What can cause inaccuracies in pulse oximetry readings?

Ambient direct light can indeed cause inaccuracies in pulse oximetry readings. Pulse oximeters work by using light-emitting diodes that measure the absorption of specific wavelengths of light by oxygenated and deoxygenated hemoglobin in the blood. When there is excessive ambient light, especially infrared or bright white light, it can interfere with the light that the oximeter uses to make its readings, leading to false results. This is particularly problematic in environments where direct sunlight or bright artificial lights are present, as they can overwhelm the sensor and distort the measurements.

The other factors, while they can influence a pulse oximeter’s accuracy, do not lead to inaccuracies in the same way as ambient light does. For instance, the patient being awake does not inherently affect the accuracy of the readings, as pulse oximeters are designed to provide readings regardless of the patient's state of consciousness. Proper perfusion is actually advantageous, as it indicates good blood flow that helps the oximeter work effectively. Additionally, a non-moving patient is generally a positive factor, because movement can sometimes lead to artifacts, but if the patient is stable, this does not imply an inaccuracy in the readings due to light interference.