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Anesthesiology > Breathing systems > Flashcards

Breathing systems Flashcards

1
Q

What are the 2 breathing systems?

A

Re-breathing: Circle/Y-piece, universal “F” Non-rebreathing: Mapleson(s), Bain

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2
Q

What are the 2 types of re-breathing systems? What are the components?

A
  • Circle/Y-piece or universal F Components:
  • Fresh gas and O2 flush
  • unidiretional valves (1 inspiratory, one expiratory)
  • breathing hoses (circle or universal F)
  • CO2 absorber (i.e. soda lime)
  • APL valve (aka pop-off), reservoir bag
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3
Q

T/F: The re-breathing system has a 2-way gas flow.

A

FALSE–it is a one-way (circular) gas flow

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4
Q

What does the CO2 absorber do in the re-breathing system?

A

Prevents rebreathing of excessive CO2

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5
Q

What are the advantages of the re-breathing system?

A

Lower fresh gas flow rate: saves $$$, decreases pollution, patient breaths warm, humidified gases

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6
Q

What are the disadvantages of the re-breathing system?

A

More components–>more potential for leaks Increased resistance for smaller patients (

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7
Q

Oxygen flush valve

A

Bypasses vaporizer: dilutes gases in breathing system and reservoir bag Delivers O2 directly to the breathing system: 35-75 L/min of 100% oxygen

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8
Q

When should you avoid using the oxygen flush valve?

A

Avoid activation with patient attached to system; NEVER NEVER NEVER use with non-rebreathing system

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9
Q

What must you check when changing breathing systems?

A

Connection of the fresh gas inlet

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10
Q

What is the adjustable pressure-limiting (APL) valve?

A

Aka pop-off valve Limits pressure buildup in breathing system

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11
Q

When is the APL valve closed?

A

OPEN ALWAYS unless: pre-use machine check (must OPEN when done); Must close to administer positive pressure ventilation (manual or controlled)

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12
Q

What happens when the APL valve is closed?

A

Closed APL valve–>increased pressure in breathing system–>cardiopulmonary injury–>DEATH

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13
Q

What is the breathing system pressure gauge?

A

Measures pressure in the breathing system; SHOULD BE ZERO

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14
Q

When will the breathing system pressure gauge NOT measure zero?

A

Performing leak checks (pre-use check) Providing positive pressure ventilation (IPPV)

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15
Q

Carbon dioxide absorber

A

Soda lime most commonly used Absorber assembly has canister to hold soda lime, 2 ports for connecting breathing tubes, fresh gas inlet, +/- unidirectional valve mount and bag mount

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16
Q

What is soda lime?

A

Calcium hydroxide with small amount of sodium hydroxide and color indicator

Indicator = ethyl violet (fresh = white; exhausted = purple)

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17
Q

What happens to soda lime when active?

A

Heat reaction and color change

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18
Q

When filling soda lime…

A

Do not pack tightly, avoid dust of broken particles Check gaskets and seals as a source of leaks (esp. if dust particles present)

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19
Q

What are the signs of soda lime exhaustion

A
  • Increase end tidal CO2
  • If at a light enough plane of general anesthesia: increased ventilation, increase in HR and BP initially (then decrease)
  • Rebreathing (seen on ETCO2)
  • Respiratory acidosis
  • Red mucous membranes (carbon monoxide production and inhalation)
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20
Q

What are the functions of a reservoir bag?

A

Observe ventilation, inspiratory reserve, administer manual positive pressure ventilation

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21
Q

How do you calculate the reservoir bag size?

A

Tidal volume (10-20 mL/kg) x 6 Round up if between sizes

22
Q

What is the typical oxygen flow rate (re-breathing) for induction and recovery in small animals?

A

HIGH: 50-100 mL/kg/min O2

23
Q

What is the typical maintenance oxygen flow rate (re-breathing) in small animals?

A

SEMI-CLOSED: 20-50 mL/kg/min O2

24
Q

What is the typical induction and recovery oxygen flow rate (re-breathing) in large animals?

A

20-50 mL/kg/min O2

25
Q

What is the typical maintenance oxygen flow rate (re-breathing) in large animals?

A

LOW: 10-20 mL/kg/min O2

26
Q

What are the components of the non-rebreathing system?

A

Fresh gas non-rebreathing tubes

APL (Mapleson D) OR open/close (Mapleson F) valve

Reservoir bag

27
Q

What are the missing components in the non-rebreathing system (compared to the re-breathing system)?

A

Soda lime canister Unidirectional valves O2 flush button (NEVER USE WITH NON-REBREATHING SYSTEM)

28
Q

What are the advantages of the non-rebreathing system?

A

Very light, with minimal dead space or resistance to ventilation (good for patients = 3-10 kg) Fewer components = fewer potential for leaks [Anesthetic gas] changes rapidly (high gas flow)

29
Q

What are the disadvantages of the non-rebreathing system?

A

High gas flow rates: $$$ to run in larger patients, increased pollution, no rebreathing = gases not as warm or humidified

30
Q

What are the oxygen flow rates in non-rebreathing systems (compared to re-breathing systems)?

A

HIGH: O2 flow is mechanism for eliminating CO2 Must be at least 2-3 x tidal volume in most cases (200-300 mL/kg/min O2)

31
Q

What are the indications of endotracheal tubes and intubation?

A
  • Maintain patent airway
  • Protect airway from foreign material (blood, regurgitation)
  • Provide intermittent positive pressure ventilation (IPPV)
  • Apply tracheal or bronchial suction
  • Administer oxygen
  • Deliver inhalant anesthesia
32
Q

What are the benefits of intubation?

A

Reduced anatomical dead space (IF correct size/position of tube; dead space = air without gas exchange)

Maintain inhalant anesthesia with minimal environmental contamination (properly inflated cuff)

33
Q

What are the 4 routes of intubation?

A
  1. Oral
  2. Nasal
  3. External pharyngotomy
  4. Tracheostomy
34
Q

What is the advantage of cuffed endotracheal tubes?

A

Protect airway and environment better, but need to inflate carefully to avoid trauma

35
Q

What are the 2 cuff types?

A

High volume-low pressure (preferred) High pressure-low volume (protect trachea)

36
Q

What connects the endotracheal tube to the breathing system?

A

15 mm OD connector

37
Q

What are the different types of endotracheal tubes? Which is most commonly used in veterinary anesthesia?

A

Murphy (most commonly used in vet med)

McGill

Wire-reinforced (avoid use in MRI)

Cole (some avian pts) tracheostomy

38
Q

How do you decide which size endotracheal tube to use?

A

Poiseuille’s law: R = 8nl/pi*r^4 Tubes with larger radius and shorter length will have LESS resistance to air flow

39
Q

What size tubes do you use for the following (general guidelines, adult):

Cat

Beagle

Labrodor

Great dane

Sheep

(~40kg) Horse

A
  • Cat = 3.5-4.5
  • Beagle = 8.0-10
  • Labrodor = 10, 11, 12
  • Great dane = 14, 16
  • Sheep = 10.0, 11, 12
  • Horse = 26, 30
40
Q

What steps are taken when preparing to intubate?

A
  • ETT: check size (diameter–ID, palpate; length–tip of nose to thoracic inlet; set up 3 sizes: 1 you think, 1 smaller, 1 larger), inflate cuff to check for leaks, ensure it’s clean and dry
  • Cuff syringe
  • Tube tie (1st tube, then around ears or muzzle) +/- special supplies (stylet, mouth gags, etc.)
41
Q

Laryngoscope–what does it do, how do you use it?

A
  • Makes intubation safer and easier
  • Allows visualization of airway
  • Light source
  • How to use it:
    • Apply light pressure to base of tongue, just rostral to epiglottis
    • Apply gentle pressure ventrally, this tilts larynx, opens glottis, and frees soft palate from epiglottis (if it was entrapped)
    • DO NOT apply significant pressure directly on epiglottis! (risk = fracture of hyoid apparatus)
42
Q

Safe ETT cuff inflation

A
  • After intubation, connect patient to breathing system with O2 flowmeter ON
  • GOAL: NO audible release of gas from around the endotracheal tube when the APL valve is closed and the reservoir bag is squeezed to 20 cmH20
  • However, at 30 cmH20 air should be audibly escaping around tube (If not, remove air from pilot balloon until heard–prevents over-inflation)
  • Do NOT inflate cuff without first checking to see if you need any air in it
  • Caution when moving patient with inflated ETT cuff
43
Q

Potential complications of ETT

A
  • Laryngeal damage (mostly small animals);
    • laryngospasm (esp. cat, sheep, pig, rabbit),
    • hematoma, edema
  • Tracheal damage (over-inflated cuff, moving/twisting inflated cuff)
    • poss. consequences = mucosa sloughing, stenosis, persistent tracheal membrane (avian), tracheal rupture, pneumothorax, pneumomediastinum
  • Tube obstruction (patient position, secretions, cuff over-inflation)
  • Endobronchial intubation
    • ETT advanced too far in airway
    • Hypoxemia, tachypnea, cynosis?
  • ETT inhalation, ingestion
    • Always extubate rostrally to avoid shearing teeth!
44
Q

What is the purpose of scavenging waste gases? What types are there?

A
  • Essential to SAFE anesthesia practices!
  • To collect and transport waste gases from anesthesia machine to safe disposal area
  • 2 types: active and passive
45
Q

What are the 4 elements of scavenging waste gases?

A
  1. Collecting system (APL valve)
  2. Transfer system/interface
  3. Receiving system
  4. Disposal system
46
Q

What is the ppm for scavenging waste gases? What should exposure to halogenated anesthetic agents such as isoflurane and sevoflurane be?

A

100% gas = 1,000,000 ppm

1% gas = 10,000 ppm

Olfactory >/= 125 ppm

Exposure should be < 2 ppm

47
Q

What are the 7 steps in scavenging waste gases?

A
  1. Scavenge everything (even in recovery)
  2. No leak technique (< 300 mL/min acceptable)
  3. Use properly inflatted cuffed ETT
  4. Check for tight fittings
  5. Maintain on closed or low flow system
  6. Good room ventilation = minimum 15 air changes per hour
  7. Leak test before every machine use
48
Q

What are the passive systems in scavenging waste gases?

A
  • Non-recirculating room ventilation systems
  • Charcoal absorption (F air canisters)*
    • does NOT scavenge nitrous oxide
  • Piping direct to atmosphere (i.e. via window)
49
Q

What is the active system when scavenging waste gases?

A

Piped vacuum (white drop and tubing)*–central vacuum system capable of handling high volume (30 L/min flow)

50
Q

What are the advantages of using charcoal absorption when scavenging waste gases?

A
  • Absorbs hydrocarbons
  • Does not release to ozone
  • Portable
51
Q

What are the disadvantages to using charcoal absorption when scavenging waste gases?

A
  • Does not absorb N2O (only absorbs hydrocarbons)
  • Flow-limited
  • Added resistance
  • Weigh before use (record # of grams)
  • Discard when 50 g + or 8-12 hours of use
    • FINITE use
52
Q

What are some other sources of pollution to consider?

A
  • Gas sampling monitors
    • Capnograph
    • Spirometry
  • Induction
    • Chamber/box
    • Face masks
  • Recovery rooms
    • Patient exhales inhalent to recover
    • 20 air exchanges per hour needed
    • Leave patient on machine with O2 and scavenge

Anesthesiology (16 decks)

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