Which condition is known to affect pulse oximeter readings due to altered hemoglobin forms?

• A. Smoke Inhalation
• B. Hypovolemia
• C. Hyperthermia
• D. Anemia

Answer: (A)

Pulse oximetry works by distinguishing oxyhemoglobin from deoxyhemoglobin using light absorption. When hemoglobin is altered into other forms, the same light signals no longer map cleanly to oxygen saturation. Smoke inhalation introduces carbon monoxide, which binds strongly to hemoglobin to form carboxyhemoglobin. This form mimics oxyhemoglobin in the wavelengths the oximeter uses, so the device can read a normal or elevated SpO2 even though tissue oxygen delivery is impaired. That misreading is the classic way smoking-related exposure alters pulse oximeter readings. While other conditions can affect readings, they do so mainly through perfusion changes or changes in total hemoglobin, not by producing a problematic hemoglobin form like carboxyhemoglobin.