This document describes the development of an electro-optical photoplethysmography (PPG) system to noninvasively monitor blood volume changes. The system uses an infrared light emitting diode as the light source, a photodiode sensor, and filter circuits to extract the pulsatile PPG signal related to heartbeats from noise. Experimental results show the PPG waveform obtained from a finger with characteristic peaks corresponding to heartbeats. The developed system provides a simple, effective method for monitoring blood volume changes using PPG.
Heamodynamic Monitoring System Using Photoplethysmographyabhijith prabha
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.
Identification of Myocardial Infarction from Multi-Lead ECG signalIJERA Editor
Electrocardiogram (ECG) is the cheap and noninvasive method of depicting the heart activity and abnormalities.
It provides information about the functionality of the heart. It is the record of variation of bioelectric potential
with respect to time as the human heart beats. The classification of ECG signals is an important application since
the early detection of heart diseases/abnormalities can prolong life and enhance the quality of living through
appropriate treatment. Since the ECG signals, while recording are contaminated by several noises it is necessary
to preprocess the signals prior to classification. Digital filters are used to remove noise from the signal. Principal
component analysis is applied on the 12 lead signal to extract various features. The present paper shows the
unique feature, point score calculated on the basis of the features extracted from the ECG signal. The point
score calculation is tested for 40 myocardial infarction ECG signals and 25 Normal ECG signals from the PTB
Diagnostic database with 94% sensitivity.
Heamodynamic Monitoring System Using Photoplethysmographyabhijith prabha
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.
Identification of Myocardial Infarction from Multi-Lead ECG signalIJERA Editor
Electrocardiogram (ECG) is the cheap and noninvasive method of depicting the heart activity and abnormalities.
It provides information about the functionality of the heart. It is the record of variation of bioelectric potential
with respect to time as the human heart beats. The classification of ECG signals is an important application since
the early detection of heart diseases/abnormalities can prolong life and enhance the quality of living through
appropriate treatment. Since the ECG signals, while recording are contaminated by several noises it is necessary
to preprocess the signals prior to classification. Digital filters are used to remove noise from the signal. Principal
component analysis is applied on the 12 lead signal to extract various features. The present paper shows the
unique feature, point score calculated on the basis of the features extracted from the ECG signal. The point
score calculation is tested for 40 myocardial infarction ECG signals and 25 Normal ECG signals from the PTB
Diagnostic database with 94% sensitivity.
A 20 gbs injection locked clock and data recovery circuitVLSICS Design
This paper presents a 20 Gb/s injection-locked clock and data recovery (CDR) circuit for burst mode
applications. Utilizing a half rate injection-locked oscillator (ILO) in the proposed CDR circuit leads to
higher speed operation and lower power consumption. In addition, to accommodate process, voltage, and
temperature (PVT) variations and to increase the lock range, a frequency locked loop is proposed to use in
this circuit. The circuit is designed in 0.18 μm CMOS and the simulations for 27-1 pseudo random bit
sequence (PRBS) show that the circuit consumes 55.3 mW at 20 Gb/s, while the recovered clock rms jitter
is 1.1 ps
FPGA based Heart Arrhythmia’s Detection AlgorithmIDES Editor
Electrocardiogram (ECG) signal has been widely used
for heart diagnoses .In this paper, we presents the design of
Heart Arrhythmias Detector using Verilog HDL based on been
mapped on small commercially available FPGAs (Field
Programmable Gate Arrays). Majority of the deaths occurs
before emergency services can step in to intervene. In this
research work, we have implemented QRS detection device
developed by Ahlstrom and Tompkins in Verilog HDL. The
generated source has been simulated for validation and tested
on software Verilogger Pro6.5. We have collected data from
MIT-BIH Arrhythmia Database for test of proposed digital
system and this data have given MIT-BIH data as an input of
our proposed device using test bench software. We have
compared our device output with MATLAB output and
calculating the error percentage and got desire research key
point of RR interval between the peaks of QRS signal. The
proposed system also investigated with different database of
MIT-BIH for detect different heart Arrhythmias and proposed
device give output exactly same according to our QRS detection
algorithm.
Simple Three-Input Single-Output Current-Mode Universal Filter Using Single V...IJECEIAES
This paper presents a second-order current-mode filter with three-inputs and single-output current using single voltage differencing current conveyors (VDCC) along with one resistor and two grounded capacitors. The design of presented filter emphasizes on the use of a single active element without the multiple terminals VDCC which is convenient to implement the VDCC using commercially available IC for the practical test. Also, it can reduce the current tracking error at current output port and can reduce the number of transistors in the VDCC. The proposed filter can realize all the five generic filter responses, namely, band-pass (BP), band-reject (BR), low-pass (LP), high-pass (HP), and all-pass (AP) functions from the same configuration under various conditions in terms of three input current signals. Furthermore, the natural frequency and quality factor are electronically controlled. The output current node exhibits high impedance. Besides, the non-ideal case is also investigated. The simulation and experimental results using VDCC constructed from commercially available IC can validate the theoretical analyses.
Measuring the cutoff frequency of a low pass filterHasnain Ali
It is required to setup an automated test and measurement system for measuring the cutoff frequency of a low pass filter using LabView and estimate the frequency response of the filter.
Debra Farmer signs her name to the last steel beam that will go into the newest building on Colorado Mountain College's Alpine Campus in Steamboat Springs.
A 20 gbs injection locked clock and data recovery circuitVLSICS Design
This paper presents a 20 Gb/s injection-locked clock and data recovery (CDR) circuit for burst mode
applications. Utilizing a half rate injection-locked oscillator (ILO) in the proposed CDR circuit leads to
higher speed operation and lower power consumption. In addition, to accommodate process, voltage, and
temperature (PVT) variations and to increase the lock range, a frequency locked loop is proposed to use in
this circuit. The circuit is designed in 0.18 μm CMOS and the simulations for 27-1 pseudo random bit
sequence (PRBS) show that the circuit consumes 55.3 mW at 20 Gb/s, while the recovered clock rms jitter
is 1.1 ps
FPGA based Heart Arrhythmia’s Detection AlgorithmIDES Editor
Electrocardiogram (ECG) signal has been widely used
for heart diagnoses .In this paper, we presents the design of
Heart Arrhythmias Detector using Verilog HDL based on been
mapped on small commercially available FPGAs (Field
Programmable Gate Arrays). Majority of the deaths occurs
before emergency services can step in to intervene. In this
research work, we have implemented QRS detection device
developed by Ahlstrom and Tompkins in Verilog HDL. The
generated source has been simulated for validation and tested
on software Verilogger Pro6.5. We have collected data from
MIT-BIH Arrhythmia Database for test of proposed digital
system and this data have given MIT-BIH data as an input of
our proposed device using test bench software. We have
compared our device output with MATLAB output and
calculating the error percentage and got desire research key
point of RR interval between the peaks of QRS signal. The
proposed system also investigated with different database of
MIT-BIH for detect different heart Arrhythmias and proposed
device give output exactly same according to our QRS detection
algorithm.
Simple Three-Input Single-Output Current-Mode Universal Filter Using Single V...IJECEIAES
This paper presents a second-order current-mode filter with three-inputs and single-output current using single voltage differencing current conveyors (VDCC) along with one resistor and two grounded capacitors. The design of presented filter emphasizes on the use of a single active element without the multiple terminals VDCC which is convenient to implement the VDCC using commercially available IC for the practical test. Also, it can reduce the current tracking error at current output port and can reduce the number of transistors in the VDCC. The proposed filter can realize all the five generic filter responses, namely, band-pass (BP), band-reject (BR), low-pass (LP), high-pass (HP), and all-pass (AP) functions from the same configuration under various conditions in terms of three input current signals. Furthermore, the natural frequency and quality factor are electronically controlled. The output current node exhibits high impedance. Besides, the non-ideal case is also investigated. The simulation and experimental results using VDCC constructed from commercially available IC can validate the theoretical analyses.
Measuring the cutoff frequency of a low pass filterHasnain Ali
It is required to setup an automated test and measurement system for measuring the cutoff frequency of a low pass filter using LabView and estimate the frequency response of the filter.
Debra Farmer signs her name to the last steel beam that will go into the newest building on Colorado Mountain College's Alpine Campus in Steamboat Springs.
Design and development of electro optical system for acquisition of ppg signa...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
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having low frequency of 300Hz, with the supply voltage of 0.8v. To reduce the power dissipation of 779nW, by
using fifth order low pass filter. The OTA-C filter is to eliminate noise voltage and increases the reliability of
the system. A chip is fabricated in a 0.18μm CMOS process is simulated and measured to validate the system
performance using HSPICE.
Denoising of Radial Bioimpedance Signals using Adaptive Wavelet Packet Transf...iosrjce
In recent years, the accurate computer aided diagnosis of the cardiovascular diseases is gaining
momentum. In addition to accuracy, non-invasiveness of the measurement techniques has become the need of
the hour. Impedance cardiography is one such method which has become a synonym for indirect assessment of
monitoring the stroke volume, cardiac output and other hemodynamic parameters by monitoring the blood
volume changes of the body. Changes occurring in the blood volume within a certain body segment due to
various physiological processes are captured in terms of the impedance variations of that segment. But this
method is affected by electrical noise such as power line hum and motion and respiratory artifacts due to
movement of the subject while acquiring the bioimpedance signal. This can cause errors in the automatic
extraction of the characteristic points for estimation the hemodynamic parameters. This paper presents two
algorithms for baseline wander removal from the bioimpedance waveform obtained at the radial pulse of the left
hand, one based on wavelet packet decomposition and the other based on the Kalman filter. The impedance
signals have been acquired by using the peripheral pulse analyzer. The results for the wavelet packet decomposition are found to be better than that of the Kalman filter.
Accelerometer and EOG Based Wireless Gesture Controlled Robotic ArmIJMER
- This paper deals with the Robotic arm controlled by arm and eye movements, where data
is acquired through the use of accelerometer and EOG amplifier. The hand movements are captured by
the Accelerometer and the eye movements are captured by EOG amplifier. The Robotic arm will pick
and place the object according to the movement of the hand and Robotic arm will move left and right
according to our eye movements. Signals are wirelessly transmitted through RF Encoder and Decoder.
Robotic arm is based on Arduino Duemilanove controller for signal processing, and interfaced with the
Controller serially. This Embedded system will help disabled persons to do work by their own. The
Robotic arm can be used to pick and place hazardous objects.
Development of a receiver circuit for medium frequency shift keying signals.inventionjournals
Frequency shift keying (fsk) mode of digital signal information transfer switches between two predetermined frequencies of the carrier wave, either by modulating one sine wave oscillator or by switching between two oscillators.The need for a receiver to decode an fsk signal along the transmitting medium from a digital source code within about 5 kilometer radius for security monitoring of environment informed this work. The design of a receiver circuit at a frequency of 500 kHzfor an input frequency shift keying (fsk) signal from a transmitter is presented. The receiver is to receive an RF signal, amplify it, filter it to remove unwanted signals, and recover the desired base band information. It consists of an amplifier, tuned circuitsand mixers which filters the base-band information. A comparator circuit is incorporated, to detect the digital signal received. The output from the comparators is the digital equivalent of the coded signals sent by the transmitter circuit, and transferred to a microcontroller circuit, to act as a coded signal representing information from the transmitting end. The bode-plot response of the receiver to the incoming signals using a FET tuned circuit, shows that only frequencies above 470kHz, and below 495kHz are allowed to pass through the network with a resonant frequency of 483.553 kHz and a gain of 27.734dB, while others are totally attenuated. The reliability of the designed receiver circuit was evaluated for a 1 year continuous operating period and was found to be 74.7%.Area of application of this work include electronic policing of a defined environment with good success
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Cyclic voltammetry readout circuitry for DNA biosensor applicationjournalBEEI
Cyclic voltammetry electrochemical biosensors reported a wide usage and applications for its fast response, able to be miniaturized and its sensitivity. However, the bulky, expensive and laboratory-based readout circuitry made it impossible to be used in the field-based environment. A miniaturized and portable readout circuitry for the DNA detection using hybridization technique had been design and developed in this work. It embedded with fabricated FR4 based sensor and produced respective current when the applied voltage was within the range of 0 to 0.5 V. The readout circuitry had been verified with five analysis environments. Bare Au with distilled water (dH2O), bare Au with ferricyanide reagent solution, DNA immobilization, DNA non-hybridization and DNA hybridization. All the results performed produced peak cathodic current when the applied input voltage is within 0.5 V to 3 V and hence proved that the miniaturized and portable readout circuitry is suitable to be implemented for cyclic voltammetry electrochemical biosensor.
This work presents investigation of passive filter performance on three-phase inverter with 180° conduction mode. The simulation model of the inverter is developed by using MATLAB/Simulink. The power circuit used Insulated Gate Bipolar Transistor (IGBT) as switching device. The inverter is controlled by using bipolar Sinusoidal Pulse Width Modulation (SPWM) technique. The IGBT was set to 25 kHz for switching frequency (fs). Three types of passive filters which are LC, RC and PI filters are used to investigate the ability to remove the unwanted signal that occurred on the inverter. The result is analyzed based on the performances of output filter in term of Total Harmonic Distortion in voltage (THDv), current (THDi), shape of output voltage and current. The THD must be less than 5% at rated inverter output voltage or current by referring to IEC 61727 Standard. The passive filter is modeled in MATLAB/Simulink environment to study the characteristics and performance of the filters.
2. DEVELOPMENT OF AN ELETRO-OPTICAL
PHOTOPLETHYMOGRAPHY SYSTEM
(Laboratory Report )
3. Abstract
A simple and effective method of displaying changes in blood volume in peripheral vascular
bed from photoplethysmography has been developed using electro-optical
photoplethysmograph system. This method is developed to be incorporated as noninvasive
monitoring of blood volume from a patient in intensive care unit. This implementation
includes Infrared emitter s IRED light source, silicon photodiode as optical sensor to convert
light detected into voltage value, active and passive band pass filter circuits to reduce noise
levels in signal, amplifier designed configured for gain of 10 and digital oscilloscope in order
to observe the PPG signal generated due to systolic and diastolic volume change in atrial
blood. PPG waveform comprising of a pulsatile AC component synchronised to ach heart
beat superimposed on a slowly varying DC component. Proper high pass filter has been used
to reduce dominant low frequencies with no distortion in pulse shape. During experiment
pulses were measured by placing index finger between the light emitter and photodetector
and resultant visible pulse shape distortion were investigated
Introduction
A photoplethysmograph (PPG) is a device used to optically obtain a volumetric measurement
of an organ. It is an qualitative measurement. Commoly measured volume changes that are
caused by
Breathing
Blood forced into vessels such as arteries, veins, capillary
Pumping of heart
Tissue or organ under investigation is bathed with a light of a suitable wavelength . Short
wavelength of light are strongly absorbed by melanin. Window in the absorption spectra of
water that allows visible red and near Infrared light to pass more easily, thereby facilitating
the measurement of blood volume at these wavelengths. Thus, red and near infrared
wavelengths are often chosen for PPG light sources. Illuminating light is reflected, absorbed
and scattered in tissue and blood. This light is measured with photodiode which produces
electrical signal. This received signal is assumed to be measure of volume changes due to
localised blood flow.
PPG can be operated in two modes; transmission mode and reflection mode.
Transmission mode: The light source is placed on one side of organ and detector is situated
on the opposite side of the organ. It is clearly illustrated in the following figure.
4. Fig.1. Photoplethysmographyprobe usedin Transmissionmode
Reflection mode: In this method, light source and photo detector are placed adjacent to each
other. Photodetector is placed to receive the light reflection from the tissues or arterial blood
.
Fig.2. Photoplethysmographyprobe used inReflectionmode
Signal generated by the phototodetector is amplified and used to generate corresponding
photoplethysmograph.
It has been proved that photoplethysmography can be a reliable tool to measure arterial
blood flow to the feet in people with diabetes(fig.3) which are particularly prone to peripheral
arterial disease.(C.Scanlon,2012) It is a non invasive technique to measure the arterial pulse
waveform from either arterial wall deflection or force at the surface of the skin above a
palpable vessel. Typically, sensors used in such technique are not directly calibrated in terms
of pressure , but ideally respond proportionally to pressure. Sensors can called as volume
sensors as they relies on the adjacent tissues surrounding the vessels as a non-deflecting
5. frame of reference. Skin deflections directly above the vessel are then measured relative to a
reference frame to represent arterial pressure.
Moreover, pulse oximetry use the technique of PPG to estimate the oxygen saturation values.
Incorporation of transreflectance PPG sensors has been reduced failure rate of pulse
oximeter which is more in the case of conventional PPG signals. (Shafiq.M, 2012) Key
factors that can that influence the amount of light received by photodetector such as blood
volume, blood vessel wall movement and orientation of red blood cells(RBCs). Following
diagram illustrates the arrangement of components to measure oxygen saturation using PPG
probe.
Fig.4 Block diagram of New multimode PPG processing system(Medical and biological
engineering and computing,2012)
Fig3.PPGfor measuringtoe bloodpressure
6. Orientation effect has been demonstrated by recording pulsatile waveforms from dental pulp
and in a glass tube where volumetric changes should not possible and more recently by Nas
lund (2006) who detected pulsatile waveform in bone. As published by the K. Hamunen
(2012),photoplethysmographic pulse wave amplitude (PPGA) and heart rate (HR) can be
used to measure cold, nociception-induced autonomic responses. Principle states that
correlation between intensity of experimental pain to changes in physiological variables
represents the autonomic nervous system response to pain.
Fig 5. Changes in PPGA after 43°C and 48°C heat stimuli in 29 volunteers.
Thus,PPG based technology can be found in wide range of commercially available medical
devices for measuring oxygen saturation,blood pressure,cardiac output,assessing autonomic
function and also detecting peripheral vascular diseases.
Methods
Systematic arrangement of the electrical and optical components to build the complete
Infrared Photoplethysmography system (PPG) system is shown in following fig.6.
The complete circuitry consist of optical components, electrical filter building components
and digital display devices to analyse data.
7. Fig.6. Block diagram of the Infrared PPG system
Sensor: Photodetector used to detect the scattered light from IRED is silicon photodiode. It
works on the photoelectric effect and capable of converting light into current or voltage
depending on mode of operation. The photodetector used in this experiment is a 5.2 mm²
silicon photodiode with transimpedance amplifier in the form of a 8- pin TO99 metal
package.
(a) (b)
Fig.7. (a)Symbol and outlook of silicone photodiode
(b) Activation of diode by current source
I-V amplifier: Transimpedance amplifier is used in connection with the photo detector to
convert current generated by photodetector into voltage for further processing. Ideally it
should have low input impedance to prevent any large value of voltage. In this experiment we
have used 8- pin TO99 metal package as an I-V amplifier.
Fig.8. Transimpedance I-V amplifier in inverting configuration
8. Infrared emitter current driver circuit: It has been designed for constant current source
using input operational amplifier in non -inverting configuration (TL 084) and a series NPN
transistor. The output intensity is depends on forward current (40mA) flowing through
IRED.
Fig.9. IRED constant current source driver circuit
Ideal Operational amplifier is characterised by :
Parameter Ideal Op-amp Practical Op-amp
Calculations: Circuit was mounted on breadboard as indicated in fig. Voltage of 9V is
supplied with voltage source and voltage across R3 is taken as 5V assuming that voltage
divides following voltage divider circuit and remaining 4 V passed through the op-amp. By
Ohm’s law;
R3 = V3 / I3
=5/ (40*10^-3
9. R3 = 125 ohms
By potential divider circuit,
Voltage across R2; V2= (R1/R1+R2)*Vin
5V=(R1/R1+R2)*9V
.....(1)
Voltage acrossR1; V1=(R2/R1+R2)*Vin
4V= (R2/R1+R2)*9V .....(2)
Solving equations (1) and (2) simultaneously for R1 and R2 we get;
R1=2KOhms ; R2=2.5K Ohms
So by proper selection of resistor values ensures the current of 40 mA flowing through the
IRED which important for the further accurate performance.
Filter Design: A circuit capable of selectively filtering one frequency or range of
frequencies out of a mixture of different frequencies is called filters is designed. It only
allows the fundamental waveform frequency to pass through, blocking all higher frequencies.
Active filter built with active components such as transistors , op-amp with resistors and
capacitors where passive filter includes passive components as resistors , capacitors ,
inductors. Filters have been used to split the AC and DC component of the photodetector I-V
amplifier circuit.
Fig.10. Band PassFilter circuit design with active and passive components
10. 2-pole Low pass active Butterworth filter: Importance of this filter is to extract the AC
component from combined ACand DC PPG signal. Frequency response of filter is depends
on Gain /bandwidth product of the op-amp being used.
(a) (b)
Fig.11. (a) circuit designed for active low pass filter (b) frequency response
(http://www.electronics-tutorials.ws/filter/filter_8.html)
High pass passive filter: It is designed in order to block the DC component of the output.
Selection of resistor and capacitor determines the breakpoint frequency;
Calculations :
High pass filter: It is given that C1=2.2μF, R1= 150K Ohm,
Hence; cut –off frequency can be given as
fc= 1/ (1/ (2п*R1*C1)= 0.482 Hz
Cut-off frequency of high pass filter= 0.482 Hz
Low pass active filter:
Cut off frequency for low pass active filter is given by
fc= 1/2 𝜋RC
= 1/2 𝜋* 2.2Mohm*0.47uF= 0.15Hz
Cut off frequency of low pass active filter= 0.15Hz
11. 2-pole low pass Butterworth filter:
Cut off frequency is given by
fc = 1/(2 𝜋 √ 𝑅2𝑅3𝐶2𝐶3) = 19.40Hz
Cut-off frequency of low pass Butterworth filter = 19.40 Hz
Calculation of Gain of 2-pole low pass butterworth filter:
Gain = (R5 + R4 ) / (R5) = 1.57 dB
Gain of Butterworth 2 pole active low pass filter = 1.57 dB
Results: The complete circuit consists of current driver , I-V amplifier and band pass filters is
mounted on breadboard and supplied with corresponding values of voltages. Output is
observed on the two channel digital oscilloscope .
Fig. 12. Photograph of final circuit mounted on breadboard for PPG system
The readings of output voltage and corresponding frequency in Hz are noted to plot the
frequency response of the filter circuit as shown in fig.11.
IRED constant
currentdriver
PhotodetectorandI-V
amplifier
Highpass and 2 pole
ButterworthLow Passfilter ,
Active Low Pass filter
Amplifier designed for
10x amplification
12. Cut-off frequency is the frequency either above or below which power output of the circuit
has fallen to a given proportion of power in passband. Most frequently this proportion is one
half the passband power, also referred to as the 3 dB point since a fall of 3 dB corresponds
approximately to half power.
Cut off frequencies of band pass and low pass filters were found to be 0.459 Hz and 19.54 Hz
respectively. Output from the filter is appears to be small so it is made pass through amplifier
with gain 10 and amplified signal is sent to the oscilloscope. When the finger is placed in
between emitter and diode waveform shows peaks at definite intervals as follows
Fig.13. Typical PPG signal waveform observed on digital oscilloscope
Discussion: PPG signal has been successfully obtained and our findings are in correlation
with the previously published experimental measurements(Hertzman and Randall,1948).
Pulse wave can be characterised in two phases; anacrotic phase being rising edge of pulse
-8
-6
-4
-2
0
2
4
6
0 5 10 15 20 25 30 35 40
Gain(dB)
Frequency (Hertz)
Frequency Response
13. concerned with systole and catacrotic phase being falling edge of the pulse concerned with
diastole and wave reflections from periphery.(Hertzman and Spealman,1937).
Phtoplethysmograph can be useful to diagnose cardiovascular patients. It becomes a non-
invasive technique to measure relative blood volume changes in blood vessels close to
skin.PPG signal of 10 patients was recorded from ear lobe. Five of them were ill patients with
2-Atrial flutter ,3 Post mayocardial infarction and remaining 5 were normal. By spectral
analysis content of PPG signal found to be different for normal patient and subjects with
abnormalities.
(a) (b)
Fig.12. PPG signal for (a) Atrial flutter patient (b) Post Mayocardial infraction patient
It has shown that in normal subjects,PPG signal peaks coincide with the R peaks of ECG.This
result states PPG can act as indicator of cardiac activity and R-R interval variability in
abnormal subjects.
It is important to maintain the temperature of the finger at 31 °C while measuring the finger
PPG waveform . If temperature is less than 28°C to 30°C then false results may appear as
output , in such case finger is warmed in hot water.(P.Lanzer) Distance between emitter and
detector is maintained at 4 to 5mm as it provides best sensitivity in terms of detecting
adequately large pulsatile photoplethysmographic signals.(Mandelson and Ochs,1988).
Use of optical fibre for data communication can reduce noise level in output. However during
lab experiment, in electronic design of filter noise can be reduced by severe approaches such
as
Capacitive coupling – which proper selection of capacitor values
Avoiding grounding loops in circuit – this can be achieved by bringing all ground
wires to same potential in a ground bus
Twisted pair wiring – which reduces electromagnetic dramatically.
For proper selection of filters it is important to consider
14. Voltage and current that will pass through the filter
Frequency range specified to adequately reject all undesirable frequencies
Insertion loss determines degree of attenuation provided by filter
Pass-band impedance, capacitive – inductive input and output.
Thus , by considering ambient temperature effects in addition to motion artefacts more
precise PPG signal can obtained followed by accurate signal conditioning.
15. References
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