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Principles of Anesthesia I - Summer 24 > Exam 2 - Breathing Circuits II (Ericksen) > Flashcards

Exam 2 - Breathing Circuits II (Ericksen) Flashcards

1
Q

What are the components of the Mapleson Circuit?

A
  1. reservoir bag
  2. corrugated tubing
    not every mapleson has a reservoir bag/corrugated tubing
  3. APL Valve
  4. Fresh gas inlet
  5. patient connection
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2
Q

What 3 things are missing in the Mapleson Circuit?

A
  1. CO2 absorber
  2. unidirectional valves
  3. separate inspiratory/expiratory limbs
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3
Q

What else are Mapleson Circuits called?

A
  • carbon dioxide washout circuits
  • flow-controlled breathing systems
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4
Q

Mapleson Circuits

What happens when there are not any unidirectional valves in the circuit?

A
  • mixing of FGF, DS gas, alveolar gas
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5
Q

What determines how the gas will be vented out w/ mapleson circuits?

A

APL Valve location
* gas is vented out during inspiration or expiration
* based on amount of FGF

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6
Q

What is the “big concept” we need to know w/ Mapleson Circuits?

A
  • which ones are efficient w/ spontaneous respiration or controlled respirations
  • things that affect this:
    – FGF high/low/intermediate
    – how much is being vented through APL
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7
Q

Mapleson Circuits

What determines how much rebreathing occurs w/ Maplesons? Why?

A
  • FGF determines how much rebreathing occurs
  • no clear separation b/w inspired & expired limbs
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8
Q

Mapleson Circuits

Where does CO2 go in Mapleson Circuits?

A
  • either vented through APL valve
  • or goes to atmosphere
  • these are not super efficient
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9
Q

Mapleson Circuits

How can we make sure CO2 is being vented out properly (and not rebreathed)?

A
  • monitor ETCO2 - can’t rely on looking @ absorber
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10
Q

What is the other name for a Mapleson A Circuit?

A

Magill’s System

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11
Q

Mapleson A

Where does FGF enter?

Where is the APL valve?

A
  • FGF enters near the reservoir bag (opposite the pt)
  • APL is near pt
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12
Q

What is the Mapleson A circuit the best for?

Worst for?

A
  • best: spontaneous ventilation
  • worst: controlled ventilation
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13
Q

With the Mapleson A circuit, how can we prevent rebreathing during spontaneous ventilation?

A
  • the FGF must be > or = the Vm to prevent rebreathing
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14
Q

With the Mapleson A, when does rebreating occur during controlled ventilation?

A
  • all the time
  • unless minute ventilation is very high (>20L/min)
  • this is wasteful b/f FGF has to be > 20L/min
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15
Q

What are the mechanics of gas flow in a Mapleson A w/ spontaneous ventilation?

A
  • End-expiration: alveolar & DS gas gets vented through APL valve
  • Inspiration: pt gets a little mixture of DS/alveolar & FGF
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16
Q

What are the mechanisms of gas flow in a Mapleson A with controlled ventilation?

A

end-expiration:
* less DS gas - more alveolar gas
inspiration:
* FGF vented out through APL valve before it goes to pt
* pt gets more DS & alveolar gas
* Need high FGF (>20L/min) to prevent rebreathing - it creates more intrinsic pressure (goes through the APL)
* wasteful in controlled respirations

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17
Q

What is a modification to the Mapleson A circuit?

A

Lack modification
* coaxial tube in it

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18
Q

Mapleson B

Where is the FGF & APL valve?

A
  • both near the pt
  • as soon as pt breathes out as FGF is flowing in - it flows up through APL valve
  • this setup is obsolete
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19
Q

Mapleson B

Where is the reservoir bag?

A
  • at the end of the system
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20
Q

Mapleson B

What happens to the FGF coming in?

A
  • it is vented through the APL on exhalation - inefficent
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21
Q

How can rebreathing be prevented w/ a Mapleson B circuit?

A
  • FGF should be 2x minute volume during spontaneous & controlled ventilation
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22
Q

What are the mechanisms of gas flow in a Mapleson B circuit?

A
  • FGF comes in and follows path of least resistance (goes out APL)
  • pt only gets a little FGF
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23
Q

What is a Mapleson C circuit similar to?

A
  • similar to Ambu bag
  • identical to mapleson B (except corrugated tubing ommited)
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24
Q

Mapleson C

What is it almost as efficient as?

A
  • Mapleson A w/ spontaneous respiration
  • depends on how long the pts expiration & expiratory pause are
  • if the expiratory pause is longer - less efficient
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25
Q

What does FGF need to be w/ a Mapleson C?

A

2x minute volume

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26
Q

What is a Mapleson C used for?

A

emergency resuscitation

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27
Q

What are the mechanisms of gas flow in a Mapleson C circuit?

A
  • not losing as much FGF to the atmosphere vented through APL
  • some are vented out - more dependent on the expiratory pause to determine how much is vented out
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28
Q

What Mapleson Circuit will we see the most?

A

Mapleson D

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29
Q

What all does the Mapleson D circuit have?

A
  • 3 way T-piece
  • pt connection
  • fresh gas inlet
  • corrugated tubing
  • PEEP valves may be added for pressure support
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30
Q

Where is the reservoir bag, APL and FGF located on a Mapleson D?

A
  • reservoir at the end
  • APL near reservoir
  • FGF inlet near pt
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31
Q

What is the most efficient Mapleson Circuit for Controlled ventilation?

A
  • Mapleson D
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32
Q

What should the FGF be at w/ a Mapleson D circuit?

A
  • 2-2.5 x minute ventilation
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33
Q

Mapleson D

What is a Bain Modification?

A
  • contains FGF coaxial inside tubing
  • like an “inspiratory & expiratory limb”
  • orange inlet line goes to pt
  • everything exhaled goes on the outside
  • still allows mixture of DS & alveolar gas to go out toward APL valve
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34
Q

What is a disadvantage to a Bain Modification on a Mapleson D circuit?

A
  • could have a disconnect inside the tubing or kinking of inner hose
  • watch for this!!
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35
Q

What are the mechanisms of gas flow in a Mapleson D circuit during spontaneous ventilation?

A
  • APL open
  • pt gets alveolar & FGF
  • through APL - some alveolar gas vented
  • Depending on how much FGF we have - some of the DS gas may or may not get vented out of the APL valve
  • some DS gas gets caught in the reservoir bag
    – when squeezing bag - some may get to pt & some may not
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36
Q

What are the mechanisms of gas flow in a Mapleson D circuit during manual ventilation?

A
  • APL partially closed - can help vent out some of the gas by squeezing the bag during inspiration
  • some DS gas & alveolar gas can be vented out through APL
  • depends on how much FGF there is pushing toward reservoir bag & if it gets vented out
  • typically b/c the FGF is closer to the pt end - it goes toward the pt
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37
Q

Why is there less resistance in a Mapleson E (Ayre’s T-piece)?

A
  • b/c no APL valve
  • it is open to the atmosphere
  • preferred use in pediatrics
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37
Q

What are the parts of the Mapleson E (Ayre’s T-Piece)?

A
  • corrugated tubing attached to the T-piece (forms reservoir)
  • there is not a reservoir bag or APL
  • FGF located at pt end
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38
Q

What is the other name for Mapleson E circuit?

A
  • Ayre’s T-piece
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39
Q

When is a Mapleson E (Ayre’s T-piece used)?

A
  • in spontaneously breathing pts to deliver O2
  • used in pedi
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40
Q

What is the mechanism of gas flow in the Mapleson E (Ayre’s T-piece) during spontaneous respirations?

A
  • the limb is open to the atmosphere
  • allows for higher flows than just n/c
  • 10-15LPM for all maplesons
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41
Q

What type of oxygen are pts usually on when they come out of the OR?

A
  • high-flow mask
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42
Q

What is the mechanism of gas flow in the Mapleson E during manual ventilation?

A
  • can only provide controlled ventilation by pinching off the end of the tubing
  • if doing w/ a neonate - pay attention to pressure & chest rise/fall
  • cannot help the pt get a bigger and deeper breath b/c there is no reservoir bag!!
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43
Q

What is the Mapleson F (Jackson Rees)

A

modification of Mapleson E
* has a reservoir bag at the end to assist w/ ventilations

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44
Q

How much does FGF need to be when using a Mapleson F (Jackson Rees)?

A
  • 2-2.5x minute ventilation
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45
Q

Jackson Rees (Mapleson F)

Why is excessive pressure less likely to develop?

What can we do if we need to increase pressure?

A
  • No APL valve present
  • pinch off the end of the reservoir bag
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46
Q

What does having a reservoir bag on the Jackson Rees (Mapleson F) allow for?

A
  • monitoring of respirations
    – see volumes in bag increase & decrease
  • can assist breaths w/ extra pressure by pinching end off
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47
Q

When is the Mapleson F (Jackson Rees) used?

A

Pt transport & pre-oxygenation

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48
Q

What is the mechanism of gas flow in the Mapleson F circuit?

A
  • similar to Mapleson D
  • DS gas going out toward reservoir bag & out to atmosphere through the hole
  • **pts mostly get alveolar gas & FGF
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49
Q

Mapleson Efficiency

Improved rebreathing efficiency is d/t the location of the ________ relative to the ________.

A

pop-off valve;FGF

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50
Q

Mapleson Efficiency

Which Mapleson Circuits have more rebreathing?

A
  • B,C
  • high amounts of FG is vented through pop-off @ end expiration
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51
Q

Mapleson Efficiency

What Mapleson Circuits allow for less rebreathing?

A
  • D,E,F
  • FGF drives exhaled alveolar gas away from the pt
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52
Q

Mapleson Efficiency

List the order of Mapleson Circuits that are best for spontaneous ventilation in order from best to worst…

A
  1. Mapleson A
  2. Mapleson DEF
  3. Mapleson CB
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53
Q

Mapleson Efficiency

List the order of Mapleson Circuits that are best for controlled ventilation… in order of best to worst

A
  1. Mapleson DFE
  2. Mapleson BC
  3. Mapleson A
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54
Q

What are the 5 advantages of Maplesons

A
  1. simple, inexpensive, light weight
  2. changes in FGF composition result in rapid changes in the circuit
  3. low resistance to gas flow (corrugated tubing)
    * wider diameter
    * increased resistance on outer edges (corrugation)
    * decreased resistance in middle
  4. No toxic products (no CO2 absorbent)
  5. no degradation w/ VAs
55
Q

Disadvantages of Maplesons (4)

A
  1. require high FGF (need fresh O2 tank)
  2. conservation of heat & humidity less efficient (no CO2 absorber for humidity/circle system for heat)
  3. Scavenging challenging (APL close to pt end - more gases will be just be vented out)
    – not mapleson D - APL further away from pt
  4. Not suitable for pts w/ MH (can’t increase FGF high enough to remove excess CO2)
56
Q

Does the Mapleson or Circle System conserve more heat/humidity?

A
  • Circle System
57
Q

What is the order gas flow in the circle system with spontaneous respiration?

A
  1. pt inspires
  2. reservoir bag collapses
  3. gas passes vent (bypassed)
  4. gas goes down CO2 absorber to get scrubbed
  5. picks up fresh gas flow
  6. goes through open inspiratory valve
  7. to pt
58
Q

What is the order of gas flow in the circle system in a spontaneous expiration?

A
  1. pt exhales
  2. gas sample line
  3. gas goes through open expiratory valve
  4. goes down to reservoir bag
  5. if high pressure - goes out the APL valve
59
Q

Circle System Function

What does the extent of rebreathing and conservation fo exhaled gases depend on?

A

FGF
* higher FGF = less rebreathing and greater waste of gas
* we do NOT need high FGF; can get away w/ 2L/min

60
Q

Circle System Function - rules to prevent rebreathing

Where must the unidirectional valve be located?

A
  • b/w the pt & reservoir bag on both insp. & expiratory limbs
  • purpose - create circle system & ensure flow goes in correct direction
61
Q

Circle system function - rules to prevent rebreathing

Where can the FGF NOT enter the circuit?

A

b/w the expiratory valve & pt
* on inspiration when the expiratory valve is closed - the incoming fresh gas would go to the patient w/ recently expired CO2
* on expiration - the FGF would go to w/ expired gases to the reservoir bag

62
Q

circle System Function - rules to prevent rebreathing

Where can the APL valve NOT be located?

A

b/w the pt and inspiratory valve
* would be just venting off the inspiratory gases
* some FGF would be vented off
* some FGF would go to the pt
* would depend on how open/closed the valve is

63
Q

Circle System Function

What happens with a Semi-closed system?

A

contemporary systems
* partial rebreathing
* some waste gas is vented through open APL valve
* some waste gas will be vented out through the waste gas valve of the ventilator

64
Q

Circle System Function

What is an example where a semi-closed system is used?

A

low-flow anesthesia
* FGF < minute ventilation
* 50% of expired breath is rebreathed after CO2 removal

65
Q

Cicle System Function

Why do we have to have rebreathing with low-flow anesthesia?

A
  • to make up the minute ventilation
  • part of the gas has to be rebreathed to make up for the part that is lost
66
Q

Circle System Function

What is a semi-open system?

What are examples of a semi-open system?

A
  • non-rebreathing systems
  • use higher FGF w/ minimal rebreathing & more venting of waste gas
  • post-op, ICU vents, scuba gear
  • there is only one way in & out for gas
67
Q

Circle System Function

What is a closed system?

What are examples of where a closed system would be used?

A
  • rate of O2 inflow exactly matches metabolic demand (ensure uptake of VA is very particular)
  • rebreathing is complete - what was going in was being rebreathed
  • no waste gas vented
  • VAs added to circuit in liquid form in precise amounts or through the vaporizer
  • impractical and rarely done
  • EX: low & minimal flow anesthesia
68
Q

Circle System Function

What are the most important things about a closed system we need to know? (4)

A
  • Low flows
  • rebreathing complete
  • no waste gas vented out
  • rate of O2 inflow matches the metabolic demand of the pt
69
Q

What are the 3 advantages to low-flow anesthesia?

A
  1. decreased use of VAs
    * don’t have to overpressurize for entire case
  2. Improved temperature & humidity control
    * conserving heat/humidity in closed/semi-closed
  3. reduced environmental pollution
    * decreased waste gases being ventilated
70
Q

What are the 3 disadvantages to low-flow anesthesia?

A
  • difficulty in rapidly adjusting the anesthetic depth
    – takes longer to get them deep
    – requires overpressurization/high flows
  • possibility of accumulating unwanted exhaled gases (CO, acetone, methane)
  • VA degradation byproducts (CO, compound A)
71
Q

What are the 5 advantages of a circle system?

A
  • low FGF can be used
  • elimination of CO2
  • relatively stable inspired gas concentration
    – what we dial in is what is delivered, see close to that come back out on the ET monitor
    – discrepancy? look for leak in system
  • conservation of moisture/heat/gases
  • prevention of OR pollution
    – not putting it all out to the atmosphere (scavenging)
72
Q

What are the 4 Disadvantages of the circle system?

A
  • complex design
    – a lot of parts
  • CO or compound A
    – not as common
  • may compromise Vt during controlled ventilation
    – Vt lost in corrugated tubing b/c its distensible & can expand
    – not common
  • ASA closed claims project
    – #1 problem: misconnection/disconnection
    – ETT, elbow, y-piece
    – expiratory/insp. limb (just enough to show decreased output of sevo)
73
Q

What are the 6 components of self-inflating manual resuscitators?

A
  1. self-expanding bag
  2. T-shaped non-rebreathing valve
  3. bag inlet valve
  4. pop-off valve
  5. excess oxygen venting valve
  6. oxygen reservoir - can be used as a little extra O2 boost for the pt (more pressure & O2 being delivered to the pt)
74
Q

What are the uses of the self-inflating manual resuscitators?

A
  • hand ventilation in the absence of an oxygen or air source
  • pt transport
  • CPR
  • emergency back-up!!!
75
Q

What are 3 hazards associated with

A
  • barotrauma or gastric insufflation
    – make sure head is positioned properly
    – some of the gas being vented to pt is still going down esophagus
  • significant variation of Vt, PIP, and PEEP
    – hard to deliver consistent Vt
    – self-inflating bags hard to get grip
    – bag is stiff, hard to gauge what pressures are there or what pt is doing
  • non-rebreathing valves generate resistance
    – when a pt has return of spont. ventilation it will be harder for them to breathe against non-rebreathing valves
76
Q

What are bacterial filters used for?

A
  • routine use to prevent contamination or infection by airborne diseases
    – M. Tuberculosis
    – COVID
    – PUI
  • preventing contamination of anesthesia machine from airborne diseases
    – will also usually have a reverse isolation room or OR w/ deep clean after
77
Q

Where are bacterial filters placed?

A
  • expiratory limb
78
Q

What are the 2 types of bacterial filters?

A
  • small-pore compact matrix
  • less dense, larger pore size arrangement
79
Q

Bacterial filters

How are small-pore compact matrix filters designed?

A
  • have high ariflow resistance b/c everything is jampacked/compact
  • pleated to create a larger SA to pick up more pathogen
80
Q

Bacterial Filters

How are the less dense, larger pore size filters designed?

A
  • less resistance
  • smaller SA
  • could still be a small bacterial filter - but it has larger pores and is not as compact
81
Q

Bacterial Filters have permanent ________ ________. They are designed to enhance ____ ____ ____ forces that hold organisms w/i the matrix.

A

Electrical polarity

  • Van Der Waals
82
Q

Bacterial filters that are ________, have what qualities?

A

hydrophobic
* prevents water penetration
* increased resistance
* decreased efficiency

83
Q

Bacterial Filters

What is a combination filter?

Where is it placed?

A

filter & HME
* placed @ y-piece
* inspiratory and expiratory barrier

84
Q

How can bacterial filters get wet from excess moisture/ventilation?

A
  • pt expiring - more moisture coming through (humidifed gas)
  • accumulation of fluid in circuit
  • sputum/vomit/blood
85
Q

What happens if bacterial filters get wet?

A
  • there will be increased resistance
  • gases cannot travel well through moisture
  • decreased efficiency of any of them
86
Q

What are 2 possible complications from bacterial filters?

A
  • obstruction
    – sputum, edema fluid, malpositioning
    – nebulized aerosols
  • leakage
    – housing of a gas line filter
    – condensation fluid can accumlate in circuit and sampling line
87
Q

How do we give nebulized aerosols and how do they cause obstruction of bacterial filters?

A
  • attached to circle system
  • use 20-30cc syringe and give squirts
  • it creates mist particles and it can cause obstruction
88
Q

APSF recommendations for breathing filters

When should an inspiratory limb filter be used?

A
  • when machine may have been contaminated by a previous pt
89
Q

APSF Recommendations for breathing filters

When should an external sampled gas filter be used?

A
  • if not part of water trap and sampled gases are returned to the breathing circuit
90
Q

APSF recommendations for breathing filters

when should an airway filter be used?

A
  • for COVID +
  • or PUI pts
  • optional for others
  • HMEF (heat and moisture exchange filter) preferred
  • electrostatic filter acceptable
91
Q

APSF recommendations for breathing filters

When should an expiratory limb filter be used?

A
  • for all patients
  • pleated mechanical filter preferred
92
Q

Humidity:

A

amount of water vapor in a gas

93
Q

absolute humidity

A

mass of water vapor present in a gas
mg H2O/L of gas

94
Q

Relative humidity:

A

percent saturation
* amount of water vapor at a particular temp

95
Q

Water vapor pressure:

A
  • pressure exerted by water vapor in a gas mixture
96
Q

Humidification in the airway

How do we humidify all of our gases when we take a breath?

A
  • through maximal contact of inspired gas w/ large mucosal SA in the nasal cavity
  • nose is like our HME
97
Q

Humidification in the Airway

At what point in the airway has humidification & heating occurred?

What heat has it reached by this point?

Absolute humidity?

Realtive humidity?

A

mid trachea

  • 34 degrees C
  • absolute humidity 34-38 mg H2O/L gas
  • relative humidity 95-100%
98
Q

Humidification in the airway

What is the isothermic saturation boundary?

A

The distal spot in the airway where gas has reached:
* temp: 37 degrees C (body temp)
* absolute humidity of 44 mg H2O/L
* relative humidity of 100%

99
Q

Humidification in the Airway

Where is the isothermic saturation boundary usually located anatomically?

A

The carina

100
Q

Humidification in the Airway

What causes variation in the the isothermic saturation boundary?

A
  • vol. of gas inhaled
  • humidification
  • temp of gas
101
Q

Humidification in the Airway

What 2 things on the ventilator can change where the isothermic saturation boundary is?

A
  • humidifier
  • heater
102
Q

Humidification in the Airway

What are the effect of breathing cold ambient temperatures?

A
  • little capacity to hold water vapor
  • low absolute humidity
  • upper airway transfers large amounts of heat & moisture
    the colder it is - the more humidity needs to be added as the pt breathes in
103
Q

Humidification in the Airway

What are the effects of breathing gas with warm ambient temperatures?

A
  • little heat energy is expended to warm inspired gases
  • body does not have to work as hard to warm gases
  • may need to add more humidifier b/c its dry
104
Q

Humidification in the Airway

What are the effects of breathing cool gas?

A
  • may trigger bronchospasm
  • poorly understood
  • esp. w/ Hx of COPD/asthma
105
Q

Which pediatric population is prone to bronchospasm?

A
  • kids who get hand held nebs @ home b/c of upper airway problems
  • not necessarily asthma
106
Q

What 3 things can underhumidification cause?

A
  1. damage to resp. tract
  2. body heat loss (conservation important in OR)
  3. tracheal tube obstruction
107
Q

Underhumidification

How does it cause damage to the resp. tract?

A
  • secretions thicken
  • ciliary function decreases
  • surfactant activity is impaired
    – decreased ease of alveoli opening/closing
  • mucosa susceptible to injury (dry & friable)
108
Q

Underhumidification

What pt population is it especially important to conserve heat/humidification in?

A

neonates/children

109
Q

Underhumification

What are the effects of tracheal tube obstruction?

A
  • increases resistance & WOB from thickened secretions
  • suction them out
  • add humidication to thin secretions
110
Q

What can overhumidification cause?

A

Condensation of water in the airway

111
Q

overhumidification

What does condensation in the airway lead to? (4)

A
  • reduced mucosal viscosity and risk of water intoxication (drowning pt)
  • inefficient mucociliary transport (condensation in the way)
  • airway resistance, risk of pulm. infection, surfactant dilution, atelectasis, V/Q mismatch
  • obstruction to sensors
112
Q

Overhumidification

What can we do when the sampling line has condensation in it?

A
  • The ETCO2 will stop reading or is inaccurate
  • get a new one or dump the deepen (housing unit)
113
Q

What is the goal of humidification devices?

A

Aim to reproduce more normal physiologic conditions in the lower resp. tract

114
Q

Which humidication device is considered passive?

A
  • Heat & moisture exchanger (HME)
  • can be modified to have a filter
115
Q

Which humidification device is “active”?

A
  • heated humidifiers
116
Q

What should ideal humidification devices do?

A

have the ability to warm & humidify gases to physiologic circumstances
* should not add DS
* should not increase infection risks
* safe/easy to use & be effective

117
Q

What is the function of an HME (heat & moisture exchanger)?

A
  • conserves exhaled heat & water - returns them to the pt
118
Q

What is the function of an HMEF (F = filter)?

A
  • bacterial/viral filtration & prevention of inhalation of small particles
119
Q

What is the design of the HME & HMEF?

A
  • disposable w/ exchange medium enclosed in plastic housing
120
Q

Where is the HME/HMEF placed?

A
  • close to pt
  • b/w y-piece & proximal end of ETT or LMA
  • increases apparatus DS
121
Q

What are the disadvantages to an HME?

A
  • low ETCO2 reading
    – happens if the sampling line is placed on the other side of the HME
    – want it to read @ the elbow for most accuracy
  • increases resistance & DS in circuit
  • efficiency may be reduced w/ large Vt
    – esp. hydrophobic models
    – will not conserve as much heat/moisture w/ larger Vt
    – large Vt may also reduce the filtering if there is a filter
122
Q

What is a hygroscopic HME made of?

A
  • paper or other fiber barrier coated w/ moisture retaining chemicals
  • may have some electrostatic properties
123
Q

How does a hygroscopic HME work?

A
  • absorbs water in exhalation and releases it in inspiration
  • it is the most efficient in retaining heat and moisture
124
Q

What is a Hygroscopic HME prone to?

What does this lead to?

A
  • becoming saturated
  • leads to:
    – incresaed insp./exp. resistance
    – reduced heat and moisture retention efficiency
125
Q

What is a hydrophobic HME made of?

What is it more efficient at?

A
  • pleated hydrophobic membrane w/ small pores
    – larger SA to catch more pathogens
  • more efficient filter of pathogens
126
Q

What are humidifiers and who do we use them?

A
  • devices used to increases the humidity in O2 supplied to patients
  • use in neonates, pts w/ difficult resp. secretions, or hypothermic pts
  • may be unheated/heated
127
Q

Humidifiers - passage of stream of gas

bubble/cascade:

A
  • active humidifiers
  • fresh gas passes over - goes down through tube & through a water reservoir
  • causing the “bubble or cascade”
  • water vapor absorbed through the bubbling as it passes through the reservoir
128
Q

Humidifiers - passage of gas stream

pass-over method:

A
  • pass gas over heated water reservoir & it picks up heat/water
129
Q

humidifiers - passage of gas stream

counter-flow method:

A
  • water is heated outside vaporizer
  • pumped to top of humidifier
  • enters into small pores
  • vapor is picked up
  • runs down and flows/gets humidified to body temp
130
Q

humidifiers - passage of gas streams

in-line method:

A
  • uses plastic capsules and it injects water vapor & heat directly into the inspiratory limb of the vent circuit just before the y-piece
131
Q

Where are humidifiers placed?

A
  • placed in insp. limb downstream of unidirectional valve
  • want what is going toward pt to be heated/humidified
  • heated humidifers should not be placed in exp. limb
132
Q

Humidifiers

Condensation can decrease the ________.

What should we change to decrease the risk of contamination/infection?

A
  • delivered Vt
  • change water traps if they are on the vent!!
133
Q

What are the advantages to a humidifier?

A
  • can deliver saturated gas @ body temp or higher
  • more effective than an HME
134
Q

What are the disadvantages to an HME?

A
  • bulky
  • potential electrical malfunction/thermal injury
  • contamination, cleaning issues
    – watch water (growing pathogens)
  • higher cost than HME
  • water aspiration risk
    – be vigilant and make sure you are not getting extra condensation/water in circuit that could pass back to pt

Principles of Anesthesia I - Summer 24 (15 decks)

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