E2- Breathing Systems II Flashcards
What is a Mapleson Circuit?
- The Mapleson Circuit Systems are used for the delivery of oxygen and anesthetic agents and the removal of carbon dioxide
How many types of Mapleson Circuits are there? Mneumonic?
- Six Types (A → F)
What are the components of the Mapleson Circuit?
- Patient connection/Facemask - Patient end
- Reservoir bag - operator end
- Corrugated tubing
- APL valve - variable positioning
- Fresh gas inlet - variable positioning
What 3 components are absent in all Mapleson Circuit Systems?
- CO2 absorber
- Unidirectional Valves
- Separate Inspiratory and Expiratory Limbs
What are 2 other names for the Mapleson Circuit Systems?
- Carbon Dioxide Washout Circuits
- Flow-controlled Breathing Systems
How does the Mapleson Circuit System prevent rebreathing without a CO2 absorber?
- FGF must be significantly greater than minute ventilation to “washout” the CO2.
What is another name for Mapleson A?
- Magill’s System
Where does fresh gas flow enter in the Mapleson A circuit?
Where is the APL valve located in the Mapleson A circuit?
- FGF = near reservoir bag
- APL valve = patient end
Of all the systems, what is Mapleson A best at?
What is Mapleson A the worst at?
- Best efficiency of all systems for spontaneous ventilation
- Worst efficiency of systems for controlled ventilation
Mapleson A
Spontaneous :: prevent rebreathing?
Controlled ventilation : rebreathing occurs unless Vm greater than ______ ?
FGF must be greater than or equal to Vm
20 L/min
Mapleson A Circuit:
What is vented out from the APL valve in spontaneous ventilation during expiration?
- Dead space gas (yellow)
- Alveolar gas (red)
Mapleson A Circuit:
What is vented out from the APL valve in controlled ventilation during expiration?
- APL valve does not open
Mapleson A Circuit:
What is vented out from the APL valve in controlled ventilation during inspiration?
- Mostly fresh gas (blue)
- Some alveolar gas (red)
- Increase the risk of rebreathing alveolar gas (red)
Where are the APL Valve and Fresh gas inlet located in the Mapleson B Circuit?
Where is the reservoir bag?
- APL and FG inlet located near the patient
- Reservoir bag = end of system
Why is the Mapleson B Circuit considered inefficient and obsolete?
- FGF is vented through APL during exhalation = Inefficient
- Blue (FGF)
- Red (alveolar gas)
FGF should be ______ times the minute volume during spontaneous and controlled ventilation to prevent rebreathing in the Mapleson B circuit.
- FGF should be 2x minute volume
Where are the APL Valve and Fresh gas inlet located in the Mapleson C Circuit?
- APL and FGF located near patient
Mapleson C is identical to Mapleson B except for what specific difference?
- Omission of the corrugated tubing
Mapleson C is almost as efficient as ____ .
What is it based on?
A
based on expiratoy pause (longer pause = less efficient)
bc losing to atmosphere
How much FGF is needed for the Mapleson C circuit to prevent rebreathing?
- FGF 2x minute volume to maintain efficiency
When are Mapleson’s C circuits usually used?
- EmergenCy resuscitation
Where are the APL Valve and Fresh gas inlet located in the Mapleson D Circuit?
- APL valve= near reservoir bag
- FGF inlet = near patient
Which circuits are known to have “T-modifications” or are known as the “T-group”?
What makes up 3 way T-Piece?
- Mapleson D
- Mapleson E
- Mapleson F
- pt connection ,, fresh gas inlet ,, corrugated tubing
Which circuit is the MOST efficient for controlled ventilation?
- Mapleson D
What kind of valve can be added to Mapleson D circuits?
- PEEP Valve
FGF rate should be _______ times minute ventilation in Mapleson D circuits.
- 2 to 2.5 times
What circuit is a modification of Mapleson D?
What is modified?
- Bain Circuit
- Fresh gas inlet through a narrow inner tube (coaxial)
- Disconnection / kinking = problem if don’t realize it
What is another name for Mapleson E?
- AryE’s T-piece
What is missing in the Mapleson E circuit?
- No reservoir bag
- No APL valve
Where does FGF enter the Mapleson E circuit?
- Near the patient
What forms the reservoir if there is no Reservoir Bag on the Mapleson E circuit?
- Corrugated Tubing
What 3 patients is the Mapleson E circuit designated for?
- Spontaneous breathing patients to deliver O2
- Pediatrics - bc decreased resistance d/t no APL
- transport from OR
How would you increase the pressure of the Mapleson E circuit without an APL valve?
- Occluding / pinching end of corrugated tubing
Mapleson F is a modified mapleson __.
What is the modification for the Mapleson F circuit called + what is it adding?
- E
- Jackson Reese Modification
- Resorvoir bag added
Guys named Jackson + Reese think they’re Funny
What is missing in the Mapleson F circuit?
- No APL Valve
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 = operator side
- Reservoir Bag is open (hole)
How can pressure be generated in the Mapleson F Circuit?
- reservoir bag hole occluded by operator’s hand to control bag distension + pressure
What does the reservoir bag on the Mapleson F circuit allow?
- Allow for easy tactile and visual monitoring of the patient’s respiratory effort.
What is the FGF rate for the Mapleson F circuit?
- 2-2.5 x minute ventilation
Improved rebreathing efficiency is due to what factor?
- Location of APL valve relative to FGF
FGF located near patients will experience less rebreathing.
Which Mapleson Circuits will experience significant amounts of fresh gas vented through APL at end-expiration?
- Mapleson B
- Mapleson C
Which systems have FGF drives that drive exhaled alveolar gas away from pt?
- Mapleson D
- Mapleson E
- Mapleson F
Rank the groupings of the Mapleson Circuit in efficiency for spontaneous ventilation.
Mapleson A > DFE > CB
Rank the groupings of the Mapleson Circuit in efficiency for controlled ventilation.
Mapleson DFE > BC > A
What are the 5 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
What are the 4 disadvantages of the Mapleson Circuit?
- Require high FGF (can be wasteful + have full O2 tank)
- Conservation of heat + 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)
Circle System: Spontaneous Inspiration
(Allows for circular and unidirectional flow)
Ventilator ???
Ventilator NOT ON !! Bc spontaneous
Circle System: Spontaneous Expiration
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.
For the Circle System, the extent of rebreathing and conservation of exhaled gases depends on _______.
- FGF
- Higher FGF = less rebreathing + greater waste gas
3 Rules to prevent rebreathing:
- Unidirectional valve = must be located between pt + reservoir bag on both the inspiratory + expiratory limbs
- fresh gas inflow= CANNOT enter circuit between expiratory valve and pt
- APL valve= CANNOT be located between the pt and the inspiratory valve (You will lose FGF)
What kind of circle systems are seen with contemporary/modern systems?
Will there be rebreathing that occurs?
Wast flow vented through?
- Semi-closed circle system
- Partial rebreathing occurs
- some waste flow is vented through APL or waste gas valve of the ventilator
What is an example of a semi-closed circle system?
- Low-flow anesthesia (what we do)
- FGF < Vm
What percentage of expired gas is rebreathed after CO2 removal during low-flow anesthesia?
- 50%
What kind of circle systems are considered non-rebreathing? Why?
- Semi-open Circle System
- Higher FGF = minimal rebreathing + more venting of waste gas
What is an example of a semi-open circle system?
- Post-Op + ICU vents
- Scuba gear
- *Mapleson Circuits**
In what Circle System will the oxygen inflow rate exactly match the metabolic demand? Rebreathing is ________ .
What is added to circuit in liquid form ?
- Closed Circle System
- Rebreathing is complete; no waste gas vented
- Volatiles = circuit in liquid form or through vaporizer
Example of a closed circle system.
- Low- and minimal-flow anesthesia
- Impractical for use – rarely done
- OBSOLETE
3 Advantages of Low-Flow Anesthesia
- Decreased use of volatiles
- Improved temperature + humidity control
- Reduced environmental pollution
3 Disadvantages of Low-Flow Anesthesia
- Difficulty rapidly adjusting the anesthetic depth (why we overpressurize)
- Possibility of accumulating unwanted exhaled gases ( ex: CO, acetone, methane)
- VA degradation by-products (ex: CO, compound A)
5 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
4 Disadvantages of Circle System
- Complex design
- CO or compound A
- May compromise Vt during controlled ventilation **
- **ASA Closed Claims Project **(Misconnections/ disconnections) **
6 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
Use of Self-Inflating Manual Resuscitators
- Hand ventilation in absence of oxygen / air source
- Pt transport
- CPR
- Emergency back-up
- ALWAYS have set up with machine
4 Hazards of Self-Inflating Manual Resuscitators
- Barotrauma
- gastric insufflation
- Significant variation of :: Vt, PIP, + PEEP
- Nonrebreathing valves = generate resistance
What is the purpose of bacteria filters? What 3 diseases
- prevent contamination / infection by airborne diseases
- TB, COVID, PUI
- preventing contamination of anesthesia machine from airborne diseases
Where are bacteria filters placed on the breathing circuit?
***** Placed on the expiratory limb
Bacteria Filters - Small-pore
Due to the small-pore compact matrix, there will be ________ airflow resistance.
The small-pore compact matrix is also _______ to create a larger ________.
- high
*pleated – surface area
Bacterial Filters
Larger Pore size = _____ resistance + ______ surface areas (compared to small pore)
Less ,, smaller
Bacterial filters = permanent electrical _____
polarity
Hydrophobic Bacterial Filters will prevent _____.
- water penetration
When the Hydrophobic Bacterial Filters become wet, it will increase ________ and decrease __________.
- Increase resistance
- Decrease efficiency
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.
2 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)
When is an inspiratory limb filter recommended? Airway filter?
- When machine may be been **contaminated by previous **patient
- Airway = **COVID + PUI **pts
- Expiratory limb = preferred for ALL
Expiratory limb filter recommended for ALL patients.
Humidity
- Amount of water vapor in a gas
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
Relative Humidity
- Percent saturation; the amount of water vapor at a particular temp
Water Vapor Pressure
The pressure exerted by water vapor in a gas mixture.
Maximal contact of inspired gas occurs with the large mucosal surface area in the _______.
- Nasal Cavity
Most of heating and humidification of inspired gas has occurred by _______.
At ___ degrees with absolute humidity of __________ + a relative humidity of _______%
- Mid-trachea
- 34 degrees – 34-38 mg/L – 95-100%
Where is the Isothermic Saturation Boundry ? What 3 things does it depend on?
- at carina
- vol gas inhaled ,, humidity ,, temp
- As gas travels _____ it is heated to body temperature.
- At 37 degrees = Absolute humidity of ___ mg/L + relative humidity of ____%
- distally
- 44 mg/L + 100%
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
Cool inspired gases may trigger _________.
- Bronchospasm
8 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
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 - ETCO2 sample line obstruction
Functions of humidification devices.
reproduce normal physiologic conditions in lower respiratory tract
Types of humidification devices
- Heat and moisture exchanger (HME- Passive and can be modified to have a filter
- Heated humidifiers- Active
Functions of Heat and Moisture Exchanger (HME)
- Conserves some exhaled heat and water + returns to pt
- Bacterial/viral filtration and prevention of inhalation of small particles (HMEF)
Where is the placement of an HME?
- Placed close to the pt, between Y piece and proximal end of ETT or LMA
What happens to the ETCO2 reading if the sensor is placed AFTER the HME?
- Low ETCO2 reading
What does the HME do to the resistance and dead space in the circuit?
- ↑ resistance
- ↑ dead space
What happens to the efficiency of the HME with a large tidal volume?
- ↓ Efficiency
- Hydrophobic models
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
What is Hygroscopic HME most efficient at?
- Most efficient at retaining heat and moisture
What is the drawback of Hygroscopic HME?
- Prone to becoming saturated
- Increased inspiratory/expiratory resistance
- Reduced heat and moisture retention efficiency
What is a Hydrophobic HME?
What is a Hydrophobic HME efficient at?
- Pleated hydrophobic membrane with small pores
- More efficient filters of pathogens
Devices used to increase the humidity in O2 supplied to pts
- Humidifiers
Who will benefit from humidifiers? 3
- Neonates
- Pts with respiratory secretions
- Hypothermic pts
What are the different ways a humidifier can pass a stream of gas?
- Bubble or cascade
- Pass-over
- Counter-flow
- Inline
Where are the humidifiers placed in the breathing circuit? Heated humidifer placed?
- Placed in the inspiratory limb downstream of unidirectional valve
- Heated humidifiers = NOT in expiratory limb
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
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.
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.
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.
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
Condensation has what effect on tidal volume?
- Decrease delivered Vt
Consideration for water traps.
- Change frequently to decrease the risk of contamination and infection
Advantages of Humidifiers
- Can deliver saturated gas at body temp or higher
- More effective than HME in longer cases in preventing hypothermia
Disadvantages of Humidifiers
- Bulky
- Potential electrical malfunction and/or thermal injury
- Contamination, and cleaning issues
- Higher cost than HME
* Water aspiration risk
