Exam 2- Breathing Systems II (6/27/23) Flashcards
1
Q
What is a Mapleson Circuit?
A
- The Mapleson Circuit Systems are used for the delivery of oxygen and anesthetic agents and the removal of carbon dioxide
2
Q
How many types of Mapleson Circuits are there?
A
- Six Types (A → F)
3
Q
What are the components of the Mapleson Circuit?
A
- Patient connection/Facemask (Patient end)
- Reservoir bag (operator end)
- Corrugated tubing
- APL valve (variable positioning)
- Fresh gas inlet (variable positioning)
4
Q
What components are absent in all Mapleson Circuit Systems?
A
- CO2 absorber
- Unidirectional Valves
- Separate Inspiratory and Expiratory Limbs
5
Q
What is another name for the Mapleson Circuit Systems?
A
- Carbon Dioxide Washout Circuits
- Flow-controlled Breathing Systems
6
Q
How does the Mapleson Circuit System prevent rebreathing without a CO2 absorber?
A
- FGF must be significantly greater than minute ventilation to “washout” the CO2.
7
Q
What is another name for Mapleson A?
A
- Magill’s System
8
Q
Where does fresh gas flow enter in the Mapleson A circuit?
Where is the APL valve located in the Mapleson A circuit?
A
- FGF enters from the operator end, near the reservoir bag
- APL valve located on patient end
9
Q
Of all the systems, what is Mapleson A best at?
What is Mapleson A the worst at?
A
- Best efficiency of all systems for spontaneous ventilation
- Worst efficiency of systems for controlled ventilation
10
Q
Mapleson A Circuit:
What is vented out from the APL valve in spontaneous ventilation during expiration?
A
- Dead space gas (yellow)
- Alveolar gas (red)
11
Q
Mapleson A Circuit:
What is vented out from the APL valve in controlled ventilation during expiration?
A
- APL valve does not open
12
Q
Mapleson A Circuit:
What is vented out from the APL valve in controlled ventilation during inspiration?
A
- Mostly fresh gas (blue)
- Some alveolar gas (red)
- Increase the risk of rebreathing alveolar gas (red)
13
Q
Where are the APL Valve and Fresh gas inlet located in the Mapleson B Circuit?
A
- APL and FG inlet located near the patient
14
Q
Why is the Mapleson B Circuit considered inefficient and obsolete?
A
- Significant fresh gas is vented through APL during exhalation
- Blue (FGF)
- Red (alveolar gas)
15
Q
FGF should be ______ times the minute volume during spontaneous and controlled ventilation to prevent rebreathing in the Mapleson B circuit.
A
- FGF should be 2x minute volume
16
Q
Where are the APL Valve and Fresh gas inlet located in the Mapleson C Circuit?
A
- APL and FGF located near the patient
17
Q
Mapleson C is identical to Mapleson B except for what specific difference?
A
- Omission of the corrugated tubing
18
Q
How much FGF is needed for the Mapleson C circuit to prevent rebreathing?
A
- FGF needs to be 2x minute volume to maintain efficiency
19
Q
When are Mapleson’s C circuits usually used?
A
- Emergency resuscitation
20
Q
Where are the APL Valve and Fresh gas inlet located in the Mapleson D Circuit?
A
- APL valve is located near the reservoir bag
- FGF inlet is located near the patient
21
Q
Which circuits are known to have “T-modifications” or are known as the “T-group”?
A
- Mapleson D
- Mapleson E
- Mapleson F
22
Q
Which circuit is the MOST efficient for controlled ventilation?
A
- Mapleson D
23
Q
What kind of valve can be added to Mapleson D circuits?
A
- PEEP Valve
24
Q
FGF rate should be _______ times minute ventilation in Mapleson D circuits.
A
- 2 to 2.5 times
25
What circuit is a modification of Mapleson D?
What is modified?
* Bain Circuit
* Fresh gas flows through a narrow inner tube (coaxial) nested within the outer corrugated tube.
* The central fresh gas tubing enters the corrugated hose near the reservoir bag, but the fresh gas actually empties into the circuit at the patient’s end. Exhaled gases pass down the corrugated hose, around the central tubing, and are vented through the pop-off valve near the reservoir bag.
* Exhaled gases passing down the outer corrugated hose add warmth to the inspired fresh gases by countercurrent heat exchange.
26
What is another name for Mapleson E?
* Arye's T-piece
27
What is missing in the Mapleson E circuit?
* No reservoir bag
* No APL valve
28
Where does FGF enter the Mapleson E circuit?
* Near the patient
29
What forms the reservoir if there is no Reservoir Bag on the Mapleson E circuit?
* Corrugated Tubing
30
What patient population is the Mapleson E circuit designated for?
* Spontaneous breathing pediatric patients to deliver O2
* Age: Less than 5 years
* Weight: Less than 20 kg
31
How would you increase the pressure of the Mapleson E circuit without an APL valve?
* Occluding the end of the corrugated tubing
32
What is the other name for the Mapleson F circuit?
* The Jackson Rees Circuit
33
What is missing in the Mapleson F circuit?
* No APL Valve
34
Where is the FGF inlet on the Mapleson F circuit?
Where is the Reservoir Bag on the Mapleson F Circuit?
Is there anything special about the Reservoir Bag on the Mapleson F Circuit.
* FGF inlet near patient
* Reservoir Bag on the operator side
* Reservoir Bag is open
35
How can pressure be generated in the Mapleson F Circuit?
* The reservoir bag hole may be occluded by the operator’s hand to control bag distension and pressure or fitted with a pop-off or PEEP valve for more precise control.
36
What does the reservoir bag on the Mapleson F circuit allow?
* Allow for easy tactile and visual monitoring of the patient’s respiratory effort.
37
What is the FGF rate for the Mapleson F circuit?
* 2-2.5 x minute ventilation
38
Improved rebreathing efficiency is due to what factor?
* Location of the pop-off valve relative to FGF
*FGF located near patients will experience less rebreathing.*
39
Which Mapleson Circuits will experience significant amounts of fresh gas vented through pop-off at end-expiration?
* Mapleson B
* Mapleson C
40
Which systems have FGF drives that drive exhaled alveolar gas away from pt
* Mapleson D
* Mapleson E
* Mapleson F
41
Rank the groupings of the Mapleson Circuit in efficiency for spontaneous ventilation.
* Mapleson A
* Maplesons DFE
* Maplesons CB
42
Rank the groupings of the Mapleson Circuit in efficiency for controlled ventilation.
* Maplesons DFE
* Maplesons BC
* Mapleson A
43
What are the advantages of the Mapleson Circuit?
* Simple, inexpensive, and lightweight
* Changes in FGF composition result in rapid changes in the circuit
* Low resistance to gas flow
* No toxic products d/t lack of CO2 absorbent
* No degradation w/ VAs
44
What are the disadvantages of the Mapleson Circuit?
* Require high FGF (can be wasteful)
* Conservation of heat and humidity less efficient
* Scavenging challenging (Except Mapleson D)
* Not suitable for patients with MH (May not be possible to increase FGF to remove excess CO2)
45
Circle System: Spontaneous Inspiration
(Allows for circular and unidirectional flow)
46
Circle System: Spontaneous Expiration
47
During what respiratory cycle phase will the CO2 absorber experience the highest potential of drying out?
* End of expiratory cycle d/t the fresh gas flow traveling retrograde because the inspiratory valve is closed.
48
For the Circle System, the extent of rebreathing and conservation of exhaled gases depends on _______.
* FGF
* Higher FGF = less rebreathing but greater amount of gas wasted
49
Rules to prevent rebreathing:
* Unidirectional valve must be located between the pt and the reservoir bag on both the inspiratory and expiratory limbs
* The fresh gas inflow cannot enter the circuit between the expiratory valve and the pt
* APL valve cannot be located between the pt and the inspiratory valve (You will lose FGF)
50
What kind of circle systems are seen with contemporary/ modern systems?
Will there be rebreathing that occurs?
* Semi-closed circle system
* Partial rebreathing occurs, but some waste flow is vented through APL or waste gas valve of the ventilator
51
What is an example of a semi-closed circle system?
* Low-flow anesthesia
* FGF is less than minute ventilation
52
What percentage of expired gas is rebreathed after CO2 removal during low-flow anesthesia?
* 50%
53
What kind of circle systems are considered non-rebreathing?
* Semi-open Circle System
* Higher FGF with minimal rebreathing and more venting of waste gas
54
What is an example of a semi-open circle system?
* Post-Op and ICU vents
* Scuba gear
* Mapleson Circuits
55
In what Circle System will the oxygen inflow rate exactly match the metabolic demand?
* Closed Circle System
* Rebreathing is complete; no waste gas is vented
* Volatiles are added to the circuit in liquid form in precise amounts or through the vaporizer
56
Example of a closed circle system.
* Low- and minimal-flow anesthesia
* Impractical for use – rarely done
57
Advantages of Low-Flow Anesthesia
* Decreased use of volatiles
* Improved temperature and humidity control
* Reduced environmental pollution
58
Disadvantages of Low-Flow Anesthesia
* Difficulty rapidly adjusting the anesthetic depth
* Possibility of accumulating unwanted exhaled gases ( ex: CO, acetone, methane)
* VA degradation by-products (ex: CO, compound A)
59
Advantages of Circle System
* Low FGF can be used
* Elimination of CO2
* Relatively stable inspired gas concentration
* Conservation of moisture/heat/gases
* Prevention of OR pollution
60
Disadvantages of Circle System
* Complex design
* CO or compound A
* May compromise Vt during controlled ventilation
* ASA Closed Claims Project (Misconnections/ disconnections)
61
Components of the Self-Inflating Manual Resuscitators (AMBU bags)
* Self-expanding Bag
* T-shaped non-rebreathing Valve
* Bag Inlet Valve
* Pop-off valve
* Excess oxygen venting valve
* Oxygen reservoir
62
Use of Self-Inflating Manual Resuscitators
* Hand ventilation in the absence of an oxygen or air source
* Pt transport
* CPR
* Emergency back-up
63
Hazards of Self-Inflating Manual Resuscitators
* Barotrauma or gastric insufflation
* Significant variation of tidal volume, PIP, and PEEP
* Nonrebreathing valves generate resistance
64
What is the purpose of bacteria filters?
* Routine use to prevent contamination or infection by airborne diseases (TB, COVID, PUI)
* Effective at preventing contamination of anesthesia machine from airborne diseases
65
Where are bacteria filters placed on the breathing circuit?
* Placed on the expiratory limb
66
Bacteria Filters:
Due to the small-pore compact matrix, there will be ________ airflow resistance.
The small-pore compact matrix is also pleated to create a larger ________.
* high
* surface area
67
Hydrophobic Bacterial Filters will prevent _____.
* water penetration
68
When the Hydrophobic Bacterial Filters become wet, it will increase ________ and decrease __________.
* Increase resistance
* Decrease efficiency
69
Where are combination filters (filter + HME) placed in the breathing circuit?
* Placed at the Y-piece
*This will cause a barrier to the inspiratory and expiratory limb, increasing resistance.*
70
Complication of Bacterial Filters.
*. Obstruction (Sputum, edema fluid, nebulized aerosols, or malpositioning)
* Leakage of the housing of the gas line filter (best to monitor ETCO2 before the filter)
71
When is an inspiratory limb filter recommended?
* When machine may be been contaminated by the previous patient
## Footnote
Expiratory limb filter recommended for ALL patients.
72
Humidity
* Amount of water vapor in a gas
73
Absolute humidity
* Mass of water vapor present in gas in mg H2O/L of gas
* 34-38 mg of H2O/ L gas in mid trachea
74
Relative Humidity
* Percent saturation; the amount of water vapor at a particular temp
75
Water Vapor Pressure
The pressure exerted by water vapor in a gas mixture.
76
Maximal contact of inspired gas occurs with the large mucosal surface area in the _______.
* Nasal Cavity
77
Most of the heating and humidification of inspired gas has occurred by _______.
* Mid-trachea
78
What are the effects of cold ambient temperatures regarding humidification in the airway?
* Little capacity to hold water vapor
* Low absolute humidity
* Upper airway transfers large amounts of heat and moisture
79
What are the effects of warm ambient temperatures regarding humidification in the airway?
* Little heat energy is expended to warm inspired gases
80
Cool inspired gases may trigger _________.
* Bronchospasm
81
Effects of underhumidifaction.
* Damage to the respiratory tract
* Secretions thicken
* Ciliary function decreases
* Surfactant activity is impaired
* Mucosa susceptible to injury
* Body heat loss (longer cases)
* Tracheal tube obstruction (thicken secretions)
* Increases resistance and work of breathing from thickened secretions
82
Effects of overhumidifaction.
* Condensation of water in the airway
* Reduced mucosal viscosity and risk of water intoxication
* Inefficient mucociliary transport
* Airway resistance, risk of pulmonary infection, surfactant dilution, atelectasis, and V/Q mismatch
* Obstruction to sensors
83
Functions of humidification devices.
* Aim to reproduce more normal physiologic conditions in the lower respiratory tract
84
Types of humidification devices
* Heat and moisture exchanger (HME- Passive and can be modified to have a filter
* Heated humidifiers- Active
85
Functions of Heat and Moisture Exchanger (HME)
* Conserves some exhaled heat and water and returns them to the pt
* Bacterial/viral filtration and prevention of inhalation of small particles (HMEF)
86
Where is the placement of an HME?
* Placed close to the pt, between Y piece and the proximal end of ETT or LMA
87
What happens to the ETCO2 reading if the sensor is placed *AFTER* the HME?
* Low ETCO2 reading
88
What does the HME do to the resistance and dead space in the circuit?
* ↑ resistance
* ↑ dead space
89
What happens to the efficiency of the HME with a large tidal volume?
* ↓ Efficiency
90
What is a Hygroscopic HME?
* Paper or other fiber barrier coated with moisture-retaining chemicals
* May have some electrostatic properties
* Absorb water in exhalation and release it in inspiration
91
What is Hygroscopic HME most efficient at?
* Most efficient at retaining heat and moisture
92
What is the drawback of Hygroscopic HME?
* Prone to becoming saturated
* Increased inspiratory/expiratory resistance
* Reduced heat and moisture retention efficiency
93
What is a Hydrophobic HME?
What is a Hydrophobic HME efficient at?
* Pleated hydrophobic membrane with small pores
* More efficient filters of pathogens
94
Devices used to increase the humidity in O2 supplied to pts
* Humidifiers
95
Who will benefit from humidifiers?
* Neonates
* Pts with respiratory secretions
* Hypothermic pts
96
What are the different ways a humidifier can pass a stream of gas?
* Bubble or cascade
* Pass-over
* Counter-flow
* Inline
97
Where are the humidifiers placed in the breathing circuit?
* Placed in the inspiratory limb downstream of the unidirectional valve
* Heated humidifiers should not be placed in the expiratory limb
98
Describe the Bubble/Cascade humidifier.
* Bubble humidifiers are a type of active humidifier that work by passing the fresh gas flow down a tube through a water reservoir causing the gas to “bubble.” Water vapor is absorbed as the bubbles pass through the reservoir
99
Describe the Passover humidifier.
What are the two varients of this humidifier?
* Passover humidifiers work by passing gas over a heated water reservoir.
* There are two variants: one that utilizes a wick and one that utilizes a hydrophobic membrane.
100
Describe the Counter-flow humidifier.
* Water is heated outside the vaporizer in counter-flow humidifiers.
* After the water is heated, it is pumped to the top of the humidifier, entering small diameter pores and running down a large surface area.
* Gas, flowing in the opposite direction, is warmed and humidified to body temperature.
101
Describe the inline vaporizer humidifier.
* Inline vaporizer humidifiers utilize a plastic capsule that injects water vapor and heat directly into the inspiratory limb of the ventilator circuit just before the patient's y-piece.
102
Most unheated humidifiers are disposable that use the bubble-through humidifier that increases the humidity in oxygen supplied to patients via a face mask or nasal cannula. They cannot deliver more than about ______ mg H2O/L.
* 9 mg H2O/L
103
Condensation has what effect on tidal volume?
* Decrease Vt
104
Consideration for water traps.
* Change frequently to decrease the risk of contamination and infection
105
Advantages of Humidifiers
* Can deliver saturated gas at body temp or higher
* More effective than HME in longer cases in preventing hypothermia
106
Disadvantages of Humidifiers
* Bulky
* Potential electrical malfunction and/or thermal injury
* Contamination, and cleaning issues
* Higher cost than HME
* Water aspiration risk
