We have certainly digressed from the OP's request, but here goes on the O2 question.
Info linked on Medlineplus.gov is screened with vigorous standards. Your taxpayers' dollars at work. Disclaimer: I am a reference librarian, not a health professional; that means I am good at looking up reputable, verified sources and that I do not interpret those sources.
from Medlineplus.gov and the Mayo Clinic:
http://www.mayoclinic.org/symptoms/hypoxemia/basics/definition/SYM-20050930?p=1 This one says blood O2 levels below 90% are considered to be low.
From Medlineplus.gov and the American Thoracic Society:
http://www.thoracic.org/patients/patient-resources/resources/pulse-oximetry.pdf This one explains pulse oximetry and states that "Normally, more than
89% of your red blood should be carrying oxygen."