how low can my o2 go at night

I'm a 30 yr old male 5'10" 250 lbs.  I experience psychological-type symptoms of chronic derealization, lightheadedness, sleepiness and the like.   I did an experiment with a friend's help, I slept with a pulse oximeter on and they checked it every few minutes...it was constantly low...91, 92, 93...but also in the mid and low 80's....i didn't stop breathing like sleep apnea, again it's just constantly low.    During the day it runs 94-98,  I see 93 sometimes but virtually never below that.   I live at 500 ft above sea level.     1 other symptom is that sometimes I wake up unable to breath with a racing pulse,   I was wearing a heart monitor and it showed sinus tachycardia of over 160.      Also, I've had normal blood tests all the way with 1 exception, my hemoglobin is persistantly on the high-normal end...usually 16.5 or so.    Chest xray, echocardiogram normal..  
I will eventually have a sleep study,  but the wait at the charity clinic is sooooo long,  in the meantime, can you tell me what MAY cause this, and is there anything I can do to improve my situation during my wait for a sleep doctor???

[National Jewish Health]

What you describe is highly suggestive of a sleep disorder, despite the apparent absence of apneas.  The "psychological-type symptoms" you describe are all consistent with this diagnosis as is the chronically high-normal hemoglobin and even the sinus tachycardia.

Sleep disorders are often associated with obesity and frequently relieved, partially or completely, by weight loss and that is something you could do while waiting.  You could also ask your doctor if he/she would be willing to prescribe treatment for the presumed sleep disorder, such as a continuous positive airway pressure (CPAP) device or a dental prosthesis, on the basis of your symptoms and the demonstration of marked night-time hypoxemia, which is saturations in the low 80's, or on the basis of a more formal home sleep study, in the absence of a formal sleep laboratory study.

Good luck.

[bluecheese]

BY the way, I haven never been diagnosed with any disease!