Which of the following will not interfere with the accuracy of a pulse oximeter?

• A. Hypertension
• B. Hypoperfusion
• C. Carbon monoxide poisoning
• D. Edema in the fingers

Answer: (A)

Pulse oximetry relies on detecting a clean pulsatile arterial signal and comparing how much red and infrared light is absorbed by hemoglobin in the bloodstream. Anything that disturbs perfusion, contact, or the light signal can skew the reading.

Hypertension by itself does not change how light is absorbed by hemoglobin, so it generally doesn’t interfere with the measurement. The device’s estimate of oxygen saturation stays reliable as long as the signal is strong and the probe is well placed.

In contrast, poor perfusion or hypoperfusion weakens the pulsatile signal, making it hard to separate arterial blood from surrounding tissue and leading to unreliable readings. Carbon monoxide poisoning skews results because carboxyhemoglobin absorbs light similarly to oxyhemoglobin, often producing falsely normal or high SpO2. Edema in the fingers can prevent good probe contact and hinder signal quality, also yielding inaccurate values.