E2- Breathing System I Flashcards
functions/definitions of breathing system
- 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 ,, + monitors the volume
Resistance
- When gas passes through tube – pressure at _______ LOWER than _____
- What part has highest pressure?
- A drop is pressure is a measure of _______.
- P2 = pressure at ____ + P1 = pressure at ____
- outlet lower than inlet
- beginning of tube
- resistance
- beginning + end
Resistance varies with ________? What can also change resistance?
- volume of gas passign through per unit time
- flow types (laminar / turbulent)
- Laminar flow is ____ and ______.
- Particles move _____ to tube walls.
- Where is the flow fastest?
- What Law relates to laminar?
- smooth + orderly
- parallel
- center
- Poiseuilles law
What is A, B, C, D, E, F
- A = laminar
- B = generalized turbulent
- C = localized turbulent d/t sharp turn or narrowing
- Turbulent flow lines are not parallel + composed of what?
- Where is turbulent flow fastest?
- Eddies = particles moving in opposite direction of general flow
- SAME across diameter of tube
Generalized vs. Localized Turbulent flow
- Generalized
o When flow of gas through tube exceeds critical flow rate - Localized
o Gas flow rate below critical flow rate … but encounters constrictions, curves, or valves
- To minimize resistance … gas-conducting pathways should have ??
- minimal length
- maximal internal diameter
- without sharp curves or sudden changes in diameter
What is the significance of resistance?
- imposes strain with ventilatory modes when pt must do work
- change parallels change in WOB
- watch flow volume loops!
What causes more resistance than breathing system?
ETT
- What is compliance?
- Measures _____ (mL/cmH2O)
- What does compliance help determine?
- Ratio of change in volume to change in pressure - V/P
- distensibility
- Vt
What are the 2 most distensible components?
Reservoir bag + breathing tubing
What is rebreathing?
What 3 things is it influenced by?
- To inhale previously **inspired gases ** – CO2 may or may not be removed
- Fresh gas flow
- Dead space
- Breathing system design
- Amt of rebreathing varies _____ with total FGF.
- What FGF is there NO rebreathing?
- At what FGF is there rebreathing ?
- What is the function of exhaled gases in rebreathing?
- inversely
- FGF/min = or > Vm – NO rebreathing
- FGF < Vm – YES rebreathing
- make up required volume
Types of dead space
- Apparatus? What is it + what decreases it
- Physiologic
- Anatomical
- Alveolar
- Apparatus – vol in breathing system by gases rebreathed without change in composition
Decreased by having inspiratory + expiratory limb separation CLOSE to patient as possible
Anything distal to Y piece (elbow, ett) - anatomic + alveolar
- conducting airways - adds H2O vapor
- vol alveoli ventilated but not perfused
- What does rebreathing reduce?
- Rebreathing causes 3 altered inspired gas tensions
- heat + moisture loss from pt
- reduce inspired oxygen tension
- Inhaled anesthetics (induction = increase ,, emergence = decrease)
- CO2 (increase)
What makes up FGF?
Air, nitrous, oxygen
NOT anesthetic gases bc they’re a pressure
6 desirable characteristics of a breathing circuit?
- 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
In closed circuit, amt of rebreathing depends on ____?
FGF
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 _______.
- Facemask is clear + what allows it to seal the face?
- interpupillary line
- mental process
- alveolar ridge
pneumatic cushion
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 3 advantages of connectors and adaptors?
* Extends distance b/w patient and breathing system
* Change angle of the connection
* Allow more flexibility/ less kinking (The accordion will give you the most flexibility)
What are 3 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.
- ALWAYS 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 d/t unidirectional valves
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
If valve no worky = appartus dead space = TEST Q!
What composes the apparatus dead space?
- Distal limb of Y-connector
- Tube/mask/LMA
The unidirectional valves are located near what 3 parts of breathing system?
- CO2 absorber canister
- Fresh gas inflow site
- APL Valve
What are 5 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? Range?
- 3 L
Can range from 0.5 to 6 L
All reservoir bags must have _____ mm female connector on the neck.
- 22 mm
reservoir bags must adhere to pressure standards
* minimum pressure of approximately ______ cm H2O
* maximum pressure of approximately ____ cm H2O
* plastic bags have ____ the distending pressure of rubber bags
- 30 cm H2O (minimum)
- *40 - 60 cm H2O (maximum)
- 2x
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 5 functions of the reservoir/breathing bag?
(1) Reservoir for anesthetic gases/oxygen
(2) A means of delivering manual ventilation
(3) assisting spontaneous breathing
(3) Serving as a visual / tactile monitor a patient’s spontaneous breathing efforts
*estimates volume of ventilation
(4) Partially protecting pt 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 + 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?
- “Pop-off valve”
- Permits **gas to leave circuit **
- Closed = gas doesn’t leave .. stays in circuit = higher pressure to open
- Open = gas leave … to scavengerDome valve loaded by a spring + screw cap
- User-adjustable
- Controls pressure in breathing system
- Releases gases to scavenging system
Clockwise motion of the APL valve will ______ pressure.
- Increase
clockwise on clock increases #s
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
Explain APL Use (chart)
Spotaneous?
Assisted/manual?
APL setting during mechanical ventilation?
BYPASSED
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
Absorbent Chemical Reaction
- Absorbent is a chemical reaction
- Carbon dioxide + water = initial reaction
- Exothermic reaction that combines CO2 with Ca hydroxide to form calcium carbonate
- Hydroxides – interact with CO2 to form exothermic reaction – exhausting absorbent
- absorbent turns to carbonates when exhausted – color change
5 types of absorbents + brand name?
- Soda Lime = SODASORB
- Calcium Hydroxide Lime = AMSORB
- Lithium Hydroxide
- Litholyme
- Spira-Lith
Name the 4 components of soda lime.
- Calcium hydroxide (80%)
- Sodium hydroxide/ Potassium hydroxide (5%)
- Water (15%)
- Small amount of silica/clay - keep from hardening/drying out
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 Soda Lime? Cause?
- Compound A formation (found in rats) = SEVO
- Carbon Monoxide formation = DES
- Destruction of inhaled gases
Caused by Na/K strong bases
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
S = sheets
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) - more acidic
- blue violet (purple)
At what pH is the soda lime exhausted + experience color change?
< 10.3
When im exhausted, im an ass (acidic)
When absorbent is exposed to bright fluroscent 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? Why?
- Capnometry
- bc regeneration can occur + color fades
CO absorbent granules are measured in what units? What is normal?
- Mesh Size
- 4-8 mesh size (most optimal for CO2 absorbers)
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 Absorption
- Minimize resistance to airflow
Roughly 50% of volume 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 5 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 5:
- Low FGF (1-2 L/min)
- Increased absorbent temperature
- Higher inspired sevoflurane concentrations (1.5 to 2 MAC)
- Dehydrated absorbent
- Absorbent containing NaOH or KOH
Carbon monoxide can occur due to what factor?
- Dry absorbent + leaving FGF on
- ‘Monday, 1st case’- gas left on over the weekend
- Increased Temperature
- Increased Concentration of anesthetic gases
- * Low FGF rate
- *** 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),
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?
What temps can absorbers reach?
What else avoided?
- Sevoflurane
- > 200 C
- strong bases ,, desiccated
Anesthesia Patient Safety Foundation = 6 Recommendations
- ALL gas flows + vaporizers turned off after each case
- 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
