Talk to General Physician on Coronavirus

My brother has covid. He is 22. His saturation keeps dropping to 79 and then goes back up till 100. It gets stable for a few secs and then again the same pattern specially at night. All through the day it remains between 97-99. Pulse rate either remains low (55 above) or normal mostly. It's his 7th day. Initial symptoms were extreme body pain, cough, vomit, headache, sore throat and fever. Current complain is extreme body pain that is not even subsiding after taking pain killers. And he has difficulty swallowing. What is the reason of such a major fluctuation in saturation? What can I give instantly to relief his body pain? Should we switch therapy to IV?