What is pulse oximetry?
Pulse oximetry is a non-invasive method that measures hemoglobin saturation with oxygen in arterial blood.
Pulse oximeter has two separate light emitting diodes that emit light. Light absorbion in those wave lenghts differs among oxyhemoglobin (infrared light) and hemoglobin that does not carry any oxygen (red light). So the oximeter measures itself the amount of light absorbion and calculates the percentage of oxyhemoglobin.
Some of the most important factors that can affect the measurement of oxygen saturation are peripheral ischaemia of fingers, use of vasoconstrictive medication, nail polish, low temperature of fingers, arrhythmias etc.