Diffuse Electrical Injury - IEEE Xplore

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Michael S. Morse*, Member, IEEE, Jennifer S. Berg, and Rachel L. TenWolde ... *M. S. Morse is with the Department of Electrical Engineering, University.
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 51, NO. 8, AUGUST 2004

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Diffuse Electrical Injury: A Study of 89 Subjects Reporting Long-Term Symptomatology That is Remote to the Theoretical Current Pathway Michael S. Morse*, Member, IEEE, Jennifer S. Berg, and Rachel L. TenWolde

Abstract—Historically, tissue damage from electrical contact was thought to arise from resistive heating of tissues along the current pathway. The modern view has accepted that tissue damage can result from cellular rupture (electroporation) induced by the presence of an electric field. There remain electrical injuries that defy explanation by either theory. In rare electrical contacts, diffuse symptomatology arises that is neither proportionate to the electrical contact nor does it occur along the theoretical linear pathway of the current from entry point to exit point. Disproportionate, remote electrical injury is most notable when the contact voltage is low (120 and 240 V). Symptoms occur, absent diagnostic evidence, that defy explanation as organic injury. A Web-based interactive survey was used to locate and query individuals suffering from rarely occurring responses to electrical contact. The results of the study suggest that there is a common symptomatology that is neither linked to voltage nor loss of consciousness at the time of contact. Index Terms—Diffuse electrical injury, disproportionate electrical injury, electrical injury, electric shock, low-voltage electrical injury.

I. INTRODUCTION

I

N RECENT years, the literature has begun to recognize that in some rare electrical contact cases the resultant injury is disproportionate to the “voltage, current, and/or wound size” of the contact [1]. Neuropsychological test performance has also been shown in some cases to be unconnected to “injury related characteristics (e.g., voltage)” [2]. A lack of a correlation has been noted between voltage and loss of consciousness, excluding those cases where the loss of consciousness and injury due to electrical shock are caused by secondary blunt force trauma [3]. Disproportionate response cases, being the exception rather than the rule, leave researchers in a quandary to explain the causal connection between electrical contact and physiological response. The problem becomes more difficult when the symptoms are not only disproportionate to the parameters of the shock or the local electric field of the shock but also occur

Manuscript received January 15, 2003; revised October 23, 2003. Asterisk indicates corresponding author. *M. S. Morse is with the Department of Electrical Engineering, University of San Diego, San Diego, CA 92110 USA (e-mail: [email protected]; [email protected]). J. S. Berg is with the Naval Medical Center, San Diego, CA 92134 USA (e-mail: [email protected]). R. L. TenWolde was with the University of San Diego, San Diego, CA 92110 USA. She is now with Unisys Corporation, Rancho Bernardo, CA 92128 USA (e-mail: [email protected]). Digital Object Identifier 10.1109/TBME.2004.827343

remotely (or distant) to the theoretical pathway of the current. (The theoretical current pathway is the linear path from entry point to exit point.) Remote symptomatology of electric shock not only includes physical ailments but often includes neurological and neuropsychological symptoms that can exist even in the total absence of a theoretical current path that includes the brain [2], [4], [5]. Studies indicate that the neuropsychological sequelae after electrical contact, even when remote to the current path, rarely occur absent other substantial physical injury [6], [7]. With much lower frequency, electrical injury is observed to manifest neuropsychological symptomatology absent substantial or even measurable other tissue injury [8]. MRIs, CTs, and nerve conduction studies offer only inconclusive support for the presence of physical injury in such cases [5], [6]. There is considerable debate as to whether such injury is of organic or psychogenic origin and it is likely that the treatment, absent diagnostic support, will be more in keeping with the nonorganic diagnoses [2], [6]. Until recently, studying this rarely occurring class of electrical injury (characterized by little or even no overt physical injury, limited or no diagnostic support for electrically induced tissue damage, and substantial neuropsychological postcontact symptoms) has been difficult given the rarity with which the injury occurs. Cases are geographically scattered and absent initial gross tissue damage, medical treatment is not centralized about any particular area of medical specialization. Through forensic consultation, a substantial number of cases with similar symptomatology following low-voltage electrical contact were noted. Over time, the most common symptoms appearing in these “diffuse electrical injury” cases were studied and compared [8]. Since litigation was a common theme to all of those cases studied, it is easily inferred that there was a strong incentive to exaggerate symptoms for which there were little or no objective diagnostic support, resulting in biased statistics. With the advent of the World Wide Web and powerful search engines, coupled with almost universal personal access to computers, it is now possible to tap the computer-using population of the world to locate individuals suffering from extremely rare (or geographically scattered) illnesses such as the electrical injury described in this paper. Today, if one has a question, the typical response is to “search the web” for the answer. It was assumed that individuals who suffered from unexplainable symptoms following an electrical contact would turn to the Web for information in hope of finding information not available otherwise. A website was established that directed those searching

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for information on their electrical injury to an interactive survey site. At the survey site, individuals self-reported the experience and effects of their electrical contact along with pertinent life demographics. Respondents were asked to check from almost 200 phrases that described that which they felt or experienced. Over 180 surveys have now been received and placed within the study database. Each electrical injury has been characterized by time since injury, voltage of contact, duration of contact, entry and exit wounds, duration of unconsciousness, age, gender, locale, race, and litigation history (or lack thereof). Symptomatology has been further broken out by time that symptoms arose following contact (preexisting, first 48 hours postcontact, within the first three weeks, between three weeks and six months, and beyond six months). Upon statistical analysis, a set of symptoms was found to occur postcontact at a statistically greater than in the baseline preshock data. The frequency results of that analysis are presented here. II. PROPORTIONAL RESPONSE TO ELECTRIC CURRENT To understand disproportionate response, one must first be able to recognize and anticipate that which is proportionate to any electrical contact. To do so, requires considering: 1) modes of tissue injury; 2) theoretical current pathway. A. Modes of Tissue Injury Thermal Injury: Thermal injury results from resistive heating of tissues and is most likely to occur where the highest tissue resistance and highest current densities are observed. In lower energy contacts, this will be limited to the entry and exit points with heating within the body tissues being negligible. In higher energy contacts, more internal heating will occur. The energy dissipated in the form of heat is described by W s

(1)

where current in amperes; resistance in ohms through which current is passed; time in seconds of exposure to current. W-s). (NOTE: One calorie Human tissue will experience first degree burns when raised to 50 C for a period of 20 s or more [9]. The current density (amps per cm ) tends to be highest at the entry and exit points before it diffuses into the internal tissues. This is most prominent when the area of entry or exit contact is small. Skin resistance can also vary wildly ranging from 100 k cm for very dry skin down to (far) less than 1% of that value for very wet skin [10]. Tissue burning for a 1-cm , dry-skin, 120-V contact is estimated to occur within approximately 40 s although severe burning is unlikely. For contact with a power line at 7200 V, the energy necessary to cause substantial external burning is imparted virtually at the instant of contact [9]. Internal burning of tissues also can occur, but, because of the bulk volume of tissues and the fairly low resistivity of some internal tissues, internal heating is negligible in low-energy electrical contacts. It can take considerable entry point current

or contact time to impart significant enough thermal energy to cause internal thermal injury [11]. With regard to neural damage, it has been reported that a current of 40 ma applied for a duration of 5 s to a 3-mm-diameter nerve is sufficient to cause lasting disorders in function and structure in peripheral nerves of cats [3]. Note that this would require a current density of over 0.5 amps per centimeter squared. Thermal injury occurs only along or near the pathway of the dictates that resistive current. The current squared term . heating can only take place along the path of the current Over time, the heating may spread by diffusion to neighboring tissues. Given the energy requirements to heat tissue and the time constraints for heat diffusion, remote injury from a shock of low voltage and brief duration would not be expected to occur as the result of tissue heating [12]–[14]. Electroporation: Frequently, electrical injury is observed absent a contact capable of generating enough tissue heating to cause damage. Lee reported an alternative to thermal heating that explains how electrical injury occurs in those circumstances where the impact of the contact would not be great enough to cause the thermal damage that the injury would suggest as when there is internal injury following a low-energy contact. In the presence of a sufficiently significant electric field, cell membranes will rupture. This rupturing or “electroporation” disrupts the metabolic functioning of the cell and can cause cell death. Per Lee, an electric field of 200 V/m in the direction of a 1-cm-long skeletal muscle should be enough to rupture the membrane [15]. This theory recognizes that significant injury can occur in low-voltage contacts if the electric field is high enough. As an example, in a 120-V contact, where the entry and exit points are very close, the electric field can be as high as 10 000 V/m, many times the field strength necessary to cause significant cellular injury [15]. Electroporation can cause slow cellular death that is consistent with the often noted delayed onset of neurological sequelae [16] following contact and might also serve to explain the delayed onset of some neuropsychological symptomatology. Electroporation explains how significant and apparently disproportionate responses can be observed following low-voltage contacts even when the contact is brief because the injury is proportionate to the electric field and not the energy of the contact. Since electroporation can only occur along the current path where there is an electric field gradient, electroporation would not explain neurological injury remote to the path of the current. Secondary (Mechanical and Thermal) Tissue Injury: It is also recognized that energy other than electrical can be imparted during an electrical contact to cause secondary injury from that caused by the direct electrical impact on tissues. Thermal, mechanical, and acoustical energy can all be imparted to damage tissue. Blunt force trauma from falls or from muscle contraction caused by the electrical contact can lead to significant injury disproportionate to the electrical energy imparted. When an arc is drawn during an electrical accident, the hot explosive blast can cause surface tissue burns, blunt force trauma, and even traumatic brain injury without any current ever entering the body. Note: the subjects in this study were limited to those not affected by any secondary type injuries.

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B. Theoretical Current Pathway

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III. DISPROPORTIONATE AND REMOTE RESPONSE

Length of the tissue through which current flows (cm);

In the overwhelming majority of electrical injuries, the postcontact symptoms can be explained as being proportionate to either the thermal impact or electroporation. Still, there are those instances where the symptomatology is clearly of an origin that is remote to the theoretical current pathway and must, by inference, also be disproportionate to the contact. In the absence of a theoretical current pathway that would dictate electrical involvement with the brain, the prevalent theory is that such unexplainable symptomatology is of a nonorganic origin. This is supported by Weeks who observed no current passage through the brain in any limb-to-limb electrical contact [17]. The most common nonorganic diagnoses assigned to such injury are posttraumatic stress disorder (PTSD) and other anxiety disorders, depression, psychological factors affecting physical conditions, and somatoform disorder (including conversion disorder, hypochondriasis, somatization disorder, and somatoform pain disorder) [4]. While it is well recognized that mental stress can give rise to organic damage (as is classically seen when a heart condition develops from a long-term stressful lifestyle), in electrical injury nonpath symptomatology will often arise fairly rapidly (within days or weeks) following the initial contact, suggesting an organic origin to the symptomatology in contrast to the implications of Week’s research. Thus far, the literature broadly recognizes remote response but has failed to develop the causal connection for its occurrence. The chronology between the time of electrical contact and the response seems to provide the only causal link. The most common remote response noted in the literature is loss of consciousness at the time of contact where there is no head involvement [18], [21]. Respiratory arrest has also been observed in instances where the respiratory center is remote to the theoretical pathway of the current [22].

cross-sectional area of the tissue through which current flows (cm ).

IV. ANALYZING ELECTRICAL CONTACTS

In every electrical injury, there must be discussion of the current pathway when considering the proportionality between the injury and the contact. The current pathway is typically characterized only by the known electrical entry and exit points—as in a “hand to hand” or “hand to foot” contact. The internal current pathway remains unknown. The historical view, which continues to be widely accepted for analyzing shock scenarios, is that the theoretical current path is along the shortest linear path as in a “structureless gel” [17]–[19]. It is of course well known that tissue is not homogenous and that, for anything but a gross analysis of current, tissues are definitely not a “structureless gel.” It is generally assumed that electrical injury by either thermal heating or by electroporation will only occur along this theoretical path. A view that comports more with physical laws (and less with the “structureless gel” theory) would need to recognize that the percentage current distribution must be inversely proportionate to pathway resistance as is required by Ohm’s Law . One must infer that the electrically shortest path may not always be the physically shortest linear path and that some current would theoretically flow in all conductive path) between entry and exit points. ways (where Obviously, for some pathways, the current would be so small as to be negligible. The resistance posed by any tissue pathway would be defined by (2) where resistivity of the tissue (

cm);

Since bulk tissues (such as muscle) have cross-sectional areas that can be orders of magnitude larger than the conductive paths offered by tissues with lower resistivity values [20], bulk tissue pathways are of dramatically lower resistance than other pathways (such as neural and vascular). Bulk tissues would thus conduct the overwhelming percentage of the current. This gives rise to the appearance of the broadly accepted “structureless gel” as described by Weeks and Alexander. The requirement that Ohm’s Law be met in all conductors coupled with the nonhomogenous nature of tissues dictates, however, that the real current pathway is far more complex than the theoretical current pathway and leaves open the idea that remote tissue damage might be possible from current that is deviating from the shortest linear path between the entry to exit point. When considering whether a response to an electrical contact is local or remote to the current pathway, it is essential to consider through what tissues the current will traverse between the entry and exit points. For the purpose of this study, remote response was considered as any tissue response that is not local to the theoretical current pathway between the entrance and exit points where the theoretical pathway is that which was defined by the widely used “structureless gel” theory.

To establish if the symptomatology from an electrical contact is proportionate with the contact and localized to the current path requires looking at the injuries received in the context of the parameters of the contact scenario. The key descriptive parameters of an electrical contact [19], [23] are: • entry point location and injuries; • exit point location and injuries; • theoretical current path (from entry to exit point); • voltage differential between entry and exit point; • path resistance (as estimated based on theoretical path and circumstances of shock); • current flow (voltage/path resistance); • duration of contact; voltage current • energy of the contact contact duration . The presence of current, duration, or energy limiters such as in ground fault circuit interruptors (GFCIs), circuit breakers, or the storage capacity of capacitors must also be considered. Often, not all of the parameters are known with complete certainty but most can be estimated from the circumstances and the description of the electrical contact. Most of what is needed to analyze any electric contact can be established by way of a de-

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tailed interview with the victim. Witnesses to the contact also provide valuable information. Objective technical and medical reports are also useful. Even if the victim and all witnesses have only lay knowledge of electricity, a properly conducted interview will yield most, if not all, of what is needed to characterize the shock. We give an example here. Interview: A shock victim says he/she had no entry or exit wounds or burns when shocked by a faulty room lamp and that he/she was thrown backward at the instant of contact. He/she did not lose consciousness and has a clear recollection of what occurred. The shock occurred immediately after the victim came in from exercising. The victim was barefoot and standing on a cement floor. The shock occurred on a hot and humid summer day. The victim’s left hand was by his/her side. No GFCI was present and the circuit was protected by a 15-A circuit breaker which did not trip. Interpretation: The victim is relating that they were shocked by 120 V (voltage to a household lamp) for a duration of less than 0.1 s. (Note: it takes 0.1 s or less for muscles to recoil in response to electrically induced contraction [24]). Had there been a GFCI that tripped, that would have further limited the duration of the contact to the trip duration of the GFCI which is a function of the fault current level. Because it was hot and humid, and the victim was exercising, the victim was probably sweating. The lack of entry or exit wounds suggests that their skin resistance was possibly very low. It also suggests that path resistance would not vary significantly as a function of time as might be observed when there is gross tissue injury that causes breakdown of the skin barrier or tissue charring. This is confirmed by the fact that no resistive burning occurred at the entry or exit. (Note: in low-voltage electrical contacts, burns occur less than 40% of the time [25]; a lack of burning is not by itself indicative of the energy of the contact.) The likely current path would be the right hand to both feet. The victim’s minimum total body resistance under these conditions might conservatively be estimated at 500 . By Ohm’s Law, the current cannot exceed 0.24 A. (Max current 120 V/500 . In certain rare instances, the current is further limited by the capability of the circuit. The Ohm’s law calculation must be less than the trip current of the circuit breaker. In most electric shocks, the available current defined by the circuit breaker is vastly more than the actual current of the shock as limited by Ohm’s law and no circuit breaker trip will occur. (Note: even for circuits with large-value circuit breakers, the fault current still cannot exceed the limitation set by Ohm’s law.) Energy of the shock is calculated to be less than 2.88 W s (maximum energy 120 V 0.24 A 0.1 s). The maximum energy in calories dissipated in the form of heat equals 0.69 calories (energy in calories 0.24 2.88 W s). Since one calorie will increase the temperature of one cubic centimeter of water, one degree centigrade and the total shock energy is less than one calorie, little tissue heating will actually occur.

Anticipated proportionate response: This type of shock would be considered a very minor electrical contact. It would be expected to have been briefly painful. The brevity and resultant low energy would have caused almost no thermal tissue heating and no internal thermal injury would be expected to result. The long distance between entry and exit point would likely not have created a large enough electric field (probably 60 V/m) at any point to cause electroporation. Because of the voltage and path through the chest, there was a small probability of ventricular fibrillation at the time of contact, but since that did not occur it need not be considered further. Proportional Response: This shock would only be expected to cause pain at the time of contact and no long-lasting effects would be expected. This type of analysis is quite common when examining electrical injury and determining what type of response is proportional to the contact. V. EXPERIMENTAL METHODS The goal of this research was to locate and identify individuals suffering from low-energy electrical contacts resulting in symptoms that were remote to the theoretical current path and would thus be disproportionate to the contact. The study was designed to look only at a focused subset of the electric shock receiving population and as such, the results are a reflection specifically of the targeted subset. By the nature of the tool, the population was further limited to those who obviously survived the shock and could report their experience via the internet. Those who experienced any form of secondary injury (e.g., blunt force trauma or blast effect) were excluded. The goal was to extract data from that targeted population so as to determine if this specific type of electrical injury presents a common symptomatology. The process followed was as follows. 1) Develop a detailed list of electrical injury symptoms for inquiry. 2) Design a Web-based survey to retrieve data from the target population from which an analysis of the electrical contact can be made and from which a study of postcontact symptoms could be conducted. 3) Make the website visible via multiple search engines. 4) Develop software to analyze the respondent data along a wide variety of axes. 5) Compare postcontact symptom data to baseline data using the Chi-squared test. 6) Determine if the results present a common symptomatology. A. List of Symptoms for Inclusion in the Web-Based Survey By surveying the literature [1], [2], [4]–[7] and reviewing over 50 medical and neuropsychological electrical injury case files, a list of symptoms and diagnoses reported following electric shock was developed. Symptoms that occurred with high frequency among the files and materials reviewed as well as those that occurred less frequently were included in the list. Common descriptions of symptoms as used by patients as well

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TABLE I LIST OF SYMPTOMS AND DIAGNOSES USED IN THE STUDY

as medical diagnoses were included on the list. Each symptom was categorized as either being systemic (e.g., general exhaustion or general physical weakness), path localized (e.g., tingling in hand where current entered), or neuropsychological (e.g., personality change, anxiety, or cognitive losses). The list also included several symptoms/diagnoses not reported with significance following electric shock (e.g., cancer, brain tumor, or muscular dystrophy). The list of symptoms used in the survey is presented in Table I. B. Development of the Web-Based Survey Current literature supports the concept that the World-Wide Web holds great promise as a mechanism for questionnaire-based research [26]. A study by Davis [27] found that findings from Web-based questionnaire research are comparable with results obtained using standard procedures such as

paper-and-pencil format in a researcher’s office. Studies have demonstrated that research subjects are just as likely to respond to a Web survey as a mail survey and that the computerized Web interface may also facilitate self-disclosure [27], [28]. Furthermore, many of the criticisms of online data collection are common to other survey research methodologies [29]. The goal of this research was to locate those with relatively rare responses to electric shock. The benefit of a Web-based survey is that it offers researchers exposure to a very broad population base that was previously impossible to access. The main drawback of conducting a Web-based survey is the foreseeable risk of misdirecting influences by placing a survey in the uncontrolled environment of the internet. Limitations that were foreseen in the survey design are as follows. • Survey respondents are searching the internet looking for answers. They probably represent a population with more

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extreme symptoms than the typical shock victim. This would skew the frequency of symptom occurrence. This is the population targeted by the survey. It serves the research goal, which was to locate and compare data from among those with more extreme or unusual responses to electrical contact. • The information is supplied by the victims of the shock and relates their perception of the shock from their perspective. The survey is designed to conduct a typical postshock interview and compare the perceptions of electrical injury from the viewpoint of the shock victim. • Data about the technical aspects of the shock are supplied by laypersons that may not understand the nature of electricity. The survey was designed with that in mind. The survey seeks general information from which one with knowledge can infer the technical aspects of the shock. The respondents need only provide what they remember, what witnesses have related to them, and what they have been told by their medical providers. • The pool of respondents is limited to those who are computer literate and have access to the World-Wide Web. Today, there is an overwhelmingly broad cross section of the world population that has access to computers and to the internet. That population probably presents a reasonable representation of electric shock victims. • There is always the possibility of respondents with agendas that may be less than pure or who wish to skew the data. Given that electrical injury is not a topic on which individuals commonly search and given the time necessary to fully complete the survey, such individuals are easily filtered. Further, text boxes filled out by respondents along with the survey provide the evaluators insight into the nature of the respondent and the reliability of each individual survey. As stated earlier, surveys that contained physical impossibilities or that were not completely filled out were rejected from the analysis. A website was established that allowed for interactive participation by electric shock victims. The website was designed to conduct a proper survey so as to gain all necessary information to describe the parameters of the electrical contact and the ensuing symptoms. Choices were presented and the respondent needed only to check the boxes that applied to their particular contact and symptom scenario. The site consisted of several sections, querying the respondent about aspects of their life, their electrical contact, and the symptoms that ensued. These sections are: 1) life demographics (gender, age, race, marital status, zip code, email address, and date of survey); 2) history of litigation (prior, present, Workman’s Compensation); 3) general information about electrical contact (place, date, voltage, entry data, exit data, loss of consciousness, and duration); 4) preexisting conditions (population baseline); 5) symptoms immediately following electrical contact (first 48 h); 6) symptoms arising within first three weeks;

7) symptoms existing between three weeks and six months following contact; 8) symptoms existing beyond six months following contact. For each section, there was a text box so that a respondent could offer any further detail they felt necessary or so they could enter symptoms or data for which there was no standardized query. The goal of the website was to gather not only a list of symptoms but to gather information from which the shock could be accurately analyzed and thus characterized when considering if the response was disproportionate to the contact. The survey was designed so that it took long enough to complete that only serious respondents would put forth the effort, but it was not so long as to be too burdensome. It was estimated that the survey could be fully completed in 20 min. While anyone was welcome to fill out the survey, the only respondents who were to be included in this analysis were those with a long-term set of symptoms (greater than three months) that presented with symptoms suggesting an origin that was remote to the theoretical current pathway. Upon completion of the interactive survey, the results were placed into a text string and automatically emailed to the author. C. Making the Website Available to Search Engines This was accomplished by regularly submitting the URL to a large number of search engines. The website was also made public by adding it as a link to an already well-established informational site maintained by the author. Those who had made prior inquiries of the author were emailed the address of the website. Responses to the survey started returning almost immediately upon placement of the site on the web. To date, over 180 valid responses have been added to the database. (Responses deemed to be incomplete were considered invalid, as were surveys where the description of the shock scenario was such deemed to be impossible (e.g., “I am being shocked daily by the government”). D. Analysis Software As data arrived, each record was placed sequentially in a text file. Only one survey per respondent was allowed, although a respondent could replace an earlier survey with a later one. Software was developed in Visual Basic to extract each survey record and calculate all statistical and demographic information for each record, as well as for the whole population. The software tracked the number of respondents for each symptom as a function of time from contact and permitted cross correlation along any of the life or litigation demographic lines, as well as along entry and exit injury and loss of consciousness. The software also calculated Chi-squared values for the population on each symptom based on the hypothesis that the postcontact frequency was significantly greater than the population baseline frequency. Each time an analysis was run, the results were time-stamped and saved. Results included: 1) survey population demographics based on the limits set on that particular run; 2) summary and analysis of each individual survey record;

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3) Excel format summary of all results based on voltage, symptom, and time from contact; 4) Chi-squared value for each symptom.

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TABLE II GROUPING

OF RESPONDENTS BY SHOCK AND LOSS OF CONSCIOUSNESS

VOLTAGE

E. Comparison of Results With Baseline Data A baseline for each symptom was established by tracking the frequency of occurrence of preexisting symptoms among the survey population. Data maintained in the baseline database are for the purpose of providing theoretically expected frequencies for each symptom assuming no electric shock has occurred. As the survey population grows, the frequency values in the baseline database should approach the correct values for the nonshocked population at large. The theoretical values are used in the Chi-squared analysis to determine if the frequency of occurrence of postshock symptoms is statistically greater than the . baseline occurrence of those symptoms F. Determination if Any Common Symptomatology is Observed A common symptomatology is demonstrated when respondent groups experiencing similar shocks suffer similar sets of symptoms occurring at statistically greater frequencies than the baseline frequency. Common symptomatology was to be demonstrated by grouping shock victims by the characteristics of the shock received and then by comparing the symptomatology among the group population. VI. RESULTS At the time of the analysis, the survey database contained data from more than 180 valid respondents. Surveys where the respondent did not include entry/exit location, entry/exit injury, shock voltage, shock duration, or loss of consciousness data were eliminated from the evaluation. A. Remote Impact So as to clearly establish a bright line distinction between localized and remote impact, all respondents whose theoretical current path was unknown or known to include the neck or head were removed from the analysis. Absent brain involvement, loss of consciousness, or presentation of other neuropsychological symptoms would thus be part of a pattern of remote impact from the electrical contact. Any respondent with no indication of long-term (greater than six months) remote impact was eliminated from the analysis. B. Disproportionate Response Low-voltage contact (household voltages) was set out as the criteria for presumed low-impact electrical injury. Such injury except in the case of very long duration contacts rarely imparts enough energy to cause internal damage. Further, at household voltage levels, the electric field from contacts where the entry and exit points are far apart would not suggest injury from electroporation. Anticipated shock impact was subcategorized based on initial remote impact in terms of loss of consciousness. Respondents who suffered similar initial remote impact were grouped together. Presence of entry and exit injury was considered as criteria for grouping, but since entry/exit injury can vary widely based on numerous environmental variables, entry/exit

injury was rejected as a grouping criteria. While voltage and loss of consciousness do not provide an absolute indication of total shock physiological impact, they provided a convenient means to group individuals who suffered similar electrical contacts that caused similar immediate physiological responses. The final set of included respondents consisted of 89 surveys. A review of the zip code demographic data revealed that the participants in the survey were diffusely distributed around the United States and the e-mail addresses revealed that there are respondents from as far away as Australia. A total of nine groups were analyzed. The group characteristics are defined in Table II. All members of all groups suffered remote impact while groups 1–3 consisted of individuals whose responses were clearly disproportionate to the shock received. Groups 4–6 would have presented responses that might be disproportionate to the shock and groups 7–9 presented remote responses that could be considered as consistent with the shock received. The demographics of the groups are presented in Table III. Group 6, although included in the analysis, only contained surveys from three respondents and as such was viewed cautiously when analyzing the data. Tables IV–VI contain the most frequently reported long-term symptoms sustained by each group where long-term symptoms are defined as those that were sustained beyond six months postcontact. Table IV presents those symptoms that occurred most commonly in the low-voltage (most disproportionate) contact groups (1–3). Table V contains the most common symptoms experienced by those who suffered mid-voltage contacts (groups 4–6) and Table VI contains the data for the high-voltage groups (7–9). For each voltage category and group, the most common symptoms are shown ranked by percentage of occurrence. (All

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TABLE III GROUP DEMOGRAPHICS

TABLE IV LOW-VOLTAGE CONTACTS

symptoms presented in Tables IV–VI occur at a statistically than that observed in the baseline higher rate preshock data. Table VII presents the list of neuropsychological symptoms found to occur most frequently (top 10 by percentage) and which also occurred most often across the boundaries of eight of the groups. (Group 6 is excluded.) Table VIII presents the list of general (diffuse) physical symptoms found to occur most frequently (top 10 by percentage) and which also occurred most often across the boundaries of eight of the groups. (Group 6 is excluded.) These two tables are used to provide an indication of whether there is a relationship between the frequency of occurrence of a symptom and the particular group(s) to which that symptom is a member.

VII. DISCUSSION A review of Tables IV–VI indicates that, for each voltage and loss of consciousness subgrouping, there is a clear set of symptoms experienced by the majority of those in the grouping. For each group, the set of symptoms can be delineated as those that are of a diffuse physical nature and those that are of a remote neuropsychological nature. The commonality of diffuse physical symptoms among any group and the high rate of occurrence suggest that often the extent of the electrical injury exceeds the narrow bounds of the linear theoretical pathway between the entry and exit points. For example, many of the respondents report general exhaustion and general physical weakness extending more than six months postinjury. Such long-term physical responses would suggest a systemic impact from the electrical shock that is inconsistent with either the theory of thermal damage from the current or electroporation from the electric field. Damage would be expected to be localized to the current pathway and would not seemingly manifest as broad and systemic weaknesses. Further, for those in groups 1–3, such a long-term response would be significantly disproportionate with the nature of the shock received. The presence of remote neuropsychological symptomatology common to the majority in each group further supports the theory that the impact of the electrical contact goes beyond the bounds of that which is localized to the theoretical current pathway. The presence of such

symptoms as anxiety, personality changes, loss of short-term memory, or moodiness suggest brain involvement that is not explained by any of the theories of electrical injury nor is it consistent with the “structureless gel” theory that describes the current pathway. As the brain is remote to the theoretical current path in all cases studied, there would be no expectation of injury that would commonly be consistent with brain involvement. The data further reveals that, even among that population who have had the most minor electrical contacts as defined by voltage and no or brief loss of consciousness (groups 1 and 2), there may still be extensive long-term symptomatology following the shock. By comparing the symptomatology among

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TABLE V MID-VOLTAGE CONTACTS

TABLE VI HIGH-VOLTAGE CONTACTS

the nine groups delineated, it is apparent that many of the symptoms observed as disproportionate for the lower voltage groups occur at similar frequencies across all group boundaries through and including groups suffering high voltage shock and longer loss of consciousness (groups 8 and 9). The fact that neither voltage nor immediate remote impact seem to correlate with the long-term symptoms is contrary to the traditional view that shock impact must be a function of shock magnitude. The fact that the symptoms occur remote to the theoretical current path is contrary to either the thermal or electroporation theory of electrical injury. This suggests that, in some number of electrical contacts, either the current path is not what might be theoretically expected or that there exists another mode of electrical injury not yet known to medical science.

The author cautiously considers that the “structureless gel” theory of current path may be flawed. Since Ohm’s law is a physical law that must apply to the flow of current in any medium including in biological tissues, the theory of a linear current path could be wrong and perhaps needs to be expanded. One might consider that it is at least theoretically possible that some amount of current might deviate from the pathways provided by the bulk conductive tissues to follow either neural pathways or fluid pathways to tissues not thought to be along the theoretical current path. In the very rare instances where this occurs, it would then be possible to accept remote tissue

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TABLE VII NEUROPSYCHOLOGICAL SYMPTOMS CROSSING GROUP BOUNDARIES (MOST COMMON SYMPTOMS)

ists a mode of injury other than path-dependent thermal or electroporation injuries. Traumatic brain injury presents a scientific analog to remote and diffuse electrical injury. Interestingly, prior to the 1980s, it was generally felt that there was no associated underlying neuropathology with mild traumatic brain injury. Patients complaining of symptoms such as headache, fatigue, memory problems, and irritability were considered to be suffering from psychiatric disorders, “compensation neurosis,” or malingering. However, work with primate acceleration-deceleration models found diffuse axonal injury after mild head injury [30]. In addition, it has now been demonstrated that at a physiological level, traumatic brain injury of any type may create neurochemical and neurometabolic cascade effects as described in Hovda’s fluid percussion model [31], [32], thus explaining symptoms which 20 years ago were felt to lack an organic cause. Perhaps future neuropathological research will identify a mode of injury for the symptomatology described by certain patients experiencing low-impact electrical contact. REFERENCES

TABLE VIII GENERAL PHYSICAL SYMPTOMS CROSSING GROUP BOUNDARIES

injury or brain involvement as outcomes from an electrical contact. Depending on circumstances, the remote injury could still be consistent with an electroporation injury or even a thermal injury to the tissue. VIII. CONCLUSION There exists a class of electrical injury that occurs very rarely but which can present following even low-impact electrical contacts. This injury is characterized by symptoms that are remote to the theoretical current path and often are disproportionate to the parametric characterization of the shock. The resultant insult to the body manifests in the form of a diffuse array of physical symptoms coupled with an array of neuropsychological symptoms. This type of injury seems to occur without proportionality to contact voltage or to initial impact in terms of loss of consciousness. If one is to accept that the similarity in symptomatology across all groups is indicative of an organic response to the electrical insult, then it must be considered that there ex-

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Michael S. Morse (M’87) received the B.S. B.M.E. and M.S. B.M.E. degrees from Tulane University, New Orlean, LA, in 1981 and 1982, respectively, the Ph.D. degree in bioengineering from Clemson University, Clemson, SC, in 1985, and the J.D. degree from the University of San Diego, San Diego, CA, in 1999. He has been a member of the Electrical Engineering Faculty of the University of San Diego since 1990, following three years with the Electrical Engineering Department, Auburn University, Auburn, AB. His research interests have focused on a study of the effects of electricity on the human body and diffuse electrical injury associated with electrical contact. He is also interested in the medical-legal issues associated with electrical injury lacking a clear causal link. Dr. Morse is a member of Sigma Xi, and Tau Beta Pi and was admitted to the California State Bar in 1999.

Jennifer S. Berg received the B.S. degree in chemistry from the University of Tennessee, Martin, and the M.D. degree from the Uniformed Services University of the Health Sciences in 1984. She completed a residency in Psychiatry at the Naval Medical Center, San Diego, CA. She is currently the Chairman of Psychiatry with the Naval Medical Center, San Diego, and has served almost 20 years as a physician in the U.S. Navy. Her research interests include medical sequelae of electrical injury, Posttraumatic Stress Disorder, and aerospace psychiatry. Dr. Berg is a Distinguished Fellow of the American Psychiatric Association and has been the recipient of numerous awards for excellence in psychiatry.

Rachel L. TenWolde received the B.S./B.A. degree in industrial and systems engineering from the University of San Diego, San Diego, CA, in 2003. She is currently with the Unisys Corporation server manufacturing facility, Rancho Bernardo, CA.