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Auscultation methods - stethescope and phono cardio gram

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  1. 1. Auscultation Techniques • There are optimal recording sites for the various heart sounds.
  2. 2. Auscultation Techniques… • Heart sounds and murmurs have extremely small amplitudes with frequencies from 0.1 to 2000 Hz. • Thus the recording device must be carefully selected for wide band frequency response characteristics. • Specially designed acoustically quiet environment is needed for noise free recording of heart sounds.
  3. 3. Stethoscope • Mechanical stethoscopes amplifies sound because of Standing wave phenomenon. • Firm application of the chest piece makes the diaphragm taut with pressure thereby causing an attenuation of low frequencies. • Loose-fitting earpiece cause leakage which reduces the coupling between the chest wall and the ear. • Electronics stethoscopes has selectable frequency response characteristics ranging from “ideal” flat-response to selectable band- pass response.
  4. 4. Stethoscope Frequency response
  5. 5. Phonocardiogram • A Phonocardiogram is a recording of the heart sounds and murmurs. • Eliminates subjective interpretation of the heart sounds • Enables evaluation of the heart sounds and murmurs with respect to the electric and mechanical events in the cardiac cycle. • Evaluation of the result is based on the basis of changes in the wave shape and various timing parameters.
  6. 6. Phonocardiogram
  7. 7. Frequency spectrum of a typical Phonocardiogram