Phonocardiography(PCG)

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.

1. PHONOCARDIOGRAPHY (PCG) Ms.P.NISHANTHI Assistant Professor/ Department of ECE KIT- Kalaignarkarunanidhi Institute of Technology

2. PCG 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) MEDICAL ELECTRONICS - MV/AP/ECE 2

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

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

5. 3 rd sound: Blood rapid movement into relaxed ventricular chambers Freq – 10 to 100 Hz and duration 0.04 to 0.08 s. 4 th sound: atrial contraction. Freq – 10 to 50 Hz and duration 0.03 to 0.06 s. MEDICAL ELECTRONICS - MV/AP/ECE 5

6. 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. MEDICAL ELECTRONICS - MV/AP/ECE 6

7. Writing methods 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. MEDICAL ELECTRONICS - MV/AP/ECE 7

8. 8 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 MEDICAL ELECTRONICS - MV/AP/ECE

9. RECORDING SET - UP MEDICAL ELECTRONICS - MV/AP/ECE 9 CONDENSER MICROPHONE ECG AMP ECG ELECTRODE FILTER PHONO AMPLIFIER FM TAPE RECORDER MONITOR SCOPE

10. Amplifiers used to process biopotentials are called biopotential amplifier. Biopotential Signals (e.g., ECG, EMG, EEG, EOG, … etc .) The basic function of biopotential amplifier is to increase the amplitude of a weak electric signal of biological origin. Biopotential amplifiers typically process voltages, but in some cases they also process currents. The frequency response of typical bioelectric amplifiers may be from dc (or near dc, i.e., 0.05 Hz) up to 100 kHz. Biopotential Amplifier

11. Some biopotential amplifiers are ac-coupled, while some are dc-coupled. The dc-coupling is required where input signals are clearly dc or changes very slowly. At frequencies as low as 0.05Hz, the ac-coupling should be used instead of dc-coupling. This is to overcome the electrode offset potential. Also, the skin-electrode interface generates dc offsets. The gain of biopotential amplifiers can be low, medium or high (x10, x100, x1000, x10000). Cont…

12. Gain factors x1 and x10 . The unity-gain amplifier is mainly for isolation, buffering and possibly impedance transformation between signal source and readout device. Used for measurement of action potentials and other relatively high-amplitude bioelectric events. Low Gain Biopotential Amplifier

13. Gain factors x100 and x1000. Used for recording of ECG waveforms and muscles potentials (EMG), etc. Medium Gain Biopotential Amplifier

14. Gain factors over x1000. Used in very sensitive measurement such as recording of brain potentials (EEG). High Gain Biopotential Amplifier

15. Body Surface Recording Electrodes Metal Plate Electrodes (historic) Suction Electrodes (historic interest) Floating Electrodes Flexible Electrodes Electrode metal Electrolyte Think of the construction of electrosurgical electrode And, how does electro-surgery work?

16. Commonly Used Biopotential Electrodes Metal plate electrodes Large surface: Ancient, therefore still used, ECG Metal disk with stainless steel; platinum or gold coated EMG, EEG smaller diameters motion artifacts Disposable foam-pad: Cheap! (a) Metal-plate electrode used for application to limbs. (b) Metal-disk electrode applied with surgical tape. (c)Disposable foam-pad electrodes, often used with ECG

17. Commonly Used Biopotential Electrodes Suction electrodes No straps or adhesives required precordial (chest) ECG can only be used for short periods Floating electrodes metal disk is recessed swimming in the electrolyte gel not in contact with the skin reduces motion artifact Suction Electrode

18. Double-sided Adhesive-tape ring Insulating package Metal disk Electrolyte gel in recess (a) (b) (c) Snap coated with Ag-AgCl External snap Plastic cup Tack Plastic disk Foam pad Capillary loops Dead cellular material Germinating layer Gel-coated sponge Commonly Used Biopotential Electrodes Floating Electrodes Reusable Disposable

19. (a) Carbon-filled silicone rubber electrode. (b) Flexible thin-film neonatal electrode. (c) Cross-sectional view of the thin-film electrode in (b). Commonly Used Biopotential Electrodes Flexible electrodes Body contours are often irregular Regularly shaped rigid electrodes may not always work. Special case : infants Material : - Polymer or nylon with silver - Carbon filled silicon rubber (Mylar film)

20. Internal Electrodes Needle and wire electrodes for percutaneous measurement of biopotentials (a) Insulated needle electrode. (b) Coaxial needle electrode. (c) Bipolar coaxial electrode. (d) Fine-wire electrode connected to hypodermic needle, before being inserted. (e) Cross-sectional view of skin and muscle, showing coiled fine-wire electrode in place. The latest: BION – implanted electrode for muscle recording/stimulation Alfred E. Mann Foundation

21. Fetal ECG Electrodes Electrodes for detecting fetal electrocardiogram during labor, by means of intracutaneous needles (a) Suction electrode. (b) Cross-sectional view of suction electrode in place, showing penetration of probe through epidermis. (c) Helical electrode, which is attached to fetal skin by corkscrew type action.

22. MEDICAL APPLICATION 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. MEDICAL ELECTRONICS - MV/AP/ECE 22

23. SPECIAL APPLICATION OF PCG Fetal PCG Esophageal PCG Tracheal PCG - Cannula MEDICAL ELECTRONICS - MV/AP/ECE 23

24. Thank you