A proposed system for combining pulse oximeter and blood pressure measuring apparatus to a single novel device. System will be using optical method, photoplethysmography (PPG) for taking the measurement, thus foolproof and hazard free method introduced.

1. Development of Heamodynamic
Monitoring System Using
Photoplethysmography
Prepared by Abhijith Prabha, L8A, ECE Dept.
Sree Narayana Gurukulam College of engineering, Kadayiruppu.

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heamodynamic
SpO2
Pulse Oximeter
Photoplethysmography
TERMINOLOGY

3. OBJECTIVE
Pulse
Oximeter
Blood
Pressure
Novel
device
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Pulse Oximeter is a device widely used equipment in the hospitals. By
introducing a new technology to measure Blood Pressure to pulse
Oximeter, a new novel device can be developed with more functionality
and better user interface. Through this paper is actually try to illustrate
how this can be done.

4. Overview
• Heamodynamic monitoring is one of the vital requirement in bio-
medical field.
• Basically it is the measurement of following cardiovascular
parameters;
⮚Blood pressure (BP)
⮚Pulse rate (PR)
⮚Blood oxygen saturation (spO2).
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5. Applications of heamodynamic monitoring
Intensive care units
Postanesthesia care units
Ambulances
Endoscopy suites
Cardiac catheterization laboratories
Sleep laboratories
Endoscopy suites
and so on…
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6. Available devices*
DEVICES BP SPO2 PR MAJOR LIMITATIONS
Infinity® Delta yes yes yes Discontinuity in readings.
CNAP™ monitor yes no yes Uncomfortable attachments to body.
CMS 50 DL no yes yes No graphical display.
CMS 50 D PLUS no yes yes Not suitable for laboratory use.
Infinity® HemoMed™ Pod yes No no Invasive method
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* Draeger Medical Systems, Inc., MedicalTestSupply.com

7. Introduction of proposed method
• Main objective : To overcome the limitations of conventional
methods.
• It utilises the principle of photoplethysmography
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8. Features of this system:
⮚Non-invasive, Continuous and viable for long term use
⮚Precise and graphical display availability
⮚Provision for storage of readings
⮚Comfortable for user (unlike sphygmomanometer).
⮚Suitable for domestic, hospitals and laboratories
⮚Alarm facility
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9. Features of this method
• No hazards to user
• Less interference with other equipment (unlike MRI).
• Low levels of energy is applying to subject (unlike defibrillator) .
• Implemented as portable equipment (similar to ECG).
• Indication for proper working of sensor.
• Leads can be attached to finger tip, toes, ear lobes, lips etc.
• Indication of health conditions from heamodynamic parameters
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10. What is photoplethysmography (PPG)?
• Photoplethysmography is the volumetric measurement of blood flow
• It is an optical and non invasive method.
• Using a light source and a photo detector the electric signal equivalent
of blood flow is obtained
• Two types of PPG are;
A. reflectance PPG
B. transmittance PPG
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Body parts where PPG
signal can be obtained
?
For adults: the
finger tip, toe,
pinna (top),lips or
lobe of the ear
For infants: the
foot, palm of the
hand, toe or thumb

12. Measurement of spO2
It is the measure of percentage value of Oxygen in blood.
Normal value of spO2 is 90-100%.
Haemoglobin: the protein in blood for O2 transport.
Oxyhaemoglobin: haemoglobin bounded with oxygen
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• Oxyhaemoglobin absorbs RED light (850-1000 nm) light and IR (600-
750 nm) light more.
• There by using 2 LEDs and photo detectors spO2 in blood can be
measured.

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Let the output of
photo detectors
corresponding to
the LEDs Red and
Infra-Red are R
and IR
Then spO2 can
be derived
from the ratio
R/IR.
This is ratio is
compared with
calibrated
‘look-up’ table
the, % value of
spO2 can be
determined.

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spO2 (%) Condition
>=94 Adequate level
90-94 Moderate level
90-75 Inadequate but allowed for a short
period
<75 Tissue hypoxia and cardiac
dysrhythmia are expected
Table: health condition at different spO2 readings

16. Measurement of Pulse Rate
• Pulse rate or heart rate is the number of contractions or relaxation of
heart per minute.
• Normal value is 72 bpm.
• It is measured by counting the number of peaks of PPG signal for 10
seconds and multiply it with 6.
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Heart rate Condition
<60 Bradycardia
60-100 Normal
>100 Tachycardia
Table: health condition at different PR readings
• Therefore PR value of subject updates automatically
in every 10 sec.

18. Measurement of Blood Pressure
• Arterial blood pressure is the force exerted by the blood on the wall of
a blood vessel as the heart pumps (contracts) and relaxes.
• Systolic and diastolic blood pressures.
• The conventional methods for BP measurements are;
i. Electronic Palpation method
ii. Volume Oscillometric (VO) method
iii. Volume Compensation (VC) method.
iv. Arterial Tonometry method etc.
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The limitations of currently existing methods are;
• Some of them are invasive methods
• high risks of embolism, arrhythmia, heart attack in malfunction.
• Discontinuous measurements
• May cause damage to muscles and arteries.
• Cuff should detach and re-attach periodically.
Using PPG technology most of these limitations can
be resolved.

20. Calibration process
• Challenge in design
• Two types calibration procedure :vertical and horizontal calibration.
• According to [1]a combination of vertical and horizontal calibration is
adapted in this system.
• Horizontal calibration: it is perform operation on independent axis of
PPG signal (time).
• Vertical calibration: PPG pulse height is considered.
• The PPG signal has a rising portion (AP) and falling portion (CP).
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Fig: PPG signal showing AP and CP, with time instances T1,
T2 and T3.
The time taken from T1 to T2 is called
Anacrotic phase (AP), corresponds to
systolic blood pressure.
The time taken from T2 to T3 is called
catacrotic phase (CP), corresponds to
diastolic blood pressure.

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Along with measuring of the maximum and
minimum ac voltage of PPG signal, AP and CP values
are also measured.
[2] By comparing this values with predetermined
look-up table corresponding Blood Pressure can be
determined.
By the combination of vertical and horizontal
calibration greater accuracy can be obtained.

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SBP DBP CONDITION
<100 <65 HYPOTENSION
100-120 65-80 NORMAL
120-139 80-89 PREHYPERTENSION
140-159 90-99 HYPERTENSION
STAGE 1
160-200 100-110 HYPERTENSION
STAGE 2
>200 >110 HYPERTENSIVE CRISIS
Table: health conditions at different blood pressures

24. miscellaneous
• Warning facility
• To notify any of the parameter has crossed threshold.
• The priority of warning can be set by using more than one frequencies of a
buzzers.
• Lead fault detector
• If the difference between 2 analog inputs are zero, sensor is not connected
to subject.
• Using this property lead fault can be detected.
• Health condition analyser
• The readings of parameters are compared to predefined table of health
conditions and it is displayed.
E.g.: if BP is 150/95; “hypertension stage 1” will displayed.
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25. Architecture of proposed system
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26. Design aspects
• PPG sensor:
• Red and Infrared LEDs, photo detectors and an amplifier stage.
• An indicator LED is also can be designed.
• Signal conditioning:
• BPF (0.75 Hz- 4.17 Hz)
• Amplifier
• Subtractor (optional)
• Impedance matching (buffer)
• ADC:
• Resolution must below 10 mV.
• 12 bit ADC is preferable (1.22 mV)
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27. Design aspects
• Processor:
• 2 channels of in-built ADC.
• At least 3 timers
• RTC and watchdog timer
• Sufficient memory availability, I/O channels, interrupt sources.
• Buzzers:
• 2 buzzers is preferable.
• Both of different frequencies which will help to provide 2 types of
warning.
• Control switches:
• For control of operations
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28. Design aspects
• Display unit:
• Graphical display
• Use either GLCD, GLED or OLED
• By using OLED overall power consumption of system can be reduced.
• Power unit:
• Either battery operated or plug-in mode.
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29. Design of sensor clamp
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Fig: circuit of sensor clamp
RED
INFRA RED

30. requirements in sensor clamp
LED sources and photo detectors:
Red (900 nm),
Infrared (700 nm)
Phototransistors (PT)
are preferable,
because it provide
amplification also.
The sensitivity of PT
must be high for
better accuracy.
Amplifier stage:
Using MCP series
opamp we can get
better frequency
response.
Output voltage
shouldn’t exceed
+5V.
Indicator:
Indication of
insertion of finger
or proper working
of sensor.
Others:
Select wire in
between clamp and
device, to ensure
min parasitic
capacitance.
The body of clamp
must block external
light.
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31. Limitations and troubleshooting
Limitation Troubleshooting
Shivering or shaking of subject Proper machine design of sensor clamp
External light sources Covering of clamp with opaque material
Nail polish or dyes in blood Use 8 wavelength technic in PPG
Lead failure Introducing Lead fault detector
Complexity in calibration nil
Abnormalities during Anaemia nil
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32. Results
• Operating pulse rate range: 45-250 bpm
• Frequency range of signals: 0.75-4.17 Hz
• spO2 range: >70%
• Blood Pressure range: Depending on calibration.
• Interval for PR reading is 10 seconds.
• Maximum length of wire should less than 100 cm.
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33. Conclusion
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Pulse
Oximeter
(spO2, PR)
Blood
Pressure
(BP)
Proposed
system

34. Reference
[1] Nivedita Daimiwal, M. Sundhararajan and Revati Shriram, “Respiratory Rate, Heart Rate and
Continuous Measurement of BP Using PPG”, International Conference on Communication and
Signal Processing, April 3-5, 2014, India.
[2] Md. Manirul Islami, Fida Hasan Md. Rafii, Abu, Farzan Mitull and Mohiuddin Ahmadl, M. A.
Rashid, Mohd Fareq bin Abd Malek, “Development of a Non-invasive Continuous Blood Pressure
Measurement and Monitoring System”, IEEE/OSA/IAPR International Conference on Infonnatics,
Electronics & Vision.
[3] Wei Chen1, Idowu Ayoola, Sidarto Bambang Oetomo, Loe Feijs, “Non-invasive Blood Oxygen
Saturation Monitoring for Neonates Using Reflectance Pulse Oximeter”.
[4] “Non-invasive Pulse Oximeter Utilizing Skin Reflectance Pho toplethy smog mphy”, IEEE
TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 35, NO. 10, OCTOBER 1988
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35. Reference
[5] Jasper Truijen, Johannes J. van Lieshout, Wilbert A. Wesselink, Berend E. Westerhof, „
Noninvasive continuous hemodynamic monitoring”, Springerlink.com
[6] Hayato Fukushima, Haruki Kawanaka, Md. Shoaib Bhuiyan and Koji Oguri, “Cuffless Blood
Pressure Estimation using only Photoplethysmography based on Cardiovascular parameters”, 35th
Annual International Conference of the IEEE EMBS Osaka, Japan, 3 - 7 July, 2013
[7] P. Shaltis, A. Reisner, H. Asada, “Calibration of the Photoplethysmogram to Arterial Blood
Pressure: Capabilities and Limitations for Continuous Pressure Monitoring”, Proceedings of the 2005
IEEE , Engineering in Medicine and Biology 27th Annual Conference Shanghai, China, September 1-
4, 2005
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Thank you...