Pulse oximetry accuracy is reduced by which condition?

• A. stable circulation
• B. excellent perfusion
• C. poor circulation
• D. normal oxygenation

Answer: (C)

Pulse oximetry relies on detecting the pulsatile arterial blood at the measurement site. A strong pulsatile signal is needed to accurately separate arterial absorption from surrounding tissue and venous blood. When circulation to the site is poor, the pulsatile signal becomes weak, so the device’s calculation of oxygen saturation is noisy or unreliable, leading to inaccurate readings or even inability to obtain a reading. Good perfusion provides a clean, robust signal and accurate results, while normal oxygenation simply describes the patient’s oxygen level and doesn’t by itself change measurement accuracy. If perfusion is compromised, warming the patient or moving to a better site (like the ear or forehead) can help, and arterial blood gas measurement can confirm true oxygenation when precise values are needed.