Pulse Oximeter and Shortness of breath

I think that I may be suffering from "pseudo dyspnea" or the false sensation of being out of breath caused by GERD. It has been very frequent to almost constant. Anyways with the shortness of breath eventually if it gets bad enough my heart rate would jump to 160 b.p.m.

I have been suffering for years on and off but never as severe as it is now. Sometimes I have 4 panic attacks in a day.

Whenever I go to the ER they never find anything wrong. My oxygen levels are always 98 to 100 despite feeling horrible and being barely able to stay composed for hours on end. The people at the ER always pointed to the reading and told me that I am fine (it's just anxiety.) Here is the thing I am curious about though. I bought myself a pulse oximeter to ensure myself it's "just" a panic attack. During an attack I would get it out and be reassured that I was not suffocating. What I noticed though is that I can't get a bad reading if I tried. I hold my breath and walk as long as possible. I get lightheaded and feel like I am going to faint but that thing always stays at 98 to 100. Obviously this is not one of my better ideas to try out but I was just wondering if the reading has any value at all? Has anybody ever messed with one? I watched a youtube video and the guy got his to drop into the 80's after holding his breath for only 45 seconds. Perhaps youtube guy had COPD or something? Perhaps my meter is not functioning correctly?

Does anybody know how much oxygen level will drop on a healthy person if they hold their breath? If it is normal that you feel out of breath before oxygen drops off due to CO2 buildup in the lungs then I don't need to look at it anymore. However if my oximeter is malfunctioning I want an accurate way to tell if I am oxygen deprived.

Turns out that my oximeter was bad, I bought a new one. I can now hold my breath for one minute and 20 seconds and see my oxygen levels drop to 90%. Funny thing is that when I got shortness of breath today I was at 99% and felt worse than when holding my breath. I don’t know if it is silent reflux or anxiety causing it…..perhaps both. What came first? The chicken or the egg? I went for a small drive around the neighborhood to push myself because I have agoraphobia. During the drive I started to burp then later if felt like I could not catch my breath. Got dizzy and looked at my meter and it was at 99% oxygen. I must have been over breathing because I have not been able to purposely get the new meter that high although I thought I was controlling my breathing well. Then again at times when I can’t catch my breath I have no anxiety at all because it has happened so many times. It’s so odd, I just want to be better and move on with my life.