This document discusses pulse oximetry, which is a non-invasive method to determine a patient's oxygen saturation level by measuring the absorption of red and infrared light as it passes through pulsating blood vessels. It works by shining two wavelengths of light (red and infrared) through a sensor placed on the patient's finger or earlobe, and measuring the amount of light absorbed. This absorption data is then used to calculate the percentage of oxygenated hemoglobin in the blood. The document outlines the history, components, working principle, advantages and limitations of pulse oximetry.

1. JIS COLLEGE OF ENGINEERING
SUBMITTED BY:
SUBHASISH KARMAKAR

2. CONTENTS:
 HISTORY.
 INTRODUCTION.
 COMPONENTS.
 PROCEDURE.
 THE INSTRUMENT.
 WORKING PRINCIPLE.
 ABSORPTION SPECTRA.
 BLOCK DIAGRAM.
 NORMAL READING.
 AREAS OF USE.
 ADVANTAGES.
 LIMITATIONS.

3. HISTORY
 Pulse oximetry was first invented in 1972, by Takuo
Aoyagi , bioengineer, at Nihon Kohden using the ratio of
red to infrared light absorption of pulsating components
at the measuring site.
 Pulse oximeter was commercialized by Biox in 1981
and Nellcor in 1983 .

4. INTRODUCTION
 PULSE-OXIMETER!!!
 So here “Pulse” is the rythmic contraction and
expansion of an artery.
 “Oximeter” is the instrument used to measure the
proportion of oxygenated hemoglobin in pulsating
blood vessels.
 A pulse oximeter machine shows the % of O2
saturation and pulse rate.

5. ???
 What is pulse oximetry?
 Pulse oximetry is a non invasive method for determining
a patient’s O2 saturation.
 The process can be of two types;
 Transmittance type.
 Reflectance type
 Transmittance type is mainly used here.
 It measures that, what % of blood is loaded with O2.

6. Components :
 A pulse oximeter mainly consists of 3 units:
An optical probe.
A circuit module.
A display unit.
 Optical probe contain two LED’s,
 Red light(660 nm).
 Infrared light(940 nm).
 Circuit module is the analog part.
 A computer for data storage ,processing and display.

7. PROCEDURE:
 In this method, a sensor is placed on a thin part of a
patient’s body.
 Then light of two wavelength is passed through the
patient to a photodetector .
 The changing absorbance at each wavelength is
measured in %.

8. The instrument

9. working principle
 Pulse oximeter measures the absorption of red and
infrared light by pulsatile blood.
 Oxygenated blood absorbs light at 660 nm(red),
where as deoxygenated blood absorbs light at 940
nm(IR).
 It contains two LED’s and two light collecting sensors.
 The relative absorption of light by oxy-hemoglobin
and deoxy-hemoglobin is processed by the device and
an O2 saturation level is reported.

12. ABSORPTION SPECTRA

17. Block diagram:

18. Normal reading:

20. Advantages:
 Pulse oximetry is particularly convenient
for noninvasive continuous measurement of blood
oxygen saturation.
 It is possible that it can also be used to detect
abnormalities in ventilation.
 Portable battery-operated pulse oximeters are useful
for pilots operating in a non-pressurized aircraft above
10,000 feet.

21. Limitations:
 It is not a substitute for blood gases checked in a
laboratory.
 In severe anemia, the blood will carry less total
oxygen, despite the hemoglobin being 100% saturated.
 Since pulse oximetry only measures the percentage of
bound hemoglobin, a falsely high or low reading will
occur when hemoglobin binds to something other
than oxygen.