I was told that, ideally, you'd like to keep your 02 sats above 90. When my sats drop below 90, I can't think clearly, have absolutelyno tolerance for exercise and my back gets sore ( muscles between shoulder blades particularly). Do you have an 02 sat monitor at home to keep track of his sats? Sats lower than 85 is pretty serious from what I understand, and if maintained at that level, could lead to a host of other problems including pulmonary hypertension and eventually heart failure. I'm not a doctor, I'm just repeating what my doctor told me. Make sure your son's doctor answers your questions to your satifaction- he works for you. Any misunderstandings will only lead to unnecessary anguish.Good luck....