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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
Entonox50/50N2O + O2
Medical Air CarbonDioxideCO2
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
GAS GENERAL PROPERTIES
GasProperty
OxygenO2
NitrousOxide N20
Entonox50/50N2O + O2
Medical Air CarbonDioxideCO2
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
GAS GENERAL PROPERTIES
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)
Medical Air Manufacturing plant
We mentioned earlier
The need to test medical air for
Carbon Dioxide
Carbon Monoxide
?????
Medical Air Manufacturing plant
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
?????
Medical Air Manufacturing plant
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
Medical Air Manufacturing plant
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
Medical Air Manufacturing plant
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
Medical Air Manufacturing plant
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
Medical Air Manufacturing plant
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
Medical Air Manufacturing plant
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
Medical Air Manufacturing plant
Medical Air Manufacturing plant
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 Air Manufacturing plant
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
MEDICAL VACUUM SYSTEM
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
MEDICAL VACUUM SYSTEM
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.
MEDICAL VACUUM SYSTEM
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.
MEDICAL VACUUM SYSTEM
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
MEDICAL VACUUM SYSTEM
MEDICAL VACUUM SYSTEM
MEDICAL VACUUM SYSTEM
MEDICAL VACUUM SYSTEM
MEDICAL VACUUM SYSTEM
MEDICAL VACUUM SYSTEM
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.
ANAESTHETIC GAS SCAVENGING SYSTEM
ANAESTHETIC GAS SCAVENGING SYSTEM
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