C02 absorption Flashcards
C02 absorber
- chemically neutralizes C02
- C02 + H20 = carbonic acid
- Base neutralizes acid
- end product = carbonate H20 & heat
4 types of absorbers
- Soda Lime
- Calcium hydroxide lime (amsorb plus)
- Litholyme (lithium hydroxide)
- Baralyme
Soda Lime components sodium hydroxide (NaOH) lime
4% NaOH sodium hydroxide
1% KOH potassium hydroxide
80% CaOH calcium hydroxide
15% water
0.2% silica
Soda Lime equation
C02 + H20 = H2C03
H2C03 + 2Na0H (K0H) = Na2C03 (K2C03 + 2H20 + HEAT
Na2C03 (K2C03) + Ca0H = CaC03 + 2Na0H (K0H) + HEAT
*quicker Rex
OR
C02 + Ca0H2 =CaC03 + H20 + HEAT
*slower rxn
C02 combines with H20 to form carbonic acid which reacts with. hydroxides to form Na or K carbonate heat and H20
Soda Lime absorption
26L of C02/ 100g of absorbent granules
1lb of CaOH absorbs 0.59lb of C02
Calcium Hydroxide Lime
Amsorb plus components
80% CaOH
1-4% calcium chloride CaCl
16% water
calcium sulfate and poly-vinyl-pyrrolidine
Calcium Hydroxide (CaOH)Lime rxn
C02 +H20 = H2C03
H2C03 + Ca0H2 = CaC03 +2H20 + HEAT
CaOH absorption
absorbs 10L/ 100g of absorbent granules
1lb of CaOH absorbs 0.59lb of C02
Lithium Hydroxide (Li0H) Litholyme components
75% lithium hydroxide (Li0H)
<3% lithium chloride (LiCl)
12-19% H20
Litholyme rxn
2Li0H x H20 + C02 = Li2C02 + 3H20 - HEAT
Litholyme absorption
almost 1:1 ratio
1lb of Li0H absorbs 0.91lb of C02
Baralyme components
20% Ba0H
80% Ca0H
small amounts of Na0H and K0h
*no water or hardening agent
Baralyme rxn
Ba0H + 2(8H20) + C02 = BaC03 + 9H20 + HEAT
9H20 + 9C02= 9H2C03
9H2C03 + 9Ca(0H) = 9CaC03 + 18H20 + HEAT
Baralyme risks
- more likely to dry out ( risk of C0)
- risk of fire
- contain some Na0H and K0H (risk of compound A)
Baralyme absorption
26L/ 100g of absorbent granules
*same as soda lime but slightly less efficient
Absorbent granule size
granule size = mesh size
4-8 mesh
mesh size = # of openings per inch in a sieve through which granular particles can pass
size and shape are intended to maximize absorption and minimize resistance
*smaller size greater surface area for absorption but more resistance
Granule Hardness
hardness needed to prevent excess powder creating resistance and caking
Silica (soda Lime)
calcium sulfate and poly-vinyl-pyrrolidine (CaOH lime)
*used for hardness
-granules tested with steel ball & screen pan
% of original remaining = hardness #
Hardness # >75
Channeling
preferred passage of exhaled gases through absorber (path of least resistance)
caused by loosely packed granules
absorbents along channel may exhaust quicker and C02 can filter through (increased C02 seen on monitor)
*if cant change right away increase FGF
air space occupied 48-55% of canister volume
some manufactures use polymer to bind granules in preformed channels to prevent channeling
Indicators
acid or base whose color depends on pH
*ethly violet pH 10.3
(what we use)
color change = absorber exhaustion
color can revert back with rest (especially in Na0H containing formula)
replace with 50-70% color change
Compound A
K0H and Na0H (in C02 absorber granules) can break down anesthetic agents (especially servo)
when servo is broken down by these chemicals it created a concentration of compound A (nephrotoxic in rats)
Sevoflurane
160 mmHg
to minimize risk of compound A formation it is recommended servo use should not exceed 2 MAC hours at flows of 1-2L/min
Carbon Monoxide
-can accumulate in dry Na0H and K0H absorbent granules
- dried out absorbent granules cause a slow rxn with volatile agents that produce C0
- if patient exposed = critically high levels of carboxyhgb (false high 02 sat)
- dryness can be cause from by high flow through system for long period of time (24-48hrs)
- increased temp can increase production of C0
- higher anesthetic concentration produce mire C0
- lower FGF rates
Desflurane
669 mmHG
highest accumulation of C0
Anesthesia Safety Foundation Recommendations for safe use of C02 absorber
- Turn of all gas flows when machine not in use
- Change absorber regularly
- Change whenever color change indicated exhaustion
- Change all absorbent not just one canister
- change when uncertain of hydration state (dry)