CO2 Absorbers in Anesthesia Breathing Circuits

How does gas flow in a circle absorption anesthesia breathing system?
In a circular pathway through separate inspiratory and expiratory channels.
What are the components of a circle absorption anesthetic breathing system?
1. Fresh gas source
2. Unidirectional valves
3. T-piece connector
4. Corrugated inspiratory
and expiratory
breathing tubes
5. Pop-off valves
6. reservoir bag
7. CO2 Absorber
Function of CO2 absorption is:
The complete removal of CO2 from the circle breathing system.
Hydroxide (base) neutralizes CO2 (acid) producing what byproducts?
H2O, carbonates, and heat.
What are the formulations of carbon dioxide absorbents commonly available today?
1. Soda Lime (most
commonly used)
2. Amsorb (Ca 2+ and OH-)
3. Baralyme
Large granules provide small surface area and _______ resistance to flow.
_______ is added to prevent drying out and ______ is added for hardness.
Moisture, Silica
Amsorb consists primarily of:
Calcium Hydroxide and calcium chloride
Elimination of sodium and potassium hydroxide in amsorb eliminates the production of what gases?
1. Carbon monoxide
2. Compound A
Baralyme consists primarily of:
1. Calcium hydroxide (80%)
2. Barium hydroxide (20%)
Differences in Sodalime and Baralyme are:
1. Baralyme is more stable
and more dense than
2. Sodalime is 15% more
When should absorbent be changed due to exhaustion?
When it changes deep purple (ethyl violet) caused by a pH below 10.3

“Purple Haze”

The average production of CO2 by the anesthetized adult is:
12 – 18 L/hr
Each CO2 absorber canister last how long?
8-10 hours
Each canister holds how much absorbent material?
1000g of granules and has a volume of 1500cc
What are the clinical signs of exhaustion
1. Rise and later fall in heart rate and BP
2. Hypercapnia
3. Resp. Acidosis
4. Dysrhythmia
5. SNS activation (i.e. flushed, cardiac irregularities, and sweating
6. Increased bleeding at surgical site
7. Increased ETCO2
If CO2 absorber becomes exhausted during case what does the CRNA need to do?
Convert to semi-open circuit by increasing FGF to > 5 L/min
What is the compromise represented in granule size of absorbent material?
Resistance to airflow and absorptive efficiency
What is the granular size of soda lime and baralyme granules?
4-8 mesh
What are the two types of spaces occupied
1. Void Space (intergranular) 50%
2. Pore Space (intragranular) 8-10%
Which absorbent degrades anesthetic agents to an extent?
Soda Lime
When anesthetic agent forms compound A when degraded?
Which degradation byproduct forms compound A, which has toxic renal and pulmonary effects.
2L of FGF is recommended for which anesthetic agent to reduce the production of compound A?
Which anesthetic has the highest accumulation of carbon monoxide production?
Desflurane requires how much 100% O2 flush prior to use to prevent accumulation of carbon monoxide?
15 mins
What part of the anatomy provides heat and moisture for inspired air?
The upper airways
How much heat is lost via the respiratory tract?
12 – 14%
What are the effects of heat loss in the airways?
1. Desiccation of mucous
2. Impaired mucociliary
3. Retention of secretions
4. Blockage of the
conducting airways
5. Atelectasis
6. Bacterial colonization
7. Pneumonia
What is the minimum recommended humidity for anesthesia?
12 mg/L or 60% RH (relative humidity)
What is the ideal temperature and humidity to administer anesthetic gases?
At body temperature and 100% RH (for cases lasting longer than 60 minutes)
How can the CRNA accomplish humidification in cases?
1. HME
2. Using a closed or semi-
closed circle system with
low O2 flows and CO2
3. Heated airway

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