Medical Gas

MEDICAL GASES

&

RELATED FACILITIESBy

Ismail Yusof

Contents

IntroductionReferencesMedical GasMedical gas Pipeline SystemsProperties of Gases and cylindersMedical Compressed AirMedical VacuumAnaesthetic Gas Scavenging SystemConclusion

This is purely an introduction to the subject ofMedical Gases – an AWARENESS SEMINAR

The intention being to give everyone a ‘feel’ ofthe subject and a common language – pointerswill be included to enable those interested toreview such installations as to their complianceand hopefully encourage some to delve deeperinto the subject and make reference

Internationally all medical gases are deemed to be drugs

Such gases and all things relating to them are subjecttherefore to very stringent regulations :

Technically (Design & construction)

Materials used

Pharmacological consideration

Maintenance and operation

Testing & commissioning

Modification

MEDICAL GAS PIPELINE SYSTEMS (MGPS)

In most parts of the world Medical Gas systems at alltimes

From design through to commissioning to operationand maintenance and periodic testing and validationof gases

Both a competent Engineer and competentPharmacist are required to sign off and certify anysystem for use

Medical Oxygen O2

Medical Air A4 + A7

Nitrous Oxide N2O

Nitric Oxide N0 - A newly used gas

Entonox N2O/O2

Medical Vacuum - VAC

Anaesthetic Gas Scavenging System – AGSS

Synthetic Air

TERMINOLOGY

Hospital Technical Memoranda (HTM’s)

HTM 2022 – published 1994 supercedes HTM22(Circa 1970’s)

Plus

C11 National Health Service Model EngineeringSpecification

SOURCE OF REFERENCE

Published in 5 Sections/Volumes

•Management Policy

•Design Considerations

•Validation and Verification

•Operational Management

•Good Practice Guide

HTM2022

•HTM2022

•C11 Model Engineering Specifications

•BS 5682 Terminal Units and Hoses

•BS 6384 WAGS/AGSS (EN 737/2)

RECOMMENDED SOURCES OF REFERENCE FORMEDICAL GAS PIPELINE SYSTEMS

•HEI 163 (Cylinder Handling)

•British Compressed Gas Association Codes ofPractice

•No. 1 – 7 (Pathology Laboratories)

•Health Service Engineering

•(HSE Manual Handling)

HEALTH ENGINEERING INFORMATION

The Pascal

Pascal French guy 1623 – 1662 – derived the unit =one Newton per square metre

Newton English guy 1642 – 1727

So a Frenchman decided that the unit of pressureshould equal one Englishman per square metre

PRESSURE

The kilo Pascal kPa

1 bar = 100 kPa ≈14.51 psi

Standard Atmosphere = 760 mmHg = 14.7 psi

PRESSURE

GasProperty

OxygenO2

NitrousOxide N20

Entonox50/50N2O + O2

Medical Air CarbonDioxideCO2

Density atSTP Kg/m3

1.43 1.98 1.61 1.3 1.98

BoilingpointAt 1.013bar gauge

-183.1 -88.6 -60 -190 -78

Colour ofGas

None None None None None

Colour ofCylinders

WhitetopsBlackbody

Frenchblue

Blue andwhite1/4tops –blue body

Black &white ¼tops greybody

Grey

GAS GENERAL PROPERTIES

GasProperty

OxygenO2

NitrousOxide N20



Odour None Faint Faint None None

Taste None SlightlySweet

Slightlysweet

None None

Flammable No No No No No

SupportsCombustion(Oxidiser)

VeryVigorously

Vigorously Vigorously Yes No


GasProperty

OxygenO2

NitrousOxide N20



State inCylinder

Gas137 bar

Liquid40 bar

Gasabove –7 ° at 137bar

Gas 137 bar Liquid50 bar

MedicalUses

Lifesupportandtherapy

AnalgesicAnd weakanaesthetic

Analgesic Respiratory,Tools, vents

Respiratorystimulant

Precaution Oils and greases to be avoided Danger ofAsphyxiationto be wellventilated

Method ofSupply

Pipelines & cylinders Cylinders


Nitric Oxide– Relaxed blood vessel

– Blue baby syndromehypoxic respiratory failure (HRF)

Medical gas cylinders are robust but should be:-

Handled with care

Personnel changing cylinders should have receivedadequate training

Naked flames are prohibited

Cylinders should never be used as rollers

Cylinders should never be lifted by their valves or caps

Cylinders, their valves and caps must be kept free from oil& grease

HANDLING OF MEDICAL GAS CYLINDERS

E & F - Used on anaesthetic trolleys, babyincubators, resuscitators, portableemergency supplies and ambulances

G - Used on Medical equipment in wardareas

J - Used on Medical gas manifolds

TYPES / SIZES OF CYLINDERS

A compressed gas cylinder can explode if damaged oroverheated

If a cylinder is damaged at its neck (its weakest point) it can takeoff like a rocket – destroying anything in its path

Discharge of high pressure gas can blast particles into eyes andat a very high pressure can pass through the skin causing death

Some gases can cause explosions if allowed to come intocontact with oils or grease

Some cylinder are filled with liquid which if discharged are socold they could cause severe frost bite or even death by freezingor hypothermia

SOME POINTS WORTH NOTING WITH CYLINDERS

Requires that manifold rooms should be well ventilated

It should be noted

With just a 4% increase in the level of oxygen in anenvironment

Combustion rate is doubled

At 100% oxygen level even steel will burn !!

HTM2022

Has a nasty habit of hanging around in the fibres ofclothing

So if you have been exposed to a high level ofoxygen go and walk around in the fresh air for at leastTEN MINUTES before running the risk of coming intocontact with a point of combustion – smoking etc.

OXYGEN

All fittings / fixtures/ pipe work etc. throughout all MGPS haveto be manufactured especially – de-arsenic – degreased etc.

All materials are provided in sealed plastic wrapping directfrom manufacturers/agent.

Seals - valves etc. cannot be replaced with standardengineering material (i.e. from the hardware store).

Flux less solder

Purge gas

Mechanical joints

Ultrasound

Medical Gas Pipeline Systems

There are 2 classifications of gas to be found in thehealthcare environment

MEDICAL GAS

Is gas prescribed for a patient by a Doctor, allowablecontaminants are controlled by national and internationalstandards

PATHOLOGY GAS

Is any gas used in a pathology department, this conforms todifferent standards. The are used to supply analyticalequipment as a carrier or fuel gases

TYPES OF GAS FOUND IN HOSPITALS

PERMANENT GASES

Are gases which remain in the gaseous condition in cylindersat normal temperatures. We can judge how much gas remainsbecause the pressure directly relates to the contents. i.e.When at ½ pressure the cylinder may assumed to be ½ full

LIQUEFIABLE GASES

These gases are provided in liquid form in the cylinder, atnormal temperature. The pressure of the gas remains constantas the liquid vaporises to provide the supply of gas. We wouldnot know the contents until suddenly the cylinder would beempty. Only by weighing the cylinder could we tell the contents

PROPERTIES OF GASES

Argon – has uses in Pathology Departments but alsoit is used for high quality welding where it acts as ashield against oxygen to produce a high quality weld

Oxygen free Nitrogen – is used as a purge andshield gas – particularly when fabricating MGPS

Ethylene Oxide – Used in certain sterilizers(Autoclaves) – it is an extremely dangerous gas

Hydrogen – tempting to use to fill up balloons –could lose your head!! IT IS VERY EXPLOSIVEWHEN MIXED IN AIR

SOME MORE ABOUT OTHER GASES

Cryogenics is the science of the cold – very very cold –below – 4000 C

Various gases may be cooled to below this temperatureand stored as a liquid in a giant thermos flask in thehospital world we see them as VIE Units which store bulkoxygen

A Vacuum Insulated Evaporator

CRYOGENIC GASES

Such a device may also be found containing liquidNitrogen in the Laboratory – usually they are 25 litreflasks

Cryogenic gases are very dangerous because as theliquid vaporises to a gas the gas comes away at a verycold temperature (typically -2000 C)

There is a very great danger of frostbite if the liquid or the‘just vaporised’ gas comes into contact with the skin

Also the possibility exists of suffocation in the case ofspilled liquid Nitrogen

CRYOGENIC GASES

It should also be remembered that Carbon Dioxide andNitrous Oxide are in their liquid form in cylindersprovided to hospitals

Whilst these are not classed as Cryogenic gases whenvaporising to provide a substantial supply demand themanifold pipe work immediately receiving the flow ofgas can drop in temperature to – 3000 C

If touched by human skin it will freeze the skin to thepipe work

CRYOGENIC PRECAUTIONS WITH OTHER GASES

Entonox (50%Oxygen + 50% Nitrous Oxide)

If a cylinder of Entonox is allowed to cool to 6 0C thegases separate - which of course is dangerous.

If this were to occur cylinders should be placedhorizontally in an environment at a temperature ofbetween 10 and 340 for 24 hours

NOTE

DON’T do itIt is very very dangerous

Something about nothing !!

Medical vacuum – it is included with other medicalgases when defining standards – it is defined as amedical gas

Pathology Departments are not allowed to utilisemedical Vacuum pipe systems

DECANTING

You may find a Green Cylinder

This will probably from America and will have containedOxygen

You may find an orange cylinder – this could containCYCLOPROPANE.

This is a highly explosive gas – never discharge anorange cylinder

NOTE

The J size cylinder (the ones fitted to a manifold) arecumbersome and heavy

They weigh on average 69Kg or 150 pounds

They must always be secured – they must never be leftfree standing LIABILITY

Proper training must be given to personnel who are tohandle cylinders

Proper PPE must be made available and used

Medical gas cylinders must be located and stored in asecure well ventilated store

NOTE

Medical gas cylinders must be located and stored in asecure well ventilated store, they should be restrained fromfalling over.

Such storage area must be exclusively for cylinders, it isnot permitted to store cylinders in a room containingMedical Air compressors or Vacuum Plant

They should be stored in a segregated manner

This is a requirement of HTM 2022 – it is therefore arequirement of the MoH – therefore a requirement of theConcession Agreement

A cylinders ‘shelf life’ is 3 years - the stock must be rotated

NOTE

Manifold rooms should not be used for storage ofcylinders

One set of ‘replenishment’ cylinders may be held in theroom (remember all cylinders have to be chained)

The room should be clean and free from grease/oil etc

Proper fire extinguishers must in place

Proper signage should be in place together with acylinder chart

The manifold room should be kept locked at all times– except when delivery is made – doors to open out

MEDICAL GAS MANIFOLD ROOMS

Various gases including air and vacuum are used bylaboratories for driving and for use by analyticalequipment

Normally management of these gases is undertakenby the laboratory

These gases should not be mixed with Medical gasesand

Medical gases should never be taken to a laboratory

Many of these gases are highly flammable and or toxic

PATHOLOGY GAS SYSTEMS

There are 2 types of Medical Air provision to be foundin a hospital – not all hospitals

Medical Air – this air provided for administering topatients, it is distributed and utilised at a pressure of400 kPa (≈ 58 psi, 4 bar)

Surgical Air – the air is provided to drive surgical tools,it is distributed and utilised at a pressure of 700 kPa

(≈ 100 psi, 7 bar)

MEDICAL COMPRESSED AIR

Dry particulate matter 0.01 mg/m³*

Oil mist and vapour 0.5 Ditto

Water 115.0 Ditto

Carbon monoxide 5.5 Ditto = 5 ppm

Carbon dioxide 500.0 Ditto = 500 ppm

*HTM2022 Statement is ‘Air should be free from visibleparticles in 75 litres

The first 3 qualities are achieved by the production processand filtration systems, the last 2 depend greatly upon thelocation, the immediate environment and air intakes (later)

MEDICAL AIR QUALITY - BOTH TYPES

As mentioned at the start of this session, In mostcountries commissioning and testing – retesting is acombined role undertaken jointly with an AuthorisedPharmacist.

This is not the case here

Yet ?

Again HTM2022 requires that such testing be donewith input from a Pharmacist so in years to come thismay happen

QUALITY TESTING

Routine testing of medical air (across the 5 conditions)

Should be undertaken quarterly and records kept

This is required by regulation – HTM2022

It is therefore a requirement of the ConcessionAgreement

QUALITY TESTING

The passage of environmental air through a system toproduce Medical Air (Refer to hand out)

•A nine stage process

•Notes

•Coalescing = sticking stuff together!! Oh the English!!

•Note that final filtration cannot remove viruses – onlybacteria

•So in the case that sterile air is required there has to bea tenth stage

MEDICAL AIR PROCESS

MEDICAL AIR PROCESS

MEDICAL AIR PROCESS

MEDICAL AIR PROCESS

It is recommended that any Medical Gascompressing station should have a back upManifold (cylinders) system capable ofproviding a 4 – 6 hour supply to the hospital incase of plant failure

BACK UP

Air intake

This is critical, regulations state that the compressorsshould have their air intake taken from a point 5m fromthe ground.

The point here is that the quality of the air to beprocessed should be ‘as good as you can get’

Even with the best filtration systems etc if you start withpolluted air you have to end up with polluted air

Medical Air Manufacturing plant

For example

If the Medical air compressors are in the same locationas the Medical Vacuum Plant AND the Medical VacuumPlant is discharging into the plant room AND the aircompressors are drawing their supply locally (within theroom).

The system will be recycling at least viruses and whoknows what else (remember normal final filtration onlyremoves bacteria)


We mentioned earlier

The need to test medical air for

Carbon Dioxide

Carbon Monoxide

?????


If the compressor’s intake air is taken from andenvironment

that is thick with traffic fumes or the like (in or close to aboiler house or incinerator)

????

If the plant room is dirty and thick with oil and grease andwater

?????


AN OVERVIEW OF WHAT TO LOOK FOR

There should be twin – identical air compressors withaftercoolers (air gets hot when being compressed) –

These are normally air cooled refrigerant type and mayrequire a ducted air supply

Reciprocating compressors should be two stage

Water sealed compressors should not be used

Air intake should be provided with a filter – take note ofprevious points regarding quality of intake air


An Air Receiver ( it is recommended and preferable to have 2)

The air receiver should be sized – at being able to hold aquantity of water equal to 50% of compressor output in l/m freeair delivery at normal working pressure

Current regulations require that the receiver should have:

A test certificate

A PRV test certificate

Automatic drains

Pressure gauge

Fusible plug (now) and a manual bypass


Although not mandatory it is highly recommended that thesystem should have two receivers

Receivers are subject to Statutory testing

NOTE

The effluent being drained from the receiver is sure tocontain oil – it therefore should not be discharged into thenormal drainage system


Next We look for the separator / pre-filter and then thatcoalescing filter thing

Next comes

The desiccant dryers (silica gel)

The dust filters

The activated carbon filters

Followed by Pressure reducing valves and lastly

The bacteriological filter

All filters – PRV’s etc. should be duplex i.e 2 of everything


GENERAL NOTES

Compressors and associated plant should be locatedin a secure room providing good ventilation and easyaccess to components

There should be adequate air intake for thecompressors and to cool all items of plant

The Medical Gas system should be connected to thehospital essential electrical supply


The system must be able to auto start afterreinstatement of the power supply

The system should have it’s own monitoring andcontrol / alarm / plant condition system – it may bemonitored by a Building Management system butmust not be controlled by it – we cover this later



ONE LAST POINT

We mentioned earlier that medical air is manufactured forMedical use (400kPa) and for Surgical use (700kPa).

Prior to 1994 it was allowed (HTM2022) to run a system toprovide Medical air at 700kPa with a pressure reducing stationbeing utilised to provide Medical air at 400 kPa

Strictly speaking this is no longer allowed – post 1994 – twoseparate systems should be used

Here in Malaysia we are allowed to manufacture Medical air fromone system at 700kPa – providing Medical Air via a pressurereducing station

This a fairly reasonable deviation to regulations and is costeffective


MEDICAL VACUUM

Medical vacuum is required to provide immediatereliable suction, particularly to Theatres

With reference to HTM2022

A minimum of two identical pumps are necessary

The type of pump is left to the discretion of theplant manufacturer but cannot be of the watersealed type

Vacuum is required to be provided at the TerminalPoint at a level of 300 mmHg with a flow rate of 40l/min

To compensate for pressure drops, the compressorsusually produce a vacuum of between 500 - 600mmHg but can be found operating to 650 mmHg

There should be a vacuum of 450mmHg at the testpoint in the vacuum plant room

MEDICAL VACUUM

Pressure – Bar/Atm/kPa/psi/

Vacuum – mmHg/inHg/Torr

Temperature – oC/oF/K/R

Standard temperature and pressure (STP) for vacuum systems

Degrees Celsius (oC) and millimetres Mercury (mmHg)

Absolute Temperature

Kelvin = oC + 273

0 to 1 Atmosphere = 760 Torr (Torricelli Italian 1608 - 1647)

The ‘Torricellian vacuum’ took over from Galileo

0 to 1 Atmosphere = 20.9213 in Hg = 33.8985 ft H2O

Absolute vacuum = 760 Torr/mmHg

TEMPERATURE AND PRESSURE MEASUREMENTS

Absolute zero ofpressure

Absolute scale Gauge scale

760 mm Hg / 0 psi / 0 bar

Atmosphericpressure (Standard)

0 mm Hg / 0 psi / 0 kPa / 0 bar

5.0135 bar / 29.2 psi /

201.2 kPa4 bar / 100kPa / 14.5 psi

Cut in 500 mmHgCut in 650 mmHg

‘Negative range’

14.7 psi / 1.0135 bar /0 mmHg

760 mm Hg / -14.7 psi / -101.35kPa / -1.0135 bar

Absolute zeroTemperature

Absolute scale Celsius scale

0 K

0 0 C273.16 K

373.16 K 100 0 C

‘Negativetemperature range’

- 273.16 0 C

273.16Degrees

The regulations require that the pumps are to be sizedso that 1 pump running on it’s own will provide 100%service

So if you see a system where both pumps are having torun to cope with demand ??

MEDICAL VACUUM SYSTEM

Although it is acceptable to have only one receiver it isrecommended to have duplex sets

In the case of a single receiver a bypass arrangementmust be provided to facilitate maintenance to thereceiver whilst the supply is being provided

Receivers must be fitted with a double valve drainarrangement for drainage – this is to allow for anyparticulate to be cleared easily

These receivers (UK) are now not subject to StatutoryTest


Bacteriology filter sets must be fitted as a duplex facility– they must never be operated in parallel or changed toa schedule

Note – maintenance to these is very stringent, filtersmust be changed in accordance to manufacturersrecommendations

They present distinct hazards to maintenancepersonnel

Such filters must be changed according tomanufacturers guidelines – a pressure differential mustnever exceed 25 mmHg across the filters


Cut in of the compressors should be set at 500 mmHg

Cut out may be set as high as 650 mmHg but actualsetting will depend on pump characteristics and systemdesign.


Normally vacuum is distributed using the same grade ofcopper pipe used for other medical gases

However approval has recently been given to use PVC

But typically although we can now use PVC the onlyother approved factor is that the pipework has to betested to a pressure of 750 mmHg approx 14.5 lbf/in2

TYPICAL !!

No mention is made on what grade of PVC, whatjointing methods are to used etc.


One great danger with Medical Vacuum systems is linecontamination

Sometimes through carelessness or oversight a vacuumreceiving jar located at a Terminal Unit may be left tooverflow

It’s contents are then drawn into the pipework andeffectively contaminate the entire system

Action must be taken quickly not just because of the risk ofspreading infection – if the ‘fluids’ are allowed to dry outthe pipework will start to block up







ANAESTHETIC GAS SCAVENGING SYSTEMAnaesthetic Gases are considered to be substanceshazardous to health, except when they are administered topatients in the course of medical treatment.

For all practical purposes it is only necessary to consider theeffects of nitrous oxide pollution.

Control of the risk of pollution is achieved by a combination ofgood housekeeping, that is, minimising leaks, room ventilationand the removal of waste anaesthetic gasses at source by ascavenging system generally used in operating theatres.

Nitrous oxide is used in other areas i.e. ITU, acute wards,dentistry, midwifery, physiotherapy. In this case goodventilation should be provided (see HTM 2025)

ANAESTHETIC GAS SCAVENGING SYSTEM

ANAESTHETIC GAS SCAVENGING SYSTEMThe performance criteria should be achieved

regardless of the number of terminal units on eachsystem; where more than one terminal unit is provided

on the system, the performance criteria should beachieved with all, or one, of the terminal units

operative.

Careful consideration should be given to sighting thedischarge outlet from the disposal system. It should be

preferably be sited at roof level, well away fromventilation inlets, opening windows and other

apertures, to prevent pollution from re entering thebuilding.



AGSS Prevention of Pollution Prolonged exposure Anaesthetic Gases can cause:• Lowered Fertility• Increased risk of spontaneous abortion• Increased risk of birth defect.Therefore HSS Staff should ensure that the AGSS system is fully

functional and should be tested annually The pumps have a tendency to collect fluff and lint from

dressings drapes and theatre clothes this can result infires within the pump or fan, consequently the pump orfan should be cleaned at least once a year!!

As mentioned earlier in this Seminar

Cylinders are not allowed to be located in plant roomscontaining medical gas or air systems – thereforemanifolds cannot be placed in such rooms

It is unfortunately allowed to have both MedicalCompressed Air and Vacuum systems located in thesame room

Special attention must be made with respect to theVacuum pump’s exhaust and the drainage from thecomponents of the vacuum system

MEDICAL GASES Conclusion

Pipelines Colour Codes– BS 1710

O2

VAC

Tests

INSTALLATION– Pressure (1.5 X pressure)

– Material

– Brazing (fluxless,dry nitrogen)

– Identification ( colour codes, labelling)

– Sleeving and support

Testing and Commissioning

Leak test Vacuum leak test Area Valve Service Units Cross-connection (anti – confusion) Functional test on terminal units Terminal unit Flowrate (flow and pressure drop Total Flowrate Purging Gas identity (purity) Pressure safety valves Warning systems (hi-lo alarm)

Validation Tests Oxygen

• Oxygen < 99 %• N2O o = %

N20• N2O < 98%• O2 = 0%

Air• O2 = 21% + 1%• N2O = 0%

Entanox• O2 = 50% + 2%• N2O= 50% + 2%

Vacuum• ?????

CEN/TC215/WG3Published British/European Standards

• BSEN737-1 - Terminal units for compressed medical gases and vacuum.

• BSEN737-2 - Anaesthetic gas scavenging systems.

• BSEN737-4 - Terminal units for anaesthetic gas scavenging systems.

• BSEN738-1 - Pressure regulators and pressure regulators with flow meteringdevices.• BSEN738-2 - Manifold and line pressure regulators.

• BSEN738-4 - Low pressure regulators intended for incorporation into medicalequipment• BSEN739 - Low pressure hose assemblies for use with medical gases.

• BSEN793 - Particular requirements for safety of medical supply units.

• BSEN738-3 - Pressure regulators integrated with cylinder valves

• BSEN737-3 - Medical Gas Pipeline Systems

• BSEN12218 - Rail systems for supporting medical equipment.

• BSEN13221 - High pressure flexible connections for use with medical gases.

THIS IS THE LAST SLIDE – HONEST

We all know that the hospital has to purchase gases andfuels

However we should also all be aware that the ConcessionAgreement places the responsibility of notifying the hospitalof the need to order, also to certify receipt, onto theConcession

To protect the Concession from liability in this activity all‘Notification of the Need to Order’ and ‘Certification ofReceipt’ activities MUST be conducted in writing

In the case where the hospital fails to place an order or doesso late, what proof would you have that notification was

given and in good time

MEDICAL GASES

Thank You

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Medical Gas