Types of Cardiac Arrhythmia Resulting From Centrifugal Acceleration

Types of Cardiac Arrhythmia Resulting From Centrifugal Acceleration Abstract Cardiac arrhythmia is one of the many health conditions that form the basis of aviation medicine. The absence of adequate information around the condition necessitates studies to that effect. The current paper sought to determine the types of cardiac arrhythmia that result from aviation related movement.Advertising We will write a custom research paper sample on Types of Cardiac Arrhythmia Resulting From Centrifugal Acceleration specifically for you for only $16.05 $11/page Learn More The study relied on findings made in centrifugal training experiments, where subjects are usually placed in a human centrifuge. The objective was to expose the subjects to +Gz forces, which are similar to the ones in a military jet or a commercial flight. During such exercises, the tolerance level of the subjects was determined relative to the G-forces. It was found that sinus arrhythmia, premature atrial contraction, premature ventricle contraction, and atrial fibrill ation are the common cardiac arrhythmias during such exercises. Introduction Aviation Medicine An Overview There are certain health-related problems that are unique to the aeronautical and aviation industry.[1] Rayman points out that aviation medicine can also be referred to as flight or aerospace therapy.[1] The idea behind this kind of healthcare is the need for a medicinal approach in tackling the wellbeing of people in aerospace industries. Pilots and astronauts are good examples of individuals who are covered by aviation medicine. The principle behind this field is the fact that the patients find themselves physiologically affected by aviation-related factors, such as gravity. Advancement in the aerospace and aviation sectors imply that most of the aforementioned factors will increasingly affect the persons in the industry. Hanada, Hisada, and Koichiro affirm that progress is inevitable in the aviation industry.[2] An example is the case of air force pilots. The need to develop faster and effective jets means that the aerodynamic factors will be modified. Consequently, the pilots end up being affected by some of these forces. The advancements made in aviation medicine rely on its relevance to the world of aerospace. Whinnery indicates this importance by outlining the fact that the United States Air Force (herein referred to as USAF) has a School of Aerospace Medicine.[3] Such institutions justify the reasoning that research in aviation medicine is important. In a study to determine the state of affairs in Singapore in relation to this field, Gan, Low and Singh focus on the military and commercial flight areas.[4] In these fields, there is constant development of new and state-of-the-art machinery. However, as aforementioned, the same comes with consequences like increased arrhythmia.Advertising Looking for research paper on health medicine? Let's see if we can help you! Get your first paper with 15% OFF Learn More Technological in novations in medicine are required in such fields as aviation physiology and performance maximization.[4] Other areas in which advancement is required include the selection of medical standards and protection of aircrew from communicable diseases, which may arise during a flight. However, for the purposes of this paper, discussions will revolve around the physiology aspect of aviation medicine. G-Forces in air planes Airplanes are constructed in such a manner that they respond to the laws of aerodynamics.[1] The operation of these laws relies on gravity and how to overcome it. Whinnery brings out the understanding that gravity, as a force, is observed as acceleration.[2] The implication is that there is motion involved. Going by the arguments made in Newton’s laws of motion, it is evident that gravity is characterized by several forces. The study restricts itself to the forces exerted on an aircraft due to gravity, which is referred to as ‘g-force’. According to Gan et al.,[4] g-forces are considered as accelerations, as previously indicated. As a result, one can determine these forces on the basis of their respective weights. By virtue of the acceleration nature of gravity, the g-forces appear to multiply the weights of a given mass. In the context of an airplane, these factors tend to reproduce the weight of the unit mass of the persons in the jet. To appreciate how a pilot will experience this multiplier effect, one ought to obtain the sum of the non-gravitational forces acting on them. The aforementioned non-gravitational forces are considered as the proper accelerations.[1] Their effects include stress and strain on persons in an aircraft. In their study, Whinnery[3] makes the claim that high amounts of g-forces are destructive to the aircraft and to the people. Effects of g-forces on human anatomy G-forces cause strain and stress on the bodies in an aircraft. In line with this, the elements have a physiological effect on human bodies. [1] Hanada et al.[2] affirm this hypothesis in their study on the effects of g-forces on military pilots. Most of the components of the human anatomy have mass. As such, the effects of stress and strain on them vary. Hanada et al.[2] indicate cerebral perfusion as a major impact of these forces. In such cases, the patients tend to suffer from a condition known as G-induced loss of consciousness (herein referred to as G-LOC). Such conditions are common among military pilots during the maneuvers displayed by the fighter jets. Arrhythmias is another common phenomenon resulting from the g-forces, especially in instances where flight crew are taken through centrifuge training.[4] In such cases, the pilots are subjected to the same conditions as those of a plane in the air. Consequently, the developments tend to alter the rhythmic patterns of an individual’s heartbeat. The effects of g-forces are so serious on the human anatomy to the extent that Hanada et al.[2] propose the presen ce of specialists during centrifuge training.Advertising We will write a custom research paper sample on Types of Cardiac Arrhythmia Resulting From Centrifugal Acceleration specifically for you for only $16.05 $11/page Learn More Effects of G-Forces on the Heart General effects An analysis of g-forces makes it apparent that human anatomy is severely affected by stress and strain, as illustrated in the previous section. Advances in aerospace technology imply that human body will continue to be subjected to such forces to determine its tolerance.[1] For the purposes of this study, it is important to understand the effects of g-forces on the heart as an organ in human anatomy. Cardiac arrhythmia The functioning of the heart is largely attributed to its electrical properties.[1] The stresses and strains brought about by the g-forces tend to affect the organ’s electrical attributes. As a result, the heart beat is altered. Conditions of this nature are wha t are referred to as cardiac arrhythmia. The condition is not age or gender specific. Whinnery[3] points out that the condition if often not fatal. However, studies illustrate that cardiac arrest is associated with arrhythmia.[2] Cardiac arrhythmia can occur in one of the compartments of the heart.[1] The same explains why there are different types of the said condition. Rayman[1] points out the existence of four types of cardiac arrhythmia. The first is supraventricular arrhythmia, which is characterized by a fast heart rate.[1] Secondly, there is bradyyarrhytmias. The condition arises when the heart beat is extremely low. In such cases, the blood hardly reaches the brain. The third type is ventricular arrhythmias. The occurence is associated with the lower chambers of the heart.[1] Finally, there is premature beats. It is a type of arrhythmia associated with the upper atria of the heart. The ‘premature beats’ are an indication of a mild form of arrhythmia, whose sympt oms are not easily noticeable.[5] Cardiac arrhythmia in aviation medicine The aviation industry is a sensitive area, which involves out of space explorations and normal flights. The machines involved are quite complex. The sophistication requires the complete application of the pilot’s cognitive abilities. Within the broad spectrum of aviation medicine, cardiac arrhythmia falls under the physiological effects. The heart plays an important role in human anatomy.[6] As such, studies have been conducted to illustrate how best to overcome the condition. Factors influencing g-force provoked arrhythmia During centrifugal training, the participants are subjected to +Gz forces. The procedure leads to stress that affects human anatomical functions. It is evident that cardiac arrhythmia results from the effects of the G-force on the heart. The rhythms are distorted from their normal patterns.[7] It is important to appreciate the factors that influence the occurrence of arrhythmia due t o the G-forces. Over the years, aviation medicine has relied on centrifugal training to obtain information about cardiac arrhythmia. Such information includes the various types of the condition and their influencing factors.[7] Experiments carried out to determine this rely on the use of human centrifuges, which are found in special units. The most common areas where such apparitions are found include special aviation medical departments in military wings.Advertising Looking for research paper on health medicine? Let's see if we can help you! Get your first paper with 15% OFF Learn More One of the factors that influence cardiac arrhythmia during centrifugal training is the magnitude of the +Gz. Ewalina and Lech[7] proved this in a study in which they sought to determine hemodynamic changes resulting from centrifugal acceleration and the corresponding cardiovascular responses. The study reveals that an acceleration of 1Gz is responsible of acute hemodynamic changes. The same magnitude of acceleration was found to be an activator of cardiovascular responses, arrhythmia being one of them.[7] Anti-G straining maneuvers (herein referred to as AGSM) are other factors that influence g-force-provoked arrhythmia. Ewalina and Lech[7] point out that the same has a direct effect on the nervous system, which impacts on the heart’s electrical properties. Such measures are seen as an attempt to reduce the effects of g-forces. They limit the impacts of +Gz on the electrical characteristics of the heart. Other factors include the health status of the subject and the duration of exposure. Latent cardiac medical histories give mixed results. Exposure durations increase the chances of cardiac arrhythmia, which further aggravates the severity of the conditions. Materials and Methods Introduction The current study is hinged on the hypothesis that centrifugal acceleration results in cardiac arrhythmia.[1] The research relies on a series of peer reviewed articles, which provide a detailed discussion of the topic. More importantly, the articles relied on address the issue of g-forces and their effects on human subjects. They illustrate the various types of arrhythmia and their relationship with g-forces. +G Acceleration and Corresponding Detection of Cardiovascular Responses In an experiment, Vettes, Viellefond, and Auffret[6] determined that g-forces have a corresponding cardiovascular response from the heart. The researchers deduced this by carrying out detailed studies on the issue. The subjects used were all male and individually volunteered for the exerci se. The studies were carried out in a laboratory in France. The location, known as the Aerospace Medicine Laboratory of the Flight and Test Center, contained the equipment necessary for this research.[6] The male volunteers had an average age of 37 years.[6] After the preliminary medical check-ups were concluded, all the subjects were found to be medically fit for exposure to g-forces. Preliminary tests carried out at the Central Medical Examination Centre for Flying Personnel, which is situated in Paris.[6] Thirteen of the participants did not have prior exposure to centrifugal acceleration. According to Vettes et al.,[6] +Gz g-forces were required for the study. The said forces are attained when a human centrifuge is rotated longitudinally. The specific centrifuge used in this research had a vertical rotating axis, whose arm was six meters.[6] A gondola is attached at the arm’s extreme end. Human subjects occupy this space. The centrifugal acceleration in this regard is obt ained by means of a perpendicular rotation of the arm relative to the gondola. During this rotation, the apparatus moves along the axis, exposing the subject to the +Gz forces arising from acceleration. To ascertain the responses, certain cardiac parameters are taken into account.[6] Such parameters as the subjects’ rate of heartbeat and arterial pressure were are determined. The study by Vettes et al.[6] required the stoke volume and the subjects’ visual fields to be recorded as part of the preliminary medical analysis. Each of the electrocardiographs was analyzed by means of a special electrode. The electrodes are placed on 3 locations on the subjects’ body. The first two are placed on each of the axillae, while the third is placed on the lumbar spine. In so doing, the researchers minimize the noise that would otherwise be present due to the muscle-related contractions. The arterial pressure on the other hand is obtained by means of a syphgamanomter.[6] The sa id machine is normally inflated by means of an electrovalve that is remotely controlled. To obtain the actual pressure in a subject, a curve on the machine is needed.[6] In addition, there is a microphone placed at a strategic point to detect specific noises. In the study, the researchers were able to record their patients’ rates of heartbeat using a phonocardiograph. However, there are exceptions where the heart rate is determined by taking measurements of 10 systoles from the machine. Safety Criterion The study by Hanada et al.[2] sought to develop a safety criterion for centrifugal training. The study relied on pilots from the Japanese Air Self-Defense forces. Each of the subjects was conversant with F-4, F-15 and F-2 fighter jets.[2] Such familiarity was a requirement to be part of the study. It was meant to ensure that the subjects were all familiar with increased G-forces due to the aircrafts’ high rates of acceleration. As expected, there was a preliminary medic al examination carried out on each of the participants.[7] In addition, the subjects were taken through a pre-determined duration of centrifugal acceleration to obtain specified results. The study created several profiles to analyze the effects of different +Gz forces. The data analysis phase was characterized by anonymity. The names of the pilots were not included in the profiles. G-Force Tolerance In their study, Blue et al.[5] examined levels of tolerance associated with g-forces during centrifugal training. The study revolved around subjects with an interest in spaceflight. The participants were part of Virgin Galactica crew and would- be passengers. An equipment referred to as a ‘Space Training Simulator’ was used in the study. The machine operates like a human centrifuge. Prior to the experiment, a medical examination was carried out. Afterwards, the subjects were taken through an anti-G straining procedure. There was a descriptive representation of the data colle cted in the study. Cardiac Arrhythmias in Flight and Centrifuge Simulations In their article, Ewalina and Lech[7] argue that centrifuge acceleration has an effect on cardiac arrhythmia. Consequently, their study analyzed the two scenarios in which such acceleration is achieved. They examined the rhythm balances when the subjects are in centrifuge training and in actual flight. Ewalina and Lech[7] point out that the two instances have similarities and differences. Ultimately, the research sheds more light on cardiac arrhythmia resulting from centrifugal acceleration. In the study, Ewalina and Lech[7] relied on 20 experienced pilots and 20 students. The student pilots were selected from a group of 3rd and 4th year cadets in the Polish Air Force Officers’ College. According to Ewalina and Lech,[7] the average age of the experienced pilots was 35.3 years. There was an allowance of 4.9 years in the positive and negative extremes. The average height was 176.6 cm, while body mass wa s 79.3kg.[7] The average flying hours of the experienced pilots was estimated at 2620. The trainee pilots, on the other hand, had an average age of 21.9 years and median height of 178.2 cm.[7] Their mean body mass was 78.7kg. They had an average of 252 flight hours on their records.[7] One of the requirements for participation in the experiment was that none of the pilots should take any form of medication. Ethical issues were also taken into consideration, where the participants were required to submit a written consent. The approval to conduct the study was granted by an ethics committee constituted by the ‘Polish Air Forces Institute of Aviation Medicine.’[7] The study required the subjects from the two groups to carry out flight protocols in pairs, where one acted as a pilot, and the other as a passenger.[7] Each of the subjects was required to make 2 flights. In the first flight, the subject was required to act as a ‘pilot’ (herein referred to as AF). The second flight demanded that they act as a passenger (herein referred to as PF). According to Ewalina and Lech,[7] the participants were required to take a break in-between the flight schedules. The study gave an allowance of 1 hour as the duration of time that each pilot should take before taking part in the next flight. To attain consistent results, all the subjects made use of the same TS-11 ISKRA Jet.[7] Once all the pilots had made their required flights, the researchers took a break of two days. During the break, the subjects underwent human centrifuge tests. It is important to note that the subjects did not wear G-suits during the study. The omission was meant to allow the +Gz effects to be conclusively examined. The forces were generated from the maneuvers carried out in the flight program. They ranged from 0.57 G.s-1 to 4Gz when the maneuver involved three successive turns.[7] With regards to the split S maneuver, the acceleration was recorded between 1.7G. s-1 and 5.6 G z.7 The ‘two-successive loop’ maneuver was characterized by an acceleration of 1.4G.s-1 to 5.0Gz. The other maneuvers carried out were the immelman and the one turn. The former had an acceleration of 5.6Gz, while the latter gave results identical to all the other maneuvers.[7] The results from the flight protocols were recorded separately. As aforementioned, the study carried out a centrifuge test. The same was realized using a centrifuge with a radius of 10 meters.[7] The equipment was provided by the Acceleration Tolerance Laboratory, which is situated within the Institute of Aviation Medicine. The latter is a department of the Polish Military. At the resting level, the acceleration was +1.4Gz. Thereafter, it was increased by 1G.s-1 to a maximum of 7Gz. When the human centrifuge was involved, the accelerations were set at levels similar to the aerobatic maneuvers.[7] +GZ and the Electrocardiographic Response Whinnery[3] sought to establish that the g-forces experience d during centrifuge training have an effect on an individual’s electrocardiographic (herein referred to as ECG) response system. The study involved a total of 59 subjects. According to Whinnery,[3] the research relied on the responses of the flight surgeons that developed the acceleration profiles of the subjects. The participants were drawn from the United States Air Force and the United States Navy.[3] The two training profiles developed for the study included the gradual and the rapid onsets. According to Whinnery,[3] observation of the subjects was carried out based on their respective ECG dysrhythmias. The first profile was developed when the participants were allowed to put on a standard anti-g suit. Whinnery[3] points out that the suit was not inflated. There various reasons why inflation was omitted. The major objective was to ensure that the subjects were relaxed and that their loss of peripheral vision was gradual. The maximum limit of +Gz was estimated at +9Gz. It is important to note that the tolerance levels during the centrifuge training were recorded from 2 extremes. There was the relaxed and the straining levels of tolerance.[3] In both cases, the aim was to obtain the proficiency of the anti-g element in the experiment.[3] The researchers analyzed the various symptoms exhibited by the subjects. To achieve this, the results were computed in terms of the average, standard deviation, minimum, and maximum.[3] Whinnery[3] used the ages of the subjects to estimate the results. Of particular interest was the comparison between the ectopy occurrences among the subjects. The incidences were analyzed by means of a correlated proportions test referred to as McNemar.[3] An elaborate outline of the results is discussed in the subsequent sections of this paper. The objective, as already mentioned, is to build on the hypothesis of the current study. The discussions will involve results from studies similar to the ones referred to in this section. Resu lts Introduction to the Results From the materials and methods discussed in the previous sections, it is apparent that there is enough evidence to support the hypothesis made in this paper. The evidence suggests that cardiac arrhythmia is caused by g-forces that result from centrifugal acceleration.[5] The results of previous studies conducted in this field highlight the various types of arrhythmias and the effect of centrifugal acceleration on the rate of heartbeat. In addition, the findings made illustrate the various cardiovascular parameters related to arrhythmia. In line with this, analysis of this condition in relation to centrifuge is outlined in this section. Types of Arrhythmias As aforementioned, there are multiple types of arrhythmias. Each of them has unique characteristics that set it apart from the others.[6] In a study to determine the safety measures needed to be put in place during g-flight training, Hanada et al.[2] found out different types of this condition. The findings are illustrated in Table 2 below: Table 1: Types of cardiac arrhythmia Number of Participants Percentage of Occurrence (%) Type of Arrhythmia 114 58.5 Single PVC 95 48.7 Sinus Arrhythmia 63 32.3 Single PAC 19 9.7 Paired PVC 5 2.6 Ventricular tachycardia 3 1.5 Paroxysmal supraventricular tachycardia 3 1.5 Repeated PAC 1 0.5 Paroxysmal Atrial Fibrillation 1 0.5 Ventricular bigeminy or trigeminy Adapted from: Hanada et al.[2] The study by Hanada et al.[2] reveals 9 types of cardiac arrhythmia associated with centrifuge acceleration. The figures listed in table 1 above were obtained from a research conducted by the Japan Air Self-Defense Force (herein referred to as JASDF). The most common condition recorded during the study was single premature ventricular contraction (herein referred to as PVC) at 58.5 percent. The occurrence of both Paroxysmal Atrial Fibrillation and ventricular bigemny or trigemny was recorded at 0.5% in one of the participants, maki ng it the least common of all. Centrifugal Acceleration and its Effects on the Rate of Heartbeat As previously mentioned, centrifugal acceleration has an effect on human anatomy. The effects of this phenomenon on human body vary between different organs. Studies reveal that centrifugal acceleration gives rise to g-forces. As such, it follows that their effects on the heart touches on its rhythms, leading to cardiac arrhythmia.[7] In their study, Whinnery[3] affirms that g-forces affect an individual’s heart rate. Table 2 below illustrates results of the study by Whinnery.[3] The effects of the forces on the human heart are documented in the table. Table 2: G-force exposure and corresponding heart beat rates Lown grade Ectopy Definition Subjects with highest Lown grade 0 Absence of ventricular premature depolarizations 12 1 5 PVC 31 2 5 PVC 3 3 Multiform PVC 1 4A Paired PVC 8 Source: Whinnery[3] In this research, Whinnery[3] relied on one type of cardiac arrhyt hmia. As illustrated in table 2 above, the study examined the rates of heartbeat in relation to the effects of exposure to +Gz forces. The analysis is based on a Lown grading system. Such a system is used to classify heartbeats with regards to cardiac arrhythmia.[8] Whinnery[3] selected a cluster from the known classifications, as shown in table 2. The experiment analyzed results from a total of 59 participants. It was found that +Gz forces affected an average of 11 subjects. The same is inferred from the data in table 2. Cardiovascular Parameters Studies aimed at examining the effects of centrifugal acceleration rely on specified cardiovascular parameters. Vettes et al.[6] posit that the +Gz forces arising from centrifugal acceleration rely on such factors. They determine such responses as cardiac arrhythmia. The said parameters include an electrogram and the visual field of the subject. In addition, the heart rate and humeral arterial pressure of the participants are factored in t he study. They make up the cardiovascular parameters recorded during such experiments.[6] Vettes et al.[6] point out that increased exposure to g-forces was followed by a corresponding increase in the rate of the individual’s heart beats. The results from their experiments illustrated that peripheral loss of vision among the subjects was an indicator of the effects of the +Gz forces. The latter is regarded as a key symptom indicating the onset of cardiac arrhythmia. The study by Vettes et al.[6] revealed that the highest recorded heart beat per minute was 113, whereas the lowest was 84. In terms of pressure, Vettes et al.[6] illustrated that increased exposure to these forces (up to levels of +3 Gz) resulted in a corresponding rise in arterial pressure. To this effect, blood pressure is treated as an essential parameter in understanding cardiac arrhythmia. The same explains the effects of exposure to g-forces. The scenario is similar to electrocardiographic recordings, which vary depending on the accelerations. In their study, Vettes et al.[6] point out that increased heart pressure was the cause of arrhythmia. The reason is that the pressure led to atrio-ventricular dissociation. Effects of Centrifuge Training on the Heart The major focus of this study is centrifugal acceleration and its effects on human anatomy.[9] Aviation regulations require pilots (and in some cases passengers) to undergo some level of centrifugal training. Such trainings simulate the acceleration likely to be experienced in fast moving aircrafts. An example of such instances involves commercial space-crafts.[5] The high acceleration associated with such crafts requires some training to acquaint the persons with the g-forces. Blue et al.[5] carried out a similar study in which occupants of a spaceflight were subjected to centrifugal-stimulated sub-orbital flight. The objective was to create conditions similar to those in a fast moving aircraft. The participants in the study by Blue et al.[5] were all healthy. The simulation was expected to provide information on how g-forces affect the heart. It was also expected to shed light on the influence of the forces on the occurrence of cardiac arrhythmia. Their study used a total of 81 participants[5]. The research by Blue et al.[5] required healthy individuals. As a result, all the participants were subjected to medical screening.[6] Consequently, the initial number was reduced to 77 subjects. Out of this, 65 were men, while 12 were women. Another batch of 21 participants was subjected to cardiac examinations to check for any latent complications. The medical examinations revealed that 16 had histories of hypertension, while 5 had diabetes. Another 5 had undergone a coronary heart bypass. In addition, 17 participants had a history of hyperlipidemia. Prior to the simulation, there were 2 individuals who were found to have severe cases of peripheral vascular disease. The objective of these tests was to obtain exact re sults from the simulations. The aim was to ensure that the findings made were due to g-forces from centrifugal acceleration and not from latent conditions. The participants with medical histories had little complaints from the centrifugal acceleration in comparison to those without backgrounds of medical conditions. However, both sets of participants complained of nausea. The same is common in cases where subjects are exposed to high centrifugal acceleration. Another effect of this development was greyout. To this end, participants complained of incidences of mild greyout. Interestingly, none of the participants experienced any form of G-LOC. There were, however, incidences where the participants would perform head movements with the sole objective of self-inducing sensations similar to coriolis. Discussion Overview From the various experiments highlighted in the current study, it appears that cardiac arrhythmia is caused by g-forces associated with aerodynamics.[10] The various stu dies made reference to centrifugal acceleration. It is not possible to obtain results from the specific aircrafts that the researchers used to generate centrifugal acceleration. As a result, most studies depend on simulations of conditions found in an aircraft.[11] During such instances, the subjects are rotated at speeds that are almost equivalent to those in an aircraft The objective of such simulations is to expose the subjects to g-forces from acceleration.[12] The specific elements observed are the +Gz forces. The designation ‘z’ implies that on a 3 dimensional plane, the said forces act on the z axis. Their effects on the subject are longitudinal. In addition, they are the most common forces that affect the rhythm of an individual’s heart when in flight.[13] The different levels of exposure to g-forces are a contributing factor to the occurrence of the various types of cardiac arrhythmia. The study by Hanada et al.[2] highlighted three types of arrhythmia c ommon among pilots, especially in military jets. The three were identified as PAC, PVC, and sinus arrhythmias. According to Hanada et al.,[2] the three occurred due to the variant levels of exposure to +Gz. For instance, sinus arrhythmia occurs in instances where subjects are exposed to high g-forces. In such cases, the resulting levels of stress are high. The same has an effect on the heart rate. It distorts the rhythm of these rates once the subject comes to rest. It is noted that PVC and PAC are the most common types of arrhythmia that result from interactions with high-G training.[14] Hanada et al.[2] addressed this issue by pointing out that the two are common in normal day-to-day exercises. The researchers found it prudent to do away with centrifuge in cases where subjects exhibited PAC and PVC.[2] The argument is strengthened by the assumption that the two arrhythmias are a normal occurrence among subjects. The study by Hanada et al.[2] introduced the element of grading the r ate of heartbeat rhythms among subjects. The system is essential in determining the degree or severity with which arrhythmia exhibits itself.[15] In this grading system, arrhythmias that are recorded at a grade of three or higher are regarded as severe. It is noted that 10% of the subjects in the study by Hanada et al.[2] exhibited a paired condition of PVC. The researchers argue that the condition is a direct physiological response to the stress experienced during the centrifugal acceleration in training sessions. The Lown grading system for ectopy was developed against the backdrop of the need to characterize the different types of arrhythmia. The same explains why, in the study by Hanada et al.[2], PAC and PVC are graded according to the degree of exposure to +Gz. An example is in the case where there is paired PVC and PAC, while at the same time single cases of PAC and PVC are noted. In both cases, the Lown format becomes vital in highlighting the severity of the different types of arrhythmia. The Lown system is one of the advancements made in aviation medicine. It is used to determine the types of arrhythmias that are permissible in centrifugal training. An example is evident in the study by Hanada et al.[2], where the system is used to sanction centrifugal training in cases where subjects exhibit paired PVC. However, training sessions are terminated in cases where the arrhythmias go beyond a specific threshold.[2] In such cases, the severity of the condition is determined by such factors as proaxysmal atrial fibrillation. Hanada et al.[2] posit that there are certain tachycardiac arrhythmias that reduce tolerance to G-stress resulting from centrifugal acceleration. In such cases, the subjects exhibit PSVT and VT. Their study revealed that PVST is possibly a major cause of loss of consciousness during centrifugal training.[15] The findings made in the current study are best understood from the perspective of a detailed discussion of centrifugal accelerati on and its effects on the heart. In so doing, the researcher aims to prove that cardiac arrhythmia is a result of centrifugal acceleration. In this section, the specific types of this condition are analyzed in detail. Protocols for Centrifugal Acceleration The findings in this study reveal that centrifugal acceleration is an important component of aviation medicine.[16] The process creates an environment that is similar to that experienced in fast moving aircrafts like fighter jets. Such individuals as military pilots and astronauts are the most affected by the G-forces arising from the acceleration of high speed aircrafts. It follows that such individuals require some form of training to acquaint themselves with the strenuous conditions and to help them bear with the stresses brought about by the forces. Centrifugal training, as already indicated, is the process through which pilots and other crew members are subjected to controlled conditions of G-stress. During such sessions, avi ation medical personnel examine individual subjects’ tolerance to G-forces.[2] It is important to take the subjects through certain protocols. Such a move is necessary as it helps in the attainment of accurate results from the exposure to the said forces. Several studies are used to elaborate the importance of these protocols as indicated in the ‘methods’ section of this paper. The first and most important protocol to follow in centrifugal training is preliminary medical check-ups.[1] The procedure is evident in the studies by Hanada et al.[2] and Whinnery[3], where the subjects are screened for heart related complications. The objective of such preliminary medical examinations is to ensure the effects of G-stress exposure are not confused with the symptoms of latent medical conditions. The second protocol during centrifugal studies is the exposure levels.[3] During the training exercises, the subjects must be exposed to varying levels of +Gz so that a proper com parison can be arrived at. For instance, Whinnery and Hickman[8] sought to study mitrial prolapsed and thus relied on centrifugal acceleration. Their subjects were exposed to stress levels of 1G.15s-1 which were gradually increased. There was also another exposure referred to as the rapid onset exposure in which the subjects experienced g-forces of 1 G.s-1. The initial tolerance level is essential in evaluating cardiovascular reflexes.[8] On the other hand the second tolerance level are useful in determining the subjects’ tolerance in terms of the hydraulics. During these exposure levels, in centrifugal training, it is expected that the subjects end up experiencing total loss of their peripheral sight. The aforementioned protocols are key in ensuring that the results are obtained as expected.[8] Arrhythmia Resulting from Centrifugal Training Overview From the findings in this paper, it is apparent that the rhythm of the heart is distorted by the G-stresses during centrifugal training.[17] As previously mentioned, centrifugal training involves rotation of subjects in a contraption referred to as a human centrifuge. The objective is to expose the participants in such exercises to +Gz forces.[3] Consequently, the individuals in such studies are observed to determine how the G-forces affect their human anatomy, of which the heart is a vital component. The contents of the articles referred to in the current paper reveal that there are 4 major types of arrhythmias that result from centrifugal acceleration.[4] The four include sinus arrhythmia, premature arterial contraction, arterial fibrillation, and premature ventricular contraction.[3] In order to categorize each of the mentioned arrhythmias, the author of the current study made observations depending on the levels of +Gz exposure. A detailed discussion is provided in this section. Sinus arrhythmia According to Rayman,[1] the heart has a specific rhythm to which it beats. Consequently, any external force l ike g-stress tends to distort the normal pattern of this organ, resulting in what is now known as cardiac arrhythmia. From the articles reviewed in this study, subjects in centrifugal training experiments were found to exhibit sinus arrhythmia among other complications known in aviation medicine.[9] The study by Hanada et al.[2] revealed that this complication is common during centrifugal training, where the subject’s heart rate normalizes immediately after a rapid heart-beat rhythm. Interestingly, there were subjects who exhibited this particular kind of arrhythmia prior to centrifuge acceleration and the subsequent exposure to the +Gz forces. As illustrated in table 2, the occurrence of the SA in the participants was recorded at 48%. It is important to appreciate that the high occurrence rate is not really due to the centrifugal acceleration. Hanada et al.[2] argue that the condition is a normal occurrence, especially among persons involved in physical training. Studies ill ustrate that the normal rate of a healthy adult lies between 60 to 100 beats every minute.[1] However, some studies indicate that the pattern varies between the genders. A normal female’s heart rate, for instance, is estimated to fall between 47 and 103 beats for every minute.[17] In men, the estimated rhythm is placed at the range of 43 to 102 beats per minute. Alterations in heart beat rhythm due to sinus arrhythmia are not fatal. There are cases where the condition cannot be detected. As such, members of a flying crew who are found to have the condition are not in danger. Premature arterial contraction (PAC) The human heart is fitted with a pace maker that has electrical characteristics.[1] as a result, when this part is exposed to external forces, there are distortions in its normal functioning. Centrifugal acceleration, as aforementioned, has an effect on the organ. The resultant +Gz forces give rise to G-stress. As mentioned earlier, these stressors tend to affect the n ormal workings of the human anatomy. The pacemaker is among the body parts affected. As a cardiac arrhythmia, premature arterial contraction is a phenomenon where the heart’s pacemaker emits signals before the ‘stipulated’ time.[18] The maker is located above the ventricles, meaning that these chambers respond to the distorted signals. As a result, the heart’s rhythm is altered by the ventricle’s ‘irregular’ response. An arrhythmia of this kind is usually common when an individual is stimulated either through exercises or as a result of such beverages as coffee. However, the same is also true when an individual undergoes centrifugal training.[2] In the study by Hanada et al.,[2] PAC exhibited itself in a number of the subjects used in the experiments. Despite the fact that the condition is not lethal, it can present itself in a manner that would require a discontinuation of the training. In such cases, it is considered as clinically sev ere. Hanada et al.[2] point out that repeated PAC is quite severe and advices intermittent discontinuation of centrifugal training among subjects who exhibit the condition. Premature ventricular contraction (PVC) The heart’s functions rely on the electrical impulses of the pacemaker.[19] In cases where +Gz forces are introduced into the human anatomy, the said impulses are interfered with. When such interferences occur, the functioning of some of the compartments of the heart is impeded, resulting in a distorted rhythm of heart beat. As an example of cardiac arrhythmia, PVC is characterized by the contraction of the heart’s ventricles before the expected electrical signal. The name ‘premature’ is sourced from this irregular contraction of the ventricles. The diagram below is an ECG representation of this condition: Graph 1: Premature ventricular beats Source: Vettes et al.[6] The study by Hanada et al.[2] points out that PVC can exhibit itself in differen t degrees. There is the occasional premature ventricular contraction, which is a mild version of the condition. Subjects who present the said condition are allowed to continue with centrifugal training owing to the fact that it is not harmful. The harmful case of PVC involves repeated PVC and Bigeminy, Trigeiny PVC. However, in spite of the fact that it is more harmful in comparison to occasional PVC, the latter case calls for the termination of centrifugal training after some time. A look at the study by Hanada et al.[2] reveals that 19 pilots exhibited the paired PVC condition. The number of subjects who presented the condition in subsequent training sessions kept on decreasing. The same indicates that despite being a common occurrence due to centrifugal training, PVC is only severe when a subject is exposed to High G-Stress over a long period of time without a break. A case in point is a pilot who travels in an aircraft at speeds that result in a stress of 5Gz.s-1 without taking a break. Such an individual is likely to experience a severe case of PVC, which might lead to cardiac arrest.[18] Artrial fibrillation Exposure to +Gz requires some form of tolerance from the persons participating in the centrifugal acceleration exercises.[19] Increased exposure and the resultant stresses affect the heart’s electrical functions. The atrial happens to be another region of the heart that is affected by the G-forces. According to Rayman,[1] the +Gz forces can increase the rate at which the pacemaker emits electrical impulses. When this happens, the ventricles contract in an irregular and erratic manner, leading to arterial fibrillation.[20] Whinnery[3] points out that exposure to G stress in such centrifugal exercises is characterized by atrial ectopy. As is the case with the other arrhythmias mentioned in this paper, this condition can be mild or severe depending on levels of exposure. For instance, Vettes et al.[6] suggest that the complication is regarded as normal when subjects are exposed to +2G for about five minutes. However, the researchers point out that the condition becomes severe in cases where the G-force is increased to +5G and the subjects exposed to the same for a period of more than five minute. Conclusion Vettes et al.[6] point out that centrifugal training, and by extension centrifugal acceleration, has a direct impact on cardiac arrhythmia. In the context of this study, centrifugal acceleration is regarded as an avenue of generating G-forces to create stress on human anatomy. Aviation medicine makes use of centrifugal training to effectively understand cardiac arrhythmia. In essence, this condition is caused by the distortion of the normal heart beat. Whinnery[3] introduced the element of human centrifuge in their study. The contraption is used in aviation medicine to conduct experiments on centrifugal acceleration. During such experiments, two main factors determine how G-forces give rise to cardiac arrhythmia. The two include the degree of +Gz and the duration of exposure. Intensity and duration are crucial elements in explaining the various types of arrhythmias. Hanada et al.[2] point out that centrifugal acceleration in centrifugal training exercises gives rise to 3 main types of arrhythmias. The analysis points out that sinus arrhythmia, premature atrial contraction, and premature ventricular contraction are the most common conditions. Atrial fibrillation is another type of arrhythmia associated with the exercises. 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