP) clinic. A pulse oximeter, also known as a blood oxygen meter, measures the pulse rate and oxygen concentration of the blood. It measures the oxygen concentration by measuring the absorption of light as it passes through the fingertip. For most adults, a healthy resting heart rate is 60-100 beats per minute. Normal oxygen saturation is between 96 and 99 percent. Here, the heart rate of 128 beats per minute is high, a symptom of the patient's heart condition (atrial fibrillation), a type of irregular heartbeat (arrhythmia).