What effect does poor perfusion have on pulse oximetry readings?

Poor perfusion can significantly impact the accuracy of pulse oximetry readings by leading to falsely low measurements. When blood flow to the peripheral tissues is compromised, there is not enough oxygenated blood reaching the sites where the pulse oximeter measures the amount of oxygen saturation in the hemoglobin. As a result, the device may incorrectly interpret the lower levels of blood flow combined with possibly inadequate levels of oxygen, displaying a lower oxygen saturation reading than actually present.

This phenomenon occurs because pulse oximeters rely on transmitting light through the tissue to detect the absorption characteristics of oxygenated and deoxygenated hemoglobin. If perfusion is poor, the light may not pass through the tissue correctly, or there may be insufficient blood volume for accurate detection. Hence, clinicians must be aware of a patient's perfusion status when interpreting pulse oximetry data to avoid misdiagnosis or inappropriate treatment decisions.