I can not get this unit to work. I bought it second hand. I am disabled and now I have ARDS. I also do not have medical coverage, I need a manual, so that perhaps I can figure out why this unit will not work. I simply can't end up in the hospital again. I can't afford it. I also can't afford a new unit. The gentlemen that sold it to me truely believed that it worked. Any help would be appeciated. Thanks Wendy