BTEC315 - Lab 4, Nawras

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Students name and ID: Mochamant Nawras Maghrebi (301019532) BTEC315 BTEC315 Lab - Defibrillator: Preventive Maintenance and its applications Objective: To be familiar with working mechanism, preventive maintenance, and application of Defibrillators Part A: Theory [1] Defibrillators and how they work Although the annual number of premature deaths in Ireland due to cardiovascular disease (CDV) has been declining since 1974, at about 52 per 100,000, it is still significantly above the EU average (42 per 100,000, prior to the accession of some Eastern European states). If treated quickly a heart attack patient’s chance of survival can be dramatically improved. The Normal Heart-Beat Cycle The cardiac cycle has two distinct phases — the diastole phase and the systole phase. In the diastole phase, the heart ventricles are relaxed and fill with blood. In the systole phase, the ventricles contract and pump blood around the body through a system of arteries . These events are triggered by the sinoatrial node — a collection of modified myocytes that acts as the heart’s pacemaker. Ventricular Fibrillation Normally the pulse rate (heartbeat rate) is appropriate for the body’s oxygen demand. Problems can arise if the heart rate is too low or too high. If the speed is very high it can lead to ventricular fibrillation (VF) in which the heart muscle quivers and does not pump efficiently, if at all. This condition is generally fatal if not treated quickly. Normal heart-beat can be restored by delivery of a controlled electric shock. This process is called defibrillation . What is a Defibrillator? Defibrillators have been in use for about sixty years. The earlier machines were comparatively large and not really portable. Emergency portable defibrillators (also called AEDs or automatic 1

Students name and ID: Mochamant Nawras Maghrebi (301019532) BTEC315 external defibrillators) are today available in many public buildings, schools, clubs etc. and small defibrillators can now be implanted surgically in patients with certain chronic heart problems. Intelligent Defibrillators Over recent decades there have been major advances in the design of defibrillators. Much of this work stemmed from efforts to produce implantable devices. Modern defibrillators include sensors that can detect the cardiac rhythm and are programmed to ‘decide’ whether a shock is required and to deliver it correctly. How Does a Defibrillator Work? In essence the ‘shock’ circuit in a defibrillator has three key components: a high voltage source, a capacitor and switches. The Voltage Source Modern defibrillators use direct current (dc) rather than the alternating current (ac) which earlier models used. This poses a problem for designers of battery-operated devices. Transformers cannot step up direct current. The problem is solved as follows. A battery drives an oscillator circuit; in effect this produces a current that is switched on and off at a high frequency (e.g. 1000 times per second), although it is still going in one direction only. If this pulsed direct current is fed into a suitable transformer the required output voltage can be generated. The factor by which the voltage is stepped up is the ratio of the number of turns on the input and output coils of the transformer. For example, if the input coil (‘primary’) has 200 turns and the output coli (‘secondary’) has 20,000 turns then the voltage is stepped up by a factor of 100. A 5 V input would then result in a 500 V output. The alternating output voltage is rectified by means of a diode and fed into a capacitor which stores the high voltage charge. The Capacitor A capacitor consists of two flat conductors or ‘plates’ (usually of aluminium foil) with an insulator between them. A conducting lead is attached to each plate. In practice the whole capacitor assembly is often rolled and inserted in a ‘can’ with two connections. 2

Students name and ID: Mochamant Nawras Maghrebi (301019532) BTEC315 Circuit The diagram shows a simplified version of a defibrillator circuit. With all switches open the ‘paddles’ are attached across the patient’s chest. S1 is then closed in order to charge the capacitor. S1 is then opened and S2 is closed; this causes the capacitor to discharge through the patient, hopefully restoring normal cardiac rhythm. Energy Considerations The capacitance of a capacitor is the amount of electric charge it can store for every volt applied to it. The unit of electric charge is the coulomb (symbol: C). The unit of capacitance is called a farad (symbol: F). One farad = 1 coulomb per volt. With regard to defibrillators the amount of energy stored in a capacitor is very important. It can be calculated as follows: E = ½ C V 2, where E is the energy in joules, C the capacitance in farads and V the electric potential (voltage) measured in volts. This energy, which may be more than 100 J, is dissipated in the patient’s body over a small time interval (about 10 milliseconds or one hundredth of a second). For example, if the capacitance is 1000 μF (microfarad) and the voltage is 500 V then the stored energy is 125 J [ E = ½ C V 2 = ½ (1000 × 10−6)(5002) = 125 J]. Early defibrillators delivering about 400 joules sometimes caused further cardiac injury. Electric Current The electrical resistance of the skin is the main contributor to the human body’s resistance. If the skin is dry the resistance from one hand to the other might be over 100, 000 ohms. This is dramatically reduced if the area of contact is large and the skin is moistened with a suitable conductive paste or gel. The electrodes provided with AEDs are generally self-adhesive and are pre-coated with conductive gel. They can reduce the body’s resistance (across the chest) to about 20 ohms. Using V=I×R we can calculate the peak defibrillation current. If V = 500 volts then the current is 25 amperes. The pulse lasts only about a hundredth of a second (10 ms) and so the risk of surface burns to the skin is reduced. Waveforms As a capacitor discharges its voltage falls and so does the current through the patient. Plotting the voltage or the current against time gives a characteristic graph or waveform . The waveform resulting from a single capacitor discharge is monophasic , i.e. the current is on one direction only. Modern defibrillators are generally biphasic ; successive current pulses are in opposite directions. Biphasic defibrillators are considered to be more effective and today virtually all new defibrillators are of this type. 3

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Students name and ID: Mochamant Nawras Maghrebi (301019532) BTEC315 Procedure [2], [3] Part B: For the following steps you either need the “ ZOLL R Series Defibrillator Operator Guide ” or watching a video clip from ZOLL Company by clicking here . (The ZOLL-R Series Defibrillator Guide is added to the Lab 5 folder on eCentennial course shell). Questions: 1- Where is the location of record paper in Zoll R series Defibrillator and how the record paper can be replaced? The record paper is located at the top left of the defibrillator. You can change this by pressing on the recorder release latch to remove and replace the paper. 2- Is there any time delay for record paper? If yes what is the reason for this delay? 6 seconds, this is because it ensures that ECG’s are recorded after critical events 3- Under what conditions recorder will be activated automatically? delivery of defibrillation shock, heart rate alarm or the rhythm analysis function is activated. 4- What is the differences between “Print Log” and “Print Chart: summary? Print log contains chronological list of all the interventions, the print chart summary provides a strip of ECG for a specific time. 5- What steps are required to generate a print log summary report? First click report data soft key>print chart>print all (if you want entire summary) or Print range (if you want specific time frame). 6- The Zoll R series defibrillator has a capability to transfer data to the external system such as a network computer through WiFi? Write the required steps for the data transition. First place the R series in ‘monitor mode’>report data>transfer mode softkey>Report to WIFI. 4

Students name and ID: Mochamant Nawras Maghrebi (301019532) BTEC315 7- What functionality of Zoll defibrillator will be verified by running the automatic Self-Test? It will ensure that circuitry for ECG, pacing and defibrillation are functioning, the battery is sufficiently charged, to make sure the electrodes have yet to expire, the device can deliver 30 joules of test shock, all cables are functional, and the printer is functional. 8- What does “Green check mark” and “Red X” signs mean as visual indicators? A green check indicates that the R series has passed all of its tests and a red x indicates that it has failed something during its self-test. 9- Explain what steps are required to validate a manual defibrillator energy test? We need to unsure the one step cable is plugged into a one step electrode, turn mode to ‘defib’, set energy to 30 joules then hit charge, when the shock buttons appear then press it. 10- Explain what steps are required to validate the pacer functionality? First turn the mode selector to pacer, turn rate control to 150 ppm (paces per minute), press recorder button, as the printer is printing press the ‘4:1’ button, put output to 0mA, disconnect the one step electrode and slowly turn to 16mA, alarm and text will flash, then reconnect cables and hit clear. 11- What steps are required for energy test validation by using internal handle of Zoll R series defibrillator? Connect internal handle set to an internal electrode, select defib mode, verify discharge button does not stick, charge defib to 2 joules and then press discharge button on handles, they won’t discharge and will give error message. 12- What items are included in daily visual inspection of Zoll R series defibrillator? This includes the device is clean and free of visible damage, cables are in good standing condition, paper tray has enough paper, defibrillators are plugged into AC power, green check mark appears, battery run time. Part C: For the following steps you either need the “ ZOLL R Series Defibrillator Service Manual ” or watching a video clip from ZOLL Company by clicking here . (The ZOLL-R Series Defibrillator Guide is added to the Lab 5 folder on eCentennial course shell). 5

Students name and ID: Mochamant Nawras Maghrebi (301019532) BTEC315 Questions: 1- As a part of Front Panel Butten Test what massage is expected if: Open the printer door then Press RECORDER button . Do this Observe this Open the printer door then Press RECORDER button . Check reorder message appears on the monitor Remove the battery. See the battery LED alternates between green and amber. Press and hold the ENERGY SELECT down arrow. Unit discharge internally and selected energy decrements to 1 joule. 2- Under the leakage current test what is the Maximum Leakage Acceptance Limits for following tests? Lead ECG 10 micro amps Hands Free Electrodes and Paddles (MFE) 10 micro amps Earth 500 micro amps 3- Consider the following error massages appear on the display, complete the table. Error Message Explanation Technical Action NIBP ARTIFACT It is unable to detect systolic, diastolic, or mean blood pressure due to excessive motion/vibration. Take single bp measurement, keep patient still, insulate the patient. NIBP FAULT 268 Device no response after power up. Replace the NIBP module. 4- Explain what steps required to remove the NIBP Module. Use illustration in your explanation. In order to remove the NIBP assembly we will need to disconnect the hose from the manifold and cut the zip tie securing the pump, disconnect the cable from power supply and remove the two screws securing it to the chassis, after this we can just slide it out. 5- Use the troubleshooting table and explain the recommended action for each following symptom. Symptom Recommended Action Excessive artifact detected when using paddles as ECG source. Make sure the paddles are selected, firmly press paddles to the patient’s skin, use the gel for paddles, clean paddles surface, check cable or use ECG electrodes. Defibrillator will not charge (energy level does not increment on display). Make sure the shock buttons on either main devices or paddles are not ‘stuck’ or replace the entire battery pack. 6

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Students name and ID: Mochamant Nawras Maghrebi (301019532) BTEC315 Conclusion: (Write how this lab can be helpful in your professional field or at your working environment) This lab will be helpful in field because it has thought me how to go through the service manual, understand the key components of the device such as how to do a manual diagnostic test to ensure it is working up to its standards. furthermore, it explained how to remove specific parts of the devices for maintenance/repair. References: [1]. Boston Scientific, Science and Technology in action, Seven edition. http://sta.ie/lesson/defibrillators-and-how-they-work [2]. ZOLL-R Series Defibrillator Operator Guide. https://www.zoll.com/-/media/public-site/products/r-series-defibrillators/9650-0912-01-sf_t.ashx [3]. ZOLL-R Series Defibrillator Service Manual. http://www.frankshospitalworkshop.com/equipment/documents/defibrillators/service_manuals/ Zoll%20R%20Series%20Defibrillator%20-%20Service%20manual.pdf 7

BTEC315 - Lab 4, Nawras

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