History of Defibrillator and How It Works - Term Paper Example

Defibrillators Introduction In the United s, coronary heart disease is the root cause of death. On average, cardiovascular distress leads to a total of 350,000 deaths annually (American Heart Association, 2006). To curb this, and thus assist these individuals succumbing to cardiovascular distress, an Automated External Defibrillator (AED) may be employed. An AED is a portable lightweight device which is capable of delivering electric shocks to aid in restarting of the constant heart rhythm after a Sudden Cardiac Arrest (SCA) (Constantine, 2005). Cardiac arrest occurs in cases whereby an individual’s heart experiences an irregular rhythm, and in most cases stops beating completely. This serves as a medical emergency, as blood ceases to be pumped to vital organs of an individual’s body, such as brain. In this regard, immediate medical attention should be sort after as an individual may succumb to death in a matter of minutes. AEDs have become more accessible in various businesses owing to the signing of the Cardiac Arrest Survival Act (CASA) by president Bill Clinton. This propagated the use of Defibrillators and set implementation guidelines relating to them. As a result, AEDs became popular, with many firms integrating them into their companies’ safety programs. Companies or businesses with no AEDs have been served with lawsuits over the past few years owing to failure to provide immediate accessibility to AEDs or AED programs. On the same breath, these devices are becoming legally required. This is so since 11 states have placed a requirement for AEDs to be implemented in schools, health care clubs, nursing homes, state buildings, and/or state vehicles for easier availability (Constantine, 2005). History of Defibrillators It is imperative to note that defibrillation has been in use since 19th century. One of the pioneers in the field of defibrillation and fibrillation was Carl Ludwig, who owned a laboratory. In 1849, one of his students, M. Hoffa witnessed, documented, as well as induced ventricular fibrillation using electrical stimulation. These findings were then published in 1850. Two scientists, Prevost and Batelli later discovered in 1899 that electric stimulation, when applied to the heart of a dog during fibrillation can lead to conversion of arrhythmia (abnormal heart rhythm) to a normal sinus rhythm. However, the first defibrillator was created 48 years later. The first defibrillator was used in 1947 by thoracic surgeon by the name Dr. Claude Beck. It was used to save the first human life by adopting the defibrillation procedure. Initial defibrillators functioned in such a way that ‘paddle type electrodes’ were directly applied to the heart. Following a publication of his results in the Journal of American Medical association, focus on defibrillation grew such that widespread research was carried out in this new area of technology and medicine. Closed chest defibrillation devices were adopted for use in 1950. They applied a total alternating current of 1000 Volts by means of externally applied electrodes. This historically important work was performed in Frunze, USSR by Dr. A. Klimiv and Dr. V. Eskin. Afterwards, 1960s witnessed the introduction of the first portable defibrillators on ambulances. This was the pioneer work of Belfast based Prof. Frank Pantridge. Owing to this, the first Automated External Defibrillator made its first appearance in the late 1970s. Figure 1: Prototype of Defibrillator Used by Dr. Claude S. Beck in 1947 Retrieved from http://americanhistory.si.edu/inventing-in-america/innovation-patent-models-and-prototypes With technological advancement, defibrillators have undergone a massive facelift. Currently, more state of the art, reliable and user-friendly defibrillators are in the markets. Additionally, the manufacture of AEDs has greatly been improved such that the public can get access to them. An example of a defibrillator used, as well as studied in the present day is the Implantable Cardioverter-Defibrillator (ICD) which is also referred to as Automatic Internal Cardiac Defibrillator (AICD) (Webster, 1988). How the Heart Works Before we delve into understanding how the Defibrillators work, it is important to know how the heart functions. The heart comprises of an electrical system which is capable of controlling the rhythm and rate of the heartbeat. With each heartbeat, there is spread of electric signals from the top to bottom of the heart. As the signal travels, the heart contracts and pumps blood as a result. This same process repeats with every new heartbeat. When there are problems with the electrical system, anomalies in the heart rhythm occurs. This is also called arrhythmias. During arrhythmias, the heart can beat slower, at a fast pace, or with irregular rhythms. Additionally, some arrhythmias can cause the heart to completely stop pumping blood to the body. This, as a result, causes Sudden Cardiac Arrest (SCA). Physics of How a Defibrillator Works Figure 2: Picture of Modern Day Defibrillator There are three major components to put into consideration when studying a defibrillator. They include the power supply, capacitor and an inductor. To be specific, interaction between these three components cordially plays a critical role in allowing the defibrillator to reinstate actual cardiac rhythm on an arrhythmias victim (Iambiomed.com). The Voltage Source Modern defibrillators adopt usage of direct current as opposed to use of alternating currents which earlier versions used. This, as a result, presents a problem for designers of devices operating on batteries. Since a transformer cannot solve the issue, another reliable means is sorted after. A step-up transformer is used, for this reason, to increase the voltage. In the case of a defibrillator, a step-up transformer plays a critical role in the conversion of the main voltage from 240 – 5000 VAC. Also, it allows doctors to be able to be able to choose among varying amounts of charge. The control switch occurs in such a way that it is calibrated in terms of energy delivered to the patient (Iambiomed.com). This is measured in Joules. With this regard, the physical impact that a patient will undergo can be determined. A battery plays a vital role in driving the oscillator circuit in a defibrillator. In effect, this generates current that is swapped on and off at elevated frequency while still proceeding in one direction. When this direct current gets fed into an appropriate transformer, a satisfactory output voltage is generated. It is imperative to note that the factor by which the voltage is increased to is equivalent to the ratio of the number of turns on the output and input coils of the transformer. Afterwards, the alternating output voltage is amended with the help of a diode and passed onto a capacitor which is tasked with reserving high voltage charge (Iambiomed.com). Capacitor This serves as one of the key components of the defibrillator. It is tasked with storing a large amount of energy in form of electrical charge. After a short period of time, the capacitor discharges the stored energy. Notably, the capacitor also contains several components which includes likes of an insulator, and metal plate conductors. Here, the conductors which are capable of losing electrons are tasked with promoting current flow. On the other hand, the insulator, which lies in the middle of the conductors, does not lose electrons. Quantitatively, a capacitor is described by establishing the capacitance; which is the ability to reserve charge. Capacitance is calculated using the formula C = Q/V with C representing Capacitance, V representing Voltage and Q representing charge. It is important to note that in relation to the formula, it is clear that there is a direct proportionate relation between Capacitance and Charge and an indirectly proportionate relationship between Capacitance and Voltage. In the case of a defibrillator, there exists a parallel plate capacitor. For this reason, a relationship can be established between the capacitance, the area of plate overlap, dielectric constant, and distance between the plates. Therefore, capacitance is indirectly proportional to distance between the plates and directly proportional to the area i.e. C = (Eo x A) / d. Figure 3: Mechanisms Involved when Defibrillator is in Action Given the switch lies on position 1 as shown in Figure 3 above, the power supply provides direct current which is supplied to the capacitor. As a result, electrons flow. As current flows, charge begin to accumulate on each electrode of the capacitor. To be more specific, the upper plate is more positive, with the lower plate being more negative. Owing to the accumulation of opposing charges, there is creation of potential difference (V) across the plates. This opposes the Electromagnetic force of the Power supply (E). In addition to this. Electromagnetic force can also be related to the dielectric current, area of the plate overlap, and the charge using the formula: E = Q / (Eo x A) (Iambiomed.com). Charging and Discharging a Capacitor Charging a capacitor is exponential. Specifically, there is work involved (W) to move charge through a potential difference (V) i.e. W=VQ. For this reason, it is imperative to note that with increasing voltage, more work is required. Charged capacitors serve as reserves for potential energy (Mushin, Jones and Macintosh, 1987). Amount of energy stored in a capacitor is CV. Thus, from this, it can be noted that in order to reserve energy, work must be done. In case of discharging a defibrillator, it is important to note that the circuit as shown in Figure 3 above is completed when the paddles are applied to patient’s switch. Electrons on the negative lower plate, as a result, move though the patient and onto the upper plate. Notably, three key steps happen in succession which involve electric current flowing, electrical energy being released, and finally the potential energy between the upper and lower plates is maintained at null. As electrons are transferred from lower plate, there is a depreciation of the potential difference. Owing to this, the rate of discharge depreciates as potential difference between lower and upper plates falls. Figure 4: Representation of the process of Charging and Discharging a Capacitor in a Defibrillator Inductors It is the work of defibrillators to shock the heart back into normal rhythm. For this reason, charge that is conveyed should go on for several milliseconds. However, charge and current is conveyed at a fast pace by the discharging capacitor. Inductors, which comprise of coils of wire capable of producing magnetic fields when current goes through them, elongate the duration of flow of current. Inductors are capable of producing electricity which is tasked with opposing the motion of current going through it (Mushin, Jones and Macintosh, 1987). How an AED works Owing to the above details, an AED functions in such a way that it uses a built-in computer system which aids it to sense whether a patient needs electric shock. The AED checks the heart rhythm by using the adhesive electrodes. On detecting the shockable rhythms, a voice alarm from the defibrillator affirms the operator to press the shock button. As a result, the shock stuns the heart thereby halting all its activities. This occurs in such a way that the heart is reset and thus given a second chance to beat and pump as earlier on. Since the modern technological advancement has allowed the makers of the AEDS to be more careful in inventions, the AEDs can be operated by people with little or no experience of defibrillators (Adgey). Conclusion When defibrillators were first introduced, they were mostly used in medical facilities. This was so since it was believed that it could not be used by people inexperienced in medicine and technology. But ever since some American States discovered that the AEDs were easy to use, less stringent measures were put on its usage. Today, many states have adopted defibrillation programs. With defibrillators becoming more prevalent in modern communities, and with the greater public awareness of its existence, the number of deaths as a result of cardiac arrest is estimated to reduce drastically. In the future, it is hoped that the access of defibrillators would be like that of fire extinguishers which are displayed everywhere to be used by anyone in distress. Nowadays, defibrillators are made in such a way that they are compact and easy to locate. For this reason, it means that they are portable and user friendly. This makes it easier for any person to use the defibrillator. References Adgey, A A J. Theory and Practice of Defibrillation: (2) Defibrillation for Ventricular Fibrillation. Heart 91.1 (2005): 118-125. Web. Constantine, Hank. On Guard Against a Major Killer. Print. Iambiomed.com. DEFIBRILLATORS. N.p., 2015. Web. 18 Nov. 2015. Mushin, William W, Peter L Jones, and R. R Macintosh. Physics for the Anaesthetist. Oxford; Boston: Blackwell Scientific Publications; Chicago, Ill.: Distributors, USA, Year Book Medical Publishers, 1987. Print. Rees, Margaret. EMAS Position Statements and Clinical Guides. Maturitas 77.4 (2014): 303-304. Web. Webster, John G. Encyclopedia of Medical Devices and Instrumentation. New York: Wiley, 1988. Print. Read More