The oxygen saturation reported using a pulse oximeter usually correlates with the actual oxygen saturation of arterial blood. However, the presence of certain conditions may make the readings unreliable.


Causes for spurious readings from a pulse oximeter:

(1) severe hypothermia

(2) severe hypoperfusion

(3) carboxyhemoglobinemia (carbon monoxide poisoning)

(4) methemoglobinemia

(5) presence of methylene blue or isosulfan blue

(6) fingernail polish (if oximeter placed on a finger tip)

(7) bright environmental light (as in the operating room)


A pulse oximeter blood oxygen saturation < 70% should be investigated as potentially spurious.


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