M20_Chapter 1_Medical Device Safety Standard.pdf

MEDICAL DEVICE SAFETY STANDARD

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UNIT 1: MEDICAL DEVICE SAFETY STANDARD

INTRODUCTION

The requirement for safety testing medical electronic (ME) equipment is regarded as

essential to ensure that apparatus does not pose any danger to users or patients. To

meet this need, many different standards have been published to describe what is

considered safe for the patients and operators of ME equipment.

The most widely used standard is IEC 60601. Although this is a type standard

associated with the design and development of ME equipment, most biomedical

engineering departments continue to use it as the basis for the regular testing of medical

devices, and/or after service or repair

LEARNING OBJECTIVES The objectives of this unit are to:

1. Introduce Standard, Act and Regulation use in medical devices

2. Recognize hazard / risk that may arise from medical devices

3. Recognize safety aspect in managing medical devices

LEARNING OUTCOMES After completing the unit, students should be able to:

1. Explain different type of standard used in medical devices

2. Identify hazard/risk produce by medical devices

3. Describe leakage current in relation to electrical safety standard

4. Describe safety aspect in managing medical devices

1.1 INTRODUCTION TO STANDARDS Standards are published documents setting out specifications and procedures

designed to ensure products, services and systems are safe, reliable and

consistently perform the way they were intended to. They establish a common

language which defines quality and safety criteria.



Some standards are national, others are international. Some national standard

are slightly alter versions of international ones.

Figure 1.1 Some National Standard are adopted from International Standard

Standards can be guidance documents including:

Malaysian Standards; eg MS

International Standards and Joint Standards; eg IEC,ISO

Codes;

Specifications;

Handbooks; and

Guidelines.

These documents are practical and don't set impossible goals. They are based

on sound industrial, scientific and consumer experience and are constantly

reviewed to ensure they keep pace with new technologies.

They cover everything from consumer products and services, construction,

healthcare, engineering, business, information technology, human services to

energy and water utilities, the environment and much more.

In general, Standard are documents which are usually prepared by expert in the

field, including from industry, which define the perceived “best practice” for the

equipment to which they relate.



Standard are NOT usually legal document but can be made so by Governments

or by them being made part of a contract between buyer and seller.

Benefit of standard

Standards protect Malaysians – at home, at play and at work are made

safer by standard

Standard support innovation – reflect the latest technologies, innovation

and community needs.

Standard boost production and productivity – save time and money, cut

production costs, use of common parts and specification.

Standard make business more competitive – have more credibility, a

competitive edge over product that don’t have standard.

Standard complement regulation and make markets work better – help

make laws and regulations consistent.

Many standards are concerned with SAFETY, others with PERFORMANCE and

others still with PROCESS (usually the process of supplying goods or services –

Quality Assurance Standards)

Most of the standards relating to Medical Equipment are concerned with SAFETY

and QUALITY. Only a few are concerned with PERFORMANCE

1.1.1 Safety Standard

The requirements for the electrical safety of medical equipment are much more

stringent than those for other electrical device. The reasons for increased

precautions include:

Patient may be connected to several medical devices simultaneously (e.g.

in intensive care)

Patient may be connected conductively to electronic circuitry (e.g. ECG

monitoring)

Contact with device may be directly to internal tissue that conducts well

(e.g. through natural orifices or breaks in the skin)

Example IEC601, UL544 BS5724



1.1.2 Performance Standard

Performance Standards state what behaviors or results are expected for

performance to be considered satisfactory. Example AAMI Standard, AHA

standard, some part of IEC601

1.1.3 Quality Standard

Quality Standard state totally features and characteristic of the product or service

that bear on its ability to meet the stated standard. Example ISO9001

1.2 REFERENCE EQUIPMENT STANDARD, GUIDANCE AND LEGISLATION A code is a document that contains mandatory requirements. It uses the word

shall, is generally adopted into law by authority that has jurisdiction.

A standard is a document that contains mandatory requirements, but compliance

tends to be voluntary.

MALAYSIAN STANDARD

The Department of Standards Malaysia (STANDARDS MALAYSIA) is the

national standards and accreditation body of Malaysia established under

Standards of Malaysia Act 1996.

The main function of the Department is to foster and promote standards,

standardization and accreditation as a means of advancing the national

economy, promoting industrial efficiency and development, benefiting the health

and safety of the public, protecting the consumers, facilitating domestic and

international trade and furthering international cooperation in relation to standards

and standardisation.

Malaysian Standards are developed through consensus by committees which

comprise of balanced representation of producers, users, consumers and others

with relevant interests, as may be appropriate to the subject in hand. To the

greatest extent possible, Malaysian Standards are aligned to or are adoption of

international standards. Approval of a standard as a Malaysian Standard is



governed by the Standards of Malaysia Act 1996 (Act 549). Malaysian Standards

are reviewed periodically. The use of Malaysian Standards is voluntary except in

so far as they are made mandatory by regulatory authorities by means of

regulations, local by-laws or any other similar ways.

The Department of Standards appoints SIRIM Berhad as the agent to develop

Malaysian Standards. The Department also appoints SIRIM Berhad as the agent

for distribution and sale of Malaysian Standards.

Figure 1.2

Department of Standards Malaysia

Standards policy development and implementation

Participation in International and Regional Bodies

Accreditation of laboratories and certification bodies

SIRIM Berhad

Managing the standards development infrastructure

Managing Malaysian representation in regional and international

standards bodies

Publishing, printing, selling and distributing Malaysian Standards



Regulating Agencies: Malaysia has two regulatory bodies for medical devices:

The Medical Device Bureau, and the Atomic Energy Licensing Board of the

Malaysian Ministry of Science, Technology, and Innovation. The Medical Device

Bureau administers the Voluntary Registration of Medical Devices Establishments

(MeDVER) program, which will likely become mandatory under the Medical

Device Act. The licensing board exclusively regulates medical devices which emit

radiation.

Laws and Regulations: In August 2007, Malaysia issued a draft Medical Device

Act which indicated an intention to follow Global Harmonization Task Force

guidance documents. In November 2011 the Medical Device Act already table

into the parliament and being gazette in February 2012.However, the issuance of

implementing regulations will determine whether adherence to the Act will be

easy or problematic for medical device importers.

Registration Procedures: Devices emitting radiation are restricted, and any

such device must be examined by the Ministry of Health before it can be used in

Malaysia. Permits for radiation emitting devices can be obtained through the

Atomic Energy Licensing Board of the Malaysian Ministry of Science,

Technology, and Innovation:

1.2.1 IEC STANDARD

Millions of devices that contain electronics, and use or produce electricity, rely on

IEC International Standards and Conformity Assessment Systems to perform, fit

and work safely together.

Founded in 1906, the IEC (International Electrotechnical Commission) is the

world’s leading organization for the preparation and publication of International

Standards for all electrical, electronic and related technologies. These are known

collectively as “electrotechnology”

IEC provides a platform to companies, industries and governments for meeting,

discussing and developing the International Standards they require.



The IEC is one of three global sister organizations (IEC, ISO and ITU) that

prepare International Standards for the world.

Figure 1.3 International Electrotechnical Commission

When appropriate IEC cooperates with ISO (International Organization for

Standardization) or ITU (International Telecommunication Union) to ensure that

International Standards fit together seamlessly and complement each other. Joint

committees ensure that International Standards combine all relevant knowledge

of experts working in related areas.

Currently IEC compromise:

Over 10,000 experts from industry, commerce, government, test and

research labs, academia and consumer groups participate in IEC

Standardization work.

174 Technical Committees with over 1,000 Working Groups

Over 6,000 International standards in IEC catalogue today

Over 500,000 Conformity Assessment certificates established

162 countries -81 Members and 81 Affiliates

An IEC International Standard is a normative document, developed according to

consensus procedures. It must be approved by the relevant IEC National

Committees and is finally published as an International Standard by the IEC

Central Office.

The word “consensus” is important. This means that the International Standard

represents a common point of view of concerned parties. Any member of the IEC

may participate in the preparatory work of an International Standard, and any



international, governmental or nongovernmental organization liaising with the IEC

can also take part in this preparation.

Adoption of IEC International Standards by any country, whether it is a member

of the IEC or not, is entirely voluntary.

The IEC handles three Conformity Assessments Systems that enable it to

determine if a product or service is what it appears to be and if a systems

performs as it should.

Three IEC Conformity Assessment Systems are:

1. IECEE (IEC System of conformity assessment schemes for electrotechnical

equipment and components)

Covers conformity testing and certification for safety and performance of

home and office equipment, home entertainment, medical device, lighting,

portable tools, etc.

2. IECEx ( IEC System for certification to standards relating to equipment for

use in explosive atmospheres) – covers certification of personnel

competencies (maintenance and repair), electrical and electronic products

and systems in the highly specialized field of explosion protection. This

includes all areas where inflammable gases, liquids, and combustible dusts

may be present, i.e., the oil and gas industry, mining, refuelling stations for

cars, trucks and planes, printing and paint industry, grain storage and

handling, sugar refineries, etc.

3. IECQ (IEC quality assessment system for electronic components) – covers

business to business supply chain management systems for avionics,

management of electrostatic discharge and the use of hazardous substances

in the manufacturing process.

The ultimate goal is to provide one test, one global certification, one mark for

every product or system.

IEC Conformity Assessment Systems help accelerate access to markets and

reduce the need for multiple testing and approval. This cuts costs. They also

allow products to reach markets faster and knock down many barriers to trade



Beyond electrotechnology, IEC work also covers:

Terminology and symbols that simply production and technology transfer,

because all partners communicate in a universally understood language.

Safety to make certain that products and systems perform as expected.

The environment – to allow the safe production, use and end-life

destruction of electrotechnical goods.

Electromagnetic compatibility and interferences – enabling undisturbed

performance of individual devices.

1.2.2 MS 838 MS 838:2007 -- Code of Practice for Radiation Protection -- Medical X-Ray

Diagnosis (First Revision), published by Standards Malaysia.

Part two of the code book, under the heading Radiological Safety, states that: "A

basic principle of protection in diagnostic radiology is that an X-ray examination

should not be performed unless the benefits accruing to the patient outweigh any

radiation risk.

1.2.3 ECRI

ECRI stand for Emergency Care Research Institute is an independent, nonprofit

organization that researches the best approaches to improving the safety, quality,

and cost-effectiveness of patient care. ECRI provide unbiased, evidence-based

healthcare research, information, and advice enable user to do:

Assess and address patient safety, quality, and risk management

Select the safest, most effective medical devices, procedures, and drugs

Procure healthcare technology in the most cost-effective manner

Develop evidence-based health coverage policies

Align hospital and health facility capital investments with user strategic

technology needs.

Establish in 1968, ECRI formally began operation focusing on research in

emergency medicine, resuscitation, and related biomedical engineering studies.

https://www.ecri.org/Products/PatientSafetyQualityRiskManagement/Pages/default.aspx

https://www.ecri.org/Products/TechnologyAcquisition/Pages/default.aspx

https://www.ecri.org/Products/TechnologyPlanningAssessment/Pages/default.aspx

https://www.ecri.org/Products/TechnologyAcquisition/Pages/default.aspx

https://www.ecri.org/Products/TechnologyPlanningAssessment/Pages/default.aspx

https://www.ecri.org/Products/TechnologyPlanningAssessment/CustomizedPlanningServices/Pages/default.aspx

https://www.ecri.org/Products/TechnologyPlanningAssessment/CustomizedPlanningServices/Pages/default.aspx



The Institute’s first evaluation of 18 brands of manually operated resuscitators

found nine to be ineffective and started ECRI as an independent evaluator and

provider of medical-device-related information and guidance.

Figure 1.4 Emergency Care Research Institute

Currently ECRI have more than 5,000 member and client list includes hospitals,

health systems, public and private, federal and state government agencies,

ministries of health, associations, and accrediting agencies worldwide.

1.2.4 AMMI

AAMI, the Association for the Advancement of Medical Instrumentation, is a

nonprofit organization founded in 1967. It is a unique alliance of more than 6,000

members from around the world united by one mission — to increase the

understanding and beneficial use of medical instrumentation

through effective standards, educational programs, and publications.

Figure 1.5

AAMI is the primary source of consensus and timely information on medical

instrumentation and technology.

AAMI is the primary resource for the industry, the professions, and

government for national and international standards.

AAMI provides multidisciplinary leadership and programs that enhance

the ability of the professions, healthcare institutions, and industry to

understand, develop, manage, and use medical instrumentation and

related technologies safely and effectively.



AAMI helps members:

o contain costs

o keep informed of new technology and policy developments

o add value in healthcare organizations

o improve professional skills and enhance patient care.

AAMI provides a unique and critical forum for members who cover a

complete range of interests, from clinical and biomedical engineers and

technicians, physicians, nurses, and hospital administrators, to educators

and researchers, manufacturers, distributors, government representatives

and other healthcare professionals with an interest in medical devices.

These diverse groups have been instrumental in making AAMI the leading

source of essential information on medical devices and equipment since

1967.

AAMI fulfills its mission through:

o continuing education, conferences

o certification of healthcare technical specialists

o the publication of technical documents, periodicals, books,

software.

1.2.5 FDA/CE

Figure 1.6

FDA is an agency within the U.S. Department of Health and Human Services. It

consists of six product centers, one research center, and two offices:

FDA is responsible for

Protecting the public health by assuring that foods are safe, wholesome,

sanitary and properly labeled; human and veterinary drugs, and vaccines

and other biological products and medical devices intended for human

use are safe and effective

Protecting the public from electronic product radiation

Assuring cosmetics and dietary supplements are safe and properly

labeled



Regulating tobacco products

Advancing the public health by helping to speed product innovations

Helping the public get the accurate science-based information they need

to use medicines, devices, and foods to improve their health

FDA regulates

foods, except for most meat and poultry products, which are regulated by

the U.S. Department of Agriculture

food additives

infant formulas

dietary supplements

human drugs

vaccines, blood products, and other biologics

medical devices, from simple items like tongue depressors, to complex

technologies such as heart pacemakers

electronic products that give off radiation, such as microwave ovens and

X-ray equipment

cosmetics

feed, drugs, and devices used in pets, farm animals, and other animals

tobacco products

CE MARKING

The CE marking (an acronym for the French "Conformite Europeenne") certifies

that a product has met EU health, safety, and environmental requirements, which

ensure consumer safety.

Figure 1.7

Manufacturers in the European Union (EU) and abroad must meet CE marking

requirements where applicable in order to market their products in Europe. A

manufacturer who has gone through the conformity assessment process, may



affix the CE marking to the product. With the CE marking, the product may be

marketed throughout the EU. CE marking now provides product access to 32

countries with a population of nearly 500 million.

Table 1.1 CE Marking Countries

Austria Hungary Poland

Belgium Iceland Portugal

Bulgaria Ireland Romania

Cyprus Italy Slovakia

Czech Republic Latvia Slovenia

Denmark Liechtenstein Spain

Estonia Lithuania Sweden

Finland Luxembourg Switzerland

France Malta Turkey

Germany Netherlands United Kingdom

Greece Norway

Figure 1.8 CE Mark in product

1.3 HAZARD OF MEDICAL EQUIPMENT

Medical electrical equipment can present a range of hazards to the patient, the

user, or to service personnel. Many such hazards are common to many or all

types of medical electrical equipment, whilst others are peculiar to particular

categories of equipment.

For this reason, various hazards associated with medical electrical equipment are

discussed briefly below.



Mechanical Hazards

All types of medical electrical equipment can present mechanical hazards. These

can range from insecure fittings of controls to loose fixings of wheels on

equipment trolleys. The former may prevent a piece of life supporting equipment

from being operated properly, whilst the latter could cause serious accidents in

the clinical environment.

Figure 1.9

Such hazards may seem too obvious to warrant mentioning, but it is unfortunately

all too common for such mundane problems to be overlooked whilst problems of

a more technical nature are addressed.

Risk of fire or explosion

All mains powered electrical equipment can present the risk of fire in the event of

certain faults occurring such as internal or external short circuits. In certain

environments such fires may cause explosions. Although the use of flammable

anaesthetics is not common today, it should be recognised that many of the

medical gases currently in use, such oxygen or nitrous oxide, vigorously support

combustion. Wherever there is an elevated concentration of such gases, there is

an increased risk of fire initiated by electrical faults.

Figure 1.10



Absence of Function

Since many pieces of medical electrical equipment are life supporting or monitor

vital functions, the absence of function of such a piece of equipment would not be

merely inconvenient, but could threaten life.

Excessive or insufficient output

In order to perform its desired function equipment must deliver its specified

output. Too high an output, for example, in the case of surgical diathermy units,

would clearly be hazardous. Equally, too low an output would result in inadequate

therapy, which in turn may delay patient recovery, cause patient injury or even

death. This highlights the importance of correct calibration procedures.

Infection

Medical equipment that has been inadequately decontaminated after use may

cause infection through the transmission of microorganisms to any person who

subsequently comes into contact with it. Clearly, patients, nursing staff and

service personnel are potentially at risk here.

Figure 1.11

Misuse

Misuse of equipment is one of the most common causes of adverse incidents

involving medical devices. Such misuse may be a result of inadequate user

training or of poor user instructions.



Risk of exposure to spurious electric currents

All electrical equipment has the potential to expose people to the risk of spurious

electric currents. In the case of medical electrical equipment, the risk is potentially

greater since patients are intentionally connected to such equipment and may not

benefit from the same natural protection factors that apply to people in other

circumstances. Whilst all of the hazards listed are important, the prevention of

many of them require methods peculiar to the particular type of equipment under

consideration. For example, in order to avoid the risk of excessive output of

surgical diathermy units, knowledge of radio frequency power measurement

techniques is required. However, the electrical hazards are common to all types

of medical electrical equipment and can minimised by the use of safety testing

and inspection regimes which can be applied to all types of medical electrical

equipment.

Figure 1.12

1.4 ELECTRIC SHOCK HAZARD

Three conditions occuring simultaneously can result in a shock

1. One part of the body is in contact with the conductive surface

2. A different part of the same body is in contact with a second conductive

surface

3. A voltage source drives current through the body between those two points of

contact.



Figure 1.13

Electric current can flow through the human body either accidentally or

intentionally. Electrical currents are administered intentionally in the following

cases.

a. For the measurement of respiration rate by impedance method, a small

current at high frequency is made to flow between the electrodes applied

on the surface body.

b. High frequency currents are also passed through the body for the

therapeutic and surgical purpose.

c. When recording signal like ECG, the amplifiers used in the preamplifier

stage may deliver small currents due to defect in design.

The severity of electric shock depends on the current flowing through the body.

I=V/R to find out how much current will flow through the body.



Figure 1.14

According to IEEE Std. 80, you can determine the maximum safe shock duration

by the formula, T=0.116/(V÷R),

For a 120V circuit, maximum shock duration =0.116÷(120V÷1,000)=1 sec

For a 277V circuit, maximum shock duration =0.116÷(277V÷1000)=0.43 sec

Factors that determine the form and severity of injury include:

a) the type and magnitude of current

b) the resistance of the body at the point of contact

– different tissues in the body will offer different electrical resistance,

c) the current pathway through the body and

d) the duration of current flow.

AC Current

Particularly of the common 50-60 Hz variety, is three to five times more

dangerous than DC of the same voltage and amperage (current strength).

The effects of AC on the body depend to a great extent on the frequency: low-

frequency currents (50 – 60 Hz) are usually more dangerous than high-frequency

currents. AC causes muscle spasm, often 'freezing' the hand (the most common

part of the body to make contact) to the circuit. The fist clenches around the

current source resulting in prolonged exposure with severe burns. Burns from



electricity are the result of extremely high temperatures (up to 5000 C) generated

at the point of skin contact with the conductor. They usually involve the skin and

the tissues beneath and may be of almost any size and depth. Generally the

higher the voltage and the amperage, the greater the damage from either type of

current.

DC Current

Tends to cause a convulsive contraction of the muscles, often forcing the victim

away from further current exposure.

Figure 1.15

1.4.1 SPECIAL ENVIRONMENT IN HOSPITAL

It is common experience that hazards due to electrical shocks are also

associated with the equipment other than that used in hospitals. However, the

equipments used in medical practice have to operate in special environment,

which differ in certain respects from the others. Some such special situations are

as follows



a. A patient may not be usually able to react in the normal way. He is either

ill, unconscious, anaesthetized or strapped on the operating table. He may

not be able to withdraw himself from the electrified object, when feeling a

tingling in his skin, before any danger of electrocution occurs.

b. The patient or the operator may not realize that a potential hazard exists.

This is because potential differences are small and high frequency and

ionizing radiations are not directly indicated.

c. A considerable natural protection and barrier to electric currents is

provided by human skin. In certain applications of electromedical

equipments, the natural resistance of the skin may be by-passed. Such

situations arise when the tests are carried out on the subject with a

catheter in his heart or on large blood vessels.

d. Electromedical equipments, e.g. pacemakers may be used either

temporarily or permanently to support or replace functions of some organs

of the human body. An interruption in the power failure of the equipment

may give rise to hazards, which may cause permanent injuries or may

even prove fatal for the patient.

e. Medical instruments are quite often used in conjunction with several other

instruments and equipment. These combinations are often adhoc. Several

times there are combinations of high power equipment and extremely

sensitive low signal equipments. Each of these devices may be safe in

itself, but can become dangerous when used in conjunction with others.

f. The environmental conditions in the hospitals, particularly in the operating

theatres, cause an explosion or fire hazards due to presence of anesthetic

agents, humidity and cleaning agents, etc.

The factor listed above indicate that the electromedical equipments may be used

in different places and under different circumstances. It is also obvious that an

optimum level of safety can only be achieved when efforts are made to include

safety measures in the equipment, in the installation as well as in the application.



Figure 1.16

1.4.2 MICROSHOK AND MACROSHOCK

There are two situations which account for hazards from electrical shock. They

are microshock and macroshock.

Figure 1.17

Microshock

In micro current shock, the current passes directly through the heart wall. This is

the case when cardiac catheters may be present in the heart chambers. Here,

even very small amounts of currents can produce fatal results.

– A physiological response to a current applied to the surface of the heart

that produced unwanted stimulation, muscle contraction or tissue injury.



– This often happens when cardiac catheters are intact with the patient.

Even small amount current can produce fatal injuries.

This makes microshock is more dangerous than macroshock with limits of 1uA

and 1mA respectively.

Figure 1.18

Macroshock

In macro current shock, the current flows through the body of the subject. E.g. as

from arm to arm.

– A physiological response to a current applied to the surface of the body

that produced unwanted stimulation, muscle contraction or tissue injury

Figure 1.19



Tissue Resistance

Skin - 5000 ohms/cm2

Blood - 100 ohms/cm2

Muscle - 200-400 ohms/cm2

Fat - 2000-3000 ohms/cm2

Bone - 3000+ ohms/cm2

Current goes to the path of least resistance

1.4.3 PHSIOLOGICAL EFFFECT OF ELECTRICITY

The electrical current induced to the body that causes unwanted physiological

effects

a) Electrolysis

The movement of ions of opposite polarities in opposite directions through

a medium is called electrolysis and can be made to occur by passing DC

current through body tissues or fluids. If a DC current is passed through

body tissues for a period of minutes, ulceration begins to occur. Such

ulcers, while not normally fatal, can be painful and take long periods to

heal.

b) Burns

When an electric current passes through any substance having electrical

resistance, heat is produced. The amount of heat depends on the power

dissipated (I2R). Whether or not the heat produces a burn depends on the

current density.

Human tissue is capable of carrying electric current quite successfully.

Skin normally has a fairly high electrical resistance while the moist tissue

underneath the skin has a much lower resistance. Electrical burns often

produce their most marked effects near to the skin, although it is fairly



common for internal electrical burns to be produced, which, if not fatal,

can cause long lasting and painful injury.

c) Muscle cramps

When an electrical stimulus is applied to a motor nerve or a muscle, the

muscle does exactly what it is designed to do in the presence of such a

stimulus i.e. it contracts. The prolonged involuntary contraction of muscles

(tetanus) caused by an external electrical stimulus is responsible for the

phenomenon where a person who is holding an electrically live object can

be unable to let go.

d) Respiratory arrest

The muscles between the ribs (intercostal muscles) need to repeatedly

contract and relax in order to facilitate breathing. Prolonged tetanus of

these muscles can therefore prevent breathing.

e) Cardiac arrest

The heart is a muscular organ, which needs to be able to contract and

relax repetitively in order to perform its function as a pump for the blood.

Tetanus of the heart musculature will prevent the pumping process.

f) Ventricular fibrillation

The ventricles of the heart are the chambers responsible for pumping

blood out of the heart. When the heart is in ventricular fibrillation, the

musculature of the ventricles undergoes irregular, uncoordinated twitching

resulting in no net blood flow. The condition proves fatal if not corrected in

a very short space of time.

Ventricular fibrillation can be triggered by very small electrical stimuli. A

current as low as 70 mA flowing from hand to hand across the chest, or

20µA directly through the heart may be sufficient. It is for this reason that

most deaths from electric shock are attributable to the occurrence of

ventricular fibrillation.



Fig 1.20 Analogy for fibrillation

g) Effect of frequency on neuro-muscular stimulation

The amount of current required to stimulate muscles is dependent to

some extent on frequency. Referring to figure 1.21, it can be seen that the

smallest current required to prevent the release of an electrically live

object occurs at a frequency of around 50 Hz. Above 10 kHz the neuro-

muscular response to current decreases almost exponentially.

Figure 1.21 Current required to prevent release of a live object.

Research shows that the minimal let go current occurs for commercial

power line frequencies 50 – 60z

Skin resistance = 10k – 1M ohm

If skin is wet or broken, body resistance may drop to 1% of its value.



Electrical currents passing through surface electrodes from one arm to the other

have serious physiological effect consequences. At 60 Hz, such currents above

5mA are considered dangerous

Table 1.2

Type of

current

Current range

(mA) Physiological effect

Threshold 1 - 5 Tingling sensation

Pain 5 –8 Intense or painful sensation

Let – go 8 – 20 Threshold of involuntary muscle contraction

Paralysis >20 Respiratory paralysis and pain

Fibrillation 80 – 1000 Ventricular and heart fibrillation

Defibrillation 1000 – 10,000 Sustained myocardial contraction and

possible tissue burns

Figure 1.22

Let go current

It is maximum current at which a person is still capable of hanging on to a

conductor by using his muscles that is directly stimulated by the current shock



Hold on current

It is minimum current before a person losses ability to control his own muscle

actions and he is viable to grip on the electrical conductor

1.4.4 PRECAUTION TO MINIMISE ELECTRICAL SHOCK HAZARDS

The following precautions should be observed to prevent hazardous situations:

1. In the vicinity of the patient, use only apparatus or appliances with three-

wire power cords.

2. Provide isolated input circuits on monitoring equipment.

3. Have periodic checks of ground wire continuity of all equipment.

4. No other apparatus should be put where the patient monitoring equipment

is connected.

5. Staff should be trained to recognize potentially hazardous conditions.

6. Connectors for probes and leads should be standardized so that currents

intended for powering transducers are not given to the leads applied to

pick up physiologic electric impulses.

7. The functional controls should be clearly

marked and the operating instructions be

permanently and prominently displayed so

that they can be easily familiarized.

8. Many of the portable medical equipment

such as dialysis unit, hypothermia units,

physiotheraphy apparatus, respirators and humidifiers are used with

adapter plugs that do not ensure a proper grounding circuit. Particular

care should be taken in such cases.

9. The operating instructions should give directions on the proper use of the

equipments. In fact, for electromedical equipment, the operating

instructions should be regarded as an integral part of the unit.

10. The mechanical construction of the equipment must be such that the

patient or operator cannot be injured by the mechanical system of the

equipment, if properly operated.

11. A potential difference of not more than 5mV should exist between the

ground point at the outlet and the ground point at any of the outlets and

any conductive surface in the same area. If there is no voltage difference



between two points or only an insignificant potential of a few millivolt

exists, the flow of possible leakage current between its source and ground

will be restricted to well below a level which could be dangerous.

12. The patient equipment grounding point should be connected individually

to all receptacle grounds, metal beds and any other conductive services.

The resistance of these connections individually should not exceed 0.15.

Figure 1.23

Natural protection factors

Many people have received electric shocks from mains potentials and above and

lived to tell the tale. Part of the reason for this is the existence of certain natural

protection factors.

Ordinarily, a person subject to an unexpected electrical stimulus is protected to

some extent by automatic and intentional reflex actions. The automatic

contraction of muscles on receiving an electrical stimulus often acts to disconnect

the person from the source of the stimulus. Intentional reactions of the person

receiving the shock normally serve the same purpose. It is important to realise

that a patient in the clinical environment who may have electrical equipment

intentionally connected to them and may also be anaesthetised is relatively

unprotected by these mechanisms.

Normally, a person who is subject to an electric shock receives the shock through

the skin, which has a high electrical resistance compared to the moist body

tissues below, and hence serves to reduce the amount of current that would



otherwise flow. Again, a patient does not necessarily enjoy the same degree of

protection. The resistance of the skin may intentionally have been lowered in

order to allow good connections of monitoring electrodes to be made or, in the

case of a patient undergoing surgery, there may be no skin present in the current

path.

The absence of natural protection factors as described above highlights the need

for stringent electrical safety specifications for medical electrical equipment and

for routine test and inspection regimes aimed at verifying electrical safety.

1.5 LEAKAGE CURRENTS

Most safety testing regimes for medical electrical equipment involve the

measurement of certain "leakage currents", because the level of them can help to

verify whether or not a piece of equipment is electrically safe. In this section the

various leakage currents that are commonly measurable with medical equipment

safety testers are described and their significance discussed. The precise

methods of measurement along with applicable safe limits are discussed later

1.5.1 Causes of leakage currents

If any conductor is raised to a potential above that of earth, some current is

bound to flow from that conductor to earth. This is true even of conductors that

are well insulated from earth, since there is no such thing as perfect insulation or

infinite impedance. The amount of current that flows depends on:

a. the voltage on the conductor.

b. the capacitive reactance between the conductor and earth.

c. the resistance between the conductor and earth.

The currents that flow from or between conductors that are insulated from earth

and from each other are called leakage currents, and are normally small.

However, since the amount of current required to produce adverse physiological

effects is also small, such currents must be limited by the design of equipment to

safe values.



For medical electrical equipment, several different leakage currents are defined

according to the paths that the currents take.

1.5.2 Earth leakage current

Earth leakage current is the current that normally flows in the earth conductor of a

protectively earthed piece of equipment. In medical electrical equipment, very

often, the mains is connected to a transformer having an earthed screen. Most of

the earth leakage current finds its way to earth via the impedance of the

insulation between the transformer primary and the inter-winding screen, since

this is the point at which the insulation impedance is at its lowest (see figure 1.24)

Figure 1.24 Earth leakage current path

Under normal conditions, a person who is in contact with the earthed metal

enclosure of the equipment and with another earthed object would suffer no

adverse effects even if a fairly large earth leakage current were to flow. This is

because the impedance to earth from the enclosure is much lower through the

protective earth conductor than it is through the person. However, if the protective

earth conductor becomes open circuited, then the situation changes. Now, if the

impedance between the transformer primary and the enclosure is of the same

order of magnitude as the impedance between the enclosure and earth through

the person, a shock hazard exists.

It is a fundamental safety requirement that in the event of a single fault occurring,

such as the earth becoming open circuit, no hazard should exist. It is clear that in

order for this to be the case in the above example, the impedance between the

mains part (the transformer primary and so on) and the enclosure needs to be

high. This would be evidenced when the equipment is in the normal condition by



a low earth leakage current. In other words, if the earth leakage current is low

then the risk of electric shock in the event of a fault is minimised.

1.5.3 Enclosure leakage current or touch current

The terms "enclosure leakage current" and "touch current" should be taken to be

synonymous. Enclosure leakage current is defined as the current that flows from

an exposed conductive part of the enclosure to earth through a conductor other

than the protective earth conductor.

Figure 1.25 Enclosure leakage current path

If a protective earth conductor is connected to the enclosure, there is little point in

attempting to measure the enclosure leakage current from another protectively

earthed point on the enclosure, since any measuring device used is effectively

shorted out by the low resistance of the protective earth. Equally, there is little

point in measuring the enclosure leakage current from a protectively earthed

point on the enclosure with the protective earth open circuit, since this would give

the same reading as measurement of earth leakage current as described above.

For these reasons, it is usual when testing medical electrical equipment to

measure enclosure leakage current from points on the enclosure that are not

intended to be protectively earthed (see figure 1.25). On many pieces of

equipment, no such points exist. This is not a problem. The test is included in test

regimes to cover the eventuality where such points do exist and to ensure that no

hazardous leakage currents will flow from them.



1.5.4 Patient leakage current

Patient leakage current is the leakage current that flows through a patient

connected to an applied part or parts. It can either flow from the applied parts via

the patient to earth or from an external source of high potential via the patient and

the applied parts to earth. Figures 1.26 and figure 1.27 illustrate the two

scenarios.

Figure 1.26. Patient leakage current path from equipment

Figure 1.27 Patient leakage current path to equipment

1.5.5 Patient auxiliary current

The patient auxiliary current is defined as the current that normally flows between

parts of the applied part through the patient, which is not intended to produce a

physiological effect (see figure 1.28).



Figure 1.28 Patient auxiliary current path

1.6 EQUIPMENT CLASSIFICATION

All electrical equipment is categorised into classes according to the method of

protection against electric shock that is used. For mains powered electrical

equipment there are usually two levels of protection used, called "basic" and

"supplementary" protection. The supplementary protection is intended to come

into play in the event of failure of the basic protection.

1.6.1 Equipment Types

As described above, the class of equipment defines the method of protection

against electric shock. The degree of protection for medical electrical equipment

is defined by the type designation. The reason for the existence of type

designations is that different pieces of medical electrical equipment have different

areas of application and therefore different electrical safety requirements. For

example, it would not be necessary to make a particular piece medical electrical

equipment safe enough for direct cardiac connection if there is no possibility of

this situation arising.



Table 1.3 shows the symbols and definitions for each type classification of

medical electrical equipment.

Type Symbol Definition

B

Non Isolated Applied Part

BF

Isolated Applied Part

CF

Isolated Applied Part, suitable for

direct cardiac application

Type BF Defib Protection

Type CF Defib Protection

Table 1.3 Medical electrical equipment types

All medical electrical equipment should be marked by the manufacturer with one

of the type symbols above.

1.6.2 Class

Class I Equipment

Class I equipment has a protective earth. The basic means of protection is the

insulation between live parts and exposed conductive parts such as the metal

enclosure. In the event of a fault that would otherwise cause an exposed

conductive part to become live, the supplementary protection (i.e. the protective

earth) comes into effect. A large fault current flows from the mains part to earth

via the protective earth conductor, which causes a protective device (usually a

fuse) in the mains circuit to disconnect the equipment from the supply.



Figure 1.29

It is important to realise that not all equipment having an earth connection is

necessarily class I. The earth conductor may be for functional purposes only such

as screening. In this case the size of the conductor may not be large enough to

safely carry a fault current that would flow in the event of a mains short to earth

for the length of time required for the fuse to disconnect the supply.

Figure 1.30

Class I medical electrical equipment should have fuses at the equipment end of

the mains supply lead in both the live and neutral conductors, so that the

supplementary protection is operative when the equipment is connected to an

incorrectly wired socket outlet.

Further confusion can arise due to the use of plastic laminates for finishing

equipment. A case that appears to be plastic does not necessarily indicate that

the equipment is not class I.

There is no agreed symbol in use to indicate that equipment is class I and it is not

mandatory to state on the equipment itself that it is class I. Where any doubt

exists, reference should be made to equipment manuals.

Ground

Live (L1)

Neutral (L2)

Class I Grounded System



The symbols below may be seen on medical electrical equipment adjacent to

terminals.

Figure 1.31 Symbols seen on earthed equipment.

Class II Equipment

The method of protection against electric shock in the case of class II equipment

is either double insulation or reinforced insulation. In double insulated equipment

the basic protection is afforded by the first layer of insulation. If the basic

protection fails then supplementary protection is provided by a second layer of

insulation preventing contact with live parts.

In practice, the basic insulation may be afforded by physical separation of live

conductors from the equipment enclosure, so that the basic insulation material is

air. The enclosure material then forms the supplementary insulation.

Figure 1.32

Reinforced insulation is defined in standards as being a single layer of insulation

offering the same degree of protection against electric shock as double

insulation.



Figure 1.33

Class II medical electrical equipment should be fused at the equipment end of the

supply lead in either mains conductor or in both conductors if the equipment has

a functional earth.

The symbol for class II equipment is two concentric squares illustrating double

insulation as shown below.

Figure 1.34 Symbol for class II equipment –double insulation (all plastic case)

Class III Equipment

Class III equipment is defined in some equipment standards as that in which

protection against electric shock relies on the fact that no voltages higher than

safety extra low voltage (SELV) are present. SELV is defined in turn in the

relevant standard as a voltage not exceeding 25V ac or 60V dc.

In practice such equipment is either battery operated or supplied by a SELV

transformer.

If battery operated equipment is capable of being operated when connected to

the mains (for example, for battery charging) then it must be safety tested as

either class I or class II equipment. Similarly, equipment powered from a SELV

Neutral (L2)

Hot (L1)

Class II Double Insulated System



transformer should be tested in conjunction with the transformer as class I or

class II equipment as appropriate.

It is interesting to note that the current IEC standards relating to safety of medical

electrical equipment do not recognise Class III equipment since limitation of

voltage is not deemed sufficient to ensure safety of the patient. All medical

electrical equipment that is capable of mains connection must be classified as

class I or class II. Medical electrical equipment having no mains connection is

simply referred to as "internally powered".

1.7 ELECTRICAL SAFETY TEST AND ANALYZERS The following sub topic and diagrams describe the electrical safety tests

commonly available on medical equipment safety testers.

Why we perform safety test?

To ensure the medical equipment is safe to be used for all even the faulty

happen to the machine.

Who should do the testing?

An adequate knowledge and practical experience of electricity, its

hazards, the required safety standard and a clear understanding of the

precautions required to avoid danger.

These criteria will include:

o Able to recognize whether it is safe for work to continue

o Able to recommend the frequency of testing should this deviate

significantly from the guide book.

o Adequate knowledge of the possible hazards of unfamiliar

equipment in unfamiliar locations.

When Electrical Safety Test is performed?

During equipment commissioning

After perform repair

After transportation

During routine PPM

Before apply to the patient



Electrical Safety Test Parameters

Mains Voltage

o Measure the voltage from the mains

o Measure the voltage from pin to pin

Current Consumption

o Measure the current consumption of the equipment

Insulation Resistance

o Measure the dielectric strength from L to N, or applied part to

earth. >2 – 20M ohm

Protective Earth Resistance

o Power cord resistance

o Apply test current 1A or 25A for 5second

o Limit : Less than 0.2 ohm

Leakage Current

o Earth Leakage

o Enclosure Leakage Current

o Patient Leakage Current

o Patient Auxillary Leakage Current

A range of electrical safety analyzers are commercially available for testing both

medical facility power systems and medical equipment. They vary in complexity

from simple volt-ohm-meter to computerized automatic measurement systems

that generate hard copies of test results.



Terminology

Figure 1.35

ANALYSERS



Figure 1.36

1.7.1 Normal condition and single fault conditions

A basic principle behind the philosophy of electrical safety is that in the event of

a single abnormal external condition arising or of the failure of a single means of

protection against a hazard, no safety hazard should arise. Such conditions are

called "single fault conditions" (SFCs) and include such situations as the

interruption of the protective earth conductor or of one supply conductor, the

appearance of an external voltage on an applied part, the failure of basic

insulation or of temperature limiting devices.

Where a single fault condition is not applied, the equipment is said to be in

"normal condition" (NC).

Many electrical safety tests are carried out under various single fault conditions in

order to verify that there is no hazard even should these conditions occur in

practice. It is often the case that single fault conditions represent the worst case

and will give the most adverse results. Clearly the safety of the equipment under

test may be compromised when such tests are performed.

Many electrical safety tests are carried out under single fault condition since

these represent the worst case and will give the most adverse results.



Normal condition: condition in which all means for protection against hazards

are intact.

Single fault condition: condition in which one means for protection against

hazard is defective. If a single fault condition results unavoidably in another single

fault condition, the two failures are considered as one single fault condition.

1.7.2 Protective Earth Continuity

The resistance of the protective earth conductor is measured between the earth

pin on the mains plug and a protectively earthed point on the equipment

enclosure (see figure 6). The reading should not normally exceed 0.2Ω at any

such point. The test is obviously only applicable to class I equipment.

In IEC60601, the test is conducted using a 50Hz current between 10A and 25A

for a period of at least 5 seconds. Although this is a type test, some medical

equipment safety testers mimic this method. Damage to equipment can occur if

high currents are passed to points that are not protectively earthed, for example,

functional earths. Great care should be taken when high current testers are used

to ensure that the probe is connected to a point that is intended to be protectively

earthed.

HEI 95 and DB9801 Supplement 1 recommended that the test be carried out at a

current of 1A or less for the reason described above.

Where the instrument used does not do so automatically, the resistance of the

test leads used should be deducted from the reading.

If protective earth continuity is satisfactory then insulation tests can be performed.



Applicable to Class I, all types (B, BF and CF)

Limit: 0.2Ω

Notes: Ensure probe is on a protectively earthed point

Figure 1.37 Measurement of protective earth continuity.

Without protective earth

~230V

50Hz

Fuses

230V

10 Ohm

0,5 - 200 kOhm

225-230 V

1,1-450 mA

1,1-450 mA



With protective earth

Figure 1.38

1.7.3 Insulation Tests

This is a test of the breakdown strength of electrical insulating materials that

provide electrical isolation between certain electrical conductors and the ground

connection at the AC receptacle

At the AC line cord of the DUT, a high voltage (500VDC) between L1 and L2

shorted together and the ground.

IEC 60601-1 (second edition), clause 17, lays down specifications for electrical

separation of parts of medical electrical equipment compliance to which is

essentially verified by inspection and measurement of leakage currents. Further

tests on insulation are detailed under clause 20, "dielectric strength". These tests

use AC sources to test equipment that has been pre-conditioned to specified

levels of humidity. The tests described in the standard are type tests and are not

suitable for use as routine tests.

HEI 95 and DB9801 recommended that for class I equipment the insulation

resistance be measured at the mains plug between the live and neutral pins

connected together and the earth pin. Whereas HEI 95 recommended using a

~230V

50Hz

Fuses

230V

10 Ohm

0,5 - 200 kOhm0,5 Ohm

~11 V

,055-22 mA~22 A

~22 A



500V DC insulation tester, DB 9801 recommended the use of 350V DC as the

test voltage. In practice this last requirement could prove difficult and it was

acknowledged in a footnote that a 500 V DC test voltage is unlikely to cause any

harm. The value obtained should normally be in excess of 50MΩ but may be less

in exceptional circumstances. For example, equipment containing mineral

insulated heaters may have an insulation resistance as low as 1MΩ with no fault

present. The test should be conducted with all fuses intact and equipment

switched on where mechanical on/off switches are present (see figure 9).

Applicable to Class I, all types

Limits: Not less than 50MΩ

Notes:

Equipment containing mineral insulated heaters

may give values down to 1MΩ. Check

equipment is switched on.

Figure 1.39 Measurement of insulation resistance for class I equipment

Satisfactory earth continuity and insulation test results indicate that it is safe to

proceed to leakage current tests.

1.7.4 Leakage current measuring device

The leakage current measuring device recommended by IEC 60601-1 loads the

leakage current source with a resistive impedance of about 1kΩ resistor in

parallel with the series combination of a 15nF capacitor and 10kΩ resistor. This is

equivalent circuit that simulates impedance of the human body. Figure 11 shows

the arrangements for the measuring device. The millivolt meter used should be

true RMS reading and should have input impedance greater than 1 MΩ. In



practice this is easily achievable with most good quality modern multimeters. The

meter in the arrangements shown measures 1mV for each µA of leakage current.

Figure 1.40 Arrangements for measurement of leakage currents.

1.7.5 Earth Leakage Current

For class I equipment, earth leakage current is measured as shown in figure 12.

The current should be measured with the mains polarity normal and reversed.

The earth leakage current is measured in normal condition (NC) and single fault

condition, neutral conductor open circuit.

Applicable to Class I equipment, all types

Limits: 0.5mA in NC, 1mA in SFC

Notes: Measure with mains normal and reversed.

Ensure equipment is switched on.

Figure 1.41 Measurement of earth leakage current.



1.7.6 Enclosure leakage current or touch current

Enclosure leakage current is measured between an exposed part of the

equipment which is not intended to be protectively earthed and true earth as

shown in figure 13. The test is applicable to both class I and class II equipment

and should be performed with mains polarity both normal and reversed.

Applicable to Class I and class II equipment, all types.

Limits: 0.1mA in NC, 0.5mA in SFC

Notes:

Ensure equipment switched on. Normal and

reverse mains. Move probe to find worst

case.

Figure 1.42 Measurement of enclosure leakage current

1.7.7 Patient leakage current

Under IEC 60601-1, for class I and class II type B and BF equipment, the patient

leakage current is measured from all applied parts having the same function

connected together and true earth (figure 14). For type CF equipment the current

is measured from each applied part in turn and the leakage current leakage must

not be exceeded at any one applied part (figure 15).



Applicable to All classes, type B & BF equipment having

applied parts.

Limits: 0.1mA in NC, 0.5mA in SFC.

Notes: Equipment on, but outputs inactive. Normal

and reverse mains.

Figure 1.43 Measurement of patient leakage current with applied parts connected

together

Applicable to Class I and class II, type CF (equipment having

applied parts.

Limits: 0.01mA in NC, 0.05mA in SFC.

Notes: Equipment on, but outputs inactive. Normal and

reverse mains. Limits are per electrode.

Figure 1.44 Measurement of patient leakage current for each applied part in turn



1.7.8 Patient auxiliary current

Patient auxiliary current is measured between any single patient connection and

all other patient connections of the same module or function connected together.

Where all possible combinations are tested together with all possible single fault

conditions this yields an exceedingly large amount of data of questionable value.

Applicable to All classes and types of equipment having

applied parts.

Limits: Type B & BF - 0.1mA in NC, 0.5mA in SFC.

Type CF - 0.01mA in NC, 0.05mA in SFC.

Notes: Ensure outputs are inactive. Normal and

reverse mains.

Figure 1.45 Measurement of patient auxiliary current.

1.7.9 Mains on applied parts (patient leakage)

By applying mains voltage to the applied parts, the leakage current that would

flow from an external source into the patient circuits can be measured. The

measuring arrangement is illustrated in figure 1.46.

Although the safety tester normally places a current limiting resistor in series with

the measuring device for the performance of this test, a shock hazard still exists.

Therefore, great care should be taken if the test is carried out in order to avoid

the hazard presented by applying mains voltage to the applied parts.

Careful consideration should be given as to the necessity or usefulness of

performing this test on a routine basis when weighed against the associated

hazard and the possibility of causing problems with equipment. The purpose of

the test under IEC 60601-1 is to ensure that there is no danger of electric shock



to a patient who for some unspecified reason is raised to a potential above earth

due to the connection of the applied parts of the equipment under test. The

standard requires that the leakage current limits specified are not exceeded.

There is no guarantee that equipment performance will not be adversely affected

by the performance of the test. In particular, caution should be exercised in the

case of sensitive physiological measurement equipment. In short, the test is a

"type test".

Most medical equipment safety testers refer to this test as "mains on applied

parts", although this is not universal. One manufacturer refers to the test simply

as "Patient leakage - F-type". In all cases there should be a hazard indication

visible where the test is selected.

Applicable to Class I & class II, types BF & CF having

applied parts.

Limit: Type BF - 5mA; type CF - 0.05mA per

electrode.

Notes:

Ensure outputs are inactive. Normal and

reverse mains. Caution required,

especially on physiological measurement

equipment.

Figure 1.46 Mains on applied parts measurement arrangement

1.7.10 Leakage current summary

The following table summarises the leakage current limits (in mA) specified by

IEC60601-1 (second edition) for the most commonly performed tests. Most

equipment currently in use in hospitals today is likely to have been designed to

conform to this standard, but note that the allowable values of earth leakage



current have been increased in the third edition of the standard as discussed

above.

The values stated are for d.c. or a.c. (r.m.s), although later amendments of the

standard included separate limits for the d.c. element of patient leakage and

patient auxiliary currents at one tenth of the values listed below. These have not

been included in the table since, in practice, it is rare that there is a problem

solely with d.c. leakage where that is not evidenced by a problem with combined

a.c and d.c. leakage.

Table 1.4. Leakage current limits summary.



Figure 1.47



IEC 62353 Medical Electrical Equipment

The most widely used standard is IEC 60601. Although this is a type standard

associated with the design and development of electro medical (EM) equipment,

most biomedical engineering departments continue to use it as the basis for the

regular testing of medical devices, and/or after service or repair.

Clearly, safety testing at the design stage and at the end of the production line

are vitally important, but what about when the equipment enters service? This

was the basis for the introduction of IEC 62353, the international standard for

medical electrical equipment—recurrent test and test after repair of medical

electrical equipment.

IEC 62353 Medical Electrical Equipment defines the requirements of ensuring the

electrical safety for medical electronic devices used in the treatment, care, and

diagnosis of patients.

The main goal of IEC 62353 is to provide a uniform standard that ensures safe

practice and reduces the complexity of the current IEC 60601-1 standard.

IEC 62353 maintaining the relation to IEC 60601-1, and minimizing the risks to

the person conducting the assessment.

For example, one of the main differences is in ground bond testing. IEC 62353

proposes a minimum test current of 200 mA instead of the 25 A required in IEC

60601-1. This means that, provided sufficient consideration is given to potential

contact resistance, test equipment can be smaller and more lightweight

compared with current practices. Also, under insulation resistance testing, unlike

IEC 60601, IEC 62353 provides methods for testing the insulation of medical

devices. Three different test methods are detailed for assessing the insulation

between mains parts and ground, between applied parts and ground, and

between applied parts and mains parts.

Importantly, the new standard recognizes that the laboratory conditions described

in IEC 60601-1 cannot always be guaranteed when in-service testing of medical

devices is undertaken.



In-Service Test Requirements

As a type-testing standard, the current IEC 60601 does not provide any guidance

to standardizing test requirements once an item of ME equipment has passed the

design phase.

Once a medical device enters into service, a number of potential test scenarios

arise, including:

Acceptance testing also referred to as initial or reference testing. This

test is carried out before a new medical device is authorized for use, and is

undertaken to ensure correct and complete delivery. Acceptance testing is often

not limited to electrical safety tests, with some basic function tests being applied

to verify correct performance.

Routine testing also referred to as PPM, preventive product

maintenance. This form of testing is often conducted at fixed intervals, which vary

among types of equipment, manufacturers' recommendations, and risk-

assessment procedures undertaken by individual biomed or medical physics

departments. Routine testing is not limited to safety testing and often includes the

verification of correct functionality.

After service and repair testing—carried out following a repair,

adaptation, or product upgrade. It is often part of a service carried out by in-

hospital mechanical or clinical engineering teams. In many cases, more rigorous

electrical safety testing is needed after the replacement of components or

reconfiguration of medical devices.

Visual inspection

In most cases, up to 70% of all potential faults in an item of ME equipment can be

detected during visual inspection. Although visual inspection is not clearly defined

in IEC 60601, its inclusion is a fundamental requirement of all routine test and

maintenance procedures.

Visual inspection is a relatively easy procedure to ensure that the medical

equipment in use still conforms to the manufacturers' specifications and has not

suffered from any external damage and/or contamination.

The following are typical visual checks that should be made:



Housing enclosure—look for damage, cracks, etc;

Contamination—look for obstruction of moving parts, connector pins, etc;

Cabling (supply, applied parts, etc)—look for cuts, wrong connections, etc;

Fuse rating—check correct values after replacement;

Markings and labeling—check the integrity of safety markings; and

Integrity of mechanical parts—check for any obstructions.

However, to identify all potentially dangerous faults, visual inspection should be

linked with a program of periodic inspection and testing that is capable of

revealing any "invisible" electrical faults such as insulation integrity, effective

ground bond connections, unacceptable leakage, and other potential problems.

IEC 62353 Insulation Resistance Test

Unlike the IEC 60601-1 tests, the new IEC 62353 includes a method of testing

the insulation of an EM device. Three different insulation test methods are

recommended for different types of ME equipment. The test methods are:

Insulation between mains parts and ground—this test is used to verify

that the mains parts are adequately insulated from ground (Class I) or the

enclosure (Class II).

Figure 1.47a: Insulation EUT on Class I

equipment

Figure 1.47b : Insulation EUT on Class 2

equipment

Insulation between applied parts and ground—this test is used to verify that

the applied parts are adequately insulated from ground (Class I) or the enclosure

(Class II). It is designed for Class I and Class II, BF, and CF equipment only.



Figure 1.48a : Insulation AP test on

Class I equipment

Figure 1.48b : Insulation AP Test on Class

II equipment

Insulation between applied part and mains—this test is used to verify

that the applied parts are adequately insulated from the mains parts and is

applicable to Class I and Class II BF and CF equipment only.

Figure 1.49 Insulation AP to Mains Test

on Class I and Class II equipment

IEC 62353 Ground Bond Test

The ground bond test proves the integrity of the low-resistance connection

between the ground conductor and any metal conductive parts, which may

become live in fault situations with Class I medical devices.

Although many Class I medical devices are supplied with an equipotential point,

most, if not all, medical devices require multiple ground bond tests to validate the

connections of additional metal accessible parts on the enclosure.



Figure 1.50 : Ground Bond Test in Class

I equipment

Higher test currents of 25A or 10A have been traditionally favored, based largely

on IEC 60601-1 requirements. The assumption was made that higher currents

could best detect any damaged conductors present. In addition, when analog

instruments were widely used for low-resistance measurement, it was often

necessary to use high-test currents to produce sufficient voltage drop across the

sample to generate the necessary needle deflection.

However, higher test currents—of 10A or more—might potentially be destructive

to parts of the device under test, which are connected to the protective ground

but have a functional purpose, such as screening. As such, consideration should

be given to the test current.

With modern electronics and digital technology, the use of higher test currents is

regarded as no longer necessary—a fact recognized by IEC62353 with its 200mA

minimum current.

On the other hand, low-test currents—of less than 8A—may not always overcome

problems associated with contact resistance caused by constriction, pressure, or

film resistance factors, and may therefore show a relatively higher reading than

there is and indicate unnecessary failures.

IEC 62353 Leakage Testing

Research has shown that it is current rather than voltage that is the source of

electricity-related injuries and deaths. As a result, there are stringent rules on the

design of medical equipment to ensure that the patient and operator are not



exposed to those currents that do not form part of the functional operation of the

device. These are called leakage currents.

In the interests of helping to guarantee safer practice and the repeatability of test

measurements, IEC 62353 defines different types of leakage current tests—one

for total equipment leakage and another for applied parts leakage currents.

IEC 62353 specifies three methods— direct, differential, and alternative—that can

be used to determine the leakage of EM equipment.

a) Direct Leakage Method

The direct leakage method included in IEC62353 is the same as that in IEC

60601, measuring the true leakage through a body model measuring device to

ground.

The main benefits of this method include the ability to measure both AC and DC

components, allowing direct comparison with the manufacturer's IEC 60601-1

tests, and measuring lower leakage values typically of less than 100µA.

However, one of the main disadvantages of this method is that the 1KV body

model resistor is connected in series with the protective ground conductor that

will form an "equal" parallel connection with the human body, thus presenting a

potential hazard to the operator.

Another disadvantage is that secondary ground connections will produce a lower

reading, thus potentially allowing faulty equipment to pass the test. The direct

method does therefore require a fully isolated device under test and must be

performed on a terre neutral supply and in each polarity of the incoming mains

supply to guarantee measurements are taken at the maximum potential leakage

current.

Keeping It Safe

Follow this checklist for safety testing and keep all the bases covered.

Ensure that the operator of safety test equipment is properly trained on both the

safety analyzer and the device under test to prevent unneccessary danger during

the safety test.



Always ensure that the device under test does not pose any danger to the user

and/or people within the vicinity of the safety test. Stay aware of moving parts,

open conductors, live components, heat, etc.

Ensure that leakage measurements are performed while the equipment is in full

operation mode, including its subsystems and components.

Ensure high accuracy and repeatability of leakage measurement readings. Some

manufacturers might specify full-scale accuracy, which will affect the accuracy of

low-leakage measurements.

Ensure that contact resistance is taken into account when measuring the ground

continuity at low currents (<8A). Contact resistance can influence the readings

and cause unnecessary failures of the device under test.

When determining the correct means of testing a specific medical device, ensure

that the chosen safety test procedures are applicable to the device under test and

are clearly documented for future use.

b) Differential Leakage Method

The differential test method measures the leakage current as a result of

imbalance in current between the live and neutral conductors.

The main advantage of using the differential leakage method is that the ground

conductor remains intact during the measurement, thus providing safer working

conditions. Differential measurement of leakage also does not require an isolated

device under test because it relies on comparing the difference in current

between the live and neutral conductors to measure the complete leakage of the

device being tested, including leakage caused by secondary connections.

The main disadvantage of using the differential method is reduced accuracy on

lower leakage values, because typical leakage values of more than 100µA are

required to obtain stable and reproducible readings. Measurements can also be

influenced by the presence of magnetic fields—the principle of measuring

differential current—and measurements must be done in both directions to

identify the worst-case scenario. The differential leakage measurement method is

also only able to measure the AC component.



c) Alternative Leakage Method

The alternative method is similar to a dielectric strength test at mains potential,

using a current limited voltage source at mains frequency. The live and neutral

conductors are shorted together and the current limited voltage is applied

between the mains parts and other parts of the equipment.

The main advantage of using the alternative method included in IEC 62353 is that

the device under test is not connected to the mains supply and provides the

safest possible test conditions for the operator. In addition, this measurement is

only taken in a single polarity and is similar to a dielectric test at mains potential

using a current limited mains frequency supply.

Leakage measurements achieved using the alternative method are highly

repeatable and provide a good indication of deterioration in the dielectrics of the

medical device under test.

The disadvantages of using the alternative method are that measurements

cannot be compared with previous IEC 60601-1 tests, and those active parts of

the circuitry that require mains potential between live and neutral cannot be

tested for possible leakage. For this reason, the alternative leakage method is

only relevant for certain types of EM devices.

IEC 62353 defines two different kinds of leakage current tests for applied parts—

equipment leakage current that tests for total leakage deriving from the applied

parts, enclosure, and mains parts combined to real ground; and applied part

leakage current that checks for total leakage deriving from the combined patient

connections within an applied part to ground and any conductive or

nonconductive parts on the enclosure.

Equipment Leakage

The equipment leakage test is applicable to both Class I and II, B, BF, and CF

equipment, and measures the total leakage (RMS) deriving from the applied

parts, enclosure, and mains parts combined to real ground.

All applied parts (B, BF and CF) and grounded (enclosure Class I), and

nongrounded accessible conductive parts or nonconductive accessible parts



(enclosure Class II) are grouped together and connected to ground via the 1kø

measuring device (body model).

Measurements are done in both polarities of the incoming mains, excluding

alternative method.

The IEC 62353 equipment leakage can be performed using a direct, differential,

or alternative method.

Figures 1, 2, and 3 provide a schematic representation of the equipment leakage

test on Class I (grounded) ME equipment.

Figure 1.51a: Equipment Leakage Direct

— Class I

Figure 1.51b: Equipment Leakage

Differential — Class I

Figure 1.51c: Equipment Leakage

Alternative — Class I

Applied Part Leakage

The applied part leakage test measures the RMS deriving from the combined

patient connections within an applied part to ground and any conductive or

nonconductive parts on the enclosure.



This test is applicable to floating-type (BF and CF) applied parts only—either

Class I or II. All patient connections of a single function within an applied part

shall be connected together (BF and CF) and measured one at a time.

The test is conducted by applying a current limited (3.5mA) mains potential

sinusoidal 50Hz or 60Hz signal between the applied part and the enclosure and

ground connection of the EUT connected to real ground.

Measurements are done in both polarities of the incoming mains—direct method

only.

The IEC 62353 applied part leakage test can be performed using a direct or

alternative method.

Figures 4 and 5 provide a schematic representation of the applied part leakage

test on Class I (grounded) ME equipment.

Figure 1.52a: Applied Part Leakage Direct

— Class I

Figure 1.52b: Applied Part Leakage

Alternative — Class I



Conclusion

Table 1.5

The electrical safety testing of ME equipment is a crucial part of the overall safety

validation of medical devices and requires specialized test equipment.

The introduction of the new IEC 62353 standard will provide:

A global test reference to allow uniform testing;

Development tools for safer and suitable test sequences; and

A method of record keeping and maintenance procedures.

Although the onus will remain on the manufacturers of medical devices to advise

on appropriate tests for their equipment, the new standard will clearly have a

significant impact on medical service companies and clinical engineering, EBME,

medical physics, and other technical departments.

In all cases, when choosing a suitable electrical safety analyzer, care should be

taken to ensure that it can be used to test in accordance with IEC 62353

requirements and that it is capable of performing accurate and repeatable test

routines.



1.8 STATISCAL BASIS FOR SAFE LEVEL ASSESSMENT

Any current, however small, has some probability of inducing ventricular

fibrillation. A reasonable linear relationship exists between the log of this total

current and the probability of the occurrence of ventricular fibrillation. IEC60601

extrapolate this relationship to zero. Studies by Watson and Wright (1973)

applied an electrode area of 0.05cm2 over subjects with varying increment of

current and found the following:

i. 100% probability of fibrillation at 0.96mA

ii. 1% probability of fibrillation at 0.67mA

iii. Worst case value is at 0.01mA that could be due to a weak heart

iv. At least one (1) test resulted in fibrillation at 15uA

This showed that no current is perfectly safe and there is a near linear

relationship between log (I) and probability of ventricular fibrillation incident.

Evaluating the findings, IEC60601 extends the results down to an effective

probability of 0.001 for zero current. With a minimum normal condition current of

10uA in a small electrode, there is a probability of 0.2% or 2 patient in a 100 that

could be at risk to fibrillation.

Studies by Stramer and Whelan looks into the effect of electrode size on current

required to produce ventricular fibrillation, the current density required. They

found that as the area of electrode is reduced by 100:1, the current is only

reduced by 10:1. Stramer and Whelan kept the electrode spacing constant and

measured the voltage applied to electrode size, approximately 0.4V. In short,

they minimize variables and maximize constant to obtain a valid and reliable

outcome. The followings are further findings of their studies:

i. The smaller the electrode size that is attached to or inside the

heart, the smaller the current required.

ii. Current density in the bulk of the heart tissue is roughly constant.

iii. A current density in heart tissue of approximately 20uAcm-2m

produced ventricular fibrillation in a significant number of trials.

iv. Currents of 200-300 uA produced ventricular fibrillation in smaller

electrodes.



The above two statistical conditions has been referred in setting the safe level

assessments of IEC60601. Current limits permitted in the standard are based on

currents needed to cause ventricular fibrillation with smaller electrodes. It is

concluded that larger electrodes are statistically safer. Table IV in IEC60601

defines allowable values of leakage current as follows:

Current Normal

Condition (mA)

Single Fault

Condition (mA)

Earth Leakage Current – Earthed Metal

Enclosure (Class I) 0.5 1

Earth Leakage Current – No Accessible Earthed

Parts, but Earthed Internal Screens (Class I) 2.5 5

Earth Leakage Current – Permanently Installed

Equipment (Class I) 5 10

Enclosure Leakage Current. Maybe Class I, II or

Internal Power Source 0.1 0.5

Table 1.6

These leakage current as per the above table, in the worst case would be flowing

through the thorax, not directly through the heart. In which case, type CF is

necessary. In IEC60601, for each amp of current flowing through the thorax,

approximately 5mAcm-2 will flow through cardiac tissue. This is the basis of

estimating the probability of ventricular fibrillation for the limits quoted in the

standard.

It can be seen that the limits quoted for different patient circuit types fit with the

general philosophy of negligible risk. Taking an example of the patient leakage

current for Type B and Type BF patients;

5mA when 240V is applied to either a single socket (Type B) or the patient (Type BF)

If applied to the chest:

Produces 25uAcm-2 (above the negligible level), with a probability of 0.8.



However, the probability of this particular type of fault condition, i.e. the

patient touching something at 240V and the current flowing through the

chest is regarded as very low.

Thus, the overall risk is negligible.

For Type CF, by definition, all currents flow through the heart. The limit is further

reduced to 50uA when mains are applied to the patient in normal and single fault

condition. This produces a probability of approximately 0.01 for ventricular

fibrillation which is again negligible.

Overall, the different current limits in IEC60601 are determined according to

probability that they will produce current in the heart big enough to produce

ventricular fibrillation. It is also noted that current flowing in the earth wire has a

different probability of doing this than current in isolated patient circuit. IEC60601

current limits are designed, in general terms, to ensure the probability of

ventricular fibrillation of 0.002 or less. The probability of mechanical stimulation

by a wire in the heart with zero current is set at 0.001.

Figure 1.53 Distance1.5 m around the patient bed

Bed

R=1,5m



Figure 1.54 Definition of patient environment from IEC60601.1.1

1.9 SAFETY ASPECT OF INTERCONNECTION OF EQUIPMENT

Equipment may be safe by itself but when there are connected together, there is a

risk that must be acknowledge. IEC60601 outlined permitted ways of equipment

interconnecting in its collateral standard, IEC60601-1-1 as per the following:

i. Use an isolation system in the signal connection

ii. Use an isolated mains transformer

iii. Coupled the earth together, sometimes mounted on the trolley or double

the earth (unofficial).

Digital signals can be easily isolated by way of optical coupled. Other collateral

standards of IEC60601 include IEC60601-1-2 which is for Electromagnetic

Compatibility and IEC60601-1-4 which is for Software Integrating.

EFFECT OF ISOLATION TRANSFORMER

Live

Earth

Neutral

Figure 1.55 Without isolation transformer



Live

Earth

Neutral

No current

Figure 1.56 One instrument on isolation transformer

Live

Earth

Neutral

No current

Equalisation current between instruments

Figure 1.57 Multiple instruments on isolation transformer

1.10 RISK MANAGEMENT / OSHA

IMPORTANCE OF SAFETY IN WORKPLACE

Works plays a central role in people’s lives.

Most workers spend at least 8 hours a day in workplace.

Therefore, work environments should be safe and healthy.

Every day workers all over the world are faced with multitude of health

hazards, such as:

o Dust

o Gases

o Noise

o Vibration

o Extreme temperatures.



Some employers assume little responsibility for the protection of worker’s

health and safety.

As a result of the hazards and a lack of attention given to health and

safety, work-related accidents and diseases are common in all parts of the

world.

MAJOR SAFETY TERMINOLOGIES

SAFETY - The condition of being safe from undergoing or causing hurt, injury

or loss.

HAZARD - A hazard introduces the potential for an unsafe condition, possibly

leading to an accident.

RISK - The probability or likelihood of a Hazard resulting in an accident.

INCIDENT - Undesired circumstance that produces the potential for an

ACCIDENT.

ACCIDENT - An accident is an unplanned event, which could result in injury

to persons, or in damage to plant and equipment or both.(James,

D.W.B.,1983,5).

ACCIDENT COST - Accident cost includes medical Payments,

Compensation, overtime for replacement workers, production delays, product

or material damage, training of replacements, accident investigation cost,

building or complex damages, equipment damages and business

interruptions. (Boley, Jack W. 1977, 19).

What is occupational health and safety?

Occupational health and safety is a discipline with a broad scope involving many

specialized fields.

Should aim at:

The promotion and maintenance of the highest degree of physical, mental

and social well-being of workers in all occupations.

The prevention among workers of adverse effects on health caused by

their working conditions.

The protection of workers in their employment from risks resulting from

factors adverse to health.



OSHA Act 1994

Occupational Safety and Health Act 1994 is aimed to foster and promote safety

awareness among health workers and also create organization with effective

safety and health regulations.

This is done through self-regulation scheme that relevant to the industry or

related organizations.

OSHA 1994 Requirement

For all industries

If >5 Employees - Safety & Health Policy

≥40 Employees (S30) - Safety & Health Policy + Safety & Health

Committee

For high risk industries (i.e. construction, ship building, gas etc.)

>100 Employees (Order 1997) - Safety & Health Policy + Safety &

Health Committee + a Certified Safety & Health Officer

For low risk industries (other than the above mentioned industries)

>500 Employees (Order 1997) - Safety & Health Policy + Safety &

Health Committee + a Certified Safety & Health Officer

Functions of Safety & Health Committee

Assist in the development of safety & health rules and safe systems of

work;

Review the effectiveness of safety & health programmes;

Carry out studies on the trends of accident, near-miss accident,

dangerous occurrence, occupational poisoning or disease, and shall

report to the employer together with recommendations for corrective

actions;

Review the safety & health policies.

Appointment of Committee

Chairman : An employer or his authorized manager

Secretary: Safety and health officer at the place of work



Employer representatives : Nominated by employer

(>100 employees – 4 representatives)

Employees representatives : Nominated by employees

(>100 employees – 4 representatives)

Duties of Safety and Health Officer

to advise employer on the safety and health measures;

to inspect and determine the safety of work place;

to investigate any accident which has happened in the work place;

to assist employer in organizing and implementing OSH programme;

to become secretary to the committee;

to assist the committee in any inspection of the work place;

to collect, analyze and maintain statistics on any accident, dangerous

occurrence, occupational poisoning and disease which have occurred

at the work place ;

to assist any officer in carrying out his duty under the Act;

to carry out other instruction made by the employer on any matters

pertaining to OSH.

Duties of an Employer

To ensure the safety, health and welfare at work of all his employees

and visitors.

To formulate safety and health policy.

Extra protection for the disabled etc.OSHA 1994

Penalty For Non Compliance

A fine not exceeding RM50,000 or

Imprisonment not exceeding 2 years

Or both

Other Penalty / Fine

Common Law:

Affected person (employee or public) may take legal action against the

organization under the Civil Law (Common Law).OSHA 1994



Duties of third party (suppliers / contractors)

To provide sufficient information.

To eliminate or reduce hazard.

To build and fix the equipment with safety feature.

Penalty for non compliance.

A fine not exceeding RM20,000 or maximum 2 years imprisonment or

both

Duties of an Employee

To take reasonable safety and health measure for himself and other

persons;

To co-operate with his employer or any other persons in the discharge

of any duty;

To use and wear at all times, any protective equipment or clothing

provided by employer;

To comply with any instruction or measure on occupational safety and

health instituted by his employer.

Penalty for non compliance

A fine not exceeding RM1,000 or

Imprisonment not exceeding 3 months

Or both

The Regulations of OSHA 1994

Employers Safety and Health General Policy Statement (Exception)

Regulation 1995

Control of Industry Major Hazards (CIMAH) Regulations 1996

Safety and Health Committee Regulations 1996

Classification, Packaging and Labeling of Hazardous Chemicals (CPL)

Regulations 1997

Safety and Health Officer Regulations 1997

Safety and Health Officer Order 1997

Use and Standards of Exposure of Chemicals Hazardous to Health

(USECHH) Regulations 2000



Notification of Accident, Dangerous Occurrence, Occupational

Poisoning and Occupational Disease (NADOOPOD) Regulation 2004

1.11 DISINFECTION / STERILISATION

The following are definition of the terminologies used in this subtopic:

i. Cleaning: General removal of debris, i.e. dirt, food, feces, blood, saliva

and other body secretions. It shall reduce the amount of organic matter

that contributes to proliferation of bacteria and viruses.

ii. Disinfection: The removal of all infective (pathogenic) microorganisms

usually by means of chemical agents. It will be necessary to remove all

spores.

iii. Sterilisation: The killing or removal of all organisms.

1.11.1 Equipment Categorization and Reprocessing Level

In reference to the practice standards that are based on Spaulding’s

Classification System, healthcare devices and equipment are designated as per

the following, which would define the level of reprocessing (cleaning, disinfection,

sterilization) required:

i. Critical

ii. Semi-critical

iii. Non-critical

Critical items would require sterilization which includes items that enter sterile

tissue or the vascular system. Examples include surgical instruments and

accessories, biopsy forceps, cardiac and urinary catheters, implants and needles.

For semi-critical items, a minimum high level of disinfection or sterilization is

required. All items that comes into contact with non-intact skin or mucous

membranes falls under this categories. Examples cover respiratory therapy

equipment, anesthesia equipment, laryngoscopes, bronchoscopes, GI

endoscopes, cytoscopes and vaginal ultrasonic probes. Under the semi-critical

category, cleaning process must precede high level disinfection.



Non-critical items require intermediate level or even low level disinfection where

necessary. This includes items in contact only with intact skin. A straightforward

example includes blood pressure cuffs, stethoscopes and durable mobile patient

equipment.

1.11.2 Cleaning, Disinfection and Sterilization of Medical Instruments

and Devices

One cannot achieve disinfection or sterilization without pre-cleaning as organic

material dilutes disinfectant and bioburden must be reduced for processes to be

effective. Thus, as a first step, all medical instruments and devices shall be clean

by removing all visible soil with any instrument parts are to be disconnected and

separated. One should also avoid organic material drying on equipment by

rinsing or soaking it in an enzymatic solution.

When cleaning soiled medical instruments, wear the necessary personal

protection equipment as per the following:

i. Long sleeved impervious gown

ii. Eyewear

iii. Mask or mask with face shield

iv. Gloves

v. Cap

vi. Chemical goggles (when mixing or changing solution)

Looking into disinfection, the goal is to eliminate or kills most bacteria, many virus

types and some spores. It is a time dependent process with a high, intermediate

or low level of disinfecting. Under the process of disinfection, it is important to

follow the manufacturer’s recommendations in order to achieve the desired

outcome and avoid from damaging the medical device. The following are

important points that have to be observed:

i. Use correct dilution (more is not better)

ii. Use correct contact time

iii. Use correct temperature



The staff should not exceed the exposure limits and is in the know of permissible

exposure levels. The following table illustrates the types of available disinfectant.

Table 1.7

Type Name Description

Environmental Phenolics “Gold Standard” in healthcare

Toxicity concerns prohibit use in nurseries,

NICU

Does not kill spores

Quaternary

Ammonium

Compound

Approved for specific pathogens (read the

label!)

Affected by water hardness

Affected by bioburden

Iodophors Can be used in food preparation areas

Inactivated by organic materials, e.g. blood

Can stain surfaces

Chlorine

(Bleach)

Inactivated by organic materials, e.g. blood

Kills spores, e.g. C. difficile

Corrosive

Highly toxic (deadly) if combined with

ammonia

Ultraviolet

Radiation

Dependent on strength and duration of

exposure to light, „line of sight‟, how well

microorganism can withstand UV

Limited to destruction of airborne organisms,

inactivation of microorganisms on surfaces,

and water purification



Sterilization is achieved through the following methods:

i. Steam

ii. Dry Heat

iii. Ethylene Oxide

iv. Peracetic Acid

v. Plasma Gas (Vaporized hydrogem peroxide)

vi. Glutaraldehyde (Using higher concentrations and exposure times)

In steam sterilization, it utilizes an autoclave to achieve rapid heating and

penetration in the process of eliminating microorganisms. It is applied in short

exposure time that is less than 20 minutes but a maintain temperature

throughout. The process pose no toxicity to workers and inexpensive. It is

however could be damaging to delicate instruments. As per the norm, items to be

sterilized must be clean and free of protein or other organic material. If a package

is used, it must allow the steam to penetrate to have the desired effect.

Rapid cycle or flash sterilization is a version of unwrapped steam sterilization. It

should only be applied when necessary and the following caution must be

observed:

i. Do not flash whole trays of instruments

ii. Items must be used immediately

iii. Maintain records or flash logs

Flash sterilization can be avoided by keeping adequate supply of frequently

dropped items.

1.10.3 Environmental Cleaning

Patient environment, as per the figure below, can facilitate transmission of

bacteria and viruses, either by direct contact or on hands of healthcare

personnel. Contaminated surfaces increase potential for transmission of bacteria

and viruses between patients. Items categorized as non-critical (intermediate or

low disinfection( or require cleaning only.



Figure 1.58

In reference to patient environment, the following policy should be taken into

consideration by a healthcare practitioner:

i. Include in policy all surfaces and equipment that can reasonably

be expected to be contaminated by bacteria (high touch surfaces).

ii. Define responsibility and frequency for cleaning and disinfection

patient care equipment and surfaces.

iii. Monitor compliance with policy.

iv. Cleaned/disinfected items should be labeled, date and time.

The following are high touch surfaces in patient rooms that are considered to be

non-critical. It must be cleaned then disinfected on a regular basis.

i. Bedrails

ii. Call bell

iii. Telephones

iv. TV remote

v. IV pump

vi. IV poles

vii. Toilet

viii. Overbed table



ix. Light switches

x. Doorknobs

xi. Respiratory and other bedside equipments

xii. Chairs

Items requiring only cleaning in a patient environment include floors, walls and

windows, chairs and other furniture used by individuals who are clothed, private

offices and other non-public and non-patient care areas.

Under the HICPAC Disinfection and Sterilization Guideline 2008, the use of

microfiber is recommended for cleaning. It shall be of densely constructed

synthetic strands 1/16th the diameter of a human hair. This attracts dust and

cleans approximately 50% better than comparable cotton and easier to use,

lighter and was designed for repeat usage.

Monitoring of environmental cleaning processes involves the following methods:

i. Bioluminescence (Outcome measure): Monitors for light emissions

produced if organism present. Results are difficult to interpret

because it is unknown whether organism remains viable and

transmissible.

ii. Fluorescence (Process measure): Monitors for chemical markers

that fluoresce with ultraviolet light if not removed during cleaning.

iii. Culturing: Implemented during outbreak investigations.

iv. Visual inspection: Routine rounds and provide feedback to

frontline staff.

1.10.4 Linens

The standard recommended procedure for all linen contaminated with blood or

body fluids are as follows:

i. Bag linen at point of use

ii. Wear PPE when sorting and agitate minimally



Laundry equipment must be maintained to prevent microbial contamination. New

laundry technologies allow linen washing without requirements for hot water and

chlorine but the following settings are the standard requirements:

i. Hot water - 160F x 25 min

ii. Cold water - 71-77F with 125 ppm chlorine bleach rinse or

equivalent detergent

1.12 MEDICAL DEVICES ACT (MALAYSIA)

The Medical Device Act 2012 (Act 737) has been gazetted on 9th February, 2012

by the Malaysian Government. The Act was effective on 1 July 2013 and

undergoes a transition period before it is fully enforced in 2014. The Act specifies

requirements for medical device product registration, establishment licensing and

conformity assessment body (CAB) registration through the Medical Device

Regulations 2012, the subsidiary legislations under the Medical Device Act 2012

that has been approved by the Minister of Health and has been published in the

Gazette on 31st December 2012.

The Act is the product of the efforts of the Ministry of Health to implement a

regulatory framework for medical devices, an area previously not regulated in

Malaysia. The Act seeks to address public health and safety issues and facilitate

medical device trade and industry. The Medical Device Authority Act 2012 (Act

738) which came into effect on 15 March 2012 established the Medical Device

Authority (“Authority”) which oversees the execution of the Act 737

.

Medical Device Authority (MDA) is charged with the role of regulating medical

device and its industry players.



EXERCISE

1. Define standard

2. Explain the following standard

i. Safety Standard

ii. Performance Standard

iii. Quality Standard

3. Discuss the benefit of standard

4. State the roles of Malaysia Standard

5. List three International Standard Organization

6. Explain hazard that may produce from medical equipment

7. State condition that can result electrical shock.

8. State factor to consider in determine form and severity of injury due to electrical

shock

9. Explain special environment in hospital that medical equipment need to operate.

10. Define microshock and macroshock.

11. Explain the physiological effect of electricity.

12. State precaution to minimize electrical shock hazards.

13. Explain 4 types of leakage current.

14. Define and sketches symbol for each type of medical equipment classification

according to method of protection against electrical shock.

15. Discuss similarities and differences between IEC60601 and IEC62353

SUMMARY In this unit we have studied Medical Device Safety Standard. This chapter provides

information on standard being used in Malaysia and worldwide. Source of leakage

current and its physiological effect together with safety standard applied to protect

patient and user is presented.

M20_Chapter 1_Medical Device Safety Standard.pdf

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