Pulse oximeters are considered a non-invasive method for determining the percentage of hemoglobin and its oxygen saturation level in the body. Generally a prob is attached to the ear lobe or the finger of a patient and information is fed to a computer or or unit which may display the strength of blood flow at the probe area. The machine may be equipped with an alarm that can be programmed to alert the patient or doctor if certain circumstances are met. Occasionally a pulse oximeter will provide a graphic display for medical professionals to read.