Anesthesia Delivery Systems Flashcards
(67 cards)
1
Q
Types of Open System
A
- insufflation
- open drop
- blow by
2
Q
Types of Semi Open Systems
A
- Mapleson (A-E)
- Brain
- Jackson Rees
- Circle
3
Q
Types of Semi Closed Systems
A
Circle System
4
Q
Closed System
A
Circle System
5
Q
Basic Functions of a Breathing circuit
A
- connects anesthesia machine to pt
- delivers C02 and other gases
- eliminates C02
- circle system = C02 absorber
- other circuits = fresh gas flow for C02 elimination
**C02 absorber recycles gas, saves money and keeps gas warmed and humidified
6
Q
3 Essential Components of a Breathing circuit
A
- low resistance conduit for gas flow
- reservoir for gas that meets inspiratory flow demand
- expiratory port or. valve to vent excess gas
7
Q
Peripheral Components of Breathing circuit
A
- humidifier (provide warmth and moisture)
- spirometer (measure ventilation
- pressure gauges
- filters (bacterial filters, placed on expiratory limb)
- gas analyzer (sampling sites for gas analysis)
- PEEP
- waste gas scavenge (keep OR from being contaminated with waste gas)
- mixing/ circulating device.
8
Q
Requirements of a Breathing circuit
A
- deliver SET CONCENTRATION of gases from machine to the alveoli in SHORTEST possible time
- effectively eliminate C02 (high C02 = dilated vessels = hypotension tachycardia, increased ICP)
- minimal apparatus dead space (space from end of tube to y connector)
- low resistance to gas flow
- allow rapid adjustment in gas concentration and flow rate
9
Q
Desirable Breathing system features
A
- economy of fresh gas (least amount possible)
- conservation of heat (warm gases)
- adequate humidification of inspired gas
- light weight
- convenience during use
- efficiency during spontaneous and controlled ventilation
- adaptability for adults, children and mechanical vents
- provision to reduce environmental pollution- safe disposal of waste gas
10
Q
Consideration of Breathing Circuit
A
- Want low Resistance (short tubing, large diameter tubing, corrugated tubing, no sharp bends, minimize connections, caution with valves
- Rebreathing benefits
But NOT rebreathing C02
(reduces cost, adds humidification/heat to gas)
*higher FGF less rebreathing C02** - Increased Dead space increased chance of rebreathing C02 (dead space ends at the Y connector; where insp and exp gas separate)
- Dry gases/ humidification
- Manipulate inspired content
(concentration of inspired gas most closely resembles the common gas outlet when rebreathing is absent/ minimal) - Bacterial Colonization;
but filters add weight and can clog
11
Q
Y connector
A
- where inspiratory and expiratory gas streams diverge/ separate
- dead space ends at the y connector
- minimize dead space by have y connector; separation of ins. and exp. streams as close to the pt as possible
12
Q
Bacterial Filters
A
American Association of Anesthesiology recommends a “bacterial filter with an efficient rating of more than 95% for particle sizes of 0.3 μm should be routinely placed in circuit where it will protect the machine from contamination with airborne infectious disease
*standard filters are placed on the EXPIRATORY limb
13
Q
HME
A
bacterial filter that both filters and performs heat and moisture exchange
*placed at y piece and serve as BOTH Inspiratory and Expiratory barrier
14
Q
Classifications of Anesthesia Delivery Systems
A
Is a Reservoir used and does rebreathing occur
- Open;
no reservoir 🚫
no rebreathing 🚫 - Semi- open;
Reservoir ✔️
no rebreathing 🚫 - Semi- closed;
Reservoir ✔️
partial rebreathing ⭕️ - Closed- reservoir;
Reservoir ✔️
complete rebreathing ✔️
15
Q
Circle system
A
*has to have a reservior
semi-open; reservoir, no rebreathing
semi-closed; reservoir and partial rebreathing
closed- reservoir; reservoir and complete rebreathing
*type of circle system is determined by type of fresh gas flow (FGF)
16
Q
Open system
A
NO gas reservoir bag
NO rebreathing of exhaled gas
NO valves
Types;
open drop
insufflation (blow by, NC, simple face mask)
17
Q
Semi- open system
A
Reservoir
NO rebreathing
ex. non rebreather face mask mapleson circuit (FGF depends on design) circle system (FGF > minute vent)
18
Q
Semi- closed system
A
Reservoir
PARTlAL rebreathing
ex. Circle system (FGF > MV
19
Q
Closed- Reservoir
A
Reservior
NO rebreathing
ex. circle system (FGF > MV
20
Q
Insufflation
A
ex. blow by, NC, tent, bronchoscopy port, insufflation under OR drapes and “steal induction”
21
Q
Insufflation Advantages
A
- No direct pt contact
- No rebreathing of C02
- Nothing to break; No reservoir bag or valves
22
Q
Insufflation Disadvantages
A
- No ability to assist or control ventilation
- May have C02 or 02 accumulation under drapes
- No control of anesthetic depth/ Fi02
- Environmental pollution (think of blow by flying al over the room
23
Q
Steal Induction
A
pediinhalation induction
- child is naturally asleep upon arrival to OR
- breathing circuit s primed with N20 and 02, with high flows you hover the mask near their face and gradually bring it closer and closer, once truly asleep, place mask on face
- after child get 1-2 min of breathing N20, sevoflurane is administered inna single increase to 8% (adequate monitoring ASA) and child tx to OR table
**once mask on face it becomes semi open; reservoir and partial rebreathing
**child is not touched or disturbed, technique is traumatic and avoids exposing child to strange OR surroundings
24
Q
Mapleson Systems Components
A
- connect to facemark or ETT
- Reservoir tubing
- Fresh gas inflow tubing
- expiratory pop off valve
25
Mapleson system types
A, B, C, D,
E (T piece)
F (Jackson Rees)
**difference in each type:
1. location of the pop- off valve
2. position of FGF input
3. presence of reservoir bag
^in relation to pt connection
Spontaneous breathing pt:
A>D>C>B
all dogs can bit
A is best for spont breathing bc of location of pop off valve right neat facemark and with spont breathing you have an end expiratory pause, so everything you inhale is fresh gas bc excess. goes out through pop off
Controlled ventilation
D>B>C>A
dog bites can ache
26
Uses of Mapleson systems.
1. Pedi
2. transport of pt
3. procedural sedation
4. weaning tracheal intubation
5. Pre-02 during out of OR airway management (ex: in radiation with pt but can't be in room with them)
27
Endtidal C02. relationship with rebreathing
loss of return to baseline on etC02 wave = rebreathing
increase FGF to eliminate rebreathing
**best measure of optimal FGF to prevent rebreathing
28
Advantages of Mapleson System
1. simple design
2. ability. to rapid change depth of anesthesia
3. Portability
4. 🚫 rebreathing of exhaled gas with adequate FGF
29
Disadvantages of Mapleson System
1. 🚫 conservation of heat/ moisture
2. limited ability to scavenge waste gases
3. Not efficient require high FGF (to prevent rebreathing of exhaled gas)
30
3 functional groups of Mapleson Systems
Mapleson A: pop-off near facemark, FGF located at opposite end (opposite of D)
*best for. spont breathing
Mapleson D,E,F: FGF near facemark, pop-off located at opposite end (opposite of A)
*best for controlled vent
Mapleson B & C: pop-off and FGF located near facemark *least efficient (wasteful, EVERYTHING leaves through pop-off on expiration
31
Mapleson best for Controlled Ventilation
D>B>C>A
Dog bites can ache
(D, E, F are the same)
32
Mapleson best for Spont breathing
A>D>C>B
All dogs can bite
ranked in order by efficieny
33
Dependent factors of C02 rebreathing
1. FGF rate
2. Minute Vent of pt
3. Mode of ventilation
(spontaneous vs controlled)
4. C02 production of pt
(increased with fever, catabolism)
5. respiratory waveform characteristics (inspiratory flow, I:E ratio, expiratory pause)
* adjusting vent pattern;
- slow iTime and low inspiratory flow allows FGF to constitute a larger portion of the inspired gas
-long expiratory pause or slow rate more completely rids exhaled gases and reduces rebreathing
34
Mapleson A
"Magill"
- most efficient for Spontaneous ventilation
- least effective for CV requires up to 20L/min of FGF
- impractical design for OR
- proximal location of pop-off valve makes scavenging difficult
- hard to adjust during head/ neck surgery
- heavy valve can dislodge small ETT
* NO rebreathing with SV when FGF is at least 1x MV
* Requires large FGF to eliminate rebreathing during CV
35
Mapleson B
* Rarely used
- Requires high FGF to prevent rebreathing
- inefficient/ impractical for SV or CV
-corrugated tubing connecting rest of system to reservoir bag
(blind limb where fresh gas, dead space and alveolar gas mix)
*close proximity of APL valve and FGF provides potential for mixing of inspiratory and expiratory gases
36
Maplseon C
'Water's circuit without absorber'
- used in resuscitation situations and pt transfer
- same as B, rarely used, requires high FGF to prevent rebreathing
* close proximity of APL valve and FGF provides potential for mixing of inspiratory and expiratory gases
37
Mapleson D
'Brain' system; inner tubing that delivers the FGF directly to pt, and exhales down outer corrugated tubing to reservoir bag and APL valve
(inner tubing not visible make sure to perform test to check for disconnect)
* Most efficient for Controlled Ventilation and second best for Spont. ventilation
- FGF close to facemark and pop-off valve located on opposite end (reverse of mapleson A)
*Controlled vent
FGF = 1-2 x MV
*Spont. vent
FGF = 2-3 x MV
38
How to test for disconnect on 'Brain' circuit
1. occlude the inner tube at the pt end using finger or end of 2ml syringe, if connected back pressure is created on the FGF and flowmeter bobbins dip
2. Rapid flushing of FGF through an intact system causes reservoir bag to collapse (Venturi effect)
* if disconnect present reservoir bag will inflate with rapid flush because it will cause an increased pressure in the expiratory limb
39
Mapleson D controlled ventilations considerations
- more efficient system
- factors affecting rebreathing (Minute Vent & Flow rate) are controlled by anesthetist
allows for a lower FGF = more efficient
FGF 70mL/kg/ min = 𝑉˙𝐴V˙A
*higher FGF >100 ml/kg/min
PaC02 dependent on MV
*lower FGF <90 ml/kg/min
PaC02 independent of MV
* increasing RR to eliminate PaC02 decreases the expiratory pause and increases rebreathing which increases inspired C02 (FiC02) and no change to PaC02
* adjustments to vent that reduce rebreathing
1. slower iTime or lower inspiratory flow = larger proportion of FGF in inspired gas
2. long expiratory pause or slow RR = more wash out of exhaled gases
40
Brain circuit
- modification of Mapleson D
- FGF enters circuit near reservoir bag BUT fresh gas delivered at pt end of circuit
- FGF tubing within large bore corrugated tubing
* *this allows exhaled gas to warm inspired gas (preserves heat and humidity with no added weight to circuit)
Risk for inner tube leaks, kinks, disconnections
41
Mapleson E
T-piece
- open ended corrugated tubing acts as inspiratory reservoir, length of tubing must exceed pt tidal volume
- NO reservoir bag - expiratory tubing acts as reservoir
- NO POP-OFF valve
- on expiration tubing fills with dead space and alveolar gas which is then flushed out by FGF
- commonly used to administer 02 in ICU and PACU settings
** SV: FGF = 2-3 x MV
42
Mapleson F
Jackson-Rees *most used*
(modification of mapleson E 'T- piece')
-unofficial 6th mapleson
- commonly used for controlled ventilation during transport of intubated pt
- adjustable pop-off valve at the end of reservoir bag
- flow inflating
- allows application of continuous positive airway pressure or hand ventilation
- provides visual indictor of respiration with reservoir bag
- degree of rebreathing depends on ventilation (spontaneous versus controlled) and adjustment of the pressure-limiting overflow valve (venting).
* FGF = 2-3 x MV to prevent rebreathing of exhaled gases
43
Advantages of Mapleson F
- minimal circuit dead space
- minimal resistance
- can be used for SV and CV
- inexpensive
- used with facemark or ETT
- lightweight
- easily repositioned
- scavenging systems can be added to reduce pollution of anesthetic gas into atmosphere
44
Disadvantages of Mapleson F
- high FGF to prevent rebreathing.
- risk of occlusion of popoff valve creating high airway pressures increasing risk of barotrauma to pt
- lack of humidification (offset it by allowing. FGF to pass through in-line heated humidifier)
45
Ambu bag
'manual resuscitator'
*critical piece of equipment and part of morning check*
- non rebreathing valve
- self inflating bag
- can deliver high Fi02 w/ 02 reservoir attached
- reservoir self fills w/ intake valve
- elimination of C02 depends on MV
46
Safety features incorporated into manual resuscitator
*biggest risk is barotrauma*
-ambu adult Mark IV; uses elasticity of outer cover go bag to limit the pressure developed
7kPa = 70 cmH20)
- pedi versions uses pressure limited valve (4kPa = 40cm H20)
- Laerdal range also used pressure limiting features
47
Non rebreathing valve of Ambu bag
- located at opposite end of bag from gas inlet
- have PEEP valve
JOB
- ensures gas flows out of bag and ONLY into pt port on inhalation
- exhaled gas escapes through expiratory port without mixing with fresh gas stored in bag on exhalation
48
Gas inlet on ambu bag
1. one- way flap valve
2. small bore nipple
3. wide bore inlet
4. reservoir system
49
reservoir system of gas inlet on ambu bag
* final concentration of 02 delivered is dependent on added 02 and how diluted it is from room air in the self inflating bag
- store the oxygen brought into system from nipple
- must have overflow valve to prevent overfilling of 02
- must have entrainment valve to allow access to room air for when 02 not available or need lower concentration of 02
* when minute vent (TV x RR) is greater than volume given bag will expand and supply all the gas for ventilation (100% 02)
50
small bore nipple of gas inlet on ambu bag
- allows admixture of 02
| * mounted on gas inlet
51
wide bore inlet of gas inlet on ambu bag
-supplies bulk of gas entering bag (usually air)
52
one-way flap valve of gas inlet on ambit bag
-fitted to inlet of self inflating bag
-bag squeezed, increased pressure inside bag, valve closes
(prevents gas going to back through inlet)
-bag released, bc its self inflating fresh gas from gas inlet it drawn in (can be air or 02 or mixture of both)
53
Circle system
* almost all anesthesia machines use some form a circle system
* C02 absorption during low flow (semi closed & closed system dependent on APL valve)
* C02 elimination via pop off valve during with FGF during high flow anesthesia (semi open system aka NO rebreathing)
- minimizes environmental pollution
- lower FGF than mapleson
- conserves heat/ humidity and anesthetic agent (rebreathing other exhaled agents)
- circular flow (unidirectional)
54
Similarities between Mapleson and Circle system
1. accept FGF (with semi-open circle system)
2. eliminate C02
3. give pt enough volume of gas from reservoir to meet inspiratory flow and volume needs
4. both can be semi open systems
5. both low resistance (mapleson a little lower)
55
Difference between Mapleson and Circle system
circle system =unidirectional flow
mapleson = bidirectional flow
circle system uses C02 absorber
mapleson uses FGF to rid C02
circle system can be be semi- closed or closed system
circle system bulkier and more complex design
56
7 commonest of Circle System
1. FGF source
2. unidirectional valves
3. inspiratory and expiratory limbs (with corrugated tubing)
4. Y- piece
5. APL valve/ Pop-off/ Over-flow
6. Reservoir bag
7. C02 absorber
57
Breathing circuit tube characteristics
-large bore 22mm, non rigid, 1 meter long corrugated tubing
(resistance to gas flow very small < 1cm H20/ L/ min of flow)
- internal volume 400-500 mL/m of length
- clear plastic (used to be rubber)
- 22 mm female fitting w/ machine
- patient end -- T-piece 22 mm male and 15 mm female coaxial fitting
58
Breathing circuit tube functions
- flexible
- low resistance
- lightweight connection
- reservoir
59
dead space
from y- connector to terminal bronchioles
60
Semi- open circle system
No rebreathing with very high FGF (10-15L/ min) to eliminate C02 and rebreathing
*C02 absorber not doing much, will last longer
- no conservation of waste gases
- no conservation of heat and moisture
- APL valve open all the way or vent in use
61
Semi- closed circle system
**most commonly used breathing system
- PARTIAL rebreathing of agents and exhaled gases (not C02 bc of absorber)
- relatively low flow rate (1-3L/ min)
- FGF less than minute vent
- conserves some heat and gases
- APL valve PARTIALLY closed, adjust as needed, or vent in use
62
Closed circle system
- used for LONG surgical cases
- third world countries (conserves gas)
-inflow gas EXACTLY matches metabolic demands
02 consumption of pt using very low flow rates
- complete rebreathing of all exhaled gases after C02 absorption
- APL valve closed
- change in gas concentration is VERY SLOW (increase volatile again and FGF)
63
Advantages of the Circle system
1. stable concentration of inspired gas
2. conservation of heat and moisture
3. saves money on anesthetics and gases
4. low resistajnce (mapleson lower)
5. fairly low FGF with no rebreathing of C02
6. can be used for closed- system anesthesia
7. can scavenge waste gases
preventing OR pollution
64
Disadvantages of Circle system
1. complex design
2. ATLEAST 10 connections
(risk of leaks, obstruction, disconnect)
**1/3 malpractice claims are r/t disconnects or misconnects of circuit
3. Risk of malfunctioning valve
stuck open = hypercarbia
stuck closed = airway obstruction
4. increased resistance to breathing ( > than mapleson)
5. Bulkier; less portable/ convenient than mapleson
6. increased dead space; which ends at end of y-piece where insp and expiratory separate
65
Circle system Leak Test
- set all gas flows to zero
- occlude y- piece
- close APL valve
- pressurize circuit to 30 cm H20 by using 02 flush valve
- ensure pressure hold for 10 seconds and activates sustained pressure alarm
- open APL valve and ensure pressure decreases
* does NOT assess unidirectional valves separate test)
66
Circle System Flow test
- assess integrity of unidirectional valves
- attach breathing bag to y-piece
- turn vent on
- assess integrity of valves
67
Breathing Circuit issues
1. misconnections and disconnections
2. leaks
3. valve failure
4. C02 absorber defect
5. bacterial filter occlusion
