Gas laws Flashcards
Daltons law states that
The total pressure exerted by a mixture of gases is equal to the sum of the pressure that would be exerted by each of the gases if it alone were present and occupied the total volume
Boyles law states
At a constant temperature, the pressure of a gas is inversely proportional to its volume
Charles law states
At a constant pressure, the volume of gas is directly proportional to its absolute temperature
The critical temperature is the temperature
above which no application of pressure along will liquefy
Name two gases which exists as a liquid
Nitrous oxide
Carbon dioxide
Composition of Entonox
50% oxygen / 50% nitrous
If a substance has a critical temperature below normal temperature it will exist in a cylinder as a
gas
If a substance has a critical temperature above normal temperature, it will exist in a cylinder as
a liquid
Medical gases can be supplied in 3 ways
fixed pipelines
flexible pipelines
cylinders
Fixed pipelines are made from
high quality copper
Colour coding of piped gas outlets for Oxygen, Nitrous Oxide and Medical air
oxygen - white (400kpa)
Nitrous oxide - blue (400kpa)))
medical air - white and black - 400kpa & (used on patient)
700 kpa ( run devices such as tourniquets and power tools)
Function of flexible pipelines
Connect wall/ceiling mounted gas outlet to anaesthetic machine
Anaesthetic machine end of pipeline is fixed by
Non interchangeable screw thread
Detachable end of flexible pipeline attached to outlet via
Schraeder valve
Cylinders are made from
molybdenum steel
Cylinders are manufactured in sizes
B-J
How should cylinders be stored
In a designated place
full cylinders should be stored separately
Keep away from heat source
Information engraved on cylinders (4)
Test pressure
Dates test performed
Chemical formula of contents
Tare weight
Information on medical gas cylinder labels
Name, chemical symbol & licence number Hazard warning and safety instruction Cylinder size code Cylinder contents (in litres) Maximum cylinder pressure (bar) shelf life & expiry date directions for use storage and handling precautions
Colour coding of cylinders in future the body of the cylinder will be —-and the shoulder will –
white body
shoulder retain same identifying colours
Colour coding of oxygen cylinder
Body - black
shoulder - white
colour coding of nitrous oxide cylinder
body blue
shoulder blue
colour coding of carbon dioxide
grey shoulder
grey body
colour coding of air cylinder
body-grey
shoulder - black and white
colour coding of Entonox cylinder
body - blue
shoulder - blue and white
purpose of cylinder valve
mounted on neck of cylinder
mechanism for opening/closing gas pathway
what is the pin index system
Non interchangeable safety system
Allows only correct cylinder to be fitted to yoke
Pins in specific position on the yoke match up with holes in the cylinder valve
The exit port on the cylinder will not seal against the washer/yoke unles the holes are alligned
Used on cylinders E and below and on F and G size entonox cylinders
Pin index for oxygen
2 & 5
Pin index for nitrous oxide
3& 5
Pin index for carbon dioxide
1 & 6
Pin index for air
1 & 5
Flowmeters measure
the flow rate of a gas passing through them
flowmeters consist of
a flow control valve
a tapered plastic/glass tube
a bobin
The reading of the gas flow is taken from the — of the bobbin
top
Why might the bobbin stick
if floor uneven
dirt trapped in machine
build up of static electricity
Design of bobbin
Top of bobbin has flutes cut into its sides causing it to rotate when gas flows past it.
White dot on bobbin which you can see moving
Alternative supply of oxygen incase pipeline fails can be supplied via
cylinder
Manifold (banks of cylinders size J)
liquid oxygen store
oxygen concentrator
Medical gases
oxygen nitrous oxide medical air carbon dioxide entonox
Liquid oxygen is stored between
-150 and -170 degrees
Uses of Co2
To stimulate breathing at end at reversal (old fashioned technique)
insufflation of abdomen for laparoscopic procedure
Co2 laser
Properties of nitrous oxide
Sweet smelling, non-irritant and colourless
Not flammable but supports combustion at high temperatures
Excellent analgesic
Weak anaesthetic
Will diffuse easily into air spaces and so increase volume within air space,eg can increase pressure in ET cuff
Filling ration 0.75
Properties of entonox
50% oxygen and 50% nitrous known as gas and air
Stored as a gas
store portable cylinders horizontally to ensure o2 and N2o mixed
if temp falls below -5.5 degree C nitrous oxide liquifies and separates from oxygen
Store above 5 degrees for 24 hours before se to prevent separation resulting in hypoxic supply of N2o to patient.
