Exam 2 Breathing Systems: Part 2 (6/24/24) Flashcards by Monterrio Jones

Why are Mapleson Circuits thought to be mostly obsolete?

They do not have a CO2 absorber

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Components of Mapleson Circuits:

Reservoir Bag (Not all of them)
Corrugated Tubing (Not all of them)
APL Valve (Not all of them)
Fresh Gas Inlet
Patient Connection

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What is missing in the Mapleson Circuits?

CO2 Absorbers
Unidirectional valves
Seperate inspiratory/expiratory limbs

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What determines how much rebreathing occurs in the Mapleson Circuits?

Fresh Gas Flow

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How would we know if CO2 is being rebreathed while using a Mapleson Circuit?

Monitor ETCO2

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Location of FGF entrance and APL valve in a Mapleson A (Magill’s System)?

FGF enters near reservoir bag (opposite of the pt.)

APL is near the pt.

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In regard to efficiency, what kind of ventilation is the Mapleson A circuit the best and worst at?

Best: Spontaneous
Worst: Controlled

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Rebreathing will occur while using a Mapleson A during controlled ventilation unless the FGF is greater than ___.

> 20 L/min

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Location of APL valve, FGF inlet and reservoir bag in a Mapleson B?

APL and FGF inlet are near pt
Reservoir Bag is at the end of the system

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The Mapleson C is almost identical to the Mapleson B, but the ____ is omitted.

Corrugated Tubing

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Compare the efficiency of the Mapleson C to Mapleson A with spontaneous ventilation:
How does the expiratory pause change the efficiency?

Mapleson C is almost as efficient as Mapleson A.

If expiratory pause is longer, this circuit becomes less efficient

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The Mapleson C closely resembles a ___.

Ambu Bag

Used for emergency resuscitation

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Location of the Reservoir Bag, APL and FGF inlet in a Mapleson D?

Reservoir at the end
APL near reservoir
FGF inlet near pt.

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This Mapleson circuit does not have a reservoir bag or an APL valve:

Mapleson E (Ayre’s T-Piece)

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The Mapleson E circuit is preferred in this population:
Why?

Preferred in Pediatrics:
There is a decreased amount of resistance

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What is the modification made to the Mapleson E that makes it a Mapleson F (Jackson Rees)?

Addition of a Reservoir bag with a hole at the end

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Select the 2 correct systems:

Significant amounts of fresh gas is vented through pop-off at end expiration :

Mapleson A
Mapleson B
Mapleson C
Mapleson D
Mapleson E
Mapleson F

Mapleson B
Mapleson C

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Select the 3 correct systems:

FGF drives exhaled alveolar gas away from pt:

Mapleson A
Mapleson B
Mapleson C
Mapleson D
Mapleson E
Mapleson F

Mapleson D
Mapleson E
Mapleson F

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Rank the efficiency of the Mapleson Circuits from Most efficient to least efficient for spontaneous ventilation:

Mapleson A
Mapleson D, F, E
Mapleson C, B

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Rank the Mapleson circuits from most efficient to least efficient for controlled ventilation:

Mapleson D, F, E
Mapleson C, B
Mapleson A

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Which Mapleson circuit is termed “Obsolete”?

Mapleson B

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This Mapleson Circuit is the most efficient system for controlled Ventilation:

Mapleson D

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This Mapleson circuit is used in spontaneously breathing pts to deliver O2:

Mapleson E

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Advantages of Mapleson Circuits:

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/ Volatiles

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A couple disadvantages to using Mapleson circuits is that they require ___ and are not suitable for patients with ___.

Require **high FGF** Not suitable for **Malignant Hyperthermia** patients

All of the Mapleson circuits have a challenge with scavenging except for ___.

Mapleson D

# Rules to prevent rebreathing in a Circle System Where must the unidirectional valves be located on both the inspiratory and expiratory limbs?

Between the patient and the reservoir bag

# Rules to prevent rebreathing in a Circle System Where must the Fresh gas flow inlet NOT enter the circuit at?

Between the patient and the **Expiratory Valve**

# Rules to prevent rebreathing in a Circle System True or False: The APL valve must be located between the pt and the inspiratory valve

False: APL valve **cannot** be located between the pt and the inspiratory valve

In a circle system these 2 things are dependent upon the Fresh Gas Flow:

The extent of rebreathing Conservation of exhaled gases

Describe the function of a circle system in a "Semi-Closed" circuit:

"Contemporary system" Partial rebreathing occurs but some waste flow is vented through APL or waste gas valve of ventilator

Example of a semi-closed circuit for a circle system: What does this mean?

Low Flow Anesthesia: * FGF is less than Minute ventilation * 50% of expired gas is rebreathed after CO2 removal

Describe the function of a circle system in a "Semi-Open" circuit:

Non-rebreathing systems Higher FGF with minimal rebreathing and more venting of waste gas

Examples of semi-open circuits for a circle system:

* Post-Op/ICU Vents * Scuba Gear

Things to remember about a "Closed" circle system:

* Use of Low/minimal Flows * Complete rebreathing * No waste gas is vented out * Obsolete * Rate of oxygen inflow matches patient'e metabolic demand

Advantages to low flow anesthesia:

* Decreased use of VAs * Improved temperature and humidity control * Reduced environmental pollution

Disadvantages to low flow anesthesia:

* Difficulty in rapidly adjusting anesthetic depth * Possibility of accumulating unwanted exhaled gases ( ex: CO, acetone, methane) * VA degradation by-products (ex: CO, compound A)

Advantages of Circle Systems:

* Low FGF can be used * Elimination of CO2 * Relatively stable inspired gas concentration * Conservation of moisture/heat/gases * Prevention of OR pollution

Disadvantages of Circle Systems:

* Complex design * CO or compound A * May compromise Vt during controlled ventilation * ASA Closed Claims Project

The number 1 problem (according to the ASA Closed claims project) associated with use of a circle system had to do with ___.

Misconnections or disconnections

Components of Self-Inflating Manual Resuscitators or "Ambu-bags":

* Self-expanding Bag * T-shaped non-rebreathing Valve * Bag Inlet Valve * Pop-off valve * Excess oxygen venting valve * Oxygen reservoir

Important uses of Self-Inflating Manual Resuscitators:

* CPR * Transport * Hand ventilation in the absence of an oxygen or air source * Emergency Back-Up

Hazards associated with the use of Self-Inflating Manual Resuscitators:

* Barotrauma or gastric insufflation * Significant variation of tidal volume, PIP, and PEEP * Nonrebreathing valves generate resistance

Bacterial Filters are effective at preventing what? Where should they be placed?

Effective at preventing contamination of the anesthesia machine from airborne diseases (TB, Covid, PUI) Placed on the Expiratory Limb

What does PUI stand for?

Person Under Investigation

Different types of Bacterial Filters discussed in lecture:

* Small-pore compact Matrix * Less dense, larger pore arrangement * Hydrophobic * Combination (Filter + HME)

Describe the small-pore compact matrix:

* High Airflow resistance * **Pleated** = creates a larger surface area

Compared to the small-pore compact matrix the larger, less dense pore arrangement has _____ and ____.

Less resistance & Smaller surface area

Hydrophobic Bacterial Filters prevent___. They have _____ resistance and _____ efficiency.

Prevent **water penetration** **Increased** Resistance **Decreased** efficiency

Where should the Combination bacterial filter be placed?

At the Y-Piece

What is one thing that can happen that would decrease the efficiency and increase the resistance in any and all of these bacterial filters?

Accumulation/condensation of water, secretions, blood or any liquid.

4 ways in which obstruction of a bacterial filter can occur?

1. Sputum 2. Edema Fluid 3. Nebulized aerosols 4. Malpositioning

Per the APSF recommendations, what is the best location for the bacterial filters to be placed?

The Expiratory Limb

What is the ONLY time that placement of the bacterial filter on the inspiratory limb is warranted?

Only recommended when the machine may have been contaminated by a previous patient.

For Covid positive patients or PUI patient's placement of an ____ is recommended, but is optional for all others.

Airway Filter

# Definitions: Amount of water vapor in a gas:

Humidity

# Definitions Mass of water vapor present in gas in mg H2O/L of gas:

Absolute Humidity

# Definitions Percent saturation; amount of water vapor at a particular temp:

Relative Humidity

# Definitions Pressure exerted by water vapor in a gas mixture:

Water Vapor Pressure

Usually, by this point heating and humidification has occurred.

Mid-Trachea

A temperature of 34 degrees C, with an absolute humidity of 34-38 mg/L corresponds to what relative humidity?

95%-100% relative humidity

An absolute humidity of ___ corresponds to 100% relative humidity. At what degree C does this also correspond to? What is this called?

44 mg/L 37 degrees C Isothermic Saturation Boundary

At what anatomical landmark is 100% relative humidity reached?

At the carina

What can cool inspired gas possibly trigger?

Bronchospasm

# Under-humidification or over-humidification? Risk of Water intoxication: Mucosa susceptible to injury: Body Heat Loss: Tracheal Tube obstruction: Risk of Pulmonary infection: Damage to Respiratory Tract: Atelectasis: V/Q Mismatch: Reduced Mucosal Viscosity:

Risk of Water intoxication: **Over-humidification** Mucosa susceptible to injury: **Under-humidification** Body Heat Loss: **Under-humidification** Tracheal Tube obstruction: **Under-humidification** Risk of Pulmonary infection: **Over-humidification** Damage to Respiratory Tract: **Under-humidification** Atelectasis: **Over-humidification** V/Q Mismatch: **Over-humidification** Reduced Mucosal Viscosity: **Over-humidification**

What specific respiratory tract issues/damages can arise with under-humidified inspired gas?

* Thick Secretions * Decreased Ciliary Function * Impaired surfactant activity * Mucosa is susceptible to injury

Over-humidification is caused by ____ in the airway.

Condensation of Water

What do humidification devices aim to do?

To reproduce more normal physiologic conditions in the lower respiratory tract

Functions of an HME:

* Conserves some exhaled heat and water and returns them to the pt * Bacterial/viral filtration and prevention of inhalation of small particles (HMEF)

Location of the HME:

Placed close to the pt, between Y piece and proximal end of ETT or LMA

Disadvantages to HME use:

* Low ETCO2 reading * Increases resistance and dead space in circuit * Efficiency may be reduced with large Vt

This type of HME absorbs water in exhalation and release it in inspiration:

Hygroscopic

This type of HME has a pleated hydrophobic membrane with small pores:

Hydrophobic

This type of HME is a more efficient filter of pathogens

Hydrophobic

This type of HME is the most efficient at retaining heat and moisture.

Hygroscopic

In which patient populations are the use of humidifiers important?

Neonates, pts with difficult respiratory secretions, or hypothermic pts.

Various Ways in which humidifiers can pass a stream of gas:

* Bubble or cascade * Pass-over * Counter-flow * Inline

Where should humidifiers be placed? Where should they definitely NOT be placed?

Placed in inspiratory limb downstream of unidirectional valve Heated humidifiers **should not** be placed in expiratory limb

Condensation in the humidifier can decrease ___?

Delivered Tidal Volume

These need to be changed frequently on humidifiers to decrease risk of contamination and infection.

Water Traps

Which is more effective? Humidifier or HME

Humidifier is more effective than HME

Disadvantages to Humidifier use:

* Bulky * Potential electrical malfunction and/or thermal injury * Contamination, cleaning issues * Higher cost than HME * Water aspiration risk