1. Pulse Oximeter
Date of Experiment:17-2-2014
Date of submission:21-2-2014
Team 4
Chaitanyakumar D (ED11B045)

2. MEDICAL DISSECTION LAB REPORT
ABSTRACT
To study and understand the structure and functioning of the Pulse Oximeter.
INTRODUCTION
The Pulse Oximeter is a device used to measure the concentration of Oxygen in a patient’s
blood. It monitors the percentage of haemoglobin that is oxygen-saturated. Oxygen
saturation should always be above 95%,
Pulse Oximetry is defined as the “determination of arterial saturation by analysis of bi-
spectral waveforms.”
Pulse Oximetry determines O2 levels of Arterial blood only and not veinous blood.
This is possible due to the fact that arterial blood is pulsatile but veinous blood is not.
DISSASSEMBLY
Front UI

3. Mother Board
LCD Board and Battery

4. S.NO TASK TOOLS REQUIRED
1 Removal of back cover Screwdrivers
2 Removal of battery Hands used.
No tools required
3 Removal of Circuit Board Hands used.
No tools required.
DESIGN CONCEPT
Oximeters work by the principles of spectrophotometry. The relative absorption of red (absorbed by
oxygenated blood) and infrared (absorbed by deoxygenated blood) light of the systolic component
of the absorption waveform correlate to arterial blood oxygen saturations.
The light rays emitted are :-
1.RED (660 NM)
2.INFRARED (910 NM)
Oxygenated haemoglobin absorbs more infrared light and allows more red light to pass through.
Deoxygenated (or reduced) haemoglobin absorbs more red light and allows more infrared light to
pass through. This difference is utilised to determine blood saturation levels of arterial blood.
Figure 1 Absorption of Red and IR light
There are two methods for measuring O2 levels :
1. REFLECTANCE
In the reflectance method, the emitter and photodetectorare next to each other on top the
measuring site. The light bounces from the emitter to the detector across the site.
2. TRANSMISSION
In the transmission method, as shown in the figure on the previous page, the emitter and
photodetector are opposite of each other with the measuring site in-between. The light can then
pass through the site.

5. Figure 2 Transmission method
Transmission method is the most commonly used method today.
Pulse Oximetry is done across reasonably translucent sites with good blood flow.
In adults, the sites are finger, toe, pinna(top) or lobe of the ear.
In infants, the sites are foot or palm of the hands and the big toe and thumb.
At the measuring site there are constant light absorbers that are always present. They are skin,
tissue, venous blood, and the arterial blood. However, with each heart beat the heart contracts and
there is a surge of arterial blood, which momentarily increases arterial blood volume across the
measuring site. This results in more light absorption during the surge. If light signals received at the
photodetector are looked at 'as a waveform', there should be peaks with each heartbeat and
troughs between heartbeats. If the light absorption at the trough (which should include all the
constant absorbers) is subtracted from the light absorption at the peak then, in theory, the
resultants are the absorption characteristics due to added volume of blood only; which is arterial.
Since peaks occur with each heartbeat or pulse, the term "pulse oximetry" was coined.
Figure 3 Relative absorption of light
Oxygen levels are calculated using the following formula :
R = ( ac 660 / dc 660 ) / (ac 910 / dc 910 )

6. MODULES
The various modules of the Pulse Oximeterare :-
1. User Interface/Display
Buttons
LCD screen
Alarm
2. Power Unit
Battery
NI-MH Battery Pack
Voltage - 6 V
Capacity – 2200mAh
Assembled in Korea
Charger
3. Circuit Boards
Mother Board
Network resistors
Diodes
Inductors
Electrolytic Capacitors
ICs
1. 74HC245D
RS232 port
Power Port
Peizoelectric Timer
Potentiometers
LCD Board
IC’s – 3
1.HT7660Made in Taiwan
4. Sensing Unit
Light Emitter
Receiver
Finger Clamp
HISTORY
1953 - Karl Matthes (German physician 1905–1962) developed the first 2-wavelength ear O2
saturation meter with red and green filters (later switched to red and infrared filters). His meter was
the first device to measure O2 saturation.

7. 1940’s - The original Oximeter was made by Glenn Allan Millikan.
1964 -Shaw assembled the first absolute reading ear Oximeter by using eight wavelengths of light.
Commercialized by Hewlett-Packard, its use was limited to pulmonary functions and sleep
laboratories due to cost and size.
1972 – Pulse Oximetry was developed, by Takuo Aoyagi and MichioKishi, bioengineers, at Nihon
Kohden using the ratio of red to infrared light absorption of pulsating components at the measuring
site.
1979 - Biox was founded, and it introduced the first pulse oximeter to commercial distribution in
1981.
1995 - Masimo introduced Signal Extraction Technology (SET) that could measure accurately during
patient motion and low perfusion by separating the arterial signal from the venous and other signals.
1995 -Masimo introduced perfusion index, quantifying the amplitude of the peripheral
plethysmograph waveform. Perfusion index has been shown to help clinicians predict illness severity
and early adverse respiratory outcomes in neonates, predict low superior vena cava flow in very low
birth weight infants, provide an early indicator of sympathectomy after epidural anaesthesia,and
improve detection of critical congenital heart disease in new-borns.
2007 - Masimo introduced the first measurement of the pleth variability index (PVI), which multiple
clinical studies have shown provides a new method for automatic, non-invasive assessment of a
patient's ability to respond to fluid administration.

8. PRODUCT ARCHITECTURE
FUNCTIONAL DECOMPOSITION
PART SUBPART/LINKED PART FUNCTIONS
Mother Board IC’s
Network resistors
Capacitors
Peizoelectric Timer
RS232 Port
Power Port
Process and filter the noise
in the values given by the
light detector
Establish communication
through RS232 port.
Output values to the LCD
screen to be displayed out.
Pulse Oximeter
Display/User
Interface
LCD
Screen
Buttons
Alarm
LED
Lights
Power
Unit
Battery
Charger
Circuit
Boards
LCD
Board
MotherBoard
Network
resistors
Potentiometers
Capacitors
Power
Port/
RS232 Port
Timer
Sensing/Dat
a Input
Light
Emitter
Light
Detector
Finger
Clamp

9. Diodes
Inductor
Potentiometers
Serve as internal clock for
the device.
Finger Clamp Light Emitter
Light Detector
Covering
Emit Red and IR light
Absorb light transmitted
through the fingers
Prevent External light from
interfering with the values
LCD Screen/
User Interface
IC’s
LCD Board
Buttons
LED lights
Alarm
Display values processed
by the Mother Board
Inputs values from the
user
Provides notification to the
user on completion of
process with alarm
Provides feedback to the
user with the help of LED
lights.
Connecting Cable - Transmit data and power
Outer Casing - Protects the device
GEOMETRIC LAYOUT

10. FUNCTION STRUCTURE
POSSIBLE IMPROVEMENTS
An improvement in mechanism allowing it give accurate values during motion and
low perfusion levels
Formulate means to measure ventilation in the patient instead of solely measuring
haemoglobin saturation.
Making the device more compact and easy to use.
CONCLUSION
The Pulse Oximeter was dissected and its components were studied. The functioning of the
Pulse Oximeter was also observed.
REFERENCES
1. http://www.patient.co.uk/doctor/Pulse-Oximetry.html
2. http://www.oximetry.org/pulseox/principles.htm
3. http://www.who.int/patientsafety/safesurgery/pulse_oximetry/en/
4. http://en.wikipedia.org/wiki/Pulse_oximetry