My father was diagnosed with covid on 29 april. He had fever for first few days and later he had cough which led to his oxygen to drop below 85. He is in hospital right now on oxygen but shows no covid symptoms. He does not have any previous medical problem. He eats right, does���t drink or smoke. He has been on oxygen since last 10 days. His oxygen has not been improving since. He gets around 90-94 oxygen when he is on oxygen mask but when he removes his oxygen mask it drops to 86-89. What should he do to improve this? Doctors tell us to wait for few more days as it takes time to oxygen level to rise but its already been 16 days. I���m really worried now. Please help us. Thank you.