OXYGEN LEVELS, are very important because of, MY ASTHMA, and the reason I purchased tracker. However, THE READINGS have gone from great to non believable. My nighttime oxygen is hardly ever 89% but now its always 98% and sleep record says I'm up when I'm a sleep. Therefore, after less than one year I will be looking for a new tracker and not from Huawei. Thought, they were a good brand for reasonable price. But, now their customer service is as terrible as their products.