what happens to the human body in the electric chair
Eplasty. 2009; 9: e44.
Published online 2009 Oct 12.
Conduction of Electrical Current to and Through the Homo Body: A Review
Raymond Grand. Fish
aBioacoustics Research Lab & Department of Surgery, University of Illinois at Urbana-Champaign
Leslie A. Geddes
bWeldon Schoolhouse of Biomedical Technology, Purdue University, W Lafayette, Ind
Abstract
Objective: The objective of this commodity is to explicate ways in which electric current is conducted to and through the homo body and how this influences the nature of injuries. Methods: This multidisciplinary topic is explained by first reviewing electrical and pathophysiological principles. In that location are discussions of how electric electric current is conducted through the body via air, h2o, earth, and man-made conductive materials. There are as well discussions of peel resistance (impedance), internal body resistance, current path through the trunk, the let-go miracle, skin breakdown, electric stimulation of skeletal muscles and fretfulness, cardiac dysrhythmias and arrest, and electric shock drowning. Afterwards the review of basic principles, a number of clinically relevant examples of accident mechanisms and their medical effects are discussed. Topics related to high-voltage burns include footing faults, ground potential slope, step and bear upon potentials, arcs, and lightning. Results: The practicing doc will have a better understanding of electrical mechanisms of injury and their expected clinical effects. Conclusions: In that location are a diversity of types of electrical contact, each with important characteristics. Understanding how electric current reaches and travels through the trunk can help the clinician sympathize how and why specific accidents occur and what medical and surgical problems may be expected.
This article explains ways in which electric current is conducted to and through the human being body and how this influences the nature of injuries. This multidisciplinary topic is explained in role A by start reviewing electrical and pathophysiological principles, and afterwards in role B past considering specific types of accidents. There are discussions of how electrical current is conducted through the body via air, water, earth, and man-made conductive materials. In that location are discussions of skin resistance (impedance), internal torso resistance, current path through the torso, the allow-go phenomenon, peel breakdown, electrical stimulation of skeletal muscles and fretfulness, cardiac dysrhythmias and arrest, and electric daze drowning. Later the review of basic principles, a number of clinically relevant examples of accident mechanisms and their medical effects are discussed in office B. Topics related to loftier-voltage burns include basis faults, footing potential slope, stride and touch potentials, arcs, and lightning. Understanding how electric current reaches and travels through the body tin assist one understand how and why specific accidents occur and what medical and surgical issues may be expected.
PART A: Basics OF ELECTRICITY AND HOW Information technology INTERACTS WITH THE Human BODY
Electrical daze is defined as a sudden violent response to electric current flow through whatever office of a person's body. Electrocution is death caused by electric shock. Primary electrical injury is tissue damage produced direct by electrical current or voltage. Secondary injuries, such equally falls, are common. Unless otherwise noted, this article is referring to currents and voltages of 60 (or fifty) Hz AC rms. Also, by resistance, we actually mean the magnitude of the impedance. High voltage refers to 600 V or more AC rms.
Very pocket-sized amounts of electrical current consequence in major physiological furnishings
Current refers to the amount of electricity (electrons or ions) flowing per 2d. Current is measured in amperes or milliamperes (ane mA=i/1000 of an ampere). The amount of electric current that flows through the trunk determines diverse effects of an electric shock. Every bit listed in Table one, various amounts of electric current produce certain furnishings. Most electric current-related effects result from heating of tissues and stimulation of muscles and nerves. Stimulation of nerves and muscles tin issue in bug ranging from a fall due to recoil from hurting to respiratory or cardiac arrest. Relatively small amounts of electric current are needed to cause physiological effects. As shown in the table, information technology takes a 1000 times more current to trip a xx-A circuit breaker than it takes to cause respiratory arrest.
Table 1
Estimated furnishings of 60 Hz AC currents*
| 1 mA | Barely perceptible |
| 16 mA | Maximum current an average human can grasp and "allow become" |
| 20 mA | Paralysis of respiratory muscles |
| 100 mA | Ventricular fibrillation threshold |
| ii A | Cardiac standstill and internal organ damage |
| 15/20 A | Common fuse breaker opens excursion† |
Skin resistance protects the body from electricity
The body has resistance to electric current flow. More than than 99% of the torso'due south resistance to electric current flow is at the skin. Resistance is measured in ohms. A calloused, dry hand may have more than 100,000 Ω because of a thick outer layer of dead cells in the stratum corneum. The internal torso resistance is about 300 Ω, being related to the wet, relatively salty tissues beneath the skin. The skin resistance can exist effectively bypassed if there is pare breakup from loftier voltage, a cut, a deep abrasion, or immersion in h2o (Table 2). The skin acts like an electrical device such as a capacitor in that it allows more current to menstruation if a voltage is irresolute chop-chop. A speedily irresolute voltage will be applied to the palm and fingers of one's hand if it is belongings a metal tool that suddenly touches a voltage source. This type of contact will requite a much greater electric current amplitude in the body than would otherwise occur.two
Table two
Means protective skin resistance can be greatly reduced
| • | Significant physical skin damage: cuts, abrasions, burns |
| • | Breakdown of skin at 500 V or more |
| • | Rapid application of voltage to an area of the pare |
| • | Immersion in water |
Voltage
Voltage can be thought of as the strength that pushes electrical current through the body. Depending on the resistance, a certain amount of current will flow for whatsoever given voltage. Information technology is the current that determines physiological effects. Nevertheless, voltage does influence the issue of an electrical shock in a number of ways, as discussed beneath.
Skin breakdown
At 500 Five or more than, high resistance in the outer layer of the skin breaks down.3 This lowers the body's resistance to current flow greatly. The outcome is an increase in the corporeality of current that flows with any given voltage. Areas of peel breakup are sometimes pinhead-sized wounds that can be easily overlooked. They are often a sign that a big corporeality of current could enter the body. This electric current can exist expected to outcome in deep tissue injury to muscles, nerves, and other structures. This is one reason why there is often significant deep tissue injury picayune in the style of skin burns with high-voltage injuries.
Electroporation
Electroporation (jail cell membrane damage) is due to the awarding of a big voltage beyond a length of tissue. This would occur with 20,000 V from hand to mitt. Electroporation would also occur with 120 V with the end of a ability cord in a child'due south mouth. In this situation, the voltage is non high, only the volts per inch of tissue is the same as in the case when high voltage is practical from paw to hand or head to foot. As a result of electroporation, even brief contact can upshot in severe muscle and other tissue injuries. Electroporation is another reason for the occurrence of deep tissue injury.
Heating
Other things beingness equal, the heat energy delivered to tissues is proportional to the square of the voltage (increasing the voltage by a gene of 10 increases the heat free energy past a factor of 100).
Alternating and directly current
Membranes of excitable tissues (eg, nerve and muscle cells) will pass electric current into cells most effectively when an applied voltage is changing. The skin is somewhat like in that it passes more than current when the voltage is irresolute. Therefore, with alternating current, there is a continuous irresolute of the voltage, with 60 cycles of voltage alter occurring per 2d. With alternating current, if the current level is loftier plenty, there will be a feeling of electric shock as long as contact is made. If at that place is enough current, skeletal muscle cells will exist stimulated every bit rapidly equally they can respond. This rate is slower than 60 times per 2nd. This will requite a tetanic musculus wrinkle, resulting in the loss of voluntary control of muscle movements. Cardiac muscle cells will receive threescore stimulations per 2nd. If the amplitude of the current is sufficient, ventricular fibrillation will occur. The heart is well-nigh sensitive to such stimulation during the "vulnerable period" of the cardiac cycle that occurs during much of the T moving ridge.
In contrast, with direct current, there is a feeling of stupor only when the circuit is made or broken unless the voltage is relatively high.iv Fifty-fifty if the current amplitude is large, it may not occur during the vulnerable period of the cardiac bicycle. With alternate current, a stupor duration of longer than 1 cardiac cycle will definitely give stimulation during the vulnerable menstruum.
How current, voltage, and resistance are related
Ohm's law is as follows:
Figure one shows a voltage source and a resistor. As an example, a 1000-Ω resistance continued to a 120-Five electrical source will accept
Voltage causes current (I) to flow through a given resistance. The somewhat circular current path is referred to as a circuit.
Electric current path(s)
Electricity flows from (at least) ane signal to some other. This is often from 1 concluding to the other terminal of the voltage source. The connection betwixt the terminals of a voltage source is often referred to every bit a "load." The load can be anything that conducts electricity, such as a low-cal bulb, a resistor, or a person. This is shown in Figure 1.
To illustrate some important problems, this circuit model tin be applied to a motorcar. For example, the negative terminal of a automobile bombardment is connected ("grounded") to the metallic chassis of the car. The positive terminal is connected to a reddish cablevision made of individual wires that become to the starter, lights, air conditioner, and other devices. Electrical current flows through many parallel paths: the radio, the starter, the lights, and many other current paths. The current in each path depends on the resistance of each device. Disconnecting either the positive or negative final of the battery will end the catamenia of current, although the other connectedness is intact.
Applying the model to the human torso
The example of the car makes it easier to sympathise current flow in the human being trunk. A person receiving an electrical stupor volition have (at least) 2 contact points to a voltage source, ane of which might be the earth ground. If either connectedness is asunder, no current will menstruum. The analogy as well explains how electric current menstruation can become through many somewhat parallel pathways, such every bit through the nerves, muscles, and bones of the forearm. The amount of current in each automobile appliance or tissue blazon depends on the resistance of each component.
Figure two takes the model a step farther. It shows the battery and headlights on a cycle. There are rusty connections on both the positive and negative battery terminals. The total resistance the voltage must button electric current through is that of the ii rusty connections in improver to the resistance of the headlights. More resistance results in less current period. The rusty connexion is analogous to skin resistance, and the headlight is analogous to the internal torso resistance. The total body resistance is equal to the internal body resistance plus the 2 skin resistances.
Rusty contacts add resistance to current flow. The headlights are analogous to the internal trunk resistance, and the rusty connections are like to skin resistance. Total trunk resistance is equal to the internal trunk resistance plus the 2 skin resistances.
Figure 3 shows a person connected to a voltage source. There are connections to the left hand and the left pes. The "total body resistance" of the person is equanimous of the very low (approximately 300 Ω) internal torso resistance plus the ii peel contact resistances. The skin contact resistance will usually exist between 1000 and 100,000 Ω, depending on contact area, moisture, condition of the skin, and other factors. The skin thus provides well-nigh of the body's protection from electric electric current.
Diagram of a person continued to a voltage source.
High-voltage contact
High-voltage (≥600 V) contacts sometimes seem paradoxical. A bird comfortably sits on a loftier-voltage electric line. But a person with piece of work boots continuing next to a truck is killed on touching the side of the truck because an elevated attachment to the truck was touching a power line. High voltage breaks downwards electrical insulators, including pigment, skin, and virtually shoes and gloves. Special shoes, gloves, and tools are rated as being protective for certain voltage levels. These items must be tested periodically for (sometimes pinpoint sized) breaks in insulation. Insulation may not exist effective if there is moisture or contamination on the surface of the item.
As noted above, current menses requires 2 or more contact points that are at different voltages. Many electrical systems are continued ("grounded") to the earth. Support structures are oft metal and also physically in the ground.
The workman was connected electrically to the electric line through the metal parts of his truck. The high voltage (7200 V) was high plenty to go through the pigment on the truck and his shoes. The bird was not close plenty to the ground or anything else to complete the excursion to ground. In that location are birds with large wingspans that practise get electrocuted when they bridge the gap between wires and structures that are at unlike voltages.
PART B: TYPES OF ELECTRICAL CONTACT
Step and touch potentials
The earth (ground) under our feet is usually considered to exist at 0 V. Power lines and radio antennas are grounded by connecting them to metallic rods driven into the basis. If a person is barefoot on the footing with his or her feet spread apart, there should be 0 V betwixt the 2 anxiety. This normal land of affairs is disrupted if a conductor from a high-voltage power line reaches the ground or if lightning strikes the ground.
Voltage from overhead power lines can reach the basis in several ways. A line tin can break or come loose from its insulated supports and brand contact with the ground itself or with structures that are themselves connected to the earth. Supporting wires (guy wires) may come loose from their connections nigh the footing and go energized when they come into contact with a power line. The energized guy wire is then at a high voltage. If the guy wire contacts the ground, the voltage on the earth at and around the contact point is no longer 0 5.
When an energized conductor contacts the ground directly or through a conductor, it is referred to as a ground mistake. The decrease of voltage with distance from the earth contact point of an energized object is called the ground potential slope. Voltage drops associated with this dissipation of voltage are chosen ground potentials.
Effigy 4 is a typical voltage-gradient distribution bend. This graph shows that voltage decreases with increasing altitude from the grounding object. On the left of the grounded, energized object, at that place is a voltage departure between the person'south 2 feet, referred to equally a pace potential. On the right, there is a voltage deviation betwixt the person'due south hand and 2 feet, referred to as a touch on potential. There is also a pace potential between the 2 anxiety of the person on the correct. (Figure 4 and this section are modifications of part of OSHA Regulations [Standards-29 CFR].)
Step and impact potentials. Actual numbers may vary with soil type and moisture as well every bit other factors.
Wink burn, electric current heating, or both
High-voltage arcs involve passage of electricity through the air. In some cases, the arc does non contact a person. In this situation, in that location can exist serious burns from the estrus of the arc (a wink burn). In that location can also be burns from called-for clothing and other substances. Burns tin can also result from touching objects that are thermally hot only not electrically energized.
High-energy arcs can produce explosion-related stupor waves.5 The blunt trauma force that results tin can throw a person, rupture eardrums, and contuse internal organs.
If the arc or an energized conductor does contact the person and electricity flows through him or her, there can be injury from the electrical electric current menstruum through the body in add-on to the injury mechanisms mentioned higher up.
It is of clinical importance to determine whether a high-voltage injury involved electric electric current flow through the body. Electric current period through the torso due to high voltage can event in conditions that must be watched over time. These conditions include myoglobinuria, coagulopathy, and compartment syndromes. Several clinical and electric contact–related bug can help 1 determine whether at that place has been current flow through the body. First, electrical current menstruation through the body requires at to the lowest degree 2 contact points. With loftier voltage, these are generally total-thickness burns. They can exist pinhead sized and are sometimes multiple due to sparking. If a conductor such equally a piece of wire contacted the peel, there may be a fire injury with the shape of the object contacted.
A flash fire with no electric current through the torso, in contrast, tends to exist diffuse and relatively uniform. Flash burns are sometimes less than full thickness, whereas a high-voltage contact burn will be full thickness.
And so-called entry and exit wounds
In that location are often just 2 contact burns that are generally referred to as entrance and exit wounds. These terms chronicle to the fact that electric current comes from a voltage source, enters the body at 1 signal, flows through the body to the other contact point, where it exits the torso, and returns to the voltage source (or a ground). This terminology is somewhat disruptive if ane considers that alternating electric current changes direction many times per second. The terminology may also be misleading considering it reminds one of bullet wounds that sometimes have small entry and larger exit wounds. With electrical injury, the size of the wound volition depend on factors such as the size and shape of the conductor, the geometry of the torso part involved, and wet. The analogy to gunshot wounds is also misleading in that there is not always a bullet go out wound considering the bullet remains lodged in the person. Thus, ii separate tertiary-caste burns propose current menstruation through the body. A diffuse, partial-thickness burn does not propose electric current flow through the trunk.
In improver to the contact-related features, at that place are clinical signs that can aid determine whether there was current menstruation through deep tissues. For example, a high-voltage contact to the hand associated with electric current flow into the arm would be expected to produce forearm firmness and tenderness. There would be pain with passive and agile finger movements, and in that location may be sensory deficits in the manus.
Lightning
Lightning typically flashes over the surface of the body, resulting in surprisingly footling damage in some persons. Wet peel and the very brief nature of the pulses of electricity encourage the current to travel on the surface of the trunk. Nevertheless, lightning does sometimes injure persons considering of current menstruum in the body, edgeless mechanical force, a blast effect that may rupture eardrums and contuse internal organs, and intense light that tin can outcome in cataracts.
Contact with conductors
Depression voltage (<600 V)
The effects of low-voltage shocks are listed in Tabular array i. The current levels given vary with the specific current path, elapsing of contact, the person'due south weight, height, and body build (especially musculature and bony structures), and other factors. The effects that practise occur in any specific case are strongly dependent on several factors related to how contact is made with the source of electricity. These factors include current path, moisture, if there was inability to allow get, and the size of the areas of contact.
Electric current path
If the electric current path goes through the chest, continuous tetanic contractions of the chest wall muscles tin result in respiratory arrest. Dalziel,6 who fabricated measurements on human subjects, relates that currents in excess of 18 mA stimulate the chest muscles so that animate is stopped during the daze.
Some other effect that occurs with a transthoracic electric current path is ventricular fibrillation. Transthoracic current paths include hand to mitt, hand to foot, and front of the chest to the back of the chest. Fauna experiments have suggested that the ventricular fibrillation threshold is inversely proportional to the square root of the duration of current menses.
The allow-become phenomenon for low (<600 V) contact
A factor that makes a large deviation in the injury sustained in depression-voltage shocks is the inability to let become. The amount of current in the arm that volition cause the hand to involuntarily grip strongly is referred to as the permit-get current.seven If a person's fingers are wrapped around a big cable or energized vacuum cleaner handle, for case, most adults will be able to let get with a electric current of less than 6 mA. At 22 mA, more than 99% of adults volition not be able to let go. The pain associated with the let-go current is then severe that young, motivated volunteers could tolerate it for only a few seconds.7 With current catamenia in the forearm, the muscles of flexion and extension are both stimulated. However, the muscles of flexion are stronger, making the person unable to voluntarily let get. Nearly all cases of inability to let go involve alternating current. Alternating current repetitively stimulates fretfulness and muscles, resulting in a tetanic (sustained) wrinkle that lasts as long as the contact is continued. If this leads to the bailiwick tightening his or her grip on a usher, the event is continued electric electric current menses through the person and lowered contact resistance.8
With alternating electric current, at that place is a feeling of electric stupor as long as contact is made. In contrast, with straight current, there is only a feeling of shock when the circuit is made or broken. While the contact is maintained, in that location is no sensation of shock. Beneath 300 mA DC rms, there is no allow-become phenomenon because the mitt is not involuntarily clamped. At that place is a feeling of warmth while the current travels through the arm. Making or breaking the circuit leads to painful unpleasant shocks. Above 300 mA, letting go may exist impossible.4 The threshold for ventricular fibrillation for straight electric current shocks longer than ii seconds is 150 mA as compared with l mA for 60-Hz shocks; for shocks shorter than 0.2 seconds, the threshold is the same as that for 60-HZ shocks, that is, approximately 500 mA.four
Heating power is also increased when a person cannot allow get. This is considering a firm grip increases the area of skin effectively in contact with the conductors. Additionally, highly conductive sweat accumulates between the skin and conductors over time. Both of these factors lower the contact resistance, which increases the corporeality of current catamenia. In addition, the heating is greater because the elapsing of the contact is often several minutes in comparing with the fraction of a second that information technology takes to withdraw from a painful stimulus.
Being unable to let get results in more current for a longer period of time. This will increase damage due to heating of muscle and nerves. At that place will also be an increment in pain and the incidence of respiratory and cardiac arrest. There can also exist shoulder dislocation with associated tendon and ligament injury, also as bony fractures in the area of the shoulders.
The permit-go phenomenon for high (>600 V) contact
Several different outcomes may occur when a person grasps a conductor giving 10 kV Air-conditioning paw-to-paw voltage. It takes over 0.5 seconds of such contact earlier most of the distal forearm cells are estrus damaged. All the same, within x to 100 milliseconds, muscles in the current path will strongly contract. The person may be stimulated to grasp the conductor more tightly, making a stronger mechanical contact. Or, the person may be propelled abroad from the contact. Which of these events occurs depends on the position of the hand relative to the conductor. Most eyewitnesses written report the victims being propelled from the usher, peradventure because of generalized muscle contractions. The time of contact is estimated to be about 100 milliseconds or less in such cases.9 (p57)
Immersion contact: Electrical shock drowning
Clinical issues
Drowning and most drowning can result from electricity in the h2o. Conditions requiring treatment of virtually drowning caused past electricity are mostly the same as weather condition related to nonelectrical almost drowning. These weather condition include myoglobin elevations that tin can consequence in renal failure (detected past creatine kinase [CPK] elevations and urine examination), adult respiratory distress syndrome, hypothermia, hypoxia, electrolyte abnormalities, and arrhythmias that include ventricular tachycardia and ventricular fibrillation. Creatine kinase and myoglobin levels in nonelectrical most-drowning events are thought to be due to a violent struggle, along with sometimes prolonged hypoxia and electrolyte imbalances. Electricity in the water tin can stimulate muscles strongly enough to requite a person severe musculus pain during and later his or her almost-drowning feel. This would further increase CPK and myoglobin levels beyond those that would result from a nonelectrical near drowning Table 3. Creatine kinase levels sometimes rise for a day or more, being influenced by treatment given, continued hypoxia or hypotension, and other conditions that might influence continuing necrosis of tissue.
Tabular array 3
Why immersion in h2o can be fatal with very low voltages
| 1 | Immersion wets the peel very finer and greatly lowers skin resistance per unit surface area |
| 2 | Contact area is a large percentage of the entire torso surface area |
| 3 | Current may too enter the body through mucous membranes, such as the mouth and throat |
| 4 | The human trunk is very sensitive to electricity. Very small amounts of current can cause loss of power to swim, respiratory abort, and cardiac arrest |
Effects of electric electric current
Many of the determinations of electrical current effects in humans were made by Dalziel.10 For whatever given upshot, such as tetanic muscle contractions, at that place is a range of electric current levels that produce the effect due to private subject differences. For case, the current needed to cause tetanic musculus contractions in the forearm (the "let-go" current) can exist from six to 24 mA (60-Hz AC rms) depending on the subject. Therefore, current levels listed in publications may be maximum, average, or minimum levels, depending on the issues being discussed. For safety problems, near-minimum values are oft appropriate.
As listed in Table 4, Dalzielvii plant that 10 mA would crusade tetanic muscle contractions and thus loss of muscle control. In addition, Smoot and Bentel12 establish that 10 mA of current was enough to cause loss of muscle control in water. They carried out measurements in table salt water and did non report voltages that were applied.
Tabular array iv
Mechanisms of decease in electric daze drowning
| Mechanism | Current needed, mA | Voltage needed, V Air-conditioning |
|---|---|---|
| Electrical stimulation of the heart causing ventricular fibrillation | 100 | 30 |
| Tetanic wrinkle (finer paralysis) of the muscles of respiration | twenty | vi |
| Loss of musculus control of the extremities: 16 mA for an average humanane | 16 | 4.8 |
| Loss of musculus control of the extremities: as little equally 10 mA for the most sensitive female7,11 | 10 | 3 |
Total body resistance in water
The total body resistance from hand to foot in h2o is considered to be 300 Ω when considering safety precautions.13 – 15 Smoot11 , 16 measured a total body resistance of 400 Ω with immersion. Much of this is due to the internal body resistance. Thus, immersion eliminates most of the skin resistance.
Table salt water is very conductive compared with the human body, making electric shock drowning in salt water relatively rare. This is because much of the current is shunted around the exterior of the body.
If in that location is a voltage difference, for example, betwixt 1 arm and the other, then electric current will menstruum through the torso. The amount of current is equal to the voltage divided by the total body resistance.
How much voltage in the water can be lethal?
Table one lists the amounts of electric current needed to crusade ventricular fibrillation and other fatal conditions. The full body resistance in water is of 300 Ω. Thus, the current needed and the resistance it must experience are known. Information technology is therefore possible to calculate the voltage needed. For ventricular fibrillation, the calculation is every bit follows:
Required voltage = Electric current × Resistance
For causing ventricular fibrillation, the required voltage is as follows:
Voltage = 100 mA × 300Ω = 30 V
Figures for other mechanisms of expiry are listed in Table 4.
H2o-related electrical contact oftentimes occurs in 2 ways. These mechanisms tin can happen in bathtubs, pond pools, and lakes. The first mechanism of contact involves a person in h2o reaching out of the water and contacting an energized conductive object. For example, a person is well-grounded past sitting in a bathtub. The resistance of the contact with his hand touching an energized object outside of the tub may be high plenty to protect him or her, especially if his or her hand is not wet and the expanse of contact is small.
The second contact machinery involves a person in the water being in an electrical field because of an energized conductor that is in the water. For example, an electrical heater connected to the hot wire of the 120 V Air-conditioning outlet falls in the water. The grounded drain is shut to the person'due south shoulders, whereas the heater is most his or her anxiety. This gives a voltage departure of 120 V Ac from shoulders to the feet. With a total body resistance of 300 Ω, 360 mA flows, more than three times the amount needed to give ventricular fibrillation.
In lakes, ponds, and other water bodies, an electric power source tin generate current into the water. The location of voltages in the water can be measured. Voltages may be nowadays in the water because of the hull of a boat connected to an on-shore power source is energized. Voltages may likewise be present in the h2o because of energized conductors in the water that release electrical current into the water.
An electric gradient (or field) can exist that is analogous to the state of affairs described in a higher place for pace and touch potentials. The state of affairs is more complex to clarify in the water because a person in the water assumes different postures and orientations in three dimensions (up, downwards, and sideways—north, south, east, and west). The transthoracic and translimb voltages volition vary as the person moves in relation to the orientation (direction) of the electrical field.
Measurements of loss of muscle command in water
Measurements similar to those of Smoot and Bentel12 were washed with blessing of the institutional review board of University of Illinois in Urbana-Champaign. Metal plates were placed inside safety containers. The metal plates were flat on the bottoms of the containers. A rubber mat with holes was placed on top of each metal plate. An (isolated) power source ground wire was connected to ane plate, and a 60-Hz AC voltage from the power source was connected to the other plate. The subject area stood with 1 foot on each safe mat, as shown in Effigy 5. Thus, the subject's contact with electric current was primarily through the water contacting the feet through the holes and also through water contacting the legs to a higher place. This pes-to-pes current path simulated the hand-to-hand and hand-to foot situations that tin can occur with swimmers in water. This setup minimized current flow through the chest. The written report involved just 1 subject area.
Measurement setup for voltage and current in h2o.
Fresh (non salt) water with electrical conductivity of 320 µmho/cm filled each saucepan to a level most the hip. It was found that electrically induced muscle contractions were greatly modified past leg position in the water.
Initial testing has shown that with 3.05 V (60-Hz AC rms) applied betwixt the plates, a current of eight.65 mA flowed, resulting in involuntary flexion of the genu to 90°. This flexion could not be overcome with voluntary effort. The articulatio genus could be flexed further voluntarily, but it would non straighten beyond 90° of flexion. The involuntary dandy flexion occurred when the leg was lifted (by hip flexion) so that the thigh was horizontal and the knee was at the h2o level. This is like to the situation when one is swimming. Muscle command was gradually regained when the foot was lowered to the bottom of the bucket (by hip extension to the neutral position) and the leg became vertical. Total body resistance would exist calculated as follows:
At 4.05 5, a current of 12.6 mA flowed. The knee was flexed to 135°, meaning that the heel was near the buttocks. This could non be overcome with voluntary effort. Again, this occurred when the leg was lifted and then that the knee was at the water level, similar to the situation when one is swimming. Bottom impairment of muscle control was noted at other leg positions. Muscle control was gradually regained when the human foot was lowered to the lesser of the bucket and the leg became vertical. The resistance would exist four.05 V/12.vi mA = 332 Ω.
The current levels measured in these experiments are consistent with those reported by Dalziel,7 Smoot,11 and NIOSH,ane as listed in Tables 1 and 4. The full resistance of the organization (water plus subject) is close to 300 Ω, so often mentioned in literature.
Decision
In that location are a variety of types of electrical contact, each with important characteristics. Agreement how electric electric current reaches and travels through the body can help the clinician sympathise how and why specific accidents occurred and what medical and surgical problems may be expected.
Acknowledgments
The authors thank Andi Fish for the illustrations.
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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763825/
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