Exam 2 Breathing System Part I [6/20/24] Flashcards
1
Q
What are the six functions/definitions of the breathing system
A
- 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
slide 2
2
Q
-
Resistance:
- What happens to pressure as gas passes through a tube?
- The drop of pressure is a measure of?
- How does resistance vary?
- What else can change resistance?
A
- When gas passes through a tube, the pressure at the outlet will be lower than the inlet
- pressure at the beginning of the ETT will be higher than at the end of the ETT
- The drop of pressure is a measure of: resistance that must be overcome (P2-P1)
- Resistance varies with the volume of gas per unit of time
- Flow types can change resistance
slide 3
3
Q
What are the 2 types of flow?
A
- Laminar
- Turbulent
S3
4
Q
- Describe the characteristics of Laminar flow
- what law does it relate to?
A
-
Characteristics of laminar flow
- Laminar flow is smooth and orderly
- Particles move parallel to the tube walls
- Flow is fastest in the center where there is less friction.
- Law: Relates to Poisueille’s Law
slide 4
5
Q
- Describe the characteristics of turbulent flow.
- What are eddies?
A
-
Characteristics:
- Flow lines are not parallel
- Flow rate is the same across the diameter of the tube
- “Eddies”: composed of particles moving across or opposite the general direction of flow.
slide 6
6
Q
What are the 2 types of turbulent flow?
A
- Generalized
- Localized
S6
7
Q
Define generalized turbulent flow
A
When gas flow through a tube exceeds the critical flow rate
S6
8
Q
Define localized turbulent flow.
A
Gas flow rates below the critical flow rate but encounters constriction, curves, or valves.
S6
9
Q
What kind of flow is depicted in the following picture.
* A
* B
* C,D,E,F
A
A: Laminar
B: Generzlized Turbulent
C, D, E, F: Localized Turbulent
10
Q
To minimize resistance, gas-conducting pathways should have what three things
A
- minimal length (short)
- maximal internal diameter (wide)
- without curves or constrictions (straight)
slide 6
11
Q
- What is the effect of resistance to the patient?
- What happens to work of breathing with resistant?
- What causes most of the resistance?
A
- Resistance imposes a strain with ventilatory modes where the pt must do all or part of the work to breathe
- Changes in resistance Parallel work of breathing for the pt if spontaneously breathing
- Increased resistance = increased WOB
- Decreased resistance = decreased WOB
- ETT causes the most resistance in the circuit
Slide 7
12
Q
How much resistance is too much resistance?
A
- no common agreement in studies
- we must watch flow volume loops for trends
slide 7
-adding more things to the circle system increases resistance
-we try to minimize resistance to make it easier for pt to breathe
13
Q
What is compliance and what are we measuring with it?
A
- Ratio of Δvolume/Δpressure
- measures distensibility (mL/cmH2O)
Compliance also helps determine Vt - some things in the circuit can stretch for a greater Vt to be delivered
slide 9
14
Q
- Define compliance
- What does compliance measure?
- What units is compliance in?
- What does it help detemine?
A
- Ratio of change in volume to change in pressure
- Measures distensibility
- mL/cm H2O
- Helps determine Vt
S9
15
Q
What are the most distensible components of the anesthesia circuit?
A
- Breathing tubes (corrugated tubing)
- Reservoir bag
slide 9
16
Q
- Definition of rebreathing
- What gasses does rebreathing include?
A
- To inhale previously inspired gases from which CO2 may or may not have been removed
- rebreathing may not just be CO2, we could be rebreathing volatile gases too: low flows will minimize the gas allowed into the system so you don’t get as much fresh gas but you are rebreathing the volatiles
- intact and working CO2 absorber should take out the CO2 so the pt can just rebreathe the volatile
slide 10 and questions during lecture
17
Q
3 things rebreathing is influenced by
A
- Fresh gas flow
- Dead space
- Breathing system design
S10
18
Q
How does high Fresh Gas Flow influence rebreathing?
A
- Amount of rebreathing varies inversely with the total FGF
- if the volume of FGF supplied to the pt per min is greater than or equal to the pt’s minute volume = no rebreathing (as long as the exhaled gas is vented)
slide 11
19
Q
How does low fresh gas flow influence rebreathing?
A
- Amount of rebreathing varies inversely with the total FGF
- if the volume of FGF supplied per min is less than the pt minute volume = rebreathing occurs
- some of the exhaled gases must be rebreathed to make up required volume
sldie 11
20
Q
- What is minute ventilation?
- Normal minute volume
A
- amount of gas inhaled or exhaled in 1 minutes.
- min ventilation = Vt x Breaths per minute
- 4-6L/min
S11 [lecture]
21
Q
What are the 4 types of dead space?
A
- Apparatus
- Physiologic: anatomical and alveolar DS
- Anatomical: conducting airways; adds H2O vapor
- Alveolar: volume of alveoli ventilated but not perfused.
slide 12
22
Q
- What is apparatus dead space?
- What does it include?
- What does it not include?
A
- The volume in a breathing system that has gases that are rebreathed without a change in the composition
-
includes: only Y-piece and everything pt side of the y-piece.
- elbow and ETT (y-piece and everything distal per lecture
- inspiratory and expiratory limbs (corregated tubing) are not included in apparatus dead space
slide 12
23
Q
How can we decrease apparatus dead space?
A
- Decreased by having inspiratory and expiratory limb separation as close to patient as possible
In lecture: keep the y-piece short and close to the pt, and don’t add unnecessary elbows or accordians between the pt and the y-piece
slide 12
24
Q
When the pt isn’t rebreathing, what does the inspired gas composition look like?
A
- Inspired gas composition is identical to the fresh gas delivered by the anesthesia machine
- any combo of gas we are giving the pt directly from the machine is exactly what they are breathing
slide 13 and lecture discussion
25
When the pt is rebreathing, what are the effects?
* Inspired gas composition is part fresh gas and rebreathed gas
* (gas from machine + rebreathed gas)
| slide 13
26
What are the measured effects of rebreathing?
* Rebreathing reduces heat and moisture loss from the pt
* Rebreathing alters inspired gas tensions
| slide 13
27
What inspired gas tensions are altered with rebreathing?
* reduction in the inspired oxygen tension [partial pressure]
* inhaled anesthetic agents (induction and emergence)
* CO2
*what the numbers do will depend on the FGF, pt's metabolic state, and what type of circuit, but rebreathing will alter the gas tensions*
| slide 13 and lecture
28
Explain what happens to CO2 if alveolar deadspace is increased?
* as alveolar deadspace increases, partial pressure of PaCO2 increases.
* Decreased ETCO2 but increased PaCO2 bc its not being blown off.
*
29
Label the breathing circuit
| slide 14
30
What are the six desirable characteristics of a breathing circuit
* Warmed humidification of inspired gas
* Low resistance to gas flow
* Rapid changes in delivered gas when required
* Removal of CO2 at rate of production
* Minimal rebreathing
* Safe disposal of waste gases
We Like Rapid Circuits Making Sounds
Making Sure, We Like Rapid Circuits.
| slide 15
31
List the four types of breathing circits
* Open
* Semi-Open
* Semi-Closed
* Closed
| slide 16
32
Characteristics of **Open** circuit
* No reservoir bag
* No rebreathing
* Example: nasal cannula or open drop ether)
| S16
33
Characteristics of **Semi-Open** circuit
* Reservoir bag
* No rebreathing d/t FGF > minute ventilation.
Minute ventilation is 4L/min and FGF is 6L/min = semi-open
| S16
34
Characteristics of **Semi-Closed** circuit
* Reservoir bag
* Partial rebreathing
* Typically used all the time.
* Gas has a way to escape
| S16
35
In a semi-closed system, patient rebreathing depends on?
* fresh gas flow
* spontaneous breathing
* APL valve open/closed/semi-open
* exhaustion of CO2 canister
Semi-closed rebreathing depends on SAFE
| S16 [lecture]
36
Characteristics of **Closed** circuit
* Reservoir bag
* Complete rebreathing
* Dependent on FGF
* always uses low flow
1. Pt has Ve 4L/min and FGF 2L/min = rebreathing
2. Pt has Ve 4L & FGF 5L/min + exhasted canisted = rebreathing
| S16
37
How do you differentiate between partial breathing and complete rebreathing?
* Partial rebreathing: gas has a way to escape
* seen in semi-closed systems
* Complete rebreathing: gas doesnt have a way to escape
* FGF is less than pt minute ventilation plus a closed system (closed APL)
* seen in closed systems.
| S16 [letcure]
38
3 times you 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
| Andy
39
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
| slide 17
40
Characteristics of the face mask:
* What color is it?
* How is a perfect seal obtained?
* How is the rubber mask holder/strap attached?
* Clear
* Inflatable cuff that provides pneumatic cushion to seal the face.
* Contains prongs for attachement to the rubber mask/head strap
*
| S19
41
The facemask needs to be placed where on the face?
* Fits between the interpupillary line and in the groove between the mental process and the alveolar ridge
| slide 18
42
The facemask will connect to the Y-piece/connector, how big is the female connection?
* 22 mm
| slide 18
43
A fitting that joins together 2 or more components.
* Connectors/ Adapters
| slide 20
44
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)
| slide 20
45
What are the disadvantages of connectors and adaptors?
* Increased resistance
* Increased dead space
* Additional locations for disconnections
connectors or adaptors are like marriage... if its DEAD, it will have Resistance and Disconnect!
| slide 20
46
* Describe the breathing tubing
* How long is the breathing tubing?
* What is the internal volume of the breathing tubing?
* large bore, corrugated, plastic and expandable
* these are low resistance and somewhat distensible
* 1 meter in length
* 400-500 mL **for each meter** in length
| slide 22
47
Describe the flow in the breathing tubing.
* Turbulent Flow d/t corrugation.
| slide 22
48
Does having 2 breathing tubes attached to each other affect deadspace?
* Longer tubes do not create deadspace
* Dead space only from Y piece to patient d/t unidirectional gas flow
| slide 22
49
Why aren't the breathing tubes (corregated tubes) considered dead space?
* the reason the limbs are not included in dead space is because of the unidirectional valves
* As long as the unidirectional valves are opening and closing we still have flow.
| slide 22 and lecture
50
Pressure check the circuit before use. What value should this be?
* 30 cm H2O
| slide 22
51
Bidirectional gas flow areas of the circuit could have...
* mixing of inspired/expired gases
| slide 23 lecture
52
When the inspiratory valve is open and delivering from the system, what is happening with the expiratory valve?
* The expiratory valve is closed.
* Expiratory & inspiratory valves are never open or closed at the same time.
| S23 [lecture]
53
What happens if the inspiratory valve is stuck closed during inspiration?
* Dont have flow going forward.
* It becomes part of the dead space - dead space is extended out from the pt into the inspiratory tube because there is no flow
| slide 23 [lecture]
54
What happens to the unidirectional valves during expiration?
* Inspiratory valve is closed so air is pushed forward into the open expiratory valve
| S23 [lecture]
55
What happens if expiratory valve is stuck closed during expiration
* the expiratory limb now becomes deadspace
| S23 [lecture]
56
* What are unidirectional valves used for?
* What are their characteristics?
* Direct respiratory gas flow in the correct direction
* Characteristic: Disks with knife edges, rubber flaps, or sleeves (rubber is old-school)
| slide 24
57
Unidirectional valves:
* resistance?
* competence?
* How should they open?
* How should they closed?
* Low resistance
* High competence
* Must open widely w/ little pressure
* Must close completely and rapidly w/ no backflow
| S24
58
* When does the inspiratory valve open?
* When does the inspiratory valve close?
* What is the purpose of the inspiratory valve?
* The inspiratory valve opens on **inspiration**.
* The inspiratory valve close on **exhalation**.
* Prevents backflow of exhaled gas
| slide 25
59
* When does the expiratory valve open?
* When does the expiratory valve close?
* What is the purpose of the expiratory valve?
* The expiratory valve opens on **exhalation**.
* The expiratory valve close on **inspiration**.
* Prevents rebreathing
| slide 25
60
Proper valve placement and functioning of the unidirectional valves prevents any part of the circle system from contributing to _________.
* Apparatus Dead Space
| slide 26
61
What composes the apparatus dead space?
* Distal limb of Y-connector
* Tube/mask/LMA
| slide 26
62
The unidirectional valves are located near what parts of the breathing system?
* CO2 absorber canister
* Fresh gas inflow site
* APL Valve
| slide 26
63
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**
MACHA
ABCs HO
| slide 27
64
Describe the resevoir bag
* non-slippery
* rubber, plastic, or latex
* ellipsoidal for 1 hand ventilation
| slide 29
65
How much volume is in a traditional reservoir bag?
* 3 L
*Can range from 0.5 to 6 L*
| slide 29
66
All reservoir bags must have _____ mm female connector on the neck.
* 22 mm
| slide 29
67
Anesthesia reservoir bags must adhere to pressure standards.
* What is the minimum pressure?
* What is the maximum pressure?
* 30 cm H2O (minimum)
* 40-60 cm H2O (rubber bag maximum)
* plastic bags-2x the distending pressure*
| slide 29
## Footnote
Although most bags adhere to these standards, some latex-free bags have exceeded the upper pressure limit.
68
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*
69
What are the functions of the reservoir/breathing bag?
1. Reservoir for anesthetic gases/oxygen
2. A means of delivering manual ventilation
3. Assisting spontaneous breathing
4. Visual/tactile monitor confirmation of ventilation.
5. Protection from excessive positive pressure in the breathing system.
RAM for PC
| slide 30
70
What is another name for the Gas Inflow site?
* Fresh gas inlet: gases are delivered from the common gas outlet to the circuit
| slide 31
71
Where is the gas inflow site located?
* near the inspiratory unidirectional valve or CO2 absorbent canister housing in circle systems
| S31
72
Where is the preferred location of the fresh gas inflow site?
* Between CO2 absorbent and unidirectional inspiratory valve
| slide 31
73
* Adjustable Pressure-Limiting Valve (APL) is also known as?
* what is its function?
* AKA: pop-off valve
* permits gas to leave the circuit
| slide 32
74
How does the APL work?
* Dome valve loaded by a spring and screw cap that can be adjusted by the CRNA
* controls pressure in the breathing system
* tighten the screw cap = more gas pressure is required to open it
* releases gas into the scavenging system
| slide 32
75
Clockwise motion of the APL valve will ____ pressure.
* Increase
| slide 33
76
Counterclockwise motion of the APL valve will ____ pressure.
* decrease
| slide 33
77
How many turns does it take for the APL valve to go from fully open to closing fully?
* 1-2 clockwise turn
*arrows must indicate the direction to close valve*
| slide 33
78
What does the needle valve do?
What does the check valve do?
- The needle valve: allows vented gas to go through to the scavenging system.
- Check Valve: still have a check valve. Think of it as the inspiratory and expiratory disk which allows gas/flow to come from the breathing circuit.
- depending on how open or closed, it goes through the scavenging system
| S33-lecture
79
Long explaination of the APL valve
* A threaded screw cap over the spring allows the pressure exerted by the spring on the disc to be varied.
* When the cap is fully tightened, the disc will prevent any gas from escaping from the system.
* As the cap is loosened, the tension on the spring is reduced so that the disc can rise.
* When the pressure in the breathing system increases, it exerts an upward force on the disc. When this upward force exceeds the downward force exerted by the spring, the disc rises and gas flows through the valve.
* When the pressure in the system falls, the disc returns to its seat.
* When the cap is at its maximum open position, there will be only minimal pressure exerted by the spring. This allows the patient’s exhalation to lift the disc with only minimal pressure.
* The weight of and pressure on the disc ensures that the reservoir bag fills before the disc rises.
| slide 34
80
APL disk orientation during spontaneous respiration
* Inspiration: closed (partially closed with CPAP pressure)
* Expiration: open
| slide 34
81
APL Disk orientation with assisted/manual ventilation
* Inspiration: partially open so the excess gas is diverted
* Expiration: Partially open
| slide 34
82
APL disk orientation with mechanical ventialtion
In both inspiration and expiration, the APL is bypassed
| slide 34
83
What is the APL valve doing with the ventilator on?
* doesnt matter what APL valve is doing because its being bypassed
| S34 *in class question from Erikson*
84
Absorption canisters
* ____ sides
* can be ____ or ____ orientation
* remove ____ before use (Ericksen harped on this)
* has valves that ____ when the canister is removed to prevent ____
* side/center tube: ____
* **transparent** sides
* can be **single or 2 in a series/stacked** orientation
* remove **wrap** before use (Ericksen harped on this)
* has valves that **close** when the canister is removed to prevent **gas loss**
*therefore you can change the canister in the middle of a case*
* side/center tube - returns gas to the pt
| slide 35
85
An absorber canister contains 4 things. What are they and its functions?
| Same FC as slide 84 just presented differently
1. **Canister**
* Transparent Sides
* single or 2 in series
* remove the wrap before use
2. **Absorbent**
3. **Housing**
* Incorporates valves that close when canister is removed to prevent gas loss.
4. **Side/Center Tube**
* Returns gas to the patient
CASH in on a canister!
| S35
86
What is the downside of having the fresh gas inflow valve so close to the CO2 absorbent?
* Fresh gas can dry out the absorbent
| Andy and lecture
87
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.*
| Andy
88
Most absorbents use calcium hydroxide to react with the expired CO2, producing what byproducts?
* Insoluble calcium carbonate (CaCO3)
* Water
* Heat/Energy
| slide 37
89
When do we have color change in the canister?
* When the absorbant turns into carbonates is when we have color change.
| S37 [lecture]
90
What are the absorbants mentioned in lecture?
* Soda lime
* Calcium hydroxide lime AKA Amsorb
* lithium hydroxide
* litholyme
* spira lith
| S38-42
91
Name the components of soda lime absorbant.
* Calcium hydroxide (80%)
* Sodium hydroxide/ Potassium hydroxide (5%)
* Water (15%)
* Small amount of silica/clay
* to keep from hardening/drying out
| slide 38
92
Because CO2 does not react quickly with calcium hydroxide, what are the catalysts required to speed up the reaction?
* Sodium hydroxide
* Potassium hydroxide
| slide 37 and 38 ???
93
How do you know when the soda lime has been fully exhausted?
* It turns from white to purple
* All hydroxides have become carbonates
| slide 38
94
Soda lime can absorb ____% of its weight in CO2.
100 grams of soda lime can absorb ____ L of CO2.
* 19%
* 26 L
| slide 38
95
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%)
| slide 39
96
Na+ hydroxide and K+ hydroxide can cause what 3 things?
* Compound A formation (found in rats)
* Carbon Monoxide formation
* Destruction of inhaled gases
| slide 39
## Footnote
Compound A presence with Sevo in rodents
CO production in the presence of Desflurane
contributes to destruction of inhaled gases so this absorber isn't generally used anymore
97
Lithium Hydroxide:
* more ____ absorption capacity
* used in what two enviornments?
* Does is have NaOH or KOH
- More CO2 absorption capacity
- Used in submarines and spacecraft
- Not usually used in anesthesia b/c expensive but also can cause burns to the skin, eyes, and lungs
*Benefit is it doesn't really react with anesthesia gases because it doens't have the sodium or potassium hydroxides*
| slide 40
98
Litholyme:
* What catalyst does it have?
* Does it react with inhaled gases?
* Why does it not form compound A or CO?
* What is the color change that occurs?
* What are its benefits?
- Has a **Lithium chloride** catalyst
- Does not react with inhaled gases
- No activators/strong bases so it does not form Compound A and carbon monoxide
- Has color change (white to purple) but no **regeneration**
**Benefits**:
- **↓** Fire Risk
- lower **exothermic** reactivity
- reduced **economic/environemental** impact
| slide 41
99
What is regeneration?
What does it mean if there is no regeneration?
* regeneration: soda lime has color change when exhausted and then reverts back to white
* the pH indicators do not become coloress, [does not revert back]
| S41
100
* What is Spira Lith?
* What is its benefits/risk?
- Anhydrous LiOH powder within a nongranular partially hydrated polymer sheet
**Benefits**:
- larger surface area for reaction
- No activators/strong bases
- ↓ Temperature production
- longer duration of use
- Cheap
**RISK**
- No color indicator, no color change
| slide 42
101
Since spira-lith has no color indicator, how do you know its exhausted?
* monitor ETCO2, baseline will start to increase on capnograph
| S42
102
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*
| slide 43
103
Which of the following absorbent is composed of 95% Lithium Hydroxide?
- Soda Lime
- Litholyme
- Spiralith
* Spiralith has 95% LiOH
| slide 43
104
Which of the following absorbent has color indication?
- Soda Lime
- Litholyme
- Spiralith
* Soda Lime
* Litholyme
| sldie 43
105
What is the most common dye for absorbent indicators?
* Ethyl Violet
*Ethyl violet causes soda lime to turn from white to purple when exhausted*
| slide 44
106
What color will ethyl orange turn when exhausted?
* Cresyl Yellow
| slide 44
107
* Carbonate formation has what effect on pH?
* Carbonate formation has what effects on CO2 canister color?
* pH becomes less alkaline (lower pH)
* white to blue violet (purple)
| slide 44
108
At what pH will the soda lime experience color change?
* pH less than 10.3 (purple, exhausted)
* fresh absorbant is colorless: with a pH of >10.3
| slide 44
109
When absorbent is exposed to bright florescent light for a period, what can happen?
* Bleaching
* Absorbent indicator does not work as well and could potetially turn it back to white even though its exhausted
| slide 44
110
Absorbents have high reliability indicating CO2 rebreathing, but what is the gold standard?
* Capnometry
* Absorbents can have regeneration causing color fading.
| S44
111
Leaving flows on (through the weekend) can have what affect on the absorbant. Whats another name for this process?
* dry out absorbent
* **desiccation**
| S44
112
* CO2 absorbent granules are measured in what units?
* what is normal?
* 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*
| slide 45
113
* The granuals have what kind of surface?
* The size and shape of the absorptive granules are intended to maximize ____ while minimizing ____ .
* rough, irregular surface
* Maximize Absorption [surface area]
* Minimize resistance to airflow
| slide 45
114
Roughly half of the volume of the CO2 canister will be composed of _______.
* gas
| S45
115
What factor can decrease the efficiency of CO2 absorption? why?
* Excess water in the canister (change canister if you see liquid)
* Liquid will decrease surface area and efficiency of CO2 absorption
| slide 45
116
Small passageways that allow gas to flow through low-resistance areas, decreasing functional absorptive capacity, is called?
* Channeling
* Picture E is an example of channeling
| S46
117
What are ways to minimize channeling?
* Circular baffles (flow-directing panels)
* Placement for vertical flow
* Permanent mounting
* Prepackaged cylinders
* Avoiding overly tight packing (we don't normally pack them anymore, thats old-school)
| slide 46
118
The decomposition of sevoflurane will form this substance.
* Compound A
| slide 48
119
sevoflurane decomposes into this when compound A is formed
2-fluoromethyl-2,2-difluoro-1-(trifluoromethyl) vinyl ether
| S48
## Footnote
erikson said we didnt need to know the name but just in case
120
Compound A causes what toxicity in rats?
* Nephrotoxic in rats
* Possible in humans
| slide 48
121
Compound A formation occurs with:
* Low FGF (1-2 L/min)
* Increased absorbent temperature
* Higher inspired sevoflurane concentrations (1.5 to 2 MAC)
* Dehydrated/dessicated absorbent
* Absorbent containing NaOH or KOH
| slide 48
## Footnote
Na or K hydroxide + SEVO = COMPOUND A
122
Carbon monoxide can occur due to what factors?
* Dry absorbent *'Monday, 1st case'- gas left on over the weekend*
* Increased carboxyhemaglobin levels
* Increased Temperature
* Increased Concentration of anesthetic gases
* *Desflurane ≥ enflurane > isoflurane > halothane > sevoflurane*
* Low FGF rate
* Strong base absorbents (KOH or NaOH)
**biggest takeaway from Ericksen: Desflurane + dried absorbant + strong base absorbant (KOH or NaOH) = CO production**
| slide 49
123
Rank the order of anesthetic gases from highest to lowest level of carbon monoxide formation.
**Desflurane** ≥ enflurane > isoflurane > halothane > sevoflurane
| slide 49
124
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
* absorbers exceed 200 degrees Celsius [392 degrees Fahrenheit] and higher w/ fire in some breathing cicuits
| slide 50
125
What are causes of absorbent heat production?
* Buildup of high temperatures
* flammable degradation products (formaldehyde, methanol, and formic acid)
* oxygen or nitrous rich gases w/in the absorber
**all provide basis for combustion**
| S50
126
Which anesthetic gas should be avoided with desiccated strong base absorbents when concerned about absorbent heat production?
* Sevoflurane
| slide 50
127
Anesthesia Patient Safety Foundation [APSF] 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 (not just 1 canister if you have 2)
* Change absorbent when uncertain about the state of hydration
* If using compact canisters, change more frequently
| slide 51
