BM8601 – DIAGNOSTIC & THERAPEUTIC EQUIPMENTS.pptx

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1. BM8601 – DIAGNOSTIC & THERAPEUTIC EQUIPMENTS

2. UNIT 1 CARDIAC EQUIPMENT INTRODUCTION.. ECG- Electrocardiograph The electrocardiograph (ECG) is  an instrument that records surface potentials associated with the electrical activity of the heart . The surface potentials are conducted to the instrument by metal contacts called electrodes which are fixed to various parts of the body.

3. NORMAL WAVE

4. EXPLANATION… Normal rhythm produces four entities – a P wave, a QRS complex, a T wave, and a U wave – that each have a fairly unique pattern. The P wave represents atrial depolarization. The QRS complex represents ventricular depolarization. The T wave represents ventricular repolarization. The U wave represents papillary muscle repolarization.

5. ABNORMAL ECG WAVES

6. Heart rate monitor Heart Rate: beats/min-The number of heart beats per unit of time.-The heart rate is based on the number of contraction of the ventricles . Derived by measuring either the average or instantaneous time intervals between two successive ‘R ’

7. Contd Pulse rate : is a measurement of heart rate • As the heart pushes blood through the arteries, the arteries expand and contract with the flow of blood . • Pulse Rate –Heart rate , heart rhythm.

8. Techniques to Calculate H.R Average Calculation Beat to Beat Calculation Combination of both

9. Average Calculation Oldest and most popular technique Average rate calculated –by counting the number of pulses in a given time Disadvantage :- does not show changes in time between beats-does not represent the hearts response to exercise, stress and environment .

10. Beat to Beat Calculation Done by measuring the time (T) in seconds b/w two consecutive pulses and converting this time into beats/min . HR = 𝑏𝑒𝑎𝑡𝑠𝑚𝑖𝑛= 60 𝑇 Accurately represents heart condition .

11. Combination of both Based on a four or six beats average . Advantage over Average Calculation-similarity with beat to beat method . Normal H.R measuring range-0-250 bpm .-Sensors : Limb or chest ECG

12. Types Of Heart Rate Monitors Average Heart Rate Meters Instantaneous Heart Rate

13. Average HRM The heart rate meters are a part of patient monitoring systems . Usually average reading types . Convert each ‘R’ wave or ECG into a pulse of fixed amplitude and duration . The determine the average current from these pulses . Specially designed with frequency to voltage converter (FVC ). FVC to display the average heart rate interms of beats/min.

14. Instantaneous Heart Rate Meters Facilitates the detection of arrhythmias and permits timely observation of incipient cardiac emergencies. Calculation of H.R from ECG is based on reliable detection of QRS complex Sensitive to artifacts and causes false alarm. QRS matched filters can be used. QRS matched filters: 15 sample –FIR whose response shape approximates the shape of a normal ‘QRS’ complex. Maximum absolute o/p when similarity shaped waveforms are

15. exp ,…. ECG is sampled every 2ms. Two adjacent 2ms samples are averaged resulting in 4 ms samples. 30Hz IIR Butter- worths filter –to remove high frequency components of the signal-improves the 8ms samples. 1.25Hz HPF –to remove any dc offset with the signal. Clamped and filtered ECG waveform is finally passed through a QRS matched filter. Beat detector recognizes QRS complexes in the processed ECG waveform value.

16. Contd … If the value exceeds the threshold value, a heart beat value, a heart beat is counted. Averaged beats is used to -calculate the heart rate for display, -alarm limit comparison-trending and recorder annotation Threshold automatically adjusted depending upon the value of the QRS wave amplitude and the time interval between the QRS complexes. Following each beat aninhibitory period of 200 ms is introduced during which no heartbeat is detected. Reduces the possibility of ‘T’ wave being counted.

17. phonocardiocraphy A  phonocardiogram  (or  PCG ) is a plot of  high-fidelity   recording of the   sounds  and  murmurs  made by the  heart  with the help of the machine called the  phonocardiograph ; thus,  phonocardiography  is the recording of all the sounds made by the heart during a  cardiac cycle ..

18. WAVEFORM