Update on my being in A&E:
They discharged me early this morning from A&E, I was kept in there overnight (partially) but not formally admitted. That's because after 5 hours plus on oxygen, with them lowering the amount, my oxygen saturation levels stabilised. I had to do a lap around A&E with a doctor and my pulse reader, to check that exercise didn't cause my levels to dip.
They didn't do an other wrist artery test in the end because of my oxygen levels improving - thanks PPs who gave advice on that.
They wrote a letter to my GP which I took home asking them to check on me in a week, and they told me to come straight back to A&E if I worsen.
I do feel better (than yesterday) today. The nurse said that sometimes people just need a kickstart with some oxygen to get their breathing going properly again. I don't have asthma or any or breathing problems previously.
What concerns me though is that any exertion, even walking to the next room, makes me feel exhausted and a bit breathless. Also as it turns into evening now, I can feel my feelings of chest constriction coming on.
@Egghead68 I saw you posted that you had slightly elevated troponin levels suggesting possible heart damage? Me too. Only one number above what's normal but it's been noted. My ECG was fine though.