Gas Supplies, Breathing Systems and Ventilators Flashcards
Critical Temperature
The temperature above which a substance cannot be liquefied irrespective of the amount of pressure applied.
Critical pressure
The minimum pressure required to liquefy a gas at its critical temperature.
Gas definition
A compressible fluid where intermolecular spacing is so large that intermolecular forces are negligible.
Vapour definition
A gas below its critical temperature, thus compression to the liquid is possible
What is a fixed gas
Gas above its critical temperature
How does a VIE work
double skinned steel tank with a vacuum of 0.16-0.3kpa between the skins
What temp is vie kept at
-160-180 (below critical temp of -118)
Critical temp of N2O
36.4
how full should an n2o cylinder be
75% of the weight of the water that would fill the cylinder
based on weight and not volume- differing densities of nitrous and water mean the cylinder willl not be 75% full by volume
What is entonox?
50:50 oxygen : nitrous by volume (not weight)
Pseudocritical temp of entonox
-5.5 c
how often are cylinder checked
5 years
What are cylinders made of
molybdenum steel
Which mapleson circuits are used in paeds?
E/F
what is a waters circuit most similar to
mapleson C
Examples of mapleson A circuits
Magill + lack
When is mapleseon A efficient/inefficient
efficient in spontaneous ventilation, inefficient in controlled ventilation
Where is the apl valve in mapleson D
machine end
Main constituent of soda lime?
calcium hydroxide (75%)
only 4% sodium hydroxide
Soda lime/CO2 reaction has what properties
exothermic
produces 1 mole water for each mole CO2 removed
What does the pethick procedure test for?
Fracture of the inner fresh gas tube at the common gas outlet in a bain circuit (results in a big increase in dead space)
Are bain circuits affecred by the length of the system?
no
HOw much fresh gas flow does a mapleson A circuit require?
70% MV
WHat is the lack modification?
Removes the APL valve from the patient mask in mapleson A circuit
