What condition can cause an inaccurate pulse oximetry reading?

Severe peripheral vasoconstriction can significantly affect pulse oximetry readings due to the reduced blood flow to the extremities. The accuracy of a pulse oximeter relies on its ability to detect light absorption by oxygenated and deoxygenated hemoglobin in the blood. When vasoconstriction occurs, the peripheral blood flow decreases, leading to a lower concentration of blood in the capillaries where the pulse oximeter is usually applied, such as a fingertip or earlobe. This reduced flow can lead to a falsely low reading, as the sensor may not receive an adequate amount of blood for accurate measurement.

In contrast, other conditions such as hyperventilation, lung infections, or blood loss can impact overall oxygenation, but they might not directly interfere with the functioning of the pulse oximeter the way severe peripheral vasoconstriction does. Hyperventilation may lead to changes in blood gases but does not typically distort the measurement of oxygen saturation peripherally. Lung infections could compromise lung function and oxygen exchange but do not inherently affect blood flow to the measuring site. Blood loss reduces overall oxygen-carrying capacity but may not necessarily impact localized blood flow to the extent that pulse oximetry is affected. Thus,