Clinical Equipment Management

20/12/200620/12/2006 Dr.Eng:Ghada M.AmerDr.Eng:Ghada M.Amer 11
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Benha UniversityBenha University

Electrical SafetyElectrical Safety
BiomedicBiomedicalal
EngineeringEngineering

Team WorkTeam Work
Waleed A. Abd El ManimWaleed A. Abd El Manim
Ab AlaaAb Alaa
Abd ELazeemAbd ELazeem
MohamidMohamid
Abd EL SAMIIAbd EL SAMII

Summary SlideSummary Slide
 NFPA STANDARDSNFPA STANDARDS
 ELECTRICITYELECTRICITY
 CONDUCTORCONDUCTOR
 INSULATORINSULATOR
 ELECTRICAL CHARGEELECTRICAL CHARGE
 ELECTRICAL CURRENTELECTRICAL CURRENT
 ELECTRICAL TERMSELECTRICAL TERMS
 TYPES OF ELECTRICITYTYPES OF ELECTRICITY
 STATIC ELECTRICITYSTATIC ELECTRICITY
 Electrical Safety TestingElectrical Safety Testing

ReferencesReferences
 BiocomputingBiocomputing
 Bioelectricity and InstrumentBioelectricity and Instrument
 BioelectricityBioelectricity
 Biomedical SensorsBiomedical Sensors
 Computer Design For BiomedicalComputer Design For Biomedical
ApplicationApplication
 Medical ImagingMedical Imaging

ELECTRICITY AND FIRE SAFETYELECTRICITY AND FIRE SAFETY
GLOSSARY OF TERMSGLOSSARY OF TERMS
ELECTRICITY – aELECTRICITY – a
fundamental Quantity offundamental Quantity of
nature usually used asnature usually used as
electric currentelectric current

CONDUCTORCONDUCTOR
 Any substance, medium, or material that allowsAny substance, medium, or material that allows
the transmission of electricity (flow of freethe transmission of electricity (flow of free
electrons)electrons)
Examples: metals, carbon, salt water, humansExamples: metals, carbon, salt water, humansSolid wire
Lamp cordMulticonductor

INSULATORINSULATOR
 A medium that does not allow the transmissionA medium that does not allow the transmission
of electricity by inhibiting the flow of electrons.of electricity by inhibiting the flow of electrons.

A non-conductive material such as rubber, glass,A non-conductive material such as rubber, glass,
porcelain, or wood.porcelain, or wood.

ELECTRICAL CHARGEELECTRICAL CHARGE
 ALL MATTER CONSISTS OF ATOMSALL MATTER CONSISTS OF ATOMS
 ATOMS ARE COMPOSED OF:ATOMS ARE COMPOSED OF:

Protons – positively charged particlesProtons – positively charged particles

Neutrons – particles with no charge, neutralNeutrons – particles with no charge, neutral

Electrons - negatively charged particlesElectrons - negatively charged particles

ELECTRICAL CHARGEELECTRICAL CHARGE
 When electrons move from one atom toWhen electrons move from one atom to
another, an imbalance occurs.another, an imbalance occurs.
 An atom which has lost electrons will carryAn atom which has lost electrons will carry
a positive charge.a positive charge.
 An atom which has gained electrons willAn atom which has gained electrons will
carry a negative charge.carry a negative charge.

ELECTRICAL CURRENTELECTRICAL CURRENT
 THE MOVEMENT OF ELECTRONSTHE MOVEMENT OF ELECTRONS
THROUGH A CONDUCTORTHROUGH A CONDUCTOR
Example:Example: a light bulb illuminatesa light bulb illuminates
because electrons move through thebecause electrons move through the
conductor of wires and metal base to theconductor of wires and metal base to the
tungsten filament in the bulb. The filamenttungsten filament in the bulb. The filament
heats up and brightens – producing light.heats up and brightens – producing light.

ELECTRICAL CURRENTELECTRICAL CURRENT
CurrentCurrent

The rate at which electricity flows.The rate at which electricity flows.

Measured in amperes.Measured in amperes.

TYPES OF ELECTRICITYTYPES OF ELECTRICITY
 Alternating Current (AC) – aAlternating Current (AC) – a
current that periodicallycurrent that periodically
reverses its direction of flow.reverses its direction of flow.

Power from external power plantPower from external power plant
 Direct Current (DC) – a currentDirect Current (DC) – a current
flowing in only one direction.flowing in only one direction.

Battery powerBattery power

ELECTRICAL TERMSELECTRICAL TERMS
 PATH OF LEAST RESISTANCE - electricity orPATH OF LEAST RESISTANCE - electricity or
the flow of electrons will act like water and alwaysthe flow of electrons will act like water and always
seek a path from highest concentration to lowerseek a path from highest concentration to lower
concentration via the easiest route.concentration via the easiest route.

 CURRENT LEAKAGECURRENT LEAKAGE
- all electricity can- all electricity can
leak causing theleak causing the
potential for shock.potential for shock.

 Ampere – the practical unit ofAmpere – the practical unit of
current strength.current strength.

The amount of current flowing inThe amount of current flowing in
a circuit. The rate of flow.a circuit. The rate of flow.
 Ohm – the unit of electricalOhm – the unit of electrical
resistance of a conductorresistance of a conductor

Measurement of the ability of aMeasurement of the ability of a
material to receive flow ofmaterial to receive flow of
electrons.electrons.

 Volt – the unit of electromotive force that movesVolt – the unit of electromotive force that moves
electrons through a material. It induces currentelectrons through a material. It induces current
to flow in one direction.to flow in one direction.

The higher the number of volts, the more direct theThe higher the number of volts, the more direct the
currentcurrent
 Voltage – the potential energy of electrons.Voltage – the potential energy of electrons.
Electromotive force of an electric currentElectromotive force of an electric current
expressed in volts.expressed in volts.

 Resistance – the opposition toResistance – the opposition to
the passage of a current.the passage of a current.
impedes or restricts the flow ofimpedes or restricts the flow of
electronselectrons

Measured in ohmsMeasured in ohms

 GENERATOR – creates a force or voltage andGENERATOR – creates a force or voltage and
moves electrons from one point to another.moves electrons from one point to another.

Like a plumbing system that utilizes a pump to createLike a plumbing system that utilizes a pump to create
water pressure and move water from one place towater pressure and move water from one place to
anotheranother

 POWER – the rate of the movement ofPOWER – the rate of the movement of
electrons from point to point or current flow.electrons from point to point or current flow.

Power = amps or current x voltagePower = amps or current x voltage

Power is measured in wattsPower is measured in watts

 LOAD – the device that uses the electricity toLOAD – the device that uses the electricity to
perform some type of functionperform some type of function

The load can change the amount of energy deliveredThe load can change the amount of energy delivered
from the power sourcefrom the power source
• Examples: surgical lamps, ESU, video monitorsExamples: surgical lamps, ESU, video monitors

 SWITCH – a deviceSWITCH – a device
used to open or closeused to open or close
a circuit and controlsa circuit and controls
the flow of electricity.the flow of electricity.

 HOT WIRE – the wire that connects to theHOT WIRE – the wire that connects to the
switch.switch.

In polarized plugs, hot wire is smaller prongIn polarized plugs, hot wire is smaller prong

Often the hot wire is colored redOften the hot wire is colored red

 NEUTRAL WIRE – serves as the pathway for theNEUTRAL WIRE – serves as the pathway for the
electrons to return to the energy source andelectrons to return to the energy source and
completes the circuit.completes the circuit.

In a polarized plug, it is the larger of the prongsIn a polarized plug, it is the larger of the prongs

Wire is often colored greenWire is often colored green

 GROUND – the connection of an electricalGROUND – the connection of an electrical
current or circuit with the earth through acurrent or circuit with the earth through a
conductor. Safely conveys any leakingconductor. Safely conveys any leaking
electrons to alternate path to ground.electrons to alternate path to ground.

Ground wires are often colored blackGround wires are often colored black

 FREQUENCY – the number of waves passingFREQUENCY – the number of waves passing
through a given point per one second. This isthrough a given point per one second. This is
measured in hertz.measured in hertz.

TYPES OF ELECTRICITYTYPES OF ELECTRICITY
 STATIC ELECTRICITY – caused by friction andSTATIC ELECTRICITY – caused by friction and
accumulates on objectsaccumulates on objects

When two static-bearing objects come in contact, theWhen two static-bearing objects come in contact, the
one bearing the higher potential discharges to the oneone bearing the higher potential discharges to the one
with the lower potential creating SPARKS.with the lower potential creating SPARKS.

STATIC ELECTRICITYSTATIC ELECTRICITY
 An electrostatic charge or spark between twoAn electrostatic charge or spark between two
objects can occur only when there is no pathwayobjects can occur only when there is no pathway
of conductivity between them; therefore the chiefof conductivity between them; therefore the chief
aim is to provide a manner of dissipating theaim is to provide a manner of dissipating the
static accumulation.static accumulation.

 Common environmental hazardCommon environmental hazard
in the ORin the OR
 Does not cause patient shock orDoes not cause patient shock or
burnsburns
 However, its production of anHowever, its production of an
electrostatic spark is its mainelectrostatic spark is its main
hazard because this provides ahazard because this provides a
source of ignition for a fire.source of ignition for a fire.

 PREVENTATIVE MEASURES INCLUDE:PREVENTATIVE MEASURES INCLUDE:

Good conductive floors prevent accumulation byGood conductive floors prevent accumulation by
providing a pathway of conductivity between personsproviding a pathway of conductivity between persons
and equipment coming in contact with the staticand equipment coming in contact with the static
electricity.electricity.

 PREVENTATIVEPREVENTATIVE
MEASURESMEASURES

Safe furniture is made ofSafe furniture is made of
electrically-conductiveelectrically-conductive
materials or contact to the floormaterials or contact to the floor
is made through electrically-is made through electrically-
conductive leg tips, casters, orconductive leg tips, casters, or
wheels.wheels.

 PREVENTATIVE MEASURESPREVENTATIVE MEASURES

Operating room floors are cleanedOperating room floors are cleaned
with materials that do not reducewith materials that do not reduce
conductivity.conductivity.


Avoid wool and synthetic fabrics thatAvoid wool and synthetic fabrics that
have not received anti-statichave not received anti-static
treatment.treatment.

Use cotton blankets, towels, etc.Use cotton blankets, towels, etc.


Use special anti-static liners inUse special anti-static liners in
trash and linen hampers and kicktrash and linen hampers and kick
buckets.buckets.

 PREVENTATIVEPREVENTATIVE
MEASURESMEASURES

Maintain room humidityMaintain room humidity
level at 50-60%level at 50-60%


Dissipate charges by frequently touching metalDissipate charges by frequently touching metal
surfaces and avoid friction causing activities.surfaces and avoid friction causing activities.
• example: avoid movement around patient’s head, especiallyexample: avoid movement around patient’s head, especially
if his/her hair is uncovered.if his/her hair is uncovered.

ELECTRICAL SHOCKELECTRICAL SHOCK
 ELECTROCUTION –ELECTROCUTION –
the most severe casethe most severe case
of electrical shock,of electrical shock,
often lethal.often lethal.

Occurs when a personOccurs when a person
becomes part of thebecomes part of the
circuit or closes thecircuit or closes the
circuit.circuit.

ELECTRICAL HAZARDSELECTRICAL HAZARDS

PRECAUTIONSPRECAUTIONS
 INSPECT THE POWER CORD AND PLUGINSPECT THE POWER CORD AND PLUG
BEFORE EVERY USEBEFORE EVERY USE

 DO NOT USE EQUIPMENT ON WHICHDO NOT USE EQUIPMENT ON WHICH
LIQUIDS HAVE BEEN SPILLED.LIQUIDS HAVE BEEN SPILLED.

 NEVER STACK THINGS ON OR BEHINDNEVER STACK THINGS ON OR BEHIND
ELECTRICAL EQUIPMENT WHICH MIGHTELECTRICAL EQUIPMENT WHICH MIGHT
INTERFERE WITH PROPER VENTILLATION OFINTERFERE WITH PROPER VENTILLATION OF
THE DEVICE.THE DEVICE.

 TWO-PRONGTWO-PRONG
EXTENSION CORDSEXTENSION CORDS
OR ADAPTORSOR ADAPTORS
SHOULD NOT BESHOULD NOT BE
USED IN THE OR.USED IN THE OR.

 USE THREE-PRONGUSE THREE-PRONG
EXTENSION CORDSEXTENSION CORDS
ONLY WHENONLY WHEN
NECESSARYNECESSARY

 DO NOT RUN OVERDO NOT RUN OVER
POWER CORDSPOWER CORDS
WITH WHEELS OFWITH WHEELS OF
EQUIPMENTEQUIPMENT

 DO NOT TIGHTLYDO NOT TIGHTLY
COIL OR KINKCOIL OR KINK
CORDS.CORDS.

Principles of Biomedical
Systems & DevicesPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404
Principles of Biomedical Systems
& Devices
Medica
l
Sensor

PBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404
20/12/2006 Dr.Eng:Ghada M.Amer 51
Summary
 Standards in biomedical
 Safety in the clinical environment: Electrical safety
 Physiological effects of electricity
 Susceptibility parameters
 Distribution of electrical power
 Isolated power systems
 Macroshock and Microshock hazards
 Electrical safety codes and standards
 Protection
 Power distribution
 Ground fault circuit interrupters (GFCI)
 Equipment design
 Electrical safety analyzers / Testing electrical systems

Safety in Clinical Environment
 Electrical hazards
 Electrical shocks (micro and macro) due to equipment failure, failure of
power delivery systems, ground failures, burns, fire, etc.
 Mechanical hazards
 mobility aids, transfer devices, prosthetic devices, mechanical assist
devices, patient support devices
 Environmental hazards
 Solid wastes, noise, utilities (natural gas), building structures, etc.
 Biological hazards
 Infection control, viral outbreak, isolation, decontamination, sterilization,
waste disposal issues
 Radiation hazards
 Use of radioactive materials, radiation devices (MRI, CT, PET), exposure
control

Standard in biomedical
CODES
IS defined as
a system of principals systemized
Body of law so it represents the accumulation
Of system which usually are in forced under active
Law by local state or federal government agency
The famous code is National Electrical Code (NEC)
And its apart of National Fire Protectio Association (NFPA)

ISO
 It means : "International Organization
for Standardization"
 It used to facility the internationals co-
ordination and unifications Of industrial
standard

Iso associated with 6
committees
1- technical committee (TC) 121
2- Anesthesia equipment (TC) 76
3- Medical transfusion equipment (TC) 150
4-Surgical implants (TC) 75
5-Streches (TC) 106
6-Density (TC) 84
7-Syringes for medical use and needle (TC)

National Fire Protection
Association
(NFPA)
The mission of the NFPA is to
reduce the worldwide burden of fire
and other hazards on the quality of life
by providing and advocating scientifically-based consensus
codes and standards, research, training and education.

NFPA stands
1- Inhalation anesthetics standard NFPA (56A)
2- Respiratory therapy standard NFPA (56B)
3-Essential electrical sys standard NFPA (76A)
4-Electricity in patient care facilities
NFPA (76 B-T)
5- high frequency electricity In health care
facilities in NFPA (76C)

Physiological Effects of
Electricity
.
Dry skin impedance:93 kΩ / cm2
Electrode gel on skin: 10.8 kΩ / cm2
Penetrated skin: 200 Ω / cm2
The real physiological effect depends on the actual path of the current

 Threshold of perception: The minimal current that an individual can detect. For AC (with
wet hands) can be as small as 0.5 mA at 60 Hz. For DC, 2 ~10 mA
 Let-go current: The maximal current at which the subject can voluntarily withdraw. 6 ~ 100
mA, at which involuntary muscle contractions, reflex withdrawals, secondary physical effects
(falling, hitting head) may also occur
 Respiratory Paralysis / Pain / Fatigue At as low as 20 mA, involuntary contractions of
respiratory muscles can cause asphyxiation / respiratory arrest, if the current is not interrupted.
Strong involuntary contraction of other muscles can cause pain and fatigue
 Ventricular fibrillation 75 ~ 400 mA can cause heart muscles to contract uncontrollably,
altering the normal propagation of the electrical activity of the heart. HR can raise up to 300
bpm, rapid, disorganized and too high to pump any meaningful amount of blood  ventricular
fibrillation. Normal rhythm can only return using a defibrillator
 Sustained myocardial contraction / Burns and physical injury At 1 ~6 A, the
entire heart muscle contracts and heart stops beating. This will not cause irreversible tissue
damage, however, as normal rhythm will return once the current is removed. At or after 10A,
however, burns can occur, particularly at points of entry and exit.
Physiological Effects of
Electricity

Important Susceptibility
Parameters
Threshold and let-go current variability

 Frequency
 Note that the minimal let-go current happens at the precise frequency of
commercial power-line, 50-60Hz.
 Let-go current rises below 10 Hz and above several hundred Hz.
 Duration
 The longer the duration, the smaller the current at which ventricular
fibrillation occurs
 Shock must occur long enough to coincide with the most vulnerable
period occurring during the T wave.
 Weight
 Fibrillation threshold increases with body weight (from 50mA for 6kg
dogs to 130 mA for 24 kg dogs.

Points of entry
Points of entry
Effect of entry points on current distribution (a)
Macroshock, externally applied current spreads
through-out the body. (b) Microshock, all the
current applied through an intracardiac catheter
flows through the heart.

Distribution of
Electrical Power
Simplified electric-power distribution for 115 V circuits. Power frequency is 60 Hz

Electrical Safety
 Electrical shock occurs when electrical current passes through the
body as a result of coming into contact with electricity.
Electrical current through the body can cause injury or death to the
person or be passed to another person .
 Prevent Electrical Shock
 Ensure all patient equipment is equipped with three-prong
(grounded) plugs
. If you receive even a small amount of shock from a device, report it to
the maintenance/
Report any hazardous conditions (exposed wires, loose
plugs/outlets/switches, damaged or wrong electrical

Prevent Electrical
Shock
 Do not bring any electrical equipment to work, e.g., heaters, coffee makers,
etc.
 ■ Have Engineering safety-check all personal electrical equipment prior to use
in the facility.
 ■ Protect equipment cords. Do not run equipment over them or allow them to
become trip hazards, knotted,
 damaged, or frayed.
 ■ Keep moisture and liquids away from electrical equipment.
 ■ If you see smoke or fire when using any electrical equipment (e.g. computers,
monitors), unplug the
 equipment if possible and activate the Fire Alarm System.
 ■ NEVER attempt to turn on any equipment or electrical mechanism with a
lockout device on it or that has
 been tagged “Out Of Service” or “Do Not Operate.”
 ■ NEVER attempt to reset tripped breakers or make electrical repairs.

Isolated Power Distribution
In fact, in such an isolated system, if a single ground-fault occurs, the system simply reverts back to
the normal ground-referenced system.
A line isolation monitor is used with such system that continuously monitors for the first ground fault,
during which case it simply informs the operators to fix the problem. The single ground fault does NOT
constitute a hazard!

Grounding Systems
Low resistance (0.15 Ω) ground that
can carry currents up to the circuit-
breaker ratings protects patients by
keeping all conductive surfaces and
receptacle grounds at the same
potential.
Protects patients from
Macroshocks
Microshocks
Ground faults elsewhere(!)
The difference between the
receptacle grounds and other surface
should be no more then 40 mV)
All the receptacle grounds and
conductive surfaces in the vicinity of
the patient are connected to the patient-
equipment grounding point. Each
patient-equipment grounding point is
connected to the reference grounding
point that makes a single connection to
the building ground.

ELECTRICAL SHOCK
 MACROSHOCK – requires a substantial voltage to drive electrons
through a highly resistant skin path.
 Can range from small tingling to electrocution
• Due to things such as frayed electrical cords, spilling of liquids on
generators, radio with no back covering, or removal of
ground plug.

Microshock
 Microshock is defined as tiny amounts of electricity that flow down
a conductor directly to a patient’s heart
muscle causing dysrhythmias or ventricular fibrillation.
 Precautions to Prevent Microshock
Always wear gloves when handling pacemaker leads.
Insulate leads by covering them with a nonconductive material.
■ Avoid touching other electrical equipment, including the light or bed
frame, while you are handling pacing
leads.
■ Before touching a lead, “dump” your static electricity by touching a
non-electrical object before touching

Fire Safety
 Common fire hazards in facilities
are:
♦ Smoking in unauthorized areas
♦ Electrical wiring or appliances
♦ faulty switches, and damaged plugs
♦ Flammable liquids near heat
sources
♦ Careless smoking especially when
oxygen is in use
♦ Improper storage of combustible
materials

The ABCs of Fire Extinguishers
Class A fires involve ordinary
combustibles such as paper, wood,
cloth,
rubber, and certain plastics.
(Acronym: A - Ash(
Class B fires involve flammable
liquids such as oil, gas, paint thinner,
grease, propane, alcohol and other
solvents. (Acronym: B - Boiling(
Class C fires involve energized
electrical equipment and other
electrical
sources such as wiring and fuse
boxes. (Acronym: C - Current(

Ground fault
D A N G E R
E a r t h g r o u n d i n g d o e s
n o t r e d u c e t o u c h
p o t e n t i a l t o a s a f e l e v e l .
C O P Y R I G H T 2 0 0 2
M i k e H o l t E n t e r p r i s e s , I n c .
V o l t s
9 0
P V C P V CP V C
G r o u n d
F a u l t
4 . 8
A m p s
E a r t h n o t a n E f f e c t i v e F a u l t - C u r r e n t P a t h
S e c t i o n 2 5 0 . 4 ( A ) ( 5 )
0 . 0 9
Amps
F a u l t c u r r e n t
r e t u r n i n g t o s o u r c e .
G r o u n d i n g m e t a l p a r t s t o t h e e a r t h a s s i s t
i n r e m o v i n g d a n g e r o u s v o l t a g e f r o m g r o u n d f a u l t s .
D O E S N O T

Clinical Equipment Management

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