Deep Breathing to Stop a COVID Crash

Hello Everyone, my OT and PT therapists both witnessed one of my "covid crashes" today. The kind that make you breathless and dizzy and unable to do much of anything. So instead of the scheduled therapy, today we focused on recovery only.
They recommend that recovery take place when you are lying flat on your back. Take in a deep breath, then without exhaling, take in as much additional air as you can. So a double breath. You should feel the expansion in your ribs. This will flood your lungs with oxygen. Then let the air out as slowly as you can. Again when you think you are done exhaling, try to force more out. Do this until you are feeling more clear headed and less dizzy. I did it for about 10 minutes. Then sit up very very slowly. And do the same thing sitting up for several more minutes.
My crashes usually last 2-10 days. We are going to try to reduce the amount of recovery time by doing these breathing exercises laying down repeatedly through out the day. I am going to try lying down and doing double breathes for 10 minutes every hour.
I will let you know how it goes.

UPDATE: I used the deep breathing technique many times through out the day yesterday, sometimes lying down, sometimes sitting or walking. Whenever I thought of it, I did it for 2--4 minutes. By the end of the day I was feeling significantly better. Now today, I actually think I can do a few of the therapy exercises that I missed yesterday. Not going to go crazy, but am definitely better than I was this time yesterday