Final answer:
Methemoglobinemia leads to the formation of methemoglobin, affecting the oxygen-carrying capacity of blood and causing pulse oximeters to inaccurately overestimate oxygen saturation due to altered light absorption characteristics.
Step-by-step explanation:
Methemoglobinemia affects the functionality of hemoglobin due to the oxidation of iron in hemoglobin from the ferrous (Fe²⁺) to the ferric (Fe³⁺) state.
As a consequence of this oxidation, the methemoglobin that forms cannot bind to oxygen, deeply impacting the oxygen-carrying capacity of the blood.
On a pulse oximeter, which measures percent saturation of oxygen in the blood, methemoglobinemia can cause inaccurate readings.
Although the device typically displays readings between 95-100 percent when functioning correctly, the presence of methemoglobin can lead it to overestimate the actual oxygen saturation of the blood.
This is because the pulse oximeter is calibrated for normal hemoglobin, not methemoglobin, which has different light absorption characteristics.