Pulse Ox is a feature available on Garmin watches that measures the peripheral saturation of oxygen in your blood (SpO2) . It is a proxy for what sports scientists call SpO2, which is the oxygen saturation within the blood; the percentage of haemoglobin carrying oxygen. The feature is designed to read SpO2 levels while you sleep, generating readings up to every minute. When you view the pulse oximeter widget while you are not moving, your watch analyzes your oxygen saturation and your elevation. The elevation profile helps indicate how your pulse oximeter readings are changing, relative to your elevation. Knowing your oxygen saturation can help you determine how your body is acclimating to high altitudes for alpine sport and expedition. The feature can also be useful for hikers, aviators, and people who engage in high-altitude sports. The pulse oximeter reading appears as an oxygen saturation percentage and color on the graph. On your Garmin Connect account, you can view additional details about your pulse oximeter readings, including trends over multiple days. However, it is important to note that not all pulse oximeters work the same way, and it’s hard for most medical civilians to judge whether its findings are significant or accurate.