5. Soda Lime Flashcards
Use
Soda lime is used to absorb CO2
ain use is to allow the rebreathing of exhaled gases within breathing systems.
This is most commonly the circle system,
Chem
chemical constituents are calcium hydroxide (Ca[OH]2) 80%, sodium hydroxide
(NaOH) 2% and water (H2O
KOH] was previously
added as an accelerator, but this is one of the strong alkalis which are implicated
in the formation of carbon monoxide and Compound A
silicates in trace amounts which harden the granules which otherwise
would disintegrate into powder. An indicator dye is present which changes the
colour of the soda lime as it is progressively exhausted
either phenolphthalein
(the colour changes from red to white
Physical
Soda lime is formed either into granules whose size is 4–8 mesh
The size of the granules or spheres is a compromise between providing the largest
surface area for absorption without providing excessive resistance to flow
kg can absorb up to 250 litres of CO2.
the chemical reaction
Full equation : CO2 + H2O -> H2CO3
2H2CO3 + 2NaOH + Ca(OH)2 –> Na2CO3 + CaCO3 + 4H2O + Heat
Simple eqn
CO2+ Ca(OH)2 - > CaCO3 + H2O
Other Compounds That Can Be Used to Absorb CO2
Barium lime (Baralyme): this consists of calcium hydroxide (Ca[OH]2) 80% and
barium hydroxide (Ba[OH]2) 20%. Water is incorporated into the structure of Ba
(OH)2. The chemical reaction is similar to that of soda lime, although it is less
efficient.
Reactions between CO2 Absorbents and Anaesthetic Agents
CO
constant flow may dry out a canister of
soda or barium lime. Under these circumstances, the reaction of the desiccated
absorbent with the CHF2 group of isoflurane, enflurane or desflurane can produce
high levels of CO.
Compound A
Compound A: sevoflurane reacts with strong monovalent hydroxide bases, such as
those which are used in soda lime and barium lime CO2-absorbers, to produce a
number of substances, including compound A.
