Saumya Mohan Kumar Phonocardiography Index Pioneers in auscultation

Saumya Mohan Kumar Phonocardiography

Index Pioneers in auscultation Development of Stethoscope Development of Phonocardiograph Heart sounds Heart Murmurs Basic Block Diagram and Instrumentation Acquisition of phonocardiographic signals Writing methods for phonocardiography Pros and Cons Scope Echocardiography vs. Phonocardiography Case Study Phonocardiography

Pioneers Hippocrates laid the foundation for auscultation Robert Hook realized diagnostic use of cardiac auscultation Biggest breakthrough in auscultation: Rene Laennec invented stethoscope Dr. Jean Bennett Maguire devised a method of real-time spectral phonocardiography for the detection and classification of heart murmurs. Phonocardiography

Way to heart is through ears…. Development of Stethoscopes Early monaural stethoscope Modern binaural stethoscope Modern electronic stethoscope Phonocardiography

Working Acoustic stethoscopes transmit sound mechanically from a chestpiece via air filled hollow tubes to the listener's ears. The diaphragm and the bell work as two filters, transmitting higher frequency sounds and lower frequency sounds, respectively. Electronic stethoscopes function in a similar way, but the sound is converted to an electronic signal which is transmitted to the listener by wire. Functionalities often included in electronic stethoscopes are amplification of the signal, filters imitating the function of the diaphragm and the bell and in some cases recording abilities to allow storage of data. Phonocardiography

Advantages Allow volume control of heart and lung sounds heard more easily without amplifying other sounds. Even subtle changes in breath sounds can be picked up and magnified Aid health-care professionals in hearing heart murmurs Electronic stethoscopes also allow the user to distinguish between body sounds of high and low frequency. They now have wireless capabilities, which allow data to be transferred to a computer or handheld device for storage and retrieval at a later time. Phonocardiography

Disadvantages Patients undergoing surgery have the sterile field invaded thereby risking infection Patients are frequently awakened and disturbed Serious developmental abnormalities in newborn infants who are frequently disturbed In the absence of airtight seal between stethoscope and skin, which determines the quality of sound wave transmission, background noise is detected and physiologic sound transmission is impaired. They are not capable of generating constructive interference of physiologic sound waves. Phonocardiography

Phonocardiograph- an intelligent Stethoscope Bioacoustic research Establish a relationship between mechanical event- conduction of heart- within the body and the sounds these events give rise to. The medical use of this knowledge is to link sounds that diverge from normality to certain pathological conditions. Phonocardiography

Phonocardiograph: Instrument used for recording sounds connected with the pumping action of heart Phonocardiography

Phonocardiogram: A high fedility recording representing the rhythmicity and heart rate Phonocardiography

Phonocardiography: the process of graphical recording of heart sounds or murmurs Phonocardiography

Heart Sounds Mechanical working processes of the heart produce sound which indicate health status of the individual. The relationship between blood volumes, pressures and flows within the heart determines the opening and closing of the heart valves. Normal heart sounds- lub and dub- occur during the closure of the valves. The valvular theory states that heart sounds emanate from a point sources located near the valves. In the cardiohemic theory the heart and the blood represent an interdependent system that vibrates as a whole and propagates sound as waves of alternate pressure. Phonocardiography

First heart sound: - occurs when the atrioventricular (AV) valves close at the beginning of ventricular contraction. - generated by the vibration of the blood and the ventricular wall - is louder, longer, more resonant than the second heart sound. Phonocardiography

First Heart Sound Initial vibrations occur when first contraction of ventricle move blood towards atria, closing AV valves Abrupt tension of closed AV valves, decelerating the blood Oscillation of blood between root of aorta and ventricular walls Phonocardiography Vibrations caused by turbulence in ejected blood flowing into aorta

Second heart sound - occurs when aortic and pulmonary semilunar valves close at the beginning of ventricular dilation - generated by the vibration of the blood and the aorta - Aortic valve closes slightly before pulmonary valve. Phonocardiography

The second sound (S 2) signals the end of systole and the beginning of diastole It is heard at the time of the closing of the aortic and pulmonary valves S 2 is probably the result of oscillations in the cardiohemic system caused by deceleration and reversal of flow into the aorta and the pulmonary artery Phonocardiography

A third heart sound (S 3) connected with the diastolic filling period. The rapid filling phase starts with the opening of the semilunar valves. attributes energy released with the sudden deceleration of blood that enters the ventricle throughout this period A fourth heart sound (S 4) connected with the late diastolic filling period occur during atrial systole where blood is forced into the ventricles. Phonocardiography

Basic Heart Sounds in a Phonocardiogram Recording Phonocardiography

Heart murmurs Murmurs are extra heart sounds that are produced as a result of turbulent blood flow which is sufficient to produce audible noise. Innocent murmurs are present in normal hearts without any heart disease. Pathologic Murmurs are as a result of various problems, such as narrowing or leaking of valves, or the presence of abnormal passages through which blood flows in or near the heart. Heart murmurs occur when the blood flow is accelerated above the Reynolds number, which induces non-stationary random vibrations, that are transmitted through the cardiac and thoracic tissues up to the surface of the thorax They are graded by intensity from I to VI. Grade I is very faint and heard only with special effort Grade VI is extremely loud and accompanied by a palpable thrill Phonocardiography

Factors involved in production of murmurs Heart Murmurs High rate of flow through valves Flow through constricted valves (stenosis) Backward flow through incompetent valve Septal defects Phonocardiography Decreased viscosity, which causes increased turbulence

Heart Cycle Events Name Pressure (k. Pa) 20 15 10 5 0 PCG ECG Time 0 0. 4 Phonocardiography 0. 8

Basic Block Diagram Phonocardiography

Instrumentation Basic transducer • • Amplifier • • Filter • • • Piezoelectric sensor to convert sound or vibrations to electricity Crystal or moving coil microphone having frequency response between 5 Hz and 1000 Hz Similar response characteristics Offer selective high pass filter to allow frequency cutoff Bandwidth : 20 - 2000 Hz Amplify signal Permit selection of suitable frequency bands Avoid aliasing Separate louder low frequency signals from lower intensity, much informative high frequency murmurs. Phonocardiography

Integrator Power Amplifier • Recording envelope of higher frequency over 80 Hz along with actual signals below 80 Hz. • Increase the power of incoming signal Efficiency is more Effect of noise is lowered • • DAC and Readout or high frequency chart recorder or oscilloscope or headphones • • Signal is converted to digital form and stored permanently For faithful recording of heart sounds Phonocardiography

Sensors used when recording sound: Microphones Accelerometers These sensors have a high-frequency response that is quite adequate for body sounds. The microphone is an air coupled sensor that measure pressure waves induced by chest-wall movements The accelerometers are contact sensors which directly measures chestwall movements For recording of body sounds, condenser microphones piezoelectric accelerometers have been recommended. Phonocardiography

Acquisition of Phonocardiographic Signals Microphones picks up (i). Heart sounds (ii). Heart murmurs (iii). Extraneous noise in the immediate vicinity of the patient Group 1(i). Contact microphone (ii). Air coupled microphone Group 2(i) Crystal microphone (ii) Dynamic microphone Phonocardiography

Group 1 Microphones § Contact Microphone also known as a pickup or a piezo microphone made of a thin piezoelectric ceramic round disc (+ve) glued to a thin brass or alloy metal disc (ve) designed to transmit audio vibrations through solid objects. contact mics act as transducers which pick up vibrations and convert them into a voltage which can then be made audible. Phonocardiography

Group 1 Microphones § Air coupled Microphones shows a low-pass frequency response because of its airchamber compliance. In the pass band, it is considered that the microphone has a flat response, where the mechanical impedance of air chamber is much higher than that of chest wall, the vibration of the measured chest-wall surface is stopped by both the air chamber and the coupler surface in contact with the chest wall. The sound pressure, or normal stress exerted on the chamber should be constant to keep a flat response. Phonocardiography

Group 2 Microphones § Crystal Microphones uses the piezoelectric effect of Rochelle salt, quartz, or other crystalline materials. This means that when mechanical stress, due to heart sounds, is placed upon the material, a voltage electromagnetic force is generated. Since Rochelle salt has the largest voltage output for a given mechanical stress, it is the most commonly used crystal in microphones. smaller in size, more sensitive than dynamic ones Phonocardiography

a crystal is mounted so that the sound waves strike it directly a diaphragm that is mechanically linked to the crystal so that the sound waves are indirectly coupled to the crystal. Phonocardiography

Group 2 Microphones § Dynamic Microphones consists of a moving coil with fixed magnetic core inside. This moving coil moves with heart sounds, and produces voltage because of its interaction with magnetic flux Phonocardiography

Technical design of Microphone It does not transform acoustic oscillations into electrical potentials uniformly for all frequencies. Hence heart sound recording done with microphone is valid for a particular type of frequency only. . Hence microphones of various types cannot be interchanged. Phonocardiography

Writing methods for phonocardiography Requires a writing system capable of responding to 2000 Hz. Types of writing methods: (i). Mechanical Recorders (ii). Optical Galvanometric Recorders (iii). Envelope detection (iv). Direct recording using Ink Jet Recorders (v). Electrostatic Recorder (vi). Thermal Recorder Phonocardiography

Ink Jet Recorders Merits very little loss of diagnostically important information eliminates the effort and delay of photographic processing immediacy of the results affords a means for continuously monitoring the records for quality and special content at the time of registration. Demerits writing recorders with an upper frequency response of 150 Hz cannot be used to write frequencies that lie beyond their working range. can only record heart sound intensity picked up every 10 msec. Phonocardiography

Envelope Detection Uses artificial frequency of about 100 Hz in heart sound amplifier Employed to oscillate stylus so that high frequency sounds are modulated by 100 Hz Phonocardiography

Pros Can provide real-time traces of heart beats, movement and breathing. Taken together this can provide a unique view of cardiac condition. Passive, therefore inherently safe and can be used for long periods. Inherently cheap, (low data rates), and ideal for screening of large populations and home monitoring. simple, low cost, houses the necessary opto-electronic elements. and non-invasive PCbased system that is capable to process real time fetal phonocardiographic signal Cons Existing microphones are bulky and obtrusive Signal to noise ratio influenced motion artifacts Inherently 1 dimensional Extended instruments are intended for a pass band from 0. 2 to 100 Hz with nonlinear distortions to 10%. Recording of frequency components above this limit is related with an appreciable drop in amplitude of recording and an increase in distortions. The use of contacting transducers to sense the vibrations is inappropriate. Phonocardiography

Scope ü Further Work 1. Design of clinical prototype 2. Improvements to signal conditioning and control electronics 3. Investigate wireless links for cordless monitoring 4. Remote measurement of small displacements at compliant surfaces ü Suggested Applications Remote sensing of sub 50 micron displacements Adult and fetal phonocardiography and phonography Remote measurements of compliant materials in wind-tunnels Infrasound intensity measurement Biomedical instrumentation Low-cost and low power confocal microscopy Cell culture measurement Phonocardiography

The two not alternative, and the less contradictory, but mutually supplementing methods. Echocardiography Phonocardiography ü better diagnosis of mitral valve defects , evaluating the degree of its stenosis and characterizing the morphological changes of the valve. ü better diagnosing of mitral insufficiency, diagnosis of aortic valve defects ü more informative about tricuspid valve defects ü more informative about state of aortic valves ü echocardiographic data on the changes in the left ventricular outflow tract help to explain the origin of the spindle-form systolic murmur. ü interpretation of systolic murmur was rather complicated, although they are often seen on phonocardiographic data of normal individuals and patients with heart diseases. Phonocardiography

Case Study Phonocardiography

Phonocardiography