I have a same weird symptoms. I get tired very quickly. I even had rhabdomyolysis after running for 10 minutes on that machine while feeling bad and while being hooked up on those EKG and oximeter wires a few years ago, and I have been in hospital for one month and i was released with unknown origin of rhabdomyolysis. Symptoms usually disappear when laying in hospital for a few days and normalize.
A few months ago I ended up in a hospital because of severe hypophosphatemia. Phosphate went back to normal after 2 days in hospital without any treatment. All results very normal, and their conclusion was that I am having chronic "Respiratory Alkalosis" caused by breathing too much air, as that causes drop in CO2 and loss of phosphate and as breathing level controls blood pH and as phosphate is main buffer for blood pH and it is also critical component of ATP (the only source of all energy for every cell---> glucose+phosphate is ATP, and glucose+oxygen+ATP is even more ATP, or you could say Adenosine + 5 molecules of Phosphate is ATP, or AMP+one molecule of phosphate equals to ADP, and ADP+1 phosphate is ATP...) and phosphatase is crucial for building DNA (as most of DNA is phosphate and some sugar, nitrogen, hydrogen and oxygen) (take a look at Wikipedia for nucleotides), that causes severe lack of energy for cells and dis-balance of pH which can cause cellular death and coma. They told me to breath in paper bag, that is to breath in air with concentrated CO2 and stop CO2 loss, as CO2 (bicarbonates) level is crucial to normalize everything.
I have same problems with my own oximeter showing me sometimes when I feel sleepy me O2 saturation of 80% and sometimes when I feel OK it constantly shows 99% and when I go to Emergency Room and they take arterial gases it shows O2 sat of 99,3%, high alkalosis, and severely low CO2 levels, and very low Phosphorous, and sometimes just a bit tiny lower potassium. I feel stupid too as doctors don't really help me at all. They tell me I breath too much oxygen and that I am "TOO HEALTHY" and that that much me psychological condition, even though I went to psychologist while in hospital and he told me that i am psychologically fine and healthy.
Which is weird I do not have panic attacks and I am very calm. I breath thru my nose and I breath slowly and which is weird when I feel bad I breath even more slowly as if someone is sitting on my chest. I started drinking a lot of regular coke as it is completely made of Phosphoric Acid and I take Vitamin D3 to increase absorption of phosphorus from coke. That helps a lot but I still get those symptoms a lot and it is in 95% of cases when I get sleepy in the evening or sometimes in the morning when I wake up. It is, it seems to me, that I get worse in periods when brain is shutting down and as brain consumes most of oxygen and energy. Also it gets worse half a day after running. Perhaps this is some condition smart people have as my IQ is over 140. They did bone density test in hospital and everything is more than fine....
But with every energy consuming act, this is awkward to say, even sex, and running increases severity of symptoms. I guess I deplete phosphorous. Also, when I eat too much sugar I get those symptoms as well, because more glucose in your blood more phosphate your cells need to use up that glucose to produce ATP. Even from taking amino-acid supplements I get worse, as it seems everything that speeds up energy usage and mythosis gets me feeling bad. i have been looking on Wikipedia and it seems that level of phosphate in the body is controlled by stem cells in our bones, as they secrete FGF-23 (fibroblast growth factor 23) but very little is known about it, as it is newly discovered thing, and it controls levels of Vitamin D, it controls how much phosphate intestines absorb, and it controls how much phosphate kidneys are eliminating.
I am truly, sorry for rude words, pissed of as this is destroying my life. I have been into sports for my whole life and now I get tired all the time, and all that with 32 years of age.
I did some research that respiratory alkalosis can be caused by asthma, but I am not sure how, and weird thing is I have had severe asthma up to when I was 9 yo, and then I guess hormones and puberty kicked in and i lost asthma.
If anyone has any suggestions or if some of us share some similar previous diseases like asthma or what ever, maybe we can eliminate some of causes because I don't thrust doctor at all anymore. i had to figure out myself that problem could be in low P, and I had to insist every time that they check for P levels as the usually check for all other electrolytes but now P levels... and I had to suggest to them that it could be respiratory alkalosis as I knew from before that i had often high blood pH while ending up in ER constantly.
I am afraid to breath in plastic bad when my oximeter shows low O2, but when they take arterial O2 it shows as too high. And I cannot stop breathing at all...and when I feel bad I breath too slow and shallow and with many pauses. So I am not sure if low P is caused by too high respiration rate.
Hope this helps someone, as I did massive amount of lab results and it is free... It is I guess good that medical care is free in my country, Croatia, as I would go bankrupt if I was in the US. But still if someone has any suggestion what to look for further, I am desperate to try.