Anesthesia Delivery Systems Flashcards
(75 cards)
1
Q
Describe basic functions of breathing circuit
A
- Interface b/w anesthesia machine and patient
- Deliver o2 and other gases( fresh gas flow)
- Eliminate CO2
- CO2 absorbent in circle system
- Other breathing circuits require FGF for elimination of CO2
- Other peripheral components: humidifiers, spirometers, pressure gauges, filters, gas analyzers, PEEP devices, waste gas scavengers, mixing and circulating devices.
Needs 3 components:
- Low resistance conduit for gas flow
- Resevoir for gas that meets inspiratory flow demand
- Expiratory port or valve to vent excess gas
DIE RVR
2
Q
What are the essential components of a breathign circuit?
A
- Low resistance conduit for gas flow
- Resevoir for gas that meets inspiratory flow demand
- Expiratory port or valve to vent excess gas
3
Q
What are the requirements of a breathing system?
A
- Deliver gases from machine or device to alveoli in same concentration as set in shortest time possible
- Effectively eliminate carbon dioxide
- Minimal apparatus dead space
- Low resistance to gas flow
- Rapid adjustment in gas concentration and flow rate
(MEDAL)
4
Q
What are some desirable breathing system features?
A
- Economy of fresh gas
- Conservation of heat (adequately warmed gases)
- Adequate humidification of inspired gas
- Light weight
- Convenience during use
- Efficiency during spontaneous as well as controlled ventilation
- Adaptability for adults, children and mechanical ventilators
- Provision to reduce environmental pollution
- Safe disposal of waste gas
5
Q
What are some considerations for a breathing circuit?
A
- LOW resistance
- Short tubing, large diameter, no sharp bends, caution with valves, minimize connections (1CM/H2O/1M of tubing)
- Rebreathing- might be beneficial
- Cost reduction
- Adds humidification/heat
- Do not want rebreathing of CO2! HIGHER FGF IS ASSOCIATED WITH LESS REBREATHING IN ANY TYPE OF CIRCUIT
- Dead spacE- increases chance of rebreathing CO2.
- Dead space ends at Y connector.
- Dead space minimized by separating inspiratory and expiratory streams as close to patient as possible
- Dry gases/humidification
- Manipulation of inspired content
- Concentration inspired resembles what is delivered from common gas outlet when rebreathing is minimal or absent
- Bacterial colonization
(Really Rancid Dead Dry Man Bacteria)
6
Q
What are ASA recommendations for infection control?
A
Bacteria filter with an efficiency rating of more than 95% for particle sizes of 0.3 micrometers should be routinely placed in anesthesia circuit
7
Q
What are HMEs?
A
Heat and moisture exchangers are filters placed on Y-piece and serve as inspiratory and expiratory barrier. Standard filters placed on expiratory limb
8
Q
What else can a breathing circuit incorporate in addition to filters?
A
- Spirometer (measure ventilation)
- Humidifier (warmth nd moisture)
- Sampling sites for gas analysis
- Scavenging devices to control atmospheric contamination
9
Q
What are classifications of anesthetic delivery systems?
A
Classification depends on whether reservoir is used and whether rebreathing occurs
- Open- no reservoir; no rebreathing
- Semi-open- reservoir;no rebreathing
- Semi-closed- reservoir; partial rebreathing
- Closed- reservoir; complete rebreathing
10
Q
What are is an open system and what are some examples?
A
NO rebreathing and NO resevoir
Insufflation
Simple face mask
NC
Open drop
11
Q
What is a semi open system and what are some examples?
A
NO rebreathing and YES to resevoir
Examples:
Mapleson (FGF dependent on design)
Circle system (FGF > MV)
Nonrebreather
12
Q
What is a semi closed system and what are some examples?
A
YES (partial) rebreathing, YES resevoir
Circle system (FGF< MV)
13
Q
What is a closed system and what is an example?
A
COMPLETE rebreathing and YES to resevoir
Circle system with very low FGF and APL closed
14
Q
What are open systems characterized by?
A
NO gas resevoir bag
NO valves
NO rebreathing of exhaled gas
- When FGF is 1-1.5 x the MV (about 10L/min in adult), dilution alone is sufficient to remove CO2. At this point, these systems behave the same as nonrebreathing system
15
Q
Describe a steal induction
A
- Inhalation induction where child is not touched or disturbed
- Mask is hovered over the child (open system) and once child is asleep, then the mask is sealed to the face (semi-open)
Adequate monitoring is institued ASAP, child then transferred to OR table
- Technique is atraumatic and avoids exposing child to strange OR sounds/surroundings while awke
16
Q
Describe insufflation method and its advantages and disadvantages.
A
Examples:
- Blow-by (insufflation under OR drapes)
- Tent
- Bronch port
- NC
- Steal induction
Advantages:
- Simplicity
- avoids direct patient contact
- no rebreathing CO2
- No reservoid bag or valves
Disadvantages:
- No ability to assist or control ventilation
- May have CO2 /O2 accumulation under drapes
- No control of anesthetic depth/Fio2
- Environmental pollution
17
Q
What determines if system is semi-open, semi closed or closed?
A
FGF!
IF FGF >MV, then it is semi-open
If FGF < MV, then semi-closed
If very low FGF and APL closed- closed
18
Q
Describe the mapleson system components, how they might be difference, and when it might be used.
A
Components
- Connection point to facemask or ETT
- Reservoir tubing
- FGF inflow tubing
- Expiratory pop off valve or port
Differences: location of pop off valve, fresh gas input and whether or not a gas resevoir is present
- ALL mapelson systems have resevoir except E
When used:
- Pediatrics
- Transport of patients
- procedural sedation
- weaning tracheal intrubation (t-piece)
- pre o2 during out of OR airway management
Best measure of optimatl FGF to prevent rebreathing: CO2
19
Q
Compare and contrast the various Mapleson devices
A
A. Pop off valve is by patient, FGF inlet by resevoir bag with corrugated tubing (AKA magill attachemnt)
B. Pop off valve and FGF right next to patient with corrugated tubing
C. FGF and Pop off valve next to patient, no corrugated tubing
D. FGF next to patient, Pop off valve next to resevoir
E. No resevoir, FGF next to patient (T-piece)
F. Pop off valve in rear of resevoir, FGF by patient with corrugated tubing between (Jackson Rees)
20
Q
What are some pros and cons of the Mapleson system?
A
Advantages (really simple portable dick)
- simplicity of design
- ability to change depth of anesthesia rapidly
- portability
- lack of rebreathing of exhaled gases (only if FGF high enough)
Disadvantages (he’s so_f_t)
- Lack of conservation of heat and moisture
- limited ability to scavenge waste gases
- high requirement for FGF
21
Q
What are the 3 funcitonal groups of the Mapleson system and how do they differ in controlled vs spontaneous ventialation?
A
Mapleson A
- pop off near facemask, FGF near resevoir
Mapleson B and C
- pop off and FGF near facemask (VERY wasteful system)
Mapleson D, E, F
- FGF located near facemask and pop off located at opposite end (oppostie of a)
Controlled
D>B>C>A
Dog bites can ache
Spontaneous
A>D>C>B
All Dogs Can Bite
“Dogs are friends” DF together
22
Q
Why is the Mapleson A system so superior for spontaneous ventilation?
A
Alveolar gas is shunted off immediately via pop off valve near face mask
FGF flow inflows from opposite end of patient, near resevoir
This allows very little alveolar gas to collect in dead space, minimizing rebreathing
23
Q
What setup do we want for Mapleson circuit?
A
FGF proximal to patient and pop off valve distal
24
Q
What does CO2 rebreathing depend on in Mapleson system?
A
- Fresh gas flow rate
- MV of patient
- Mode of ventilation (spon v controlled)
- CO2 production of patient (increased with fever, catabolism)
- Respiratory waveform chracteristics
- inspiratory flow, I:E time, I:E ratio, expiratory pause
Adjustments to ventialtory pattern that allow FGF to constitue larger portion of inspired gas (slow inspiratory time or low flow) or that enable exhaled gases to be completely washed out (long expiratory pause or slow rate) reduce amt of rebreathing.
25
Describe a Mapleson A System
* MOST effecient for SV
* warm, humidified, exhaled dead space gas i resused
* Least efficient for controlled ventilation- Requires **20L/min** FGF to prevent rebreathing
* No rebreathing during SV when FGF is 1X MV
* Requires larger FGF to eliminate rebreathing durign controlled ventilation
* Impractical design in the OR
* Proximal location of overflow makes scavenging difficult
* Difficult to adjust during head and neck sx
* Heavy valve can dislodge a small tracheal tube
26
What is the air flow in a Mapleson A system during spontaneous ventilation?
* Patient inhales fresh gas and partially empties the reservoir bag
* Patient begins to exhale, anatomical dead space gas then alveolar gas, down tube towards reservoir bag.
* as the bag fills, pressure within system opens APL valve to vent exhaled gases which are mainly alveolar
* During expiratory pause, the FGF flushes the remaining alveolar gas away from pt and out of APL valve.
* If FGF matches alveolar ventilation, then just as much gas flows into the system as is exhaled, leaving only fresh, humidified dead space, gas in the circuit
27
Describe air flow during IPPV in the Magil system
* With APL valve closed, the bag is squeezed, generating an inspiratory breath which partially empties the bag
* Subsequent expiratory breath fills reservoir bag and tubing with dead space and alveolar gas
* If this is not flushed out with high FGF, rebrathing of exhaled CO2 occurs
28
Describe common characteristics of Mapleson B and C circuits
* Require high FGF, limiting the use
* B circuit has length of corrugated tubing connecting system to rest of reservoir bag
* inefficient
* impractical for clinical use for either spontaneous or controlled ventilation
* FGF in both systems need to be high to prevent rebreathing. The proximity of APL valve and FGF provides potential for mixing of inspiratory and expiratory gases
* Mapleson C (water's circuit without absorber) used in resuscitation situations and for patient transfer
*
29
Describe the Mapleson D circuit
* Reversed from configuration of Mapleson A
* Can be used for both spontaneous and controlled ventilation
* Spontaneous respirations FGF= 2-3 x MV
* Controlled FGF=1-2x MV
* Most efficient Mapleson durign controlled ventilation
* Mostly used in coaxial form known as "Bain" system
* has inner tubing of FGF directly to patient who then exhales down outer corrugated tubing into reservoir bag and APL valve.
30
What are some issues with the Mapleson D circuit?
* Disconnectiong of inner tubing can result in increased dead space and massive rebreathing
* Tests must be performed to check for disconnection
* inner tube of pt end is occluded using tip of finger or plunger of 2cc syringe
* if tube is connected, causes back pressure on FGF and flowmeter bobbin dips
* if disconnected, leads to venturi effect and causes reservoir bag to collapse
* High FGF needed
31
What is Mapleson D circuit commonly known as?
Bain circuit
32
Describe air flow in Mapleson D circuit during spontaneous ventilation?
* Patient takes inspiratory breath from fresh gas which fills OUTER corrugated tubing and reservoir bag
* On expiration, the exhaled gases, mixed with continuous FGF, tavel down corrugated tubing towards reservoir bag and APL valve.
* once pressure high enough, the APL valve opens, venting excess gas
* Expiratory PAUSE allows FGF to flush out the exhaled gas and fill corrugated tubing with any axcess vented
* high FGF are **required** to prevent rebreathing
33
Describe Mapleson D circuit during IPPV?
* Reservoir bag is squeezed in order to generate inspiratory breath
* expiratory phase: alveolar gases, mixed with continous FGF, travel down corrugated tubing towards reservoir bag and APL valve. Once pressure is high enough, APL valve opens, venting exhaled gases
* Factors affecting rebreathing (MV and inspiratory flow rate) controlled by anesthetist, allowing a lower FGF and then a more **efficient** system
* **FGF of 70 ml/kg/min** to prevent rebreathing
* when FGF \>100/mL/kg/min, PAco2 is governed by minut ventilation
* FGF\<90 mL/kg/min, PAco2 **independent** of minute ventilation. Is function of rebreathing, which is governed by FGF
34
Which circuit is most widely used for pediatric anesthesia?
Mapleson D circuit
35
What do you do to fresh gas flow in Mapleson D circuit to prevent rebreathing during IPPV?
Increase FGF
36
Which ventilatory adjustments would allow fresh gas flow to constitue larger proportion of inspired gas?
Slow inspiratory time or low inspiratory flow
37
Which ventilatory patterns would enable exhaled gases to be completely washed out?
Long expiratory pause
slow RR
38
Describe the bain circuit along with advantages and disadvantages
* Coaxial modification of Mapleson D
* Used for controlled or SV
* FGF- same as mapleson D
* SV- requires FGF 200-300 mL/kg/min
* Controlled 70 mL/kg/min
**Advantage**
* FGF tubing is within large bore corrugated tubing
* allows exhaled gases to warm the inspired gas
* this allow humidity to be preserved
* Lower resistance to breathing
* low profile of single hose attached to patient
* Ease of scavenging waste from overflow valve
**Disadvantage**
* Potential for inner tube leaks, kinking or disconnection
* inability ot directly inspect integreity of inspiratory limb
39
Describe the Pethick test.
Fresh O2 flush passed through circuit for several seconds iwth patient end occluded.
* If inspiratory limb intact, reservoir bag deflates
* If leak present, fresh gas escapes into expiratory limb and reservoir bag remains inflated
Recommended to test integrity of Bain circuit
40
What is a bain circuit?
Mapleson D circuit
41
Describe components and use of Mapleson E system
* Commonly used in ICU or PACU setting
* NO RESERVOIR BAG (expiratory limb is reservoir)
* No pop off valve
* If SV FGF= MVX2-3
* Minimal dead space
* no valves
* very little resistance
FGF is sole determinant of whether rebreathign occurs and influences the o2 concentration of inspired gas
If FGF not equal ot inspiratoyr flow rate, then air will be entrained and dilute O2
42
Describe compenents, uses, advantage disadvantage of Jackson-Rees system?
* Type of Mapleson F system
* VERY popular in pediatrics
* FGF 2-3x MV to prevent rebreathing
* Modification fo mapleson E with pop off valve located at end of reservoir bag
**Advantages**
* Allows application of continous positive airway pressure or hand ventilation
* Provides visual indicator of respiration with reservoir bag
* Lightweight, repositions easily
* adaptation for scavenging system
**Disadvantage**
* Need for high FGF to prevent rebreathing
* possibility of high airway pressure and barotrauma if overflow vlve occluded
* no humidification in system. must be attached
43
Describe characteristics of ambu bag
* Manual respirator
* Critical piece of equipment and part of morning checks
* has non rebreathing valve and self inflating bag
* can deliver high FIO2 with O2 reservoir attached
* CO2 washout depends on MV
44
What is the purpose of the one way flap valve on the ambu bag?
Prevents escaping of gas back through inlet. The pressure from squeezing causes flap valve to close. When bag is release, the self-inflating characteristic causes fresh gas from respirable gas inlet to be indrawn
45
What is the purpose of the wide bore inlet?
Supplies bulk of gas entering bag and is usually air, unless O2 added.
46
Talk about the reservoir system in an ambu bag
* Used in almost all manual resuscitators.
* Purpose is to store o2 fed into system from nipple/
* If MV of o2 supplised is \> than volume givent o pt, bag will expand
* Reservoir must be fit with overflow valve ot prevent overfilling from too high flow o2
* Must also allow entraintment of RA when O2 is not used or when lower o2 concentrations desired
47
What is the purpose of the nonrebreathing valve on an ambu bag
* Housed on opposite end of gas entrainment system
* Ensures gases from bag go to patient
* On exhalation, ensures exhaled gas escapes through expiratory port without mixing with the FG stored in the bag
* Allow for addition of peep valve
48
What are some safety features of an ambu bag?
* All manual respirators have risk of barotrauma. Some manufacturers incorporate and device to limit pressure
* more important in infant and peds
* Mark IV bag limits elasticity of outer cover of bag to limit pressure to 7kPa
* Pediatric verison has pressure limiting valve on upstream section. Preset at 4 kPa
49
Describe similarities and differences for Mapleson and Circle system
**Similarities to circle system**
* Accept a FGF
* Supply patient with suff volume of gas form reservoir to satisfy inspiratory flow and volume requirements
* Eliminates CO2
**Differences**
* **Bidirectional** flow
* Do not use on absorber
* Depends on appropraite rate of FG inflow to eliminate CO2
* Circle system minimizes environmental pollution and enables lower FGF than mapleson while conserving heat, humidity and anesthetic agent
* Changes in anesthetic concentration can take some time to reahc equilibrium unless high FGF used
* Need to be vigilant with mapleson for manifestations of stuck (resistant) or floating (rebreathing) valves
50
Describe the circle system
* Hallmark is unidirectional gas flow via unidirectional vlaves
* Components arranged in circle
* Can be used as semi open, semi closed or closed
* Depends on APL valve
* depends on FGF
* Prevent rebreathing of CO2 though chemicla neutralization
* If CO2 absorbant needs to be replaced, can increase FGF in order to remove CO2 until absorbant can be replaced
* Allows rebreathing of other exhaled gases (i.e. anesthetics)
51
What are the components of a circle system
1. FGF source
2. Inspiratory and expiratory unidirectional valves
3. inspiratory and expiratory limbs/corrugated tubing
4. Y-piece connector
5. APL valve (overflow, pop off valve)
6. Reservoir bag
7. CO2 absorber
4 quadrants A,B,C,D
52
Describe FGF in circle system
* Common gas outlet
* Gas inflow incorporated with inspiratory unidirectional valve or CO2 absorbent canister housing
* Preferred FGF inflow site is between co2 absorber and inspiratory valve
53
What is the purpose and characteristics of unidirectional valves
* Gas flowing into valve raises disc from seat, then passes though valve
* Reversing gas flow causes disc to connect to seat, stopping retrograde flow
* Cage prevents lateral or vertical displacement of disc
* Transparent dome allows observation of disc movement
* Essential characteristics are **low resistance and high competence**.
* must open widely with little pressure and close rapidly and completely with no backflow
* One must be place on inspiratory and expiratory limb b/w reservoir bag and pt
* Prevent any part of circle system to contribute to dead space
* Must be **hydrophobic**
54
Primary source of reseistance in anesthesia delivery system?
* Tracheal tube
* Valves
* CO2 absorber
55
Describe the functions of a reservoir bag.
1. They serve as reservoir for anesthetic gases or O2
* Optimally sized bag can hold volume that exceeds respiratory inspiratory capacity (0.5L-6L)
2. Visual assessment of SV and rough estimate of volume
1. Visual assessment affected by FGF
3. Means for manual ventilation
56
What are the minimal and maximal pressures a reservoir bag needs to hold?
Minimal pressure 30cmH2O- 60 cmH2O
57
Describe purpose fo APL valve
* AKA pressure relief, pop off, safety relief valve
* Permits PEEP durign SV or allowed pressure limited controlled respiration
* Releases gas to scavenge or atmosphere exhaust port
* User adjustable
* clockwise-closes and increase pressure in system
* Provides contorl of pressur ein system- pressure gauge on absorber
58
What happens with APL vavle during spontaneous respiration
Valve fully open
Close paritally only if reservoir bag collapses
59
What happens with APL valve on assisted ventialtion?
* Valve partially open
* Bag squeezed on inspiration
* carefel and frequent adjustment necessary
60
Where is the APL valve in mechanical ventialtion
APL left open
61
What are two types of APL valves?
* Spring loaded disgn
* Adjustable needle valve
62
What are the characteristics to breathing tube used
* Large bore, non rigid corrugated tubing
* corrugated allows for gas mixing radially and longitudinally
* clear plastic
* 22 mm fematle fitting with machine
* patient end T-piece, 22mm male, 15 mm female coaxial fitting
* Functions
* Flexible, low resistance, lightweight
* reservoir- internal volume 400-500 mL/m
63
Describe what is dead space in a circle system.
If valves working properly, dead space is the distal limb of y-connector to any tube or mask between it and patient's airway
64
Describe the semi-oepn circle system (more in depth than rebrathing and reservoir)
* No rebreathing occurs; very high flow of FGF (10-15l/min) needed to eliminate rebreathing of gases
* No conservation of waste gases and heat
* APL valve open all the way or ventilator in use
65
Describe the semi-closed circle system (more in depth than rebrathing and reservoir)
* Most commonly used breathign system in US practice
* Allows some rebreathign of agents and exhaled gases (minus co2)
* Relatively low flow rates (1-3L/min)
* FGF is **less than** MV
* Conserves some heat and gas
* APL valve is partially closed and adjusted as needed or ventialtor in use
66
Describe closed circle system(more in depth than rebrathing and reservoir)
* Used in long surgical cases in 3rd world countries
* inflow gas exactly matches metabolic needs/o2 consumption (o2 flow rate 250mL/min)
* Total rebreathing of exhaled gases
* APL closed
* change in gas concentration VERY slow
67
Advatages of circle system
* Relative stability of concentration of inspired gases
* conservation of moisture and heat
* low resistance
* can be used for closed system anesthesia
* can be used with fairly low flow rates with no rebreathing of co2
* economy of anesthetics and gases
* scavenge waste gases
* prevent o2 pollution
68
Disadvantage of Circle system
* Complex design
* has 10 connections
* sets the stage for leaks, obsturciton or disconnection
* third malpractice claims for disconnects or misconnects of circuit
* Potentail of malfunctioning valves
* Increased resistance to breathing
* Less portable and conveninet than Mapleson
* Increased dead space BUT dead space ends at y-piece
69
What are the potential issues with malfuncitoning valves
Stuck open-rebreathing
Stuck closed- airway obstruction
70
Describe Universal F circuit
A coaxial system that can be mounts on standard circle system hardware.
Inspiratory gases in green inner hose.
Can be adapted for transport by putting o2 supply source to inspiraotyr limb and reservoir and pop off valve to expiratory limb
71
Trouble shoot increased inspired CO2?
* co2 absorber exhaustion
* temp fix to increase FGF
* incompetent unidirectional valve
* if increasing FGF does not help, most likely stuck valve
72
Describe the leak test
* Set all gas flows to zero
* Occlud y piece
* close apl valve
* pressurize circuit to 30 cm H2O using O2 flush valve
* Ensure pressure holds 10 seconds
* Listen for sustain pressure alarm
* Open APL valve and ensure pressure decreases
## Footnote
**DOES NOT TEST COMPETENCY OF UNIDIRECTIONAL VALVES**
73
Describe flow test.
* Attach breathing bag to Y piece
* Turn on ventilator
* Assess integrity of unidirectional valves
74
What are some common circuit issues?
* Misconnections or disconnections
* Leaks
* Valve failure
* CO2 absorber defect
* Bacterial filter occlusion
75
What is gas flow needed for open systems?
