In which conditions is a pulse oximeter reading likely inaccurate?

• A. In healthy adults at rest
• B. In patients with fingernail polish
• C. In anemic patients
• D. In patients in shock and hypothermic, with fingernail polish, and anemic patients

Answer: (D)

Pulse oximetry relies on a clear, pulsatile arterial signal and good light transmission through a perfused fingertip or toe. When perfusion is poor, such as in shock or hypothermia, the pulse signal can be weak and readings become unreliable. Nail polish or artificial nails can block or alter the light signal, leading to inaccurate values. Anemia by itself doesn’t change the percentage of saturated hemoglobin, but in the presence of other problems it can complicate interpretation of oxygen delivery.

All of these factors together create conditions where the reading is most likely inaccurate, which is why the option listing shock and hypothermia, fingernail polish, and anemia is the best answer.