Medical gas supply(cylinder system)

1. Medical Gas Supply
Cylinder System
By
Muhammad Tayyeb.
Lecturer Anaesthesiology
BKMC, Mardan.

2. Contents
• General principles of compressed gas cylinders
• Cylinder System
• Supplementary information
• Components
• Cylinder identification
• Maintenance
• Cylinder size and construction
• Cylinder storage
• Color coding
• Pin index system
• Troubleshooting
• Case Scenario

3. Medical Gas Supply
cylinders
a piped gas system

4. Supplementary information
Gas exists in the gaseous state at room temperature and
pressure.
Vapour is the gaseous state of a substance when its below
its critical temperature. Or vapor can be condensed to liquid
by increasing the pressure on it without reducing the
temperature.
Critical temperature is the temperature above which a
gas cannot be liquefied whatever pressure is applied.
The critical temperatures for nitrous oxide and oxygen are
36.5 and -118°C respectively.

5. Cylinders
● Made of thin-walled molybdenum steel to withstand high pressures.
Lightweight O2 cylinders can be made from aluminum alloy used during transport.
● Are made in different sizes (A to J).; size E is used on anaesthetic machine; size J is
used in cylinder banks.
● O2 cylinders contain gas , while N2O cylinders contain a mixture of liquid and vapour.
filling ratio = weight of fluid in cylinder / weight of water required to fill the cylinder
filling ratio of N2O is 0.75. In hotter climates, it is reduced to 0.67
● are colour-coded.

6. Components
• The top end of the cylinder is called the neck, and this ends in a
tapered screw thread into which the valve is fitted. The thread is
sealed with a material that melts if the cylinder is exposed to intense
heat. This allows the gas to escape so reducing the risk of an
explosion.
• There is a plastic disc around the neck of the cylinder. The year when
the cylinder was last examined can be identified from the shape and
color of the disc.

7. Continue
• Cylinders are manufactured in different sizes (A to J). Sizes A and H
are not used for medical gases. Cylinders attached to the anesthetic
machine are usually size E while size J cylinders are commonly used
for cylinder manifolds. Size E oxygen cylinders contain 680 L, whereas
size E nitrous oxide cylinders can release 1800 L. The smallest sized
cylinder, size C, can hold 1.2 L of water, and size E can hold 4.7 L while
the larger size J can hold 47.2 L of water.
• Lightweight cylinders can be made from aluminum alloy with a fiber
glass covering in epoxy resin matrix. These can be used to provide
oxygen at home, during transport or in magnetic resonance scanners.
They have a flat base to help in storage and handling.
• 1 bar = 14 psi=100kpa= 1atm

8. •

9. Aluminum alloy made cylinder

10. Continue
• Oxygen is stored as a gas at a pressure of 13 700 kPa whereas nitrous
oxide is stored in a liquid phase with its vapour on top at a pressure
of 4400 kPa. As the liquid is less compressible than the gas, this
means that the cylinder should only be partially filled. The amount of
filling is called the filling ratio. Partially filling the cylinders with liquid
minimizes the risk of dangerous increases in pressure with any
increase in the ambient temperature that can lead to an explosion. In
the UK, the filling ratio for nitrous oxide and carbon dioxide is 0.75. In
hotter climates, the filling ratio is reduced to 0.67.
• The filling ratio is the weight of the fluid in the cylinder divided by
the weight of water required to fill the cylinder.

11. • At constant temperature, a gas-containing cylinder shows a linear and
proportional reduction in cylinder pressure as it empties. For a
cylinder that contains liquid and vapour, initially the pressure remains
constant as more vapour is produced to replace that used. Once all
the liquid has been evaporated, the pressure in the cylinder
decreases. The temperature in such a cylinder can decrease because
of the loss of the latent heat of vaporization leading to the formation
of ice on the outside of the cylinder.

12. Cylinder identification and Storage and Handling of Gas
Cylinders Guidelines

13. Labelling

14. Problems in practice and safety features
1. The gases and vapours should be free of water vapour when stored in
cylinders. Water vapour freezes and blocks the exit port when the
temperature of the cylinder decreases on opening.
2. The outlet valve uses the pin-index system to make it almost
impossible to connect a cylinder to the wrong yoke.
3. Cylinders are color-coded to reduce accidental use of the wrong gas
or vapour. In the UK, the color-coding is a two-part color, shoulder and
body. To improve safety, there are plans to change the colors of the
bodies of cylinders using medical gas to white while keeping the colours
of the shoulders according to the European Standard EN 1089-3.

15. 4. Cylinders should be checked regularly while in use to ensure that
they have sufficient content and that leaks do not occur.
5. Cylinders should be stored in a purpose built, dry, well ventilated
and fireproof room, preferably inside and not subjected to extremes of
heat. They should not be stored near flammable materials such as oil
or grease or near any source of heat. They should not be exposed to
continuous dampness, corrosive chemicals or fumes. This can lead to
corrosion of cylinders and their valves.
6. To avoid accidents, full cylinders should be stored separately from
empty ones. F, G and J size cylinders are stored upright to avoid
damage to the valves. C, D and E size cylinders can be stored
horizontally on shelves made of a material that does not damage the
surface of the cylinders.
7. Over pressurized cylinders are hazardous and should be reported to
the manufacturer.

16. absolute pressure = gauge pressure + atmospheric pressure
“At a constant temperature, the pressure in a GAS cylinder
decreases linearly and proportionally as it empties. “
This is not true in cylinder containing liquid / vapour.

17. COLOR CODING SYSTEM

18. Body colour
(UK)
Shoulder colour
(UK)
Pressure, kPa
(at room temperature)
Physical state
in cylinder
Oxygen Black
(Green in USA)
White 13 700 Gas
Nitrous
oxide
Blue Blue 4 400 liquid / vapour
Carbon
dioxide
Grey Grey 5 000 liquid / vapour
Air Grey
(Yellow in USA)
White/black
quarters
13 700 Gas
Entonox Blue White/blue
quarters
13 700 Gas
Oxygen/helium
(Heliox)
Black White/brown
quarters
13 700 Gas

19. Oxygen White
Nitrous oxide Light blue
Medical air Black and white
Suction Yellow
Nitrogen Black
Carbon dioxide Grey
Helium Brown
Standard colour

21. Size Capacity (liters)
Oxygen Nitrous oxide
E 680 1800
J 6800 18000

22. Cylinder Tests

23. Cylinder valves
● They are mounted on the neck of the cylinder.
● Act as an on/off device for the discharge of cylinder contents.
● Pin index system to make it almost impossible to connect a cylinder
to the wrong yoke ( O2 2&5 , N2O 3&5 , CO2 1&6 , Air 1&5 )
O2
2,5
N2O
3,5
CO2
1,6
Index positions of a cylinder valve

24. ● Bodock sealing washer must be placed between
the valve and the yoke of the anaesthetic machine.

25. Gas Supply or Oxygen Failure
• Failure of liquid oxygen supply from
• Manifold of large oxygen cylinder
• These cylinder remote from patients
• In OT/OR reserve oxygen cylinder should be available
• In case of complete oxygen failure, the anesthesia machine should
discontinue the flow of nitrous oxide and entrain the room air

26. Estimating remaining oxygen in E-cylinder
•Boyle’s Law
Volume is inversely proportion to pressure
Pi*Vi=Pr*Vr
Pi= initial pressure (Psi)
Vi= initial volume (L)
Pr= remaining pressure (Psi)
Vr= remaining volume (L)
Vi=Q*t
Q= flow rate (liter/minute)
T= remaining time (minutes) put value in main formula
Pi*Q*t=Pr*Vr to find remaining time “t”

27. T= (Pr*Vr)/ Pi*Q*t(60).
where t= remaining time in hours.
Since for a E size cylinder, Pi= 1900 psi and Vr=660L.
t (hours)= (Pr*600)/(2000*Q*60). Rounding Vr 600-660L.
Rounding Pi 1900-2000 Psi.
t= Pr/ (200*Q)
A typically fully filled size E oxygen cylinder
• Can deliver 130 times its capacity of oxygen
• Last for 2 hours and 50 minutes delivering 4L/min oxygen
• Last 45 min delivering 15L/min of oxygen.

28. Case Scenario
• E 680 L
• MV= Td*RR
• Td= weight in kg *7 (6-8ml/kg)
• MV= 500ml *14= 7000ml or 7L/min
• 1 min= 7L
• X=680L

29. References
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3821267/
• Essentials of anesthetic equipment’s.by Baha Al sheikh &Simon Stacy.
• Simon Bricker. The anaesthesia Science Viva book.
• Physics, Pharmacology and physiology for anesthetists Cross,
Mathew.
• Primary FRCA: OSCE in anesthesia Cambridge university press 2013.
• Atlas G. a method to quickly estimate remaining time for an oxygen E
cylinder. Anesth analg 2004; 98:1190-4.

30. THANK YOU