Use of LED and Photodiode in Pulse Oximetry

Pulse-oximetry technology was available in 1930's it became easily available only in the 1980's with advances in the Light Emitting Diode (LED), microprocessors, optical plethysmography and spectro-photometry. Today pulse-oximetry provides a simple, non-invasive, portable and inexpensive method to continuously monitor oxygen saturation and heart rate with good accuracy.

A pulse oximeter is a particularly convenient noninvasive and measurement instrument. It has a pair of small light-emitting diodes (LEDs) facing a photodiode through a translucent part of the patient's body, usually a fingertip or an earlobe. One LED is red, with wavelength of 660 nm, and the other is infrared, 905, 910, or 940 nm. Absorption at these wavelengths differs significantly between oxyhemoglobin and its deoxygenated form, therefore from the ratio of the absorption of the red and infrared light the oxy / deoxyhemoglobin ratio can be calculated. The absorption of oxyhemoglobin and deoxyhemoglobin is the same (isosbolic point) for the wavelengths of 590 and 805 nm; earlier oximeters used these wavelengths for correction for hemoglobin concentration.

Pulse oximetry is a non-invasive and continuous method of determining the amount of oxygenated and deoxygenated hemoglobin in a person's blood supply.

A pulse oximeter is a particularly convenient noninvasive and measurement instrument. It has a pair of small light-emitting diodes (LEDs) facing a photodiode through a translucent part of the patient's body, usually a fingertip or an earlobe. One LED is red, with wavelength of 660 nm, and the other is infrared, 905, 910, or 940 nm. Absorption at these wavelengths differs significantly between oxyhemoglobin and its deoxygenated form, therefore from the ratio of the absorption of the red and infrared light the oxy / deoxyhemoglobin ratio can be calculated. The absorption of oxyhemoglobin and deoxyhemoglobin is the same (isosbolic point) for the wavelengths of 590 and 805 nm; earlier oximeters used these wavelengths for correction for hemoglobin concentration.

Uses of pulse oximetry-
– This helps clinician in
– Noninvasive arterial oxygen saturation monitoring.
– Pulse rate monitoring.
– Trending of saturation and pulse rate

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Source by Stev Thomas

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