You obtain an SpO2 reading of 90% using an oximeter with an approximate accuracy of 5%. This could indicate a PO2 as low as what level?

a. 55 mm Hg
b. 60 mm Hg
c. 65 mm Hg
d. 70 mm Hg

ANS: A
However, with the accuracy of some oximeters being only ±4%, an SpO2 reading of 90% could mean an actual SaO2 reading as low as 86%, corresponding to a PO2 level of 55 mm Hg or less!