This document discusses various biomedical recorders used to measure electrical signals from the body. It focuses on electrocardiography (ECG) which measures the heart's electrical activity, and phonocardiography (PCG) which records heart sounds. For ECG, it describes the typical waveform, applications in diagnosis, and 12-lead measurement setup. For PCG, it explains the different heart sounds recorded, microphones used, writing methods, medical applications in detecting murmurs and valvular lesions, and special applications including fetal and esophageal PCG.

1. BIOMEDICAL RECORDERS
R.GOWRI
ASSISTANT PROFESSOR/ECE
KIT-KALAIGNAR KARUNANIDHI INSTITUTE OF TECHNOLOGY
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2. What are biopotentials
Biopotential:
 An electric potential that is measured between points in living cells, tissues, and
organisms, and which accompanies all biochemical processes.
 Also describes the transfer of information between and within cells
 This book focuses strictly on the measurement of potentials
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3. 3

4. Electrocardiography (ECG)
 Measures galvanically the electric activity of the heart
 Well known and traditional, first measurements by
Augustus Waller using capillary electrometer (year 1887)
 Very widely used method in clinical environment
 Very high diagnostic value
1. Atrial
depolarization
2. Ventricular
depolarization
3. Ventricular repolarization
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5. ECG basics
 Amplitude: 1-5 mV
 Bandwidth: 0.05-100 Hz
 Largest measurement error sources:
 Motion artifacts
 50/60 Hz powerline interference
 Typical applications:
 Diagnosis of ischemia
 Arrhythmia
 Conduction defects
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6. ECG
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 Electrical activity of heart.
 Used in catheterization laboratories, coronary care
units and routine diagnostic applications in
cardiology.
 LEAD – Two electrodes are placed over different
areas of the heart, the resulting tracing of voltage
difference at any sites due to electrical activity of
heart.

7. EFFECTS OF ARTIFACTS
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 Interference from the power line
 Shifting of the baseline
 Muscle tremor

8. Vectorcardiogram (VCG or EVCG)
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 Instead of displaying the scalar amplitude (ECG
curve) the electric activation front is measured and
displayed as a vector
 It has amplitude and direction
 Diagnosis is based on the curve that the point of this
vector draws in 2 or 3 dimensions
 The information content of the VCG signal is roughly
the same as 12-lead ECG system. The advantage
comes from the way how this information is
displayed
 Increase in sensitivity
 A normal, scalar ECG curve can be formed from this
vector representation, although (for practical
reasons) transformation can be quite complicated

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 Display in 2 perpendicular axis
 Loop type pattern
 Provides direction of depolarization and
repolarization of atria and ventricle
 3 loops – P wave,QRS axis(high amp – predominate
and T wave.
 3 images – frontal,sagittal and transverse planes.
 Recognition of undetected atrial and ventricular
hypertrophy, myocardial infraction.
CONT…

10. 12-Lead ECG measurement
 Most widely used ECG measurement setup in clinical environment
 Signal is measured non-invasively with 9 electrodes
 Lots of measurement data and international reference databases
 Well-known measurement and diagnosis practices
 This particular method was adopted due to historical reasons, now it is already
rather obsoleteEinthoven leads: I, II & III Goldberger augmented leads: VR, VL & VF Precordial leads: V1-V6

11. CONT..
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12. PCG
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 Graphic record heart sound - Phonogram.
 Recording the sounds connected with the pumping
action of heart.
 Sound from heart – phonocardiogram
 Instrument to measure this – phonocardiograph
 Basic function – to pick up the different heart
sound,filter the required and display.
 Two categories –
 heart sound – transient characteristics with short
duration.(closing and opening of valves)
 murmurs – noisy characteristics with long
duration.(turbulent blood flow in heart)

13. Origin of sound
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 Valve closure
 Movement of heart wall
 Valve opening
 Extra cardiac sounds
1. Frequency – 10 to 1000 Hz.
LOW RANGE – 10 – 60 Hz(3rd and 4th)
MEDIUM RANGE – 60 – 150 Hz(1st and 2nd)
HIGH RANGE – 150 – 1000 Hz
2.Amplitude
3.Quality

14. Origin of sound
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 1st sound:
Closure of mitral and tricuspid valves.
Freq – 30 to 100 Hz and duration 50 to 100 ms
 2nd sound:
Closure of aortic and pulmonary valves(slight back
flow of blood).
Freq – 30 to 100 Hz and duration 25 to 50 ms .
 3rd and 4th low intensity and inaudible.(heard among
children).

15. Origin of sound
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 3rd sound:
Blood rapid movement into relaxed ventricular
chambers
Freq – 10 to 100 Hz and duration 0.04 to 0.08 s.
 4th sound:
atrial contraction.
Freq – 10 to 50 Hz and duration 0.03 to 0.06 s.

16. CONT..
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 Microphones for PCG:
Crystal microphone – contains wafer of piezo-
electric material, which generates potentials when
subjected to mechanical stresses due to heart sound.
Smaller in size, high sensitivity.
Dynamic microphone – consists of a moving coil
having a fixed magnetic core inside it. The coil moves
with the heart sound and produce a voltage because
of interaction with the magnetic flux.
New acoustic sensors – polymer based adherent
differential-output sensors.

17. Writing methods
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 Light beam galvanometer – expensive and require
more power from amplifiers when used for high freq.
 Direct writing recorders – upper freq 150 Hz.(used
for only low freq).
 Technique – envelope detection.
Fans, Air conditioners and other noise producing
gadgets will result in artefacts on the recordings.

18. Heart Sounds
 S1 – onset of the ventricular contraction
 S2 – closure of the semilunar valves
 S3 – ventricular gallop
 S4 – atrial gallop
 Other – opening snap, ejection sound
 Murmurs
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19. RECORDING SET - UP
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CONDENSE
R
MICROPHO
NE
ECG AMP
ECG
ELECTRODE
FILTER
PHONO
AMPLIFIER
FM TAPE
RECORDER
MONITOR
SCOPE

20. MEDICAL APPLICATION
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 Rheumatic valvular lesions
Allergic disease in which the heart valves are likely to be damaged. This creates
abnormal heart sound.
 The murmurs of aortic steonosis
The blood is ejected from the left ventricles through a small opening of aortic
valve. High pressure 350 mm of Hg and causes turbulent flow of blood.
 The murmurs of aortic regurgitation
During diastole, blood flow backward from aorta to left ventricles,causing a
blowing murmur.
 The murmurs of mitral regurgitation
During systole, blood flow backward through mitral valve.
 The murmurs of mitral steonosis
It produce murmurs when,Blood passes with difficulty from LA into the LV
due to pressure difference.

21. SPECIAL APPLICATION OF PCG
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 Fetal PCG
 Esophageal PCG
 Tracheal PCG - Cannula

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