Defibrillator.pptx. Jei3j

This is ppt made for biomedical engineering students

1. UNIT OUTCOME 3 N ee d o f d e f i b ril l a t o r D C D e f i b r i ll a t o r AED (advisory external defibrillator ) I m p l a n t a b l e D e f i b r i ll a t or D e f i b r i ll a t or e l e c t r ode s

2. Conducting system of heart

3. VENTRICULAR FIBRILLATION

4. Need of defibrillator Life-threatening cardiac arrhythmias specifically ventricular fibrillation (V-Fib) and non-perfusing ventricular tachycardia (V-Tach). Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults – is called tachycardia, and a resting heart rate that is too slow – below 60 beats per minute – is called bradycardia. Ventricular fibrillation (V-fib or VF) is an abnormal heart rhythm in which the ventricles of the heart quiver. It is due to disorganized electrical activity. Ventricular fibrillation results in cardiac arrest with loss of consciousness and no pulse. This is followed by sudden cardiac death in the absence of treatment. Ventricular fibrillation is initially found in about 10% of people with cardiac arrest. Ventricular tachycardia (V-tach or VT) is a fast heart rate arising from the lower chambers of the heart.Although a few seconds of VT may not result in permanent problems, longer periods are dangerous; and multiple episodes over a short period of time are referred to as an electrical storm. lightheadedness , palpitations, or chest pain. Ventricular tachycardia may result in ventricular fibrillation (VF) and turn into cardiac arrest. It is found initially in about 7% of people in cardiac arrest.

5. NEED OF DEFIBRILLATOR Ventricular fibrillation is serious cardiac emergency resulting from asynchronous contraction of heart muscle. This uncoordinated movement of ventricle walls of the heart may result from electric shock or from abnormalities of body chemistry. Main problem of fibrillation is continuously stimulation of adjacent cells of heart muscle fibers. So there is no synchronized succession of events that follow heart action. This Fibrillation leads to loss of cardiac output and irreversible brain damage or death if not reversed within 5 minutes of onset Ventricular fibrillation can be converted into more efficient rhythm by applying a high energy shock to the heart. This sudden surge across the heart cause all muscle fibers to contract simultaneously ,possibly the fibers then respond to normal physiological intrinsic pulse.

6. What is Cardioversion Defibrillator is a device that deliver a therapeutic dose of electrical energy (electric shock) to the affected heart (fibrillated heart or other shockable rhythm) to force the heart to produce normal cardiac rhythm. It is any process that aims to convert an arrhythmia back to sinus rhythm by therapeutic dose of electrical energy Unlike defibrillation, which is used in cardiac arrest patients, synchronized cardioversion is performed on patients that still have a pulse What is defibrillator

7. Defibrillator

8. CARDIO VERSION

9. DEFIBRILLATION VS. CARDIO VERSION

10. WHAT IS DEFIBRILLATOR

11. MANUAL DEFIBRILLATOR

12. HOW DEFIBRILLATOR IS USED

13. DC DEFIBRILLATOR V ar i able A u to tr an s form e r T1: Forms primary of high voltage of transformer T2. T1 variable autotransformer is usually designed with a significant number of primary windings to produce a secondary voltage for T2 which can be adjusted from a few volts Auto transformers ensure a consistent linear regulation of AC voltage to provide high output and negligible waveform distortion. Step-up transformer T2: It forms secondary of variable auto transformer T2. A transformer transfers power from the primary coil to the secondary coil. Since the power must stay the same, if the voltage increases, the current must decrease. (P=VI) Diode Rectifier: The output voltage of the transformer is rectified and is connected to vacuum type high voltage change-over switch. It converts an alternating current into a direct one by allowing a current to flow through it in one direction only.

14. DC DEFIBRILLATOR Switch: It is a vacuum type high voltage change over switch. Its one end is connected to Diode rectifier at 1 and another to one end of an oil-filled 16 micro-farad capacitor. In position A the capacitor charges to a voltage set by the positioning of the auto transformer. When the high voltage switch changes over the position 2, the capacitor is discharged across the heart through the electrodes. Capacitor: Oil filled 16 micro farad capacitor is used. During transthoracic defibrillation an energy storage capacitor is charged at relatively slow rate in order of seconds by means of step-up transformer and then delivered rapid rate in order of milliseconds to the chest of the patient. Inductor: The rapid discharge rate impairs (weaken/damage) the contractibility of ventricles. To overcome it , a current limiting inductor is inserted in series with the patient circuit. The inductor slows down the discharge from the capacitor by the induced counter voltage. This gives the output pulse a physiologically favorable shape.

15. DC DEFIBRILLATOR T2 T1

16. Block Diagram of DC defibrillator POWER SUPPLY CHARGING CIRCUIT ENERGY STORAGE WAVEFORM SHAPING CHARGE CONTROL DISCHARGE CONTROL AC POWER SOURCE USER INPUT TO PATIENT PADDLE

17. Energy: E=1/2 CV 2 C= 16 microfarad E= 400 Ws V= 7000V with load resistance 50-200 ohms For internal defibrillation E= 100Ws with load resistance 25-50 ohms Most of the defibrillator will deliver between 60% and 80% of their stored energy to a 50 ohms load.

18. The sha p e of the wavefo r m th a t appears across electrodes will depend on the va l u e of c a p a c i tor a nd t h e inductor used in the circuit (100mH) . The discharge resistance which patient represents for the defibrillating pulse may be regarded as purely 50 to 100 ohms with electrode size 80cm2. The most common waveform utilized in the RLC circuit employs an under damped response with damping factor less than unity. This particular waveform is called as Lown waveform. This waveform is more or less of an oscillatory character, with both positive and negative portions. LOWN WAVEFORM

19. MONOPHASIC VS BIPHASIC DEFIBRILLATION Terms M o n o p hasi c De f ib r i l la t ors B i p has i c De f i b ri ll a t o r s Definition The type waveform formed during this process where the shock gets delivered to the heart with the help of just one vector and hence gets the name. The type waveform formed during this process where the shock gets delivered to the heart with the aid of two vectors and hence gets the name. Usage Different life-threatening cardiac dysrhythmias and ventricular fibrillation. Various life-threatening cardiac dysrhythmias and ventricular fibrillation. Devices Implantable Defibrillators detects the irregular heart rate. External Defibrillators moves the high-level values without any problems Nature Most common used process. Most common available process. Energy On a monophasic defibrillator, this is usually 360 joules. On a biphasic defibrillator, this is usually between 120 joules to 200 joules.

20. DC DEFIBRILLATOR

21. IMPLANTABLE DEFIBRILLATOR

22. IMPLANTABLE DEFIBRILLATOR The use of automatic implantable defibrillator (AID) is recommended for patients who are at high risk for ventricular fibrillation. It used integrated circuits to reduce the device size. It has enhancing functionality of the device. It has ability to store recording of the patient’s heart signals and collects extensive therapy history and diagnostic data files. This device is hermetically (airtight) sealed, biocompatible, and able to survive a temperature range of -30 degree Celsius to 60 degree Celsius. This device allows the physician to non-invasively program it. It has sophisticated algorithms for rhythm classification and storage of patient’s heart signal.

23. IMPLANTABLE DEFIBRILLATOR An implantable defibrillator is continuously monitors a patient’s heart rhythm. If the device detects fibrillation, the capacitor within the device are charged up to 750 V . The capacitor then discharged into the heart which mostly represents a resistive load of 50 ohm and to bring the heart into normal rhythm. The shock duration is approximately 4-8 ms which results in the delivery of approximately 30-35 J at 750 volts. Implantable defibrillator system have main system component: AID The Lead system The programmer recorder/monitor (PRM) Pulse generator Battery

24. IMPLANTABLE DEFIBRILLATOR SYSTEM ARCHITECTURE AID LEAD SYSTEM PULSE GENERATOR BATTERY

25. IMPLANTABLE COMPONENTS AID It houses the power source , sensing, defibrillation, pacing and telemetric communication system. The lead system provides physical and electrical connection between the defibrillator and the heart tissue. The PRM communicates with the AID and allows the physician to view status information and modify the function of the device as needed. Leads The defibrillating high energy pulse is delivered to the heart via 6cm*9cm titanium mesh patch with electrodes placed directly on the surface of heart. Electrode is placed invasively through leads screwed in the heart. Leads are used for defibrillating and sensing.

26. IMPLANTABLE COMPONENTS Programmer Recorder/Monitor (PRM): The PRM is an external device that provides a bidirectional communications link to an implanted AID. A telemetry link is established between PRM and AID. Telemetry channel is used to retrieve real time and stored intracardiac ECG, therapy history, battery status and other information. It allows the programmer to change the algorithm as per the require for patients abnormality. Pulse generator: It has a microprocessor which controls overall system functions. ROM provides non-volatile memory for system start-up task and some program space RAM is r equi r ed f or st o rage o f ope r a t ing par a m e t ers and st o rage of electrocardiogram data. System Control supports the circuitry of microprocessor like a telemetry interface, t y p i c a l l y i m pl e me n ted w ith a UA R T - li k e (univers a l as y nch r onous receiver/transmitter) interface and general purpose timers.

27. IMPLANTABLE COMPONENTS Battery: Two connected in series to form approximate 6 V Lithium Silver Vanadium oxide (LiSVO) Separate voltage supplies are generally used for pacing(5V) i.e. low volt supply and control of the charging circuit (10-15 V) i.e. high volt supply. High power circuits convert 3-6V battery voltage to the 750V necessary for defibrillation. DC to DC convertor coverts 6 V battery to 750V, the output storage capacitor and high output switch are used for defibrillation. Sen s e Amplif ier Proper sensing of heart requires precise sensing and discrimination of each of the component to differentiate tachycardia and ventricular fibrillation. It should be able to sense 30 to 360 bpm. It should be able to quickly respond to widely varying signals present during arrhythmia. Heat signals lies in the range of 100micoV to 20microV as a result needs to amplify to be processed further.

28. AID/ICD

29. A ID

30. AUTOMATIC OR ADVISORY EXTERNAL DEFIBRILLATORS Smart automatic or advisory external defibrillator (AED) are capable of accurately analyzing the ECG and making reliable shock decisions. The are designed to detect ventricular fibrillation with sensitivity and specificity comparable to that of well trained paramedics then deliver(automatic) or recommend (advisory) an appropriate high energy defibrillating shock. AED require self adhesive electrodes instead of hand held paddles. ECG signal are acquired are faster and more accurate and with less noise and higher quality. Hands-off defibrillation is a safer procedure for the operator especially when operator has no training. Multifunction self adhesive electrodes are commonly used with defibrillator-monitor- pacer instruments. AED has the ability of the device to accurately assess the patient heart and make therapy decision. The defibrillator performs this evaluation by sensing electrical signals from the patient heart via electrodes and using a computerized algorithm to interpret the electrical signals.

31. DC Defibrillator with synchronization

32. A ED

33. DEFIBRILLATOR ELECTRODES Types of Defibrillator electrodes:- a) Spoon shaped electrode Applied directly to the heart. b)Paddle type electrode Applied against the chest wall c)Pad type electrode Applied directly on chest wall The electrodes for external defibrillation are metal discs about 3-5 cm in diameter (or rectangular flat paddles 5x10 cm ) and attached to highly insulated handle. The size of electrodes plays an important part in determining the chest wall impedance which influence the efficiency of defibrillation. The capacitor is discharged only when the electrodes make a good and firm contact with the chest of the patient. For internal defibrillation when the chest is open, large spoon- shaped electrodes are used. Self adhesive pre-gelled electrodes :Self-adhering, solid gel construction ensures easy use with no extra gel needed. Flexible design allows electrodes to better conform to body contours.

34. METAL DISC AND SPOON ELECTRODE

35. DEFIBRILLATOR ELECTRODE