Pulse Oximetry Summary
Pulse oximetry is the non-invasive continuous measurement of the oxygen saturation of hemoglobin. It exploits the fact that oxy- & deoxy hemoglobin differentially absorb red and infra-red light.
Shine Red and IR light through the skin and measure the absorption → DeoxyHb and OxyHb have different light absorption profiles → The signal that varies with time represents the pulsatile blood flow. Using a standard curve, the ratio of Red/IR absorption (modulation ratio) is used to calculate the SaO2
The plethysomograph waveform shows signal over time, corresponding to pulse
Amplitude may increase with greater SV (such as after a pause)
Perfusion index indicates the signal strength
Nick Mark MD @nickmmark
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