What causes affect the results of SpO2 measurement?

These reasons can affect the results of measuring the pulse oximeter, such as the patient's low blood pressure or cardiac arrhythmia. The following is a non-exhaustive list:

hypertension
hypothermia
heart rhythm disturbance, such as arrhythmia or tachycardia
Incorrect sensor position
Nail polish is applied to the finger where the sensor is placed
patient overexertion
anemia
Patient morphology (size and thickness of fingers)
Measured at higher altitudes (oxyhemoglobin levels will be lower due to lack of oxygen in the environment)
If the oximeter is a single sensor and the same device is used for both neonatal/child and adult measurements.