Defibrillator Biomedical instrumentation.pptx

Defibrillator in biomedical instrumentation

1. Lakshmi Prabha A.P,Dept of Biomedical Engg,SRM IST ‹#›

2. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

3. ⦿ It is an electronic Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST device that creates a sustained myocardial depolarization of patient heart in order too stop ventricular fibrillation or atrial fibrillation ⦿ Sudden voltage given to heart cause all muscle fiber to contract simultaneously. ⦿ The instrument used for administrating electric shock is called defibrillator . ‹#›

4. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

5. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

6. ⦿ Irregular contraction of muscle fibre or quivering of heart is said to be fibrillation ⦿ Rapid spread of action potential over the surface of atria causes 2 chambers of heart to contract together and pump blood through two atrioventricular valves into the ventricles. ⦿ A condition in which the necessary synchronism is lost is known as fibrillation. ⦿ Fibrillation of atrial muscles is called atrial fibrillation ⦿ Fibrillation of ventricles is called ventricular fibrillation Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

7. ⦿ Quivering of atria or unsynchronized contraction of atria ⦿ Ventricle functions normally ⦿ Circulation is still maintained but inefficient Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

8. ⦿ Quivering of venticle or unsynchronized contraction of ventricle ⦿ More dangerous ⦿ ventricles unable to pump blood. ⦿ If fibrillation not corrected, results in death in few minutes Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

9. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

10. ⦿ Internal defibrillator ⦿ External defibrillator Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

11. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

12. ⦿ It is used when the chest is opened ⦿ Large spoon electrode with insulated handle is used ⦿ In dc defibrillator maginitude of shock voltage is 50V-1000V ⦿ Since electrode is in direct contact with the heart , contact impedance is 50Ω ⦿ Current:1-20ampere ⦿ Energy:15-50J ⦿ Duration :2.5-5ms Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

13. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

14. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

15. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

16. Anterior-anterior or anterior-posterior paddles: Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ⦿ Anterior-anterior- both paddles on chest ⦿ Anterior-posterior- chest wall and back Special pediatric paddles are available. Disadvantage: ⦿ Difficult to determine accurately the procedures. amount of energy needed for counter shock ‹#›

17. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

18. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

19. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

20. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

21. External defibrillator shaped electrode Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST is used on the chest using paddle ⦿ The bottom of electrode consist of copper disc with 3-5cm diameter for pediatric patient ⦿ 8-10cm diameter for adult patient ⦿ Required voltages are in range from 1000V to 6000V ⦿ Contact impedance on the chest 100Ω ⦿ Energy 50-400 joule ⦿ Duration 1-5 millisecond ⦿ Current 10-60 ampere ‹#›

22. Depending upon nature of voltage applied the defibrillator is divided in to six types ac defibrillator Dc defibrillator Synchronised dc defibrillator Square pulse defibrillator Double square defibrillator Biphasic dc defibrillator Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

23. AC defibrillation: Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ⦿ Application of electric shock to area of heart ⦿ Sufficient current to stimulate all the musculatures of heart simultaneously is applied for brief period and then released,after which normal heart action resume ⦿ 6A,60HZ for 0.25 to 1 sec ⦿ Application of an electrical shock to resynchronize the heart is called countershock ⦿ This method of counter shock is called ac defibri llation ‹#›

24. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

25. ⦿ It consist of step up transformer with various tapping on secondary side ⦿ Timer circuit is connected on primary side ⦿ T he timer connect output to the electrode for preset time ⦿ Timing device can be simple capacitor and resistance network which is triggered by foot switch or push button. ⦿ Counter shock vary from 0.1s-1sec ⦿ Voltage 250V-750V Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

26. ⦿ Cannot be used to correct atrial fibrillation Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ⦿ If attempted, leads to more serious ventricular fibrillation ⦿ Ac defibrillation is no longer used. ⦿ Large current are required in AED which result in occasional burning of skin under the electrode ‹#›

27. ⦿ A capacitor is charged to high dc voltage Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST and then rapidly discharged through electrodes across the chest of the patient. Advantages: few repetitions . less likely to harm the patients. Amount of electrical energy discharged by capacitor (100 to 400)w-sec or joules ‹#›

28. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

29. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

30. ⦿ A Variable autotransformer T1 forms primary of high voltage transformer T2 ⦿ The o utput voltage of transformer T2 is rectified by diode rectifier and connected to vacume type high voltage change over switch ⦿ In p osition A the switch is connected to one end of oil filled capacitor having capacitance of 16µF .During delivery of shock to a patient a foot switch or push button is operated ⦿ So high voltage switch changes to position B and capacitor is discharged across the heart through electrode. ⦿ Inductor L slow down the discharge from capacitor. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

31. ⦿ For internal defibrillator energies up to 100 joules ⦿ external defibrillator energies up to 400J ⦿ Duration 5-10ms Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

32. ⦿ If C=16µF and voltage is 6000V then energy stored in the capacitor? Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

33. ⦿ Peak value of current is 20A and it is monophasic ⦿ An inductor shape waveform to eliminate sharp and undesirable current spike. ⦿ Disadvantage: ⦿ Damage to myocardium and chest wall because high voltages as high as 6000v Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

34. ⦿ To overcome the disadvantage d ual peak defibrillator or delay capactive discharge defibrillator is used in trancated defibrillator Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST effective defibrillation is obtained T he discharge is adjusted so that the at desirable lower voltage level. ⦿ Here voltage level is constant but duration is extended to obtain required energy ‹#›

35. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

36. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

37. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

38. ⦿ For termination Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST of tachycardia,atrial other fibrillation essential and arrythmias it is to use defibrillator with synchronised circuit . ⦿ Two vulnarable zone in normal cardiac cycle is T wave and U wave. ‹#›

39. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

40. ⦿ Here capacitor is Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST discharged through the subject by turning on a series s ilicon controlled rectifier(SCR) ⦿ When sufficient energy is delivered to the subject shunt SCR short circuit the capacitor and terminate the pulse. ⦿ Here defibrillation is obtained with less peak current so no side effects. ‹#›

41. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

42. ⦿ It used during open heart surgery ⦿ When the 1 st pulse is delivered some of the fibrillating cell will be excitable and will depolarised.however cell which are refractory during the occurance of first pulse will continue to fibrillate.2 nd pulse occur later group of cell. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

43. ⦿ Similar to double square pulse as it delivers a pulse alternatively in opposite direction Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

44. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

45. Lakshmi Prabha.P,A.P,Dept of Biomedical Engg,SRM IST ‹#›

46. Implantable Defibrillator A utomatic implantable defibrillators (AID) is recommended for patients who are at high risk for ventricular fibrillation An implantable defibrillator is continuously monitors a patient’s heart rhythm. If the device detects fibrillation, the capacitors with in the device are charged up to 750 V. The capacitors are then discharged into the heart which mostly represents a r esistive load of 50 W and to bring the heart into normal rhythm. The biphasic waveforms are more efficient and probably safer than monophasic waveforms and produce successful defibrillation at lower energies ‹#›

47. I mplantable defibrillator The systems have three main system components: the defibrillator itself (AID), the lead system, and the programmer recorder/monitor (PRM) . The AID houses the power source, sensing, defibrillation, pacing, and telemetric communication system. The leads system provides physical and electrical connection between the defibrillator and the heart tissue. The PRM communicates with the implanted AID and allows the physician to view status information and modify the function of the device as needed. ‹#›

48. I mplantable defibrillator system architecture L eads: T itanium mesh patch with electrodes placed directly on the external surface of the heart. Sensing was provided through leads screwed in the heart. pulse generator : It has a microprocessor which controls overall system functions. An 8-bit device is sufficient for most systems. ROM provides non-volatile memory for system start-up tasks and some program space, whereas RAM is required for storage of operating parameters, and storage of electro-cardiogram data. The system control part includes support circuitry for the microprocessor like a telemetry interface, typically implemented with a UART-like (universal asynchronous receiver/transmitter) interface and general purpose timers. ‹#›

49. Pacer Cardioverter It is composed of five battery-powered units: sensing circuit, high voltage converter, switching circuit, defibrillation control circuit, and pacing control circuit. The heartbeat signal, which is detected by a catheter type heartbeat sensor, is amplified for heartbeat monitoring. The absence of a heartbeat for 3.5 s causes the fibrillation detecting circuit to deliver the turn-on signal which then switches on the high voltage converter . At a predetermined voltage level (800 V), the thyristor switch allows the capacitor to discharge its current through the right ventricular electrode. ‹#›

50. Defibrillator analysers A defibrillator analyzer is basically meant to measure the energy content in the discharge pulse. It works on the principle that the energy contained in a pulse of arbitrary shape and time duration is given by where E = energy in watt-seconds e(t) = voltage as a function of time, i(t) = current as a function of time, T = time duration of the pulse. When the voltage exists across a fixed resistance, the energy dissipated in the resistance is given by where R is the resistance of the load ‹#›

51. Basic block diagram of defibrillator energy meter The defibrillating pulse is applied across a standard 50 W load and the voltage developed across it is given to a squaring circuit. The squaring circuit consists of a four-quadrant multiplier followed by an operational amplifier. The output of this device is a current which is proportional to the product of the two inputs. In the squaring mode, the two inputs are connected together so that the output is a square of the input voltage. The operational amplifier acts as a current to voltage converter producing an output voltage which is proportional to the output current, from the multiplier. ‹#›

52. LVDT A Left Ventricular Assist Device (LVAD) is a mechanical pump that is surgically implanted into the patient's chest to help a weakened or failing heart pump blood more effectively. It assists the left ventricle in pumping oxygen-rich blood from the heart to the rest of the body. The procedure involves attaching the LVAD to the heart's left ventricle and aorta, and it can be used as a bridge to heart transplantation or as destination therapy for patients who are not eligible for a heart transplant. ‹#›