Pulse Oximetry
A non-invasive medical monitoring method measuring arterial blood oxygen saturation (SpO₂) using differential optical absorption of red and infrared light.
Governing formula
Ratio R = (AC₆₆₀/DC₆₆₀) / (AC₉₄₀/DC₉₄₀) ⇒ % SpO₂
SI unit
Percentage (% SpO₂)
In depth
Oxygenated hemoglobin (HbO₂) absorbs more 940 nm infrared light, while deoxygenated hemoglobin (Hb) absorbs more 660 nm red light. Transmitting red and IR LEDs through a finger calculates SpO₂ from arterial pulsation ratios.
Examples in the real world
Clip-on fingertip pulse oximeters monitoring patient arterial oxygen saturation in intensive care units.