Exam 2- Breathing System I (6/26/23) Flashcards
What are the six functions/definitions of the breathing system per Dr. Erickson?
- Receives gas mixture from the machine
- Delivers gas to the patient
- Removes CO2
- Provides heating and humidification of the gas mixture
- Allows spontaneous, assisted, or controlled respiration
- Provides gas sampling, measures airway pressure, and monitors the volume
What are the six desirable characteristics of a breathing circuit per Dr. Erickson?
- Low resistance to gas flow
- Minimal rebreathing
- Removal of CO2 at rate of production
- Rapid changes in delivered gas when required
- Warmed humidification of inspired gas
- Safe disposal of waste gases
Name and Describe the four classifications of breathing circuits.
- Open - No reservoir bag and no rebreathing (nasal cannula)
- Semi-Open - Reservoir bag but no rebreathing d/t FGF > minute ventilation.
- Semi-Closed - Reservoir bag w/ partial rebreathing
- Closed- Reservoir bag and complete rebreathing, FGF equivalent to patient uptake
When would you want a closed breathing circuit?
- Conserve patient’s temperature
- Trying to be economical and not waste any gas
- Trying to perform low flow anesthesia
Name the components of the breathing system.
- Facemask, LMA, ETT
- Y-piece with mask/ tube connectors
- Breathing tube (corrugated tubing)
- Respiratory Valves (unidirectional)
- Fresh gas inflow site
- APL (Pop-off) Valve leading to scavenger
- CO2 absorption canister
- Reservoir Bag
The facemask needs to fit between the _____________ and in the groove between the ___________ and alveolar ridge.
- interpupillary line
- mental process
The facemask will connect to the Y-piece/connector, how big is the female connection?
- 22 mm
A fitting that joins together 2 or more components.
- Connectors/ Adapters
What are the benefits of connectors and adaptors?
- Extends the distance b/w patient and breathing system
- Change the angle of the connection
- Allow more flexibility/ less kinking (The accordion will give you the most flexibility)
What are the disadvantages of connectors and adaptors?
- Increased resistance
- Increased dead space
- Additional locations for disconnections
How long is the breathing tubing?
What is the internal volume of the breathing tubing?
- 1 meter in length
- 400-500 mL for each meter in length
Describe the flow in the corrugated breathing tubing.
- Turbulent Flow
True/False: Breathing tubes connected together to increase tube length will increase dead space.
- False
- Longer tubes do not create deadspace
- Dead space is only from Y-piece to patient
Pressure check the circuit before use. What value should this be?
- 30 cm H2O
With a normal tidal volume. How much air is in the anatomical deadspace?
- 150 mL
That is why we deliver at least 300 mL of tidal volume in simulation for adequate ventilation.
What directs respiratory gas flow in the correct direction?
- Unidirectional valves
These unidirectional valves must open widely with very little pressure. Low resistance, high competence. Open/Close rapidly with no backflow.
The inspiratory valve opens on ___________.
The inspiratory valve close on _________.
What does the inspiratory valve prevent?
- The inspiratory valve opens on inspiration.
- The inspiratory valve close on exhalation.
- Prevents backflow of exhaled gas
The expiratory valve opens on ___________.
The expiratory valve close on _________.
What does the expiratory valve prevent?
- The expiratory valve opens on exhalation.
- The expiratory valve close on inspiration.
- Prevents rebreathing
Proper valve placement and functioning prevents any part of the circle system from contributing to _________.
- Apparatus Dead Space
What composes the apparatus dead space?
- Distal limb of Y-connector
- Tube/mask/LMA
The unidirectional valves are located near what parts of the breathing system?
- CO2 absorber canister
- Fresh gas inflow site
- APL Valve
What are the requirements of unidirectional valves?
- Arrows/ Directional words
- Hydrophobic - needs to repel water/moisture
- Must open and close appropriately
- Clear dome - need to visualize if valves are working
- Must be placed between patient and reservoir bag
How much volume is in a traditional reservoir bag?
- 3 L
Can range from 0.5 to 6 L
All reservoir bags must have _____ mm female connector on the neck.
- 22 mm
Anesthesia reservoir bags must adhere to pressure standards, which mandate a minimum pressure of approximately _____ cm H2O and a maximum pressure of approximately ____ cm H2O when the bag is filled to four times its stated capacity.
- 30 cm H2O (minimum)
- 60 cm H2O (maximum)
Although most bags adhere to these standards, some latex-free bags have exceeded the upper pressure limit.
Which unidirectional valve is more likely to be stuck? Inspiratory or Expiratory?
- The expiratory valve is more vulnerable because it is subject to greater moisture exposure.
Miller pg. 605
What are the functions of the reservoir/breathing bag?
(1) Reservoir for anesthetic gases/oxygen
(2) A means of delivering manual ventilation or assisting spontaneous breathing
(3) Serving as a visual or tactile means of monitoring a patient’s spontaneous breathing efforts
(4) Partially protecting the patient from excessive positive pressure in the breathing system.
What is another name for the Gas Inflow site?
- Fresh gas inlet
Where is the preferred location of the fresh gas inflow site?
- Between CO2 absorbent and inspiratory valve
When does the fresh gas scrub out the CO2 absorber?
- During expiration
During expiration, the inspiratory valve will be closed. When this occurs, fresh gas will travel to the CO2 absorber.
What is the downside of having the fresh gas inflow valve so close to the CO2 absorbent?
- Fresh gas can dry out the absorbent
What is the Adjustable Pressure-Limiting Valve (APL) / Pop-off Valve?
The APL valve is an operator-adjustable relief valve that vents excess breathing circuit gas to the scavenging system and provides control of the breathing system pressure during spontaneous and manual modes of ventilation.
Tightened screw cap (closed) = more gas pressure required to open it
Clockwise motion of the APL valve will ______ pressure.
- Increase
Counterclockwise motion of the APL valve will ______ pressure.
- decrease
How many turns does it take for the APL valve to go from fully open to closing fully?
- 1-2 clockwise turn
Can the absorbent be replaced in the middle of a surgical case?
- Yes, the housing compartment incorporate valves that closes when removed to prevent gas loss
Name the components of soda lime.
- Calcium hydroxide (80%)
- Sodium hydroxide/ Potassium hydroxide (5%)
- Water (15%)
- Small amount of silica/clay
Most absorbents use calcium hydroxide to react with the expired CO2, producing what byproducts?
- Insoluble calcium carbonate (CaCO3)
- Water
- Heat/Energy
Because CO2 does not react quickly with calcium hydroxide, what are the catalysts required to speed up the reaction?
- Sodium hydroxide
- Potassium hydroxide
How do you know when the soda lime has been fully exhausted?
- It turns from white to purple
- All hydroxides have become carbonates
Soda lime can absorb _____% of its weight in CO2.
100 grams of soda lime can absorb _______ L of CO2.
- 19%
- 26 L
Name the components of Calcium Hydroxide Lime (Amsorb Plus).
- Calcium hydroxide (70%)
- Calcium chloride (0.7%)
- Calcium sulfate (0.7%)
- Polyvinylpyrrolidone (0.7%)
- Water (14.5%)
What is the drawback of Baralyme?
- Compound A formation (found in rats)
- Carbon Monoxide formation
- Destruction of inhaled gases
Calcium hydroxide lime decreases Compound A formation, CO formation, and destruction of inhaled gases.
Name This Absorbent:
- Reacts with CO2 to from carbonate
- More CO2 absorption capacity
- Used in submarines and spacecraft
- Not usually used in anesthesia
- Lithium Hydroxide
Name This Absorbent:
- Has a Lithium chloride catalyst and does not react with inhaled gases
- No activators/strong bases
- Does not form Compound A and carbon monoxide
- Has color change (white to purple) but no regeneration
- ↓ Fire Risk
- Litholyme
Name this Absorbent:
- Anhydrous LiOH powder, hydrated polymer sheets
- No activators/strong bases
- ↓ Temperature production
- Cheap
- No color indicator, no color change
- Spira-Lith
Which of the following absorbent does not have any Calcium Hydroxide in it?
- Soda Lime
- Litholyme
- Spiralith
- Spiralith has 0% CaOH2
Soda Lime (Sodasorb) and Litholyme both contain about 75% Calcium Hydroxide
Which of the following absorbent is composed of 95% Lithium Hydroxide?
- Soda Lime
- Litholyme
- Spiralith
- Spiralith has 95% LiOH
Which of the following absorbent has color indication?
- Soda Lime
- Litholyme
- Spiralith
- Soda Lime
- Litholyme
What is the most common dye for absorbent indicators?
- Ethyl Violet
Ethyl violet causes soda lime to turn from white to purple when exhausted
What color will ethyl orange and cresyl yellow turn when exhausted?
- Yellow
Carbonate formation will cause pH to become less ________ and cause the contents of the CO2 canister to turn from white to _______.
- less alkaline (lower pH)
- blue violet (purple)
At what pH will the soda lime experience color change?
- pH less than 10.3 (purple, exhausted)
When absorbent is exposed to light for a period, what can happen?
- Bleaching
- Absorbent indicator does not work as well
Absorbents have high reliability indicating CO2 rebreathing, but what is the gold standard?
- Capnometry
CO absorbent granules are measured in what units?
- Mesh Size
- 4-8 mesh size (most optimal for CO2 absorbers)
Mesh size refers to the number of openings per linear inch in a sieve through which the granular particles can pass. For example, a 4-mesh screen means that there are four quarter-inch openings per linear inch
The ability of the workstation’s absorber to remove CO2 is related to three main factors:
- The amount of absorbent surface area exposed to the exhaled gas
- The intrinsic capacity of the absorbent to remove CO2
- The amount of non-exhausted absorbent remaining.
The size and shape of the absorptive granules are intended to maximize ________ while minimizing ________ .
- Maximize Surface Area/ Absorption
- Minimize resistance to airflow
Roughly half of the volume of the CO2 canister will be composed of _______.
- gas
What factors can decrease the efficiency of CO2 absorption?
- Excess water in the canister (change canister if you see liquid)
- Decrease surface area
Small passageways that allow gas to flow through low-resistance areas, decreasing functional absorptive capacity.
- Channeling
What are ways to minimize channeling?
- Circular baffles (flow-directing panels)
- Placement for vertical flow
- Permanent mounting
- Prepackaged cylinders
- Avoiding overly tight packing
The decomposition of sevoflurane will form this substance.
- Compound A
2-fluoromethyl-2,2-difluoro-1-(trifluoromethyl) vinyl ether
Compound A causes what toxicity in rats?
- Nephrotoxic in rats
- Possible in humans
Compound A formation occurs with:
- Low FGF (1-2 L/min)
- Increased absorbent temperature
- Higher inspired sevoflurane concentrations (1.5 to 2 MAC)
- Dehydrated absorbent
- Longer anesthetic
- Absorbent containing NaOH or KOH
Carbon monoxide can occur due to what factor?
- Dry absorbent from leaving the fresh gas flow on
- If the CO2 absorber hasn’t been used for a prolonged period of time (months)
- ‘Monday, 1st case’- gas left on over the weekend
- Increased Temperature
- Increased Concentration of anesthetic gases
- Low FRF rate
- Smaller patients (can’t rehydrate a desiccated absorbent)
- Strong base absorbents (KOH or NaOH)
Rank the order of anesthetic gases from highest to lowest level of carbon monoxide formation.
Desflurane ≥ enflurane > isoflurane > > halothane = sevoflurane
How does an exothermic reaction leading to fires and explosions occur with anesthetic gases?
- Desiccated strong base absorbents interact with sevoflurane
- Examples of strong base absorbents: Baralyme, anhydrous LiOH
Buildup of high temperatures, flammable degradation products (formaldehyde, methanol, and formic acid), and oxygen or nitrous rich gases w/in the absorber all provide basis for combustion
Which anesthetic gas should be avoided with desiccated strong base absorbents?
- Sevoflurane
Anesthesia Patient Safety Foundation Recommendations
- ALL gas flows turned off after each case
- Vaporizers turned off when not in use
- Absorbent changed regularly
- Change when color change indicates exhaustion
- Change all absorbent
- Change absorbent when uncertain about the state of hydration
- If using compact canisters, change more frequently
