John, there is a test to quantify breathing. The best I remember, you take a deep breath, and exhale while counting as fast as possible. I think I did 50.

While I was hospitalized for a MG Respiratory CRISES , the neurologist on a daily basis had me take a deep breath then count . Anything heading less than around 20- 15 is a concern . This was a way to know what my respiratory status is and to determine if I was improving.
Awesome quick tool I learned to use in the future , a Great way to know if you are in a MG respiratory impending crises trouble when you are not sure it is going sideways and need to make a decision to go to the ER immediately. .
In the ER even if your oxygen level is normal this is not a true indication of you NOT having a MG respiratory crises . A respiratory therapy specialist will test you with a NIFoMeter test . This is the appropriate evaluation of your RESPIRATORY MUSCLE STRENGTH and gives the ER the valuable information of your MG status , the need to be hospitalized for treatment & close observation and if you may be heading to the ICU and needing intubation.

Didn't finish. If you can't get to 20, it's time to go

A crisis is related to a severe breathing issue, pneumonia, heart rate, that sends you to the e.r.
If you're experiencing anything that inhibits your ability to breathe, walk, your heart, call 911 right away if you can or press "0" on your cell or shake your phone . If a person is nearby ask them to call 911 if you can. Always keep your medical info in a place easily accessible to anyone in emergencies.
I wear a medical alert bracelet
And it tells anyone to use my biometrics to open my phone and call my son.

I have had multiple crises. I couldn’t breathe, speak, or count to 10. I’ve been intubated many times. When I have trouble swallowing, speaking and feeling very short of breath, I go to the hospital.