What may cause a pulse oximetry reading of SpO2 to show zero?

A pulse oximetry reading of SpO2 showing zero typically indicates that there is an issue with the probe's ability to accurately measure the oxygen saturation in the blood. When the probe is improperly placed on the patient, it may not be able to detect the pulsatile flow of blood, which is essential for obtaining a reading. Proper placement of the probe is crucial because it needs to be positioned over an area with good blood flow and in a way that allows the device to differentiate between oxygenated and deoxygenated hemoglobin.

In addition, an improperly placed probe could lead to insufficient light transmission, resulting in a failure of the device to calculate oxygen saturation correctly. The device relies on light absorption properties of hemoglobin in the blood as it pulses, which achieves accurate readings if the probe is in the correct location. If the probe is off-center, not making full contact, or at a location where blood flow is compromised, the readings could fail, contributing to a reading of zero.

The other options are less likely to lead to a reading of zero. High hemoglobin levels may affect the accuracy of readings but wouldn't typically cause a complete failure to read. A probe not being plugged in would usually result in the device not turning on, while low blood