Hi, after getting lots of help, advice and reassurance as a newbie, I can report that I saw my respiratory nurse and my oxygen levels are good. I was able to walk unaided up and down the corridor several times before getting breathless. Most of my problems seem to be anxiety and constantly worrying about work. Kathryn put mind at rest and I feel a lot more positive about the future.
While I am here, I read that someone regulates their breathing using a McDonald's drinking straw. I now have the straws but can't find the "instructions". If the author reads this, I would be grateful.
Once again, my thanks to everyone who helped me that first night.