Electrical trauma. Cold injury.

Indicate what types of damage are observed when the body is exposed to an electric current?

1. $ Mechanical

2. $ Electrochemical

3. $ Thermal

4. $ Beam

5. $ General biological

% Answer: 1,2,3,5

# 2. For the I degree of electric shock, it is characteristic:

4. $ Clinical death

# 3. For the II degree of electric shock, it is characteristic:

1. $ Convulsive muscle contraction without loss of consciousness

2. $ Convulsive muscle contraction with loss of consciousness, but with preserved breathing and heart function

3. $ Loss of consciousness and impaired heart or breathing (or both)

4. $ Clinical death

#4. For the III degree of electric shock, it is characteristic:

1. $ Convulsive muscle contraction without loss of consciousness

2. $ Convulsive muscle contraction with loss of consciousness, but with preserved breathing and heart function

3. $ Loss of consciousness and impaired heart or breathing (or both)

4. $ Clinical death

#five. For the IV degree of electric shock, it is characteristic:

1. $ Convulsive muscle contraction without loss of consciousness

2. $ Convulsive muscle contraction with loss of consciousness, but with preserved breathing and heart function

3. $ Loss of consciousness and impaired heart or breathing (or both)

4. $ Clinical death

# 6. A feature of electrical injury is:

1. $ Tissue damage along the entire path of electricity

2. $ oppression central nervous system, respiratory and cardiovascular system

3. $ Local injuries predominate (ruptures of muscles, tendons, bone fractures)

% Answer: 1.2

# 7. The severity of an electric shock depends on:

1. $ Current

2. $ Mainly from stress

3. $ Kind of current, duration of action

4. $ Paths of current

% Answer: 1,3,4

#eight. What type of electric current is the most dangerous:

1. $ Constant current

2. $ alternating current

3. $ The danger is proportional only to the magnitude of the current



#nine. A feature of the biological effect of electric current is:

1. $ Paralysis of skeletal and smooth muscles

2. $ Excitation of skeletal and smooth muscles

3. $ Tonic cramps

4. $ Clonic seizures

% Answer: 2.3

#ten. When providing first aid during an electric shock, you must:

1. $ Applying aseptic dressings to wound surfaces

2. $ Interrupt the electrical circuit

3. $ Artificial ventilation and chest compressions

4. $ Introduce respiratory analeptics

5. $ Cardiac defibrillation

% Answer: 2,3,5

#eleven. Specify the features of electric burns:

1. $ Electric burns are always I-IIIa degree

2. $ Electric burns are always IIIb-IV degree

3. $ Electric burns are painless

4. $ There is a pronounced pain syndrome in the area of \u200b\u200belectric burn

5. $ Progression of necrosis due to vascular thrombosis is noted

6. $ Tissue necrosis is always superficial

7. $ For a long time there is no demarcation

8. $ There is a clear border between healthy and affected parts

% Answer: 2,3,5,8

#12. The surgical treatment of burns caused by electricity is characterized by:

1. $ Wait-and-see tactics

2. $ Early necrotomy, necrectomy



3. $ Does not differ from methods of treatment of thermal burns

4. $ Possible preventive bandaging of nearby vessels

5. $ Early closure of skin defects

% Answer: 2.4.5

What is a current loop?

1. $ Variant of current propagation in the body

2. $ Current entry point

3. $ Current outlet

4. $ Electrochemical reactions in the body

#fourteen. The most dangerous are "current loops" passing through:

1. $ Upper limbs

2. $ Heart

3. $ Lower limbs

4. $ Central nervous system

% Answer: 2.4

#fifteen. Acute cold injury includes:

2. $ Chills

3. $ Cold neurovasculitis

4. $ Frostbite

% Answer: 1.4

#sixteen. Chronic cold injury includes:

1. $ Freezing (general cooling)

2. $ Chills

3. $ Cold neurovasculitis

4. $ Frostbite

% Answer: 2.3

# 17. Specify the degree of frostbite by the depth of the lesion:

2. $ Ia, Ib, II, III, IV

3. $ I, II, III, IV

4. $ I, II, IIIa, IIIb, IV

#18. Specify, what degree of frostbite are superficial:

1. $ I degree

2. $ II degree

3. $ III degree

4. $ IV degree

% Answer: 1.2

#nineteen. Specify what degree of frostbite is deep:

1. $ I degree

2. $ II degree

3. $ III degree

4. $ IV degree

% Answer: 3.4

#20. For frostbite of the 1st degree it is characteristic:

5. $ Death of the entire thickness of the skin

# 21. For frostbite of II degree, it is characteristic:

1. $ Bubbles with transparent content

2. $ Necrosis of the entire thickness of the skin and deep-lying tissues (subcutaneous tissue, muscles, tendons, bones)

3. $ Bubbles with hemorrhagic content

4. $ Necrosis of the stratum corneum, granular, partially papillary layers of the epithelium

5. $ Death of the entire thickness of the skin

6. $ Disorder of blood circulation without necrotic tissue changes (hyperemia and edema)

% Answer: 1.4

# 22. For frostbite of the III degree it is characteristic:

1. $ Bubbles with transparent content

2. $ Necrosis of the entire thickness of the skin and deep-lying tissues (subcutaneous tissue, muscles, tendons, bones)

3. $ Bubbles with hemorrhagic content

4. $ Necrosis of the stratum corneum, granular, partially papillary layers of the epithelium

5. $ Death of the entire thickness of the skin

6. $ Disorder of blood circulation without necrotic tissue changes (hyperemia and edema)

% Answer: 3.5

# 23. For frostbite IV degree is characteristic:

1. $ Bubbles with transparent content

2. $ Necrosis of the entire thickness of the skin and deep-lying tissues (subcutaneous tissue, muscles, tendons, bones)

3. $ Bubbles with hemorrhagic content

4. $ Necrosis of the stratum corneum, granular, partially papillary layers of the epithelium

5. $ Death of the entire thickness of the skin

6. $ Disorder of blood circulation without necrotic tissue changes (hyperemia and edema)

# 24. The main causes of frostbite include:

1. $ Low ambient temperature

2. $ High humidity and wind speed

3. $ Alcoholic intoxication

4. $ Vascular diseases of the extremities

5. $ Previously transferred frostbite

% Answer: 1.2

# 25. Common factors contributing to frostbite include:

1. $ Overwork and exhaustion

2. $ High humidity, high wind speed

3. $ Alcoholic intoxication

4. $ Hypo- and adynamia

5. $ Previously transferred frostbite

6. $ Loss of consciousness

% Answer: 1,3,4,6

# 26. Local factors contributing to frostbite include:

1. $ Vascular diseases of the extremities

2. $ Previously transferred frostbite

3. $ Limb injuries

4. $ Tight shoes

5. $ Loss of consciousness

6. $ Hypo- and adynamia

% Answer: 1,2,3,4

# 27. Specify the periods of frostbite:

1. $ Pre-reactive

2. $ Reactive

3. $ Erectile

The duration of the passage of current through the human body

The longer the effect of the current on the body, the greater the likelihood of a serious or fatal injury.

At low current values, this is due to the possibility of electrical breakdown of the skin. At high currents, the likelihood of ventricular fibrillation increases.

The greatest likelihood of fibrillation occurs when a current pulse passes through the heart at a certain point in the cardiac cycle - the T wave in the ECG, duration is about 0.2 seconds.

If the duration of the current flow is less than a long cardiocycle, then the probability of the coincidence of the moment of current flow with the vulnerable period of the cardiocycle and the risk of fibrillation decreases sharply.

Paths of passage of current through the human body

The most dangerous is the passage of current through the respiratory muscles and heart. Paths:

"Hand-hand" through the heart passes 3.3% of the total current,

"Left arm - legs" through the heart is 3.7% of the total current,

"Right arm - legs" through the heart passes 6.7% of the total current,

"Leg - leg" through the heart passes 0.4% of the total current,

"Head - legs" through the heart passes 6.8% of the total current,

"Head - hands" through the heart passes 7% of the total current.

The most severe damage is likely if the heart, lungs, chest, brain or spinal cord are in the path of the current, since the current acts directly on these organs. If the current passes in other ways, then its effect on the organs can be reflex, and not direct. At the same time, although the danger of severe damage remains, its probability is sharply reduced.

The most dangerous are the head-arms and head-legs loops, when current can pass through the brain and spinal cord (but these loops are relatively rare).

The least dangerous path is the leg-to-leg path, which is called the lower loop and arises when a person is exposed to the so-called step voltage. In this case, a small current, obviously, passes through the heart. But it must be borne in mind that there were facts of a fatal outcome when the current flowed through the finger, from one side to the other.

According to statistics, disability for 3 days or more with the current path "hand-arm" in 83% of cases, "left arm-legs" in 80%, "right arm-legs" -87%, "leg-leg" in 15 %. Thus, the current path affects the outcome of the lesion; the current in the human body does not necessarily follow the shortest path, which is explained by the large difference in resistivity

Fig. 1 Paths of current passage: a) left hand - legs; b) hand - hand; c) right hand - legs; d) leg - leg

Influence of direct and alternating current of various frequencies on the outcome

Values \u200b\u200bof current passing through a person, mA

The nature of the impact

Alternating current, 50-60 Hz

D.C

Onset of sensation, slight trembling of fingers

Not felt.

Violent trembling of fingers. The sensation reaches the wrist.

Not felt.

Light cramps in the hands, pain.

Itching. Feeling of heat.

Hands are difficult, but you can still tear them off the electrodes. Severe pain in fingers, hands, and forearms.

Enhanced heating sensation

Paralysis of the hands, it is impossible to tear them off the electrodes. Very severe pain. Breathing is difficult.

An even greater increase in heating. Slight contraction of the arm muscles.

Stop breathing. Onset of cardiac fibrillation.

Strong heating sensation. Contraction of the arm muscles. Convulsions, difficulty breathing.

Stop breathing. For more than 3 sec. Heart failure.

Stop breathing.

When the circuit breaks quickly, even a small direct current (below the sensation threshold) gives very sharp blows, sometimes causing muscle cramps in the arms. The most dangerous current is 50-60 Hz. The danger of the action of the current decreases with increasing frequency, but the current at 500 Hz is no less dangerous than at 50 Hz.

In practice, it has been established that the path of current passage through the human body plays an essential role in the outcome of the lesion. So, if vital organs - the heart, lungs, brain - are in the path of the current, then the danger of injury is very high, since the current acts directly on them.

If the current passes in other ways, then its effect can only be reflex, and not direct.

There are a lot of possible paths of current through the human body, which are also called current loops. The most common current loops are shown in table. 1 .

Table 1

Characteristics of the most common paths of electric current through the human body *

Current path

How often this path occurs,%

The proportion of those who lost consciousness during exposure to current,%

Fraction of current passing through the heart area,%

Hand - hand

Right arm - legs

Left arm - legs

Leg - leg

Head - legs

Head - hands

* The table shows the data on a person's electric shock that caused disability, i.e. leading to an accident.

Most dangerous are the loops: head - arms and head - legswhen an electric current can pass through the brain and spinal cord. Fortunately, these loops are relatively rare.

Next in danger is the way right arm - legs, which ranks second in frequency.

Least dangerous is the way leg - leg, which is called the lower loop and occurs when a person is exposed to the so-called step tension.

3. The effect of electric current on a person

Electric current passing through the human body has a thermal, chemical, biological and mechanical effect on his body.

Thermal - leads to dangerous heating of tissues and the occurrence of injuries such as burns, electrical signs, metallization of the skin.

Chemical - leads to electrolysis of blood and other solutions contained in the body, a change in their chemical composition, a violation of their physiological functions.

Biological - is expressed in irritation of living tissues of the body, sharp, involuntary convulsive muscle contractions, reflex excitation of the nervous system and disruption of internal bioelectric processes.

The variety of actions of electric current on the human body often leads to various electrical injuries, which can be reduced to two types: local damage to the body and general electrical injuries - the so-called electrical shock, when the whole body is affected due to disruption of the normal activity of vital organs and systems. It has been established that the most vulnerable organ of the human body when electric current passes through it is the heart (Table 2).

Local electrical injuries include:

    electric burns of two types- current (contact) and arc. There are four degrees of burns: Ι - skin redness; ΙΙ - the formation of bubbles; ΙΙΙ - necrosis of the entire thickness of the skin; ΙV– tissue carbonization. Currents arise at a voltage not exceeding 1–2 kV and are, in most cases, burns of ΙΙ and ΙΙ degrees. Arc arcs between the live part and the human body (an arc with a very high energy and a temperature of over 3500 ° C) cause severe burns of ΙΙΙ and епV degrees;

    electrical signs- well-defined spots of gray or pale yellow color on the surface of human skin exposed to the current. Signs are also in the form of scratches, wounds, cuts or bruises, warts, skin hemorrhages and calluses;

    electrophthalmia- eye damage caused by intense radiation of an electric arc, the spectrum of which contains ultraviolet and infrared rays harmful to the eyes;

    mechanical damage- arise as a result of sharp involuntary convulsive muscle contractions under the action of a current passing through the human body; as a result, ruptures of the skin, blood vessels and nerve tissues can occur, as well as dislocation of joints and even bone fractures.

Electric shocks (excitation of living tissues of the body by an electric current passing through it, accompanied by involuntary convulsive muscle contractions), depending on the outcome of the effect of the current on the body, are of four degrees:

    Ι degree- convulsive muscle contraction without loss of consciousness;

    ΙΙ degree- convulsive muscle contraction, loss of consciousness, but preservation of breathing and heart function;

    ΙΙΙ degree- loss of consciousness and impaired cardiac activity and / or breathing;

    ΙV degree– clinical death, i.e. lack of breathing and blood circulation.

D

table 2

the effect of electric current on the human body

Types of electrical injuries

Clinical manifestations

Local electro injuries

Electrical burn (60-65%) from all electrical injuries

Current burn (contact)

Burns of I and II degrees of the skin at the place of contact of the body with the live part. Occur on electrical installations with a voltage not higher than 1-2 kV.

Arc burn

Skin burns of III and IV degree, can be extensive with tissue burnout to a great depth. They arise in networks with voltages over 1-2 kV.

Electrical signs; current signs; electrical tags (19-21% of all electrical injuries)

The appearance of spots of gray or yellow-gray color on the skin at the place of touching live parts (sometimes the form of scratches, cuts, warts, calluses)

Skin metallization (10% of all victims)

Penetration of metal inclusions into the skin in places of contact with an electric arc, accompanied by pain due to burns and tension of the skin

Electrophthalmia (1-2% of all victims)

Inflammation of the mucous membranes of the eyes caused by ultraviolet radiation when an electric arc occurs; manifests itself after 2-6 hours. Accompanied by lachrymation, photophobia, partial blindness

Mechanical damage (rare)

Tears of the skin, blood vessels, nerve fibers, dislocations due to convulsive muscle contractions under the influence of an electric current

Electric shock

I degree

Convulsive muscle contraction without loss of consciousness

II degree

Convulsive muscle contraction and loss of consciousness. Preservation of breathing and work of the heart

III degree

Loss of consciousness, impaired heart activity or breathing

IV degree

Clinical (imaginary) death;

lack of breathing and heart function; pupils are dilated, do not react to light

Termination of the heart (direct action of the current on the heart muscle), fibrillation of the heart muscle (coincidence of the action of the current with T-phase of the heart). Cessation of breathing, paralysis (direct or reflex action of the current on the muscles of the chest). Electric shock (severe neuro-reflex reaction, accompanied by disorders of blood circulation, respiration, metabolism); lasts from several tens of minutes to a day

For the occurrence of electric shock, the paths along which the electric current passes, the so-called current loops, are of great importance. In fig. 2.3 shows the possible paths of current propagation in the human body.

The main difference between electrical injuries with different loops is through which organs the current passed. The main conductors of current in the body are not large vessels, but muscle masses along with the capillary network feeding them. It should be borne in mind that in some cases (for example, when a victim falls), the position of the limbs may change and, accordingly, the initial path of current propagation to another may change. The danger to the victim's life largely depends on the current loop. For example, the lower loop through the lower limbs is less dangerous than the upper loop when the current flows through both upper limbs and the trunk.

Mechanisms of the damaging effect of electric current

When the body is damaged by electric current, a specific and nonspecific effect of the current is released. The specific effect of the current is manifested in biological, electrochemical, thermal and mechanical effects.

The biological effect of the current is diverse. As a result of the action of the current, irritation of the smooth and skeletal muscles, the endocrine and nervous systems, and internal organs occurs. As a result of tonic contraction of the diaphragm and spasm vocal cords the function of external respiration is disturbed. The action of the current on the heart muscle leads to the development of ventricular fibrillation. Spasm of the muscles of the arteries leads to a sharp increase in blood pressure. The organs of internal secretion respond with the release of hormones (primarily catecholamines). Electric current has a variety of effects on nerve receptors and conductors.

The electrochemical effect of the current is manifested in the divergence of ions and their concentration at different poles. As a result, coagulation necrosis occurs at the anode, and colliquation necrosis at the cathode. The gases and water vapors formed during electrolysis often impart a cellular structure to the tissues. In some cases, the skin is impregnated with the conductor metal (metallization effect).

The thermal effect of the current is more susceptible to tissues with low electrical conductivity. It is in the tissues with high resistance (primarily in the skin and bones), in accordance with the Joule-Lenz law, the greatest amount of heat is released. The amount of heat released is directly proportional to the current strength, electrical resistance of tissues and the duration of contact. The higher the voltage, the more heat is generated at the points of contact, where burns occur. As a result of the passage of current through the skin, burns of the skin and underlying tissues occur, up to carbonization. In the bone tissue, pearl beads can form, which are molten and then solidified calcium phosphate in the form of white balls with voids formed during the evaporation of the liquid in the bones.

The mechanical action of the current leads to separation and rupture of tissues. The passage of high voltage currents through tissues is accompanied by an instantaneous release a large number heat and mechanical energy. With the rapid release of a large amount of thermal energy, an explosive effect takes place, as a result of which a person can be thrown aside or a limb can be detached. The higher the voltage in the electrical network, the higher the mechanical action of the current.

The nonspecific action of the electric current is due to the release of other types of energy, into which electricity is converted outside the body. In particular, from a flash of a voltaic arc or from hot (when an electric current passes through them) conductors, thermal burns of the skin occur. A flash of a voltaic arc is accompanied by the emission of light energy. As a result of the action of light radiation (visible, ultraviolet and infrared spectrum), various types of damage to the organ of vision (corneal burns, electrophthalmia, and others) can develop. The defeat of a person with high-voltage electricity can be accompanied by an explosion, as a result of which damage to the organ of hearing occurs (ruptured eardrum, hearing loss). Spattering and high temperature combustion of metal particles from electrical conductors can cause metallization of the skin.

A frequent occurrence is mechanical damage that has developed as a result of a victim falling from a height or falling of body parts between moving mechanisms. The victim may drown if dropped into water. Clothing soaked in oil, gasoline, or other flammable liquids can ignite the victim with thermal burns. In addition, when an electric current (low voltage - less than 1000 V) passes through the tissues of the body, as a result of a sharp contraction of the muscles, dislocations, avulsion and compression fractures can occur. This phenomenon takes place in places where large muscle mass is attached. Electrical trauma causes severe disorders in the functioning of internal organs, often contributes to the exacerbation of diseases.

The most important condition for an electric shock to a person is the path of this current. If vital organs (heart, lungs, brain) are on the way, then the danger of fatal injury is very great. If the current passes in other ways, then its effect on vital organs can only be reflexive. At the same time, although the danger of fatal injury remains, its probability is sharply reduced.

The current flows only in a closed circuit. Therefore, there is both the entry point of the human body and the exit point of the electric current. The possible paths of current in the human body are innumerable. However, the following can be considered characteristic:

hand leg; hand-hand; leg-leg; head-hand; leg-head, etc.

the degree of danger of various current loops can be assessed by the relative number of cases of loss of consciousness, as well as by the value of the current passing through the region of the heart.

The most dangerous are the “head-hand” and “head-foot” loops, when the current can pass not only through the heart, but also through the brain and spinal cord.

Ticket number 14

What electrical receivers in terms of ensuring reliability belong to the second category electrical receivers, permissible interruptions in the power supply?

PUE (clause 1.2.18-1.2.21)

Category II electrical receivers - electrical receivers, the interruption of the power supply of which leads to a massive undersupply of products, massive downtime of workers, mechanisms and industrial transport, disruption of the normal activities of a significant number of urban and rural residents;

For power consumers of category II, in the event of a power failure from one of the power sources, power supply interruptions are permissible for the time required to turn on the backup power by the actions of the personnel on duty or the mobile operational team.

What are the employees who repair the electrical installation personally responsible for?

PTEEP clause 1.2.9

For disturbances in the operation of electrical installations, personal responsibility is borne by: workers carrying out equipment repairs - for disturbances in work caused by the poor quality of repair.

Frequency of knowledge testing of administrative and technical personnel.

PTEEP clause 1.4.20-1.4.21

1.4.20. The next check should be carried out in the following terms:

  • for electrical personnel who directly organize and carry out maintenance work on existing electrical installations or perform commissioning, electrical installation, repair work or preventive tests in them, as well as for personnel entitled to issue orders, orders, conduct operational negotiations - once a year;
  • for administrative and technical personnel who do not belong to the previous group, as well as for labor protection specialists admitted to inspect electrical installations - once every 3 years.

1.4.21. The time of the next test is set in accordance with the date of the last knowledge test.

4. What is meant by an order? Its validity period, registration procedure.

POTEE (clause 7.1-7.7)

An order is a written task for the production of work, which determines its content, place, time, safety measures (if they are required) and the workers who are entrusted with its implementation, with an indication of the electrical safety group.

The order has a one-time nature, its validity period is determined by the duration of the working day or change of executors.

If it is necessary to continue work, if the working conditions or the composition of the brigade change, the order must be given again.

In case of breaks in work within one day, the re-admission is carried out by the work manufacturer.

7.2. The order is given to the manufacturer of the work and the admitting one. In electrical installations that do not have local operating personnel, in cases where access to work at the workplace is not required, the order is given directly to the worker performing the work.

7.4. The order is allowed to be issued for work alternately on several electrical installations (connections).

7.5. Admission to work by order must be registered in the log book of work on orders and orders.