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1: Intro to Anesthesia > Delivery Systems > Flashcards

Delivery Systems Flashcards

1
Q

What are the basic functions of a breathing circuit?

A

interface between anesthesia machine and pt, deliver O2/other gases, eliminates CO2 (circle - CO2 absorbents, other systems - FGF)

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2
Q

3 essential components of breathing circuit?

A

low resistance conduit for gas flow - make breathing easier for pt reservoir for gas that meet inspiratory demand expiratory port or valve to vent excess gas and prevent barotrauma

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3
Q

5 requirements of a breathing system?

A

allow rapid adjustment of gas concentration and flow rate (depends on FGF) low resistance to gas flow minimal dead space eliminate CO2 deliver gas from machine to alveoli in same concentration as set and in fastest time possible

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4
Q

Name 8 desirable features of a breathing system:

A

economic FGF, conservation of heat, adequate humidification, light weight - prevents ett kinking, convenience of use, efficiency during spont/controlled vent., adaptability for adults/peds/mech vent., reduce environment pollution/safe disposal of waste gas

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5
Q

Is low resistance achieved in a breathing system? (5)

A

minimize connections, short tubing, large diameter, avoid sharp bends, caution w/ valves

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6
Q

Why is rebreathing gases beneficial? (2)

A

cost reduction/gas economy, adds humidification/heat to gases

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7
Q

______ FGF is associated with ______ rebreathing in every type of circuit.

A

higher, less

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8
Q

If your CO2 absorbent fails what can you do to prevent rebreathing of CO2?

A

increase FGF rate and convert to semi open system

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9
Q

What increases chance of rebreathing CO2? Where is it? How is it minimized?

A

dead space, where inspiratory and expiratory gas stream diverge (Y-piece connected to ett), apparatus dead space can be minimized by separating the I & E streams as close to pt as possible, minimize extra connections.

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10
Q

What is dead space?

A

Ventilated air that doesn’t participate in gas exchange

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11
Q

Why is humidifying and warming gas important?

A

Dry, cold gases contribute to pt hypothermia and increased secretions

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12
Q

Concentration of the gas inspired most closely resembles that delivered from the __________ when rebreathing is ________.

A

common gas outlet, minimal/absent.

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13
Q

How can you protect from bacterial colonization in a breathing system? What do you need to consider with this item?

A

> 95% 0.3 micrometer filter HME - humidity and moisture exchanger Adding a filter adds deadspace, can increase WOB and resistance (may be an issue for peds pt), add to expiratory limb for these pts where it is an issue

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14
Q

What are the 4 classifications of anesthetic delivery systems?

A

open: no reservoir or rebreathing semi open - reservoir, no rebreathing semi closed - reservoir, partial rebreathing closed - reservoir, complete rebreathing

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15
Q

Describe open systems.

A

No reservoir, no rebreathing. No valves. Examples are NC, open drop, simple face mask, insufflation, Steal induction, Schimmelbusch mask

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16
Q

What is an appropriate gas flow rate to ensure no rebreathing of CO2 in a open system?

A

1-1.5 MV or approx 10 L/min

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17
Q

Describe Steal induction.

A

For children who are already asleep and we don’t want to wake them. Meant to be an atraumatic way of sedating pt.Tubing primed w/ N2O and O2, mask brought close to pt’s face until brought closer and closer until pt breathing it for 1-2 min. Sevoflurane is then used. Monitors must be placed asap.

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18
Q

Describe advantages (3) and disadvantages (4) of insufflation.

A

simple, avoids direct pt contact, no CO2 rebreathing, no reservoir bag/valves no ability to assist or control vent. CO2 or O2 accumulation under drapes - fire risk no control of anesthetic depth/FiO2 environmental pollution

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19
Q

Describe semi-open systems.

A

No rebreathing. Reservoir present. Examples include some Maplesons, Circle system if FGF > MV

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20
Q

What is minute ventilation (VE) and how is it calculated?

A

RR x Tv = VE It is volume of gas leaving and entering lungs per minute.

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21
Q

What are components of Mapleson system?

A

connection to facemask/ett reservoir tubing (large diameter) FGF tubing expiratory pop off valve

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22
Q

What is only Mapleson type without a reservoir bag?

A

E, t tube acts as reservoir

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23
Q

When are Maplesons used?

A

peds - lower resistance, transport (still need ambu), procedural sedation, weaning trach, pre O2 during out of OR aw management

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24
Q

What is the best measure of optimal FGF to prevent rebreathing?

A

etCO2

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25
Q

Advantages and Disadvantages of Mapleson system?

A

simple, ability to change depth of anesthesia quickly, portable, no rebreathing if adequate FGF lack of conservation of heat/moisture, limited ability to scavenge waste gas - pollutes environment, high FGF - wastes volatile

26
Q

Which Maplesons are opposites of one another? Why? Describe other Maplesons

A

A and D. A: FGF distal to pt, reservoir bag, corrugated tubing, APL, mask - best for spont vent D: reservoir bag distal to pt, APL Distant, corrugated tubing, FGF, mask - best for controlled vent. but can be used for spont. ——- B: reservoir bag, corrugated tubing, FGF, APL, mask C: reservoir bag, no corrugated tubing, FGF, APL, mask E: no reservoir bag, corrugated tubing, FGF, mask F: APL Far, reservoir bag, corrugated tubing, FGF, mask

27
Q

Rank order of efficiency of Maplesons for controlled vent.

A

D > B > C > A dog bites can ache

28
Q

Rank order of efficiency of Maplesons for spont. vent.

A

A > D > C > B all dogs can bite

29
Q

Where is the deadspace in Maplesons during spont vs controlled vent?

A

A: close to pt, just after APL vs closer to reservoir bag B: proximal to reservoir bag and in reservoir bag for both C: in reservoir bag for both D: some in reservoir bag, out APL vs reservoir bag and proximal to reservoir bag E: distal to pt for both F: distal to pt, out APL, proximal to reservoir bag vs in reservoir bag

30
Q

The relative efficiency for preventing rebreathing during SV in Mapleson is:

A

A > DF > C > B all dogs find cats boring

31
Q

The relative efficiency for preventing rebreathing during CV in Mapleson is:

A

DF > B > C > A dog friends betray cats always

32
Q

What are the 5 factors that determine CO2 rebreathing?

A

FGF, VE of pt, spont vs controlled vent., CO2 production of pt - increased w/ fever, catabolism etc., resp. waveform characteristics (I:E, insp flow, expira. pause, insp/exp times)

33
Q

How can rebreathing be managed using inhalation and expiration control?

A

make sure FGF is larger proportion of inspired gas by slowing inspiratory time or using low inspiratory flow or enable exhaled gases to be more completely washed out by using a long expiratory pause or slow rate

34
Q

Why is Mapleson A inefficient for controlled vent? During SV how do you prevent rebreathing? Why is it best for SV? Why is it impractical for OR?

A

requires uneconomical amount of FGF, 20 L/min to prevent rebreathing FGF at least 1x VE Warm, humidified exhaled dead space gas reused Scavenging difficult bc location of APL, difficult to adjust during head and neck surg, heavy valve can dislodge small trach

35
Q

Why are the use of Mapleson B & C prohibitive?

A

require high flows of FGF

36
Q

How much FGF required in Mapleson D in SV vs CV? When is it most efficient?

A

SV: FGF 2-3 x VE CV : FGF 1-2 x VE CV

37
Q

What is the Bain system?

A

Mapleson D but FGF is delivered inside corrugated tubing to conserve humidity and heat. Disadvantage of system is that kinks and disconnects are hard to see so tests must be performed ti monitor for rebreathing.

38
Q

Mapleson E AKA T-piece is used in what situations? What acts as a reservoir in this system and why is this significant? What does FGF need to be at?

A

peds, wt less than 20 kg, very little resistance to breath the open-ended corrugated tubing, length must exceed Tv of pt FGF must be 2-3x VE

39
Q

Mapleson F requires how much FGF? What type of pts typically use this system and when? Why is the circuit ideal? What are disadvantages of the system? What are modifications that can be made to the system?

A

2-3x VE intubated, peds, for transport circuit deadspace and resistance minimal high FGF, barotrauma possible, lack of humidifier ***can add humidification and modifications to APL can allow for scavenging****

40
Q

Describe ambu bags. Safety concerns? Features to prevent this?

A

Manual resuscitator. Contains: non rebreathing valve, self inflating bag, high FiO2 delivery w/ O2 reservoir attached, reservoir is self filling w/ intake valve, CO2 washout determine by VE. barotrauma risk d/t high pressures. pop off valve has highest setting to 30, releases extra gas if pressure higher than that achieved, can disable if needed for diff to vent pts

41
Q

Compare and contrast Mapleson and Circle Systems.

A

similarities: FGF, reservoir to supply pt w/ sufficient volume of gas, eliminates CO2 differences: bidirectional flow, no absorber, depend on FGF to eliminate CO2

42
Q

Describe Circle System. Talk about resistance in circuit. What are some considerations?

A

minimizes environment pollution, lower FGF than Mapleson, conserves heat/humidity/volatile, unidirectional flow of gas, can be used as semi-open, semi-closed, or closed system (dependent on APL and FGF) Most resistance comes from ETT, so unidirectional valves and CO2 absorber canister dont add much. Can take time for changes in anesthetic to reach equilibrium unless higher FGF used. Be aware of stuck (resistance) or floating (rebreathing) unidirectional valves.

43
Q

What components of circle system (7)?

A

FGF, I & E unidirectional valve, I & E limbs/corrugated tubing, Y piece connector, APL valve, reservoir bag, CO2 absorber

44
Q

In a circle system what is absolutely necessary when FGF is low? Why?

A

CO2 absorber bc FGF do not exceed VE so no way to get rid of CO2

45
Q

How are gases delivered to the anesthesia machine? Where is it on machine?

A

common gas outlet, in between CO2 absorber and inspiratory limb

46
Q

What are the largest sources of resistance in anesthesia circuit?

A

ETT, unidirectional valves, CO2 absorber wet valves can add resistance

47
Q

What can happen with fault unidirectional valves?

A

rebreathing

48
Q

What are the 3 functions of a reservoir bag?

A

reservoir for anesthetic gases, O2 (volume 0.5-6L), visual assessment SV rough estimate of Tv, means for manual vent.

49
Q

Whats the purpose of APL?

A

permits PEEP during SV and permits pressure limited controlled respiration, releases gas to scavenge/atmosphere exhaust port, provides control of pressure in system

50
Q

When is an APL valve open? When is it partially open?

A

spont. vent (close partially if reservoir bag empties), mech vent assisted vent. - bag squeezed on inspiration, need careful freq adjustments

51
Q

Describe the tubing in breathing circuit.

A

1 m in length, 22 mm connector to minimize resistance, its corrugated to improve flexibility and minimize kinks, internal volume 400-500 mL

52
Q

Where is the dead space in a circle system?

A

Y connector (if unidirectional valves working)

53
Q

Describe a semi-open circle system.

A

no rebreathing, uses high FGF (10-15 L/min) to eliminate gases, no conservation of heat or waste gas, APL open or mech vent.

54
Q

Whats the common breathing system in the US?

A

semi-closed

55
Q

Describe semi-closed system.

A

allows some rebreathing of agents and gases (not CO2), uses low flow rates (1-3 L/min), FGF < VE, conserves some heat and humidity, APL partially closed/adjusted or mech vent in use

disadvantage: lots of connection so misconnections possible, and deadspace

56
Q

When are closed systems used?

A

long surgical cases, developing countries

57
Q

How is the inflow of FGF determined in closed system? What are other traits of closed systems?

A

enough to meet metabolic demand/pt’s O2 consumption, O2 flow rates < 250 mL/min, total rebreathing after CO2 absorbed, APL closed so nothing wasted, changing gas concentration takes a long time, no rapid adjustments

58
Q

What are some advantages of circle system?

A

stability of concentration of gases, conservation of warmth and heat, low resistance (not as low as Mapleson), economy of gases, scavenge gases/prevent OR pollution

59
Q

What are some disadvantages of circle system?

A

complex, 10 connections - potential for DCs, malfunc valves (open - re breath, closed - airway obstruc), more resistance than Mapleson, less portable, increased deadspace (at Y piece)

60
Q

Describe a circle system leak test. How often is it done?

A

Set all gas flows to zero, occlude the Y-piece, close the APL valve, pressurize the circuit to 30 cm of water pressure using the O2 flush valve, ensure pressure holds for 10 seconds, listen for sustained pressure alarm, open APL valve and ensure pressure decreases QD

61
Q

Describe flow test. How often is it done?

A

Attach breathing bag to Y- piece, turn on ventilator, and assess integrity of unidirectional valves QD

62
Q

What are some possible circuit system issues? (5)

A

misconnections/disocnnections

leaks

valve failure

CO2 absorber defect

bacterial filter occlusion

1: Intro to Anesthesia (12 decks)

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