'Lack of oygen'

[Orbitolina]

Hiya all,

I'm new here, female, 42 and sporty.
Since 2014 I'm experiencing episodes of breathing difficulties. Not the typical asthma type though inhalers work. Each major episode started at night and lasted 6-2 weeks. I wake up with a feeling of being totally out of breath and the air lacks oxygen. It's difficult to exhale with the normal day-to-day breathing, but no problem with a bit more force. Still, it feels like the air lacks oxygen. My breathing always stops somewhere at exhaling and I actively have to breath again. This repeats 1-2 times for the coming nights and always gets better when I sit upright, and vanishes if I take an inhaler. Sometimes it also happens at daytime, but less extreme. Sometimes if I don't have an acute episode I try to run but have to walk every few minutes because my chest gets tight. I think I have very mild breathing problems then.

Heart rate not faster than normally during such moment, no hyperventilating, no feeling of panic, I can think clearly, no change in peak flow though apparently a lung test in a glass cabin during the first episode showed difference between before and after Ventolin.

Used my running HR sensor a few times during the current episode: just a minimal change in HR, if at all before I wake up with breathing problems (last night at 00:00, went to loo without breathing problems at around 1:30) - though I did catch a 30 minute tachycardia episode last night, through which I just slept without waking up (http://imgur.com/JRtUzB7). I do see those during running or walking every now and then, usually when I reached the top of an uphill slope and go downhill again. Not worried about those as they tend to be well below my maximum heart rate and vanish again either by themselves or by very slight carotid massage.

Any suggestion of what this might be? First episode occurred hours after a massive dust storm during which I worked out inside (poor windows though). Chest Xray seems to be ok in that respect, and no fluids observed either. Reflux might play a role and I'm taking omeprazole now; improvement of the current breathing problem might be coincidence though.