A pulse oximeter is a small, lightweight device used to monitor the amount of oxygen in the body. This tool attaches painlessly to your fingertip, sending two wavelengths of light through the finger to measure your pulse rate and how much oxygen is in your system.

Once the oximeter finishes its assessment, its screen will display the percent of oxygen in your blood coming from your heart—as well as your current pulse rate. This is very useful in diagnosing the patient.