circle system Flashcards
what is the benefit of rebreathing alveolar gas
conserves heat & humidity
what is the purpose of the carbon dioxide absorbent?
elimination of CO2 to prevent hypercarbia
CO2 absorbents contain hydroxide salts that are capable of neutralizing carbonic ac
Name one common absorbent material used for CO2 absorbers ?
soda lime
capable of absorbing up to 23 L of CO2/100 g of absorbent.
what acid is produced produced when CO2 combines with water?
carbonic acid
what are the end products of the neutralizing reaction provided by the CO2 absorber?
heat
water
calcium carbonate
In regards to soda lime, what minimizes the risk of inhalation of sodium hydroxide dust
adding silica to increase hardness
what prevents dust formation in the CO2 absorbers?
hardness of the lime agent
In regards to the CO2 absorber, how could it delay the induction or emergence?
Absorbent granules can absorb & later release significant amounts of volatile anesthetic. The drier the soda lime, the more likely it will absorb & degrade volatile anesthetics.
you’re checking your machine in the a.m., the CO2 absorbent looks to be a new canister, but after 2 hours into your first case you notice rebreathing on the monitor and notice the canister is now 75% puprle. what is this phenomenon
peaking or regeneration
seen with absorbents that contain strong bases, absorbent appears to be reactivated with rest
what are indications to change absorbent?
CO2 in inspired gases (FiCO2)
Color change
Heat in canisters
True or false. Double CO2 canisters lower gas flow resistance.
True
which canister goes on top when loading a new CO2 absorbent canister in a double canister system?
the new one goes on bottom, the older bottom canister is moved to the top
what should be done after changing out the CO2 canisters?
circuit leak check
what is the puprose of the unidirectional valves?
check valves that prevent flow in opposite directions, make the circle circuit possible
which valve is exposed to humidity of alveolar gas?
expiratory
discuss the valves at inspiration
Inhalation opens the inspiratory valve allowing the patient to breath a mixture of fresh & exhaled gas that has passed thru the CO2 absorber. Simultaneously, the expiratory valve closes to prevent rebreathing of exhaled gas that still contains CO2.
discuss the valves at expiration
exhalation opens the expiratory valve. This gas is vented thru the APL valve or rebreathed by the patient after passing thru the absorber. Closure of the inspiratory valve during exhalation prevents expiratory gas from mixing with fresh gas in the inspiratory limb.
What are some problems that could come about due to damaged valves?
rebreating CO2 – related to both
a stuck inspiratory valve- pressure build up in machine
a stuck expiratory valve - pressure build up in patient
what is true of deadspace in the breathing circuit.
- occurs where there is bi-directional flow
- occurs from y piece to patient
- The length of the tubes does not affect the amount of dead space
what is an advantage of concentric patient circuit? Disadvantage?
a. outer corrugated tube carrries exhaled gas that can moderately warm inspired tube gases
b. disadvantage - increased resistance, hypercapnea due to inner tube leak
what is true of the Y piece
- contains deadspace
- has (2) male ports at 22 mm
- has (1) female port at 15 mm
what size is the facemask orifice?
22 mm
what is function of APL (adjustable pressure limit) valve ?
Controls pressure in breathing system
Releases gases to scavenging system
what happens when the pressure has reached APL valve setting?
the valve opens & excess gas is vented to the scavenging system during inspiration.
