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Medical Gases
Study guide
Medical gas and suction safety
CQC Regulation 12, 15 and 18 • HTMO2-O1B
(Department of Health)
Introduction to medical gas and
suction safety
Basic medical gas and suction safety training course
for staff.
Objective: To understand the basic principles of
medical gas and suction safety in your workplace.
European Pharmacopoeia and the Medicines
Act define standards for the manufacturing and
composition of medical gases.
A medical gas is prescribed for a patient and
classified as a drug.
In an emergency, oxygen may be administered
without a prescription, but in all cases must be
recorded in the patient records.
Most common medical gases
Oxygen (O2)
Medical air
Introduction
Medical gases are widely used around our hospitals
and in the community and are supplied in cylinders
or piped into wards and clinical areas. They are safe
if handled correctly, however, misuse or mishandling
can have catastrophic consequences.
The purpose of this training is to raise awareness
of the types of gases commonly used, the risks and
hazards associated with their use and handling,
identifying faulty cylinders and the appropriate
action to be taken.
What are medical gases?
Defined as ‘‘a gas, in any form, intended for
administration to a patient; either by inhalation
(including ventilation), application, inflation of
a body cavity or by any other means (including
cardiopulmonary bypass and extracorporeal
ventilation equipment)’’.
Medical vacuum/suction (not actually a gas at all
but is an essential medical gas service)
Entonox (50 percent O2 /50 percent N2O)
Nitrous oxide (N2O)
Heliox 21 (79 percent He/21 percent O2)
Carbon dioxide (CO2)
Helium (He).
You must familiarise yourself with the product data
sheets for all the medical gases you use.
Links to data sheets can be found on the medical
gases page on the Trust Intranet.
Categories of medical gases
Permanent – these remain in a gaseous state
under normal temperatures (eg medical air,
oxygen, Heliox 21)
Liquefiable – these are supplied under normal
temperatures but in a liquid state (eg nitrous
oxide and carbon dioxide)
Cryogenic – these gases are supplied and stored
at extremely low temperatures (eg liquid nitrogen
and liquid oxygen).
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Identification of medical gas cylinders
The shoulder of a medical gas cylinder is colour
specific to each gas:
Wound cleaning or suturing
Minor surgery
Dressing changes
Physiotherapy.
Training is required to use Entonox and is provided
by the Barts Health Pain Service Team.
Oxygen
An estimated 17.5 percent of UK hospital
patients are receiving oxygen at any given time
Regulations cover transport of cylinders by car –
including use of TREM card, Transport Emergency
Card. (Transporting cylinder recommendations can
be found in medical gases section of the Intranet).
About 18,000 people every day
More than two million per year
Essential for life in humans and animals
Widespread use in hospitals and home.
The majority of oxygen use is in the areas of:
Critical care areas – ITU, HDU, CCU
Operating theatres – intra and postoperatively
Most wards – A&E, respiratory and surgical.
Nitrous oxide
Used predominantly by anaesthetists/dentists
Its anaesthetic effects allow a reduction in the
dose of other anaesthetic agents, thus reducing
cost and side effects
Also used to induce anaesthesia in children
The commonest situation is when O2 and N2O
(30:70) are used with a volatile agent. Eg one
percent isoflurane
Must always be used with oxygen.
Medical air
Piped or cylinder gas
4 bar used for patient’s needs eg delivery of
nebuliser medications
7 bar used in theatres to drive medical
equipment eg orthopaedic drills, saws,
suction devices. Must never be administered
to a patient.
Heliox
Used in emergency situations where the airways
become partially-obstructed due to disease or
foreign body
Increases volume of gas into lungs due to
lower density
Resistance to breathing reduced.
Entonox
Analgesic (short term and acute pain relief), primarily
used in:
Midwifery
Ambulances
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MEDICAL GAS AND SUCTION SAFETY
Note the batch label contains the gas cylinder
expiry date – usually three years shelf life and
must not be used after this date.
Carbon dioxide
Use in laparoscopic surgery to insufflate body
cavity for increased access
Also used in specialist areas eg endoscopy.
Hazards
Symbol Hazard
Medical Gas
Oxidising
Oxygen, nitrous oxide and
Entonox will encourage
things to burn vigorously
Pressure
All gases supplied in
cylinders. The stored
pressure in medical gas
cylinders can be up to
300bar
Cold
The storage temperature
of liquid cryogenic N2 is –
196°C and O2 is – 183°C
Helium
Nitrogen, carbon dioxide
and nitrous oxide can
Asphyxiation cause oxygen deficient
atmospheres
Used in intra-aortic balloon pump therapy to
improve coronary artery perfusion.
Cylinder collar information
Hazard: oxygen enrichment and oxidisation
Oxygen itself is not flammable but it supports
combustion and will react with most substances
causing them to become highly flammable and to
burn vigorously.
The main hazards from oxygen-enriched
environments are fire and explosion and even
materials considered ‘non-flammable’ and ‘fire
retardant’ can combust and burn.
Oxygen enrichment can result from:
Leaks from poor connections, damaged or poorly
maintained equipment
Using excessive flow rates of oxygen or
oxidising gases
Oxygen equipment left on when not required
Poor ventilation in areas where oxygen or
oxidising gases are used or stored.
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An increase in oxygen concentration of only
four percent doubles the risk of ignition and rate
of combustion for many common items. Ignition
can occur from low-energy ignition sources (eg
small electrical/static sparks or light friction). At
higher oxygen concentrations ignition may require
so little heat or energy that combustion may appear
to be spontaneous.
If a ward or clinical area is oxygen-enriched, the
following common items are particularly vulnerable
to combustion:
Hair and clothing
Bed linen, mattresses, pillows and curtains
Dressings, especially if medicated or ‘wet’ (treated
with ointments, emollients, etc.)
Surgical skin disinfectants
Sanitising hand-gels and hand-rubs and any oils,
greases, ointments or creams
Hazard: pressure
It is important to be aware of pressures at which
gases are stored and used. Medical gas cylinders are
filled to pressures of 127 to 300 bar (up to 150 times
that of your car tyre!).
Pressure itself is not necessarily dangerous. Hazardous
situations occur when pressure is mishandled or
improperly contained. In terms of medical gases it is
appropriate to consider pressure as a form of stored
energy that when released can be deadly.
Exploding cylinders are able to travel in excess of
300 metres.
Cardboard and paper items
Chemicals and equipment used for cleaning and
disinfection
Electrical and electronic equipment.
Best practice to minimise the risks of oxygen
enrichment and oxidation fires are:
Ensure hands and clothing are clean and free
from oil, grease, hand-sanitising gels/rubs or hand
creams
Use only equipment designed specifically for use
with oxygen or oxidising gases
Ensure flowmeters and regulators are within their
service date
Use the appropriate flow rate of gas according to
the method of delivery (mask, nasal ‘specs’, etc.)
as prescribed
Always turn gases off at the outlet source when
not in use
Store cylinders only in designated gas storage
areas.
Oxygen and nitrogen are supplied to the hospital
in both gaseous and liquid form. The liquid forms
(cryogenic liquid gas) are stored at less than – 180°C.
Liquid gases and their vapours can cause cold burn to
exposed parts of the body.
Prolonged exposure can also cause frostbite, possibly
leading to loss of bodily extremities such as fingers,
toes and nose.
Special training must be completed by all staff
required to handle and work with cryogenic gases.
When working with cryogenic liquids, such as
filling nitrogen flasks from Dewars, personnel must
wear the following personal protective equipment
(PPE) designed specifically for protection from
cryogenic gases:
– Full-face visor
Set up the cylinder for patient use before placing
it close to the patient
– Protective gloves
Place the cylinder in an appropriately-designed
holder if available
– Apron
Avoid placing the cylinder on the bed next to the
patient if possible.
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Hazard: temperature
– Safety shoes
MEDICAL GAS AND SUCTION SAFETY
clinical areas. You should familiarise yourself with the
piped services available in your work area.
Piped gases
Hazard: asphyxiation
Asphyxiation may occur where the local environment
has become oxygen deficient (oxygen concentration
below 20 percent).
Nitrogen, nitrous oxide, carbon dioxide and helium
can cause this.
Risk assessments should be carried out and
recorded for all situations in which these gases are
used and stored.
These gases are supplied by plant equipment located
at each of the hospital sites. The status of each
system is monitored from central ‘switchboards’
through the use of master alarm panels with local
alarms located in wards and departments. You
should familiarise yourself with the piped gas services
and the alarm panel in your work area:
The following table shows the effects of low
concentrations of oxygen in the local environment.
Atmospheric
Effects
oxygen percent
21 percent to
18 percent
No easily discernible
symptoms detected.
18 percent to
11 percent
Reduction of physical and
intellectual performance.
Sufferer not aware of this.
11 percent to
8 percent
At 11 percent fainting may
occur within a few minutes
without warning.
Death may result below 11 percent.
8 percent to
6 percent
Fainting will occur after a very
short time.
Successful resuscitation possible
if performed immediately.
6 percent to 0
Area Valve Service Unit
(AVSU) and emergency
isolation of medical gas
supplies:
Valves contained in locked
boxes (ASVUs) are found
in or around wards and
clinical areas.
Nursing staff should be
aware of the location of
each AVSU for their area.
Each AVSU should be
clearly labelled identifying
the gas, the areas served
and the number of outlets.
Fainting and deep unconsciousness
occurs almost immediately.
Successful resuscitation unlikely.
Brain damage highly probable
even if resuscitation is successful.
Supply and storage of medical gases
Medical gases are supplied in compressed gas
cylinders or piped to wards and clinical areas
through complex systems collectively known as
the medical gas pipeline services (MGPS). Where
possible the piped gas services should always be
used in preference to cylinders. The availability of
piped medical gas services varies between wards and
Caution
Special care should be exercised when medical air
and medical oxygen outlets are piped to the same
bed, as the flow meters and equipment are very
similar and could be confused. It is recommended
that when not in use, medical air flow meters are
removed from the outlet.
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Compressed gas cylinders
Compressed gas supplied in cylinders is a convenient
way to deliver medical gases to patients in situations
where piped services are unavailable or impractical,
such as patient transfers, self-ambulatory patients
and ‘crash’ trolleys.
Cylinders are available in many different sizes,
with a variety of valve types and can supply a
variety of medical gases.
For ease of reference, suppliers of compressed
medical gases assign different letter codes to all
their cylinders depending on size, construction and
valve type.
Please take a moment to look at the medical
gas cylinder data chart on the Intranet. http://
bartshealthintranet/About-Us/CAGs/ClinicalSupport-Services/Clinical-physics/Clinicalengineering/Medical-Device-Training/Medicalgases.aspx
Some cylinders may require the fitting of a pressureregulating device, known simply as a regulator,
before they can be used. This is carried out by our
trained porters. However, newer lighter-weight
cylinders with ‘integral valve systems’ are available
for some gases. These newer cylinders come
equipped with a regulator and flowmeter built in,
and have two outlets (except for Entonox which
has only an integral regulator and Schrader valve).
http://bartshealthintranet/About-Us/CAGs/
Clinical-Support-Services/Clinical-physics/Clinicalengineering/Documents/Entonox-Cylinders.pdf
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Designated cylinder areas:
Cylinders at ward level should be kept to a
minimum
They should be kept secured or in trolleys in a
defined store or ‘cylinder parking area’
Those kept on ‘crash’ trolleys and anaesthetic
machines must be held securely
Cylinder stock levels in wards and clinics should
be checked daily.
Full and empty cylinders should be segregated.
Ready to use cylinder stores:
In theatres or A&E and ICUs it may be necessary
to hold a small number of cylinders for
immediate use
No combustible material or non-medical gases to
be stored in the same area
Numbers of cylinders should be kept to 24hr use
Cylinders should be stored in racks, with
sufficient space to manoeuvre cylinder on and
off trolleys
The room must be clearly labelled with adequate
prohibition and warning signs:
MEDICAL GAS AND SUCTION SAFETY
MEDICAL LIQUID NITROGEN
All staff required to handle liquid nitrogen must
be aware of the hazards and receive cryogenic
safety training.
Contact the Medical Device Training Team for details.
Faulty cylinders
Cylinders are described as faulty where the complaint
is minor and the patient is not put at risk. This may be
due to:
Empty or part-full cylinders (not needed
immediately)
Faulty valve outlet
Damaged outlet
Minor leaks.
Empty when required for immediate use
Abnormal patient reaction to gas
Been involved in an accident/fire.
Follow the Barts Health incident reporting procedure
via the Trust Intranet and inform the gas supplier.
Suction
The following wall suction units are found in many
clinical areas throughout Barts Health. Ensure that you
are familiar with what is used in your ward or clinical
area and that you are trained to use any portable
suction required for your patients.
Policy links/further reading
Barts Health NHS Trust Intranet medical gas
section
If a cylinder is faulty it should be removed from service
and the clinical area or home.
Contacts
Email: Medical Device Training Team
Tel: 020 359 46589
Incident cylinders
BOC:
www.bochealthcare.co.uk
Cylinders are described as incident where the
complaint is serious and the patient is considered to
be put at risk. May be due to:
Gas contamination
Incorrect labelling
Ignition damage
British Thoracic Society:
www.brit-thoracic.org.uk
MUST DO’s
Successfully complete the Medical Gas and
Suction Safety quiz
Following successful completion your records
will be updated automatically
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