Exam 2 Breathing System Part I [6/20/24] Flashcards
What are the six functions/definitions of the 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, and monitors the volume
slide 2
-
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?
- 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
What are the 2 types of flow?
- Laminar
- Turbulent
S3
- Describe the characteristics of Laminar flow
- what law does it relate to?
-
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
- Describe the characteristics of turbulent flow.
- What are eddies?
-
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
What are the 2 types of turbulent flow?
- Generalized
- Localized
S6
Define generalized turbulent flow
When gas flow through a tube exceeds the critical flow rate
S6
Define localized turbulent flow.
Gas flow rates below the critical flow rate but encounters constriction, curves, or valves.
S6
What kind of flow is depicted in the following picture.
* A
* B
* C,D,E,F
A: Laminar
B: Generzlized Turbulent
C, D, E, F: Localized Turbulent
To minimize resistance, gas-conducting pathways should have what three things
- minimal length (short)
- maximal internal diameter (wide)
- without curves or constrictions (straight)
slide 6
- What is the effect of resistance to the patient?
- What happens to work of breathing with resistant?
- What causes most of the resistance?
- 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
How much resistance is too much resistance?
- 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
What is compliance and what are we measuring with it?
- 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
- Define compliance
- What does compliance measure?
- What units is compliance in?
- What does it help detemine?
- Ratio of change in volume to change in pressure
- Measures distensibility
- mL/cm H2O
- Helps determine Vt
S9
What are the most distensible components of the anesthesia circuit?
- Breathing tubes (corrugated tubing)
- Reservoir bag
slide 9
- Definition of rebreathing
- What gasses does rebreathing include?
- 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
3 things rebreathing is influenced by
- Fresh gas flow
- Dead space
- Breathing system design
S10
How does high Fresh Gas Flow influence rebreathing?
- 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
How does low fresh gas flow influence rebreathing?
- 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
- What is minute ventilation?
- Normal minute volume
- amount of gas inhaled or exhaled in 1 minutes.
- min ventilation = Vt x Breaths per minute
- 4-6L/min
S11 [lecture]
What are the 4 types of dead space?
- Apparatus
- Physiologic: anatomical and alveolar DS
- Anatomical: conducting airways; adds H2O vapor
- Alveolar: volume of alveoli ventilated but not perfused.
slide 12
- What is apparatus dead space?
- What does it include?
- What does it not include?
- 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
How can we decrease apparatus dead space?
- 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
When the pt isn’t rebreathing, what does the inspired gas composition look like?
- 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
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
What are the measured effects of rebreathing?
- Rebreathing reduces heat and moisture loss from the pt
- Rebreathing alters inspired gas tensions
slide 13
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
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.
*
Label the breathing circuit
slide 14
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
List the four types of breathing circits
- Open
- Semi-Open
- Semi-Closed
- Closed
slide 16
Characteristics of Open circuit
- No reservoir bag
- No rebreathing
- Example: nasal cannula or open drop ether)
S16
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
Characteristics of Semi-Closed circuit
- Reservoir bag
- Partial rebreathing
- Typically used all the time.
- Gas has a way to escape
S16
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]
Characteristics of Closed circuit
- Reservoir bag
- Complete rebreathing
- Dependent on FGF
- always uses low flow
- Pt has Ve 4L/min and FGF 2L/min = rebreathing
- Pt has Ve 4L & FGF 5L/min + exhasted canisted = rebreathing
S16
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]
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
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
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
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
The facemask will connect to the Y-piece/connector, how big is the female connection?
- 22 mm
slide 18
A fitting that joins together 2 or more components.
- Connectors/ Adapters
slide 20
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
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
- 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
Describe the flow in the breathing tubing.
- Turbulent Flow d/t corrugation.
slide 22
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
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
Pressure check the circuit before use. What value should this be?
- 30 cm H2O
slide 22
Bidirectional gas flow areas of the circuit could have…
- mixing of inspired/expired gases
slide 23 lecture
Where is the preferred location of the fresh gas inflow site?
- Between CO2 absorbent and unidirectional inspiratory valve
slide 31
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
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
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
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
Most absorbents use calcium hydroxide to react with the expired CO2, producing what byproducts?
- Insoluble calcium carbonate (CaCO3)
- Water
- Heat/Energy
slide 37
Since spira-lith has no color indicator, how do you know its exhausted?
- monitor ETCO2, baseline will start to increase on capnograph
S42
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
Which of the following absorbent is composed of 95% Lithium Hydroxide?
- Soda Lime
- Litholyme
- Spiralith
- Spiralith has 95% LiOH
slide 43
Which of the following absorbent has color indication?
- Soda Lime
- Litholyme
- Spiralith
- Soda Lime
- Litholyme
sldie 43
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
