Which of the following factors can interfere with pulse oximetry readings?

High ambient light can significantly interfere with pulse oximetry readings because pulse oximeters work by shining light through a patient's skin and measuring changes in light absorption by oxygenated and deoxygenated hemoglobin. When there is excessive ambient light, particularly from sources like sunlight or bright artificial light, it can introduce noise into the measurement. This noise may cause the device to misinterpret the readings, leading to inaccurate results. Therefore, ensuring a controlled light environment can help in obtaining precise and reliable pulse oximetry measurements, making this factor crucial for the accuracy of the readings.

Low oxygen saturation and rhythm abnormalities could affect the accuracy of pulse oximetry, but they pertain more to the physiological status being assessed rather than external factors that influence the device's basic functionality. A patient's blood type does not affect pulse oximetry readings since the device measures the absorption characteristics of hemoglobin regardless of its type.