Photoplethysmography (PPG) is a non-invasive optical technique used to detect blood volume changes in the microvascular tissue bed. PPG sensors use light to detect changes in blood flow by either transmitting light through tissues (transmissive mode) or detecting reflected light (reflective mode). The PPG waveform contains information about heart rate and blood flow. PPG is inexpensive, portable, and can be used to develop wearable sensors. It has advantages for ambulatory monitoring and obtaining clinically relevant parameters from the PPG signal.

1. Wearable Photoplethysmographic
Guided by -
Mrs. Debarati Ganguly
Assistant Professor
Dept. of ECE
Presented by -
S Vivekanand
Roll No. 17
S7 EC-B
Sensors

2. OUTLINE
 What is Photoplethysmography
 Types
 Principle
 Different modes
 Advantages

3. HOW PHOTOPLETHYSMOGRAPHY ?
Photo Plethysmography
Photoplethysmography

4. Plethysmography (PG) ?
 Plethysmography is a measurement technique that can be used to
measure the volume changes in different parts of the body.
A plethysmograph is an instrument for measuring changes in volume
within an organ or whole body.

5. TYPES OF PLETHYSMOGRAPHY
 Air-Displacement
 Photo
 Strain gauge
 Impedance

6. PRINCIPLE OF PPG
 Most changes in blood flow occur mainly in the arteries . (but not in the
veins).
 PPG sensors optically detect changes in the blood flow volume via
reflection from or transmission through the tissue.
 The changes in light intensity are associated with small variations in
blood perfusion.

7. MODES OF PPG
 Two modes :
 Transmissive mode - fingers / toes / earlobe
 Reflective - forehead / cheek

8. TRANSMISSIVE MODE
 In transmission mode, the light transmitted through
the medium is detected by a photodiode opposite to
the LED source.
 The measurement site is limited.
 It can be placed at fingertips, nasal septum, cheek,
tongue, earlobe etc.

9. Absorption
Reflection at capillary bed
Diffuse Transmission
Specular Reflection
IR - LED
Venule Arteriole
Photodiode
Capillary Bed
Skin
Fat
Transmissive PPG

10. REFLECTIVE MODE
 In reflective mode, the photodiode detects light
that is back-scattered or reflected from the
tissues, bone and blood vessels.
 It eliminates the problems associated with sensor
placement.
 A variety of measurement sites can be used.

11. Absorption
Reflection at capillary bed
Diffuse Transmission
Specular Reflection
Reflective PPG
IR - LED Photodiode
Capillary Bed
Skin
Fat
Venule Arteriole

12. HOW PPG IS OBTAINED ?
The waveform is represented by two
components of current :
 Direct current - detected signals from
tissues
 Alternating current – detected signals from
blood volume changes

13. LIGHT WAVELENGTH
 The shorter wavelengths of light are strongly absorbed by melanin,
however red and near-IR light passes easily.
 Light with wavelengths b/w 500-600nm (green yellow region) gave better
results shallow tissues.
 IR and near IR were better for deep tissue blood flow.

14. Ear piece PPG sensor
PPG ring sensor Fingertip PPG sensors

15. ADVANTAGES
PPG is inexpensive and cheap.
 Since it consumes very less power, it is an ideal ambulatory device.
 does not need special training or guidance.
 A range of clinically relevant parameters can be obtained from PPG signal.

16. CONCLUSION
 They offer a simple, reliable, low-cost means of monitoring pulse rate non-invasively.
 PPG technology has been used to develop small wearable, pulse rate sensors.
 More than ten companies producing these sensors commercially.
(MIO alpha-MIO Global and Philips)

17. Authenticity is more powerful than perfection. Don’t worry about perfection
just let it go…
-Adrienne Osborn
THANK YOU