Pulse oximeters are medical devices that indirectly measure the oxygen saturation of a patients blood and changes in the blood volume in the skin. Pulse oximeters are useful in any situation where a patients oxygenation could be unstable. Pulse oximeters are especially important in emergency medicine and are also very useful for patients with respiratory or cardiac problems or for diagnosis of some sleep disorders such as apnea. Finger pulse oximeters are used for their simplicity and speed. Finger pulse oximeters are widely used medical devices in all health care facilities as well as diagnostics for monitoring certain illnesses such as COPD, cardiac issues, respiratory issues, asthma and more. Portable pulse oximeters are of good use anytime supplemental oxygen may be in need. Portable pulse oximeters may be used by athletes whose oxygen levels may decrease with altitude or exercise.