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NURA 641 Intro to Nurse Anesthesia > 190708_ Delivery Systems > Flashcards

190708_ Delivery Systems Flashcards

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1
Q

breathing circuit

A

•Interface between the anesthesia machine and the patient
•Deliver O2 and other gases (FGF?)
•Eliminates carbon dioxide
- CO2 absorbents eliminate CO2 in circle systems
- Other breathing circuits require fresh gas flow (FGF) for elimination of CO2
•3 essential components:
- low resistance conduit for gas flow
- reservoir for gas that meets inspiratory flow demand
- expiratory port or valve to vent excess gas

***Recycled gas - warms, humidifies, decrease $

***Alveolar gas + Dead space + FGF = ?

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2
Q

Requirements of a Breathing System

A
  • deliver the gases from the machine or device to the alveoli in the same concentration as set and in the shortest possible time
  • effectively eliminate carbon dioxide
  • minimal apparatus dead space
  • low resistance to gas flow
  • allow rapid adjustment in gas concentration and flow rate
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3
Q

Breathing System Features

A

Desirable:
 economy of fresh gas
 conservation of heat (adequately warm 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

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4
Q

Breathing System Considerations

A

•Resistance- want low resistance
- Short tubing, large diameter tubing (22mm int. dia.), avoid sharp bends, caution with valves, minimize connections (more connections = more potential leaks)
***Correlation = turbulent flow for better mixing of gases while minimizing resistance
•Rebreathing- may be beneficial
- Cost reduction
- Adds humidification/heat to gases
- BUT: Do not want rebreathing of CO2
- *Higher FGF is associated with less rebreathing in any type of circuit~but….increases $
•Dead Space- increases the chance of rebreathing CO2 - - Dead space ends where the inspiratory and expiratory gas streams diverge (Y connector)
– Apparatus dead space can be minimized by separating the inspiratory and expiratory streams as close to the patient as possible
•Dry gases/humidification
•Manipulation of inspired content
- The concentration inspired most closely resembles that delivered from the common gas outlet when rebreathing is minimal or absent
•Bacterial colonization

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5
Q

Classification - Open system

A

no reservoir; no rebreathing (no valves)

Insufflation (blow by)
Open Drop (Simple Face Mask, Nasal Cannula)
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6
Q

Classification - Semi-Open

A

reservoir; no rebreathing

Mapleton circuit (FGF dependent on design) 
circle system (FGF > MV)
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7
Q

Classification - Semi-Closed

A

reservoir; partial rebreathing

circle system (FGF < MV)

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8
Q

Classification - Closed

A

reservoir; complete rebreathing

circle system w/ very low FGF and APL valve closed

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9
Q

Insufflation

A

•Examples: Blow-by (or insufflation under OR drapes), tent, bronchoscopy port, nasal cannula, “steal” induction •Advantages: Simplicity
- Avoids direct patient contact
- No rebreathing of CO2
- No reservoir 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
- elevated fire risk

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10
Q

Inhalation Induction (steal)

A

***open at first
• child is already asleep on arrival in the OR
• the child is not touched or disturbed
• breathing circuit is primed with N2O in O2 and the mask is gently placed near the child’s face and gradually brought closer and closer until it is gently applied to the face (semi-opem)

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11
Q

Mapleson Systems

A

• Mapleson systems components
- connection point to a facemask or ETT (15mm)
- reservoir tubing (22mm?)
- fresh gas inflow tubing (22mm?)
- expiratory pop-off valve or port
• Differences: locations of pop-off valve, fresh gas input, and whether or not a gas reservoir bag is present
- Note: all Mapelson systems EXCEPT E also have a reservoir bag
• When are these used?
- pediatrics
- transport of patients
- procedural sedation
- weaning tracheal intubation (the T-piece)
- Pre-02 during out-of-the-OR airway management
• Best measure of optimal FGF to prevent rebreathing: etCO2
• Reservoir bag inflation requires FGF, unlike ambu bag

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12
Q

Mapleson Pros

A

•simplicity of design
•ability to change the depth of anesthesia rapidly •portability
•lack of rebreathing of exhaled gases
- NOTE: ONLY if FGF is adequate

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13
Q

Mapleson Cons

A
  • lack of conservation of heat and moisture
  • limited ability to scavenge waste gases
  • high requirements for FGF
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14
Q

Mapleson A

A

pop-off located near facemask

FGF located at opposite end

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15
Q

Mapleson B & C

A

pop-off and FGF located near facemask

***very wasteful of FGF, not really used

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16
Q

Mapleson D, E, F

A

FGF located near facemask

popoff located at opposite end

(OPPOSITE OF MAPLESON A)

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17
Q

Efficiency: Controlled

A

D&F > B > C > A

mnemonic: Dog Bites Can Ache

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18
Q

Efficiency: Spontaneous

A

A > D&F > C > B

mnemonic: All Dogs Can Bite

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19
Q

CO2 Rebreathing will depend on:

A

•Fresh gas inflow rate
•Minute ventilation of patient
•Mode of ventilation (spont v controlled)
•CO2 production of individual patient (increased with fever, catabolism, etc)
•Respiratory waveform characteristics
- e.g., inspiratory flow, inspiratory and expiratory times, I:E ratio, and expiratory pause
•Type of ventilation (spontaneous or controlled)

20
Q

Mapleson A “Magill”

A

• MOST EFFICIENT FOR SV
• Least efficient for controlled ventilation
- requires up to 20L/min
• No rebreathing during SV when the fresh-gas flow is at least 1x minute ventilation
• Requires a larger fresh-gas flow to eliminate rebreathing during controlled ventilation
• Impractical design in the operating room
- proximal location of the overflow valve makes scavenging difficult
- difficult to adjust during head and neck surgery
- heavy valve can dislodge a small tracheal tube

21
Q

Mapleson B & C

A

• Require high FGF, limiting their use
• The ‘B’ circuit has a length of corrugated tubing connecting the rest of the system to the reservoir bag
- inefficient
- impractical for clinical use for either spontaneous or controlled ventilation
• The FGF in both systems needs to be very high in order to prevent rebreathing – the close proximity of the APL valve to the fresh gas port provides the potential for mixing of inspiratory and expiratory gases
• The Mapleson C (often referred to as a ‘Water’s circuit without absorber’) is used in resuscitation situations and for patient transfer

22
Q

Mapleson D

A

• Mapleson D is reversed configuration of Mapleson A
• Can be used for both spontaneous and controlled ventilation
- During spontaneous respiration, FGF = 2-3 x MV
- During controlled ventilation, FGF = 1-2 x MV
• Most efficient Mapleson during controlled ventilation

  • **increased RR = decreased EEP = increased RB
  • **decreased IT = increased ET = increased RB?

**Conditions that increase carbon dioxide production (e.g., fever, catabolic state, or malignant hyperthermia) must be met with a proportional increase in fresh-gas flow and ventilation.

23
Q

Bain system or circuit

A

consists of inner tubing that delivers FGF directly to the patient who then exhales down the outer corrugated tubing to the reservoir bag and APL valve.

•Is a coaxial modification of Mapleson D
•FGF tubing within the large bore corrugated tubing
- allows the exhaled gas to warm the inspired gas
- preserves heat and humidity
•Used for controlled OR SV
•FGF requirements
- same as Mapleson D.
•Disadvantage
- Potential for inner tube leaks, kinking or disconnection
- Disconnection of the inner tubing can result in increased dead space leading to massive rebreathing so tests must be performed to check for a disconnection
- Pethic test = + leak and collapses the bag?

24
Q

Mapleson E (T-Piece)

A 
•Modification of Ayre’s T-Piece commonly used to administer O2 in ICU and PACU settings 
•NO RESERVOIR BAG 
- the expiratory limb is the reservoir
•NO POP-OFF VALVE!!! 
•If SV, FGF = MV x 2-3

***see PP slide 27 for animation

25
Q

Mapleson F (Jackson-Rees)

A

•A modification of the Mapleson E Ayre’s T piece with an adjustable pop-off valve at the end of reservoir bag •Very popular in pediatrics
•Allows the application of continuous positive airway pressure or hand ventilation
•Provides a visual indicator of respiration with the reservoir bag
**see and feel pt compliance
**Adjustable pop off valve for SV & CV

26
Q

Ambu Bag

A
  • Manual resuscitator needed for emergency
  • Critical piece of equipment and part of morning checks
  • Contain non-rebreathing valve & self inflating bag
  • Capable of delivering high FiO2 with O2 reservoir attached
  • Reservoir self filling w/intake valve
  • CO2 wash-out depends on minute ventilation
27
Q

Mapleson Systems v. Circle Systems:

Similarities

A
  • accept a FGF
  • supply the patient with a sufficient volume of gas from a reservoir to satisfy the inspiratory flow and volume requirements
  • eliminate carbon dioxide
28
Q

Mapleson Systems v. Circle Systems:

Differences

A
  • bidirectional flow
  • do not use an absorber
  • depend on an appropriate rate of fresh gas inflow to eliminate carbon dioxide
29
Q

Circle System

A
  • Almost all anesthesia machines are equipped with some form of a circle breathing circuit
  • Allows carbon dioxide absorption during low-flow anesthesia and elimination through the pop-off valve during high-flow anesthesia.

• Hall mark is unidirectional gas flow via unidirectional valves
• Components are arranged in a circle
• Can be used as a semi-open, semi-closed, or closed system
- Depends on the adjustment of the APL valve
- Depends on FGF rate
• Prevents re-breathing of CO2 by chemical neutralization
• Allows re-breathing of other exhaled gases

30
Q

Circle System: Characterized by 7 components

A
  1. FGF source
  2. Inspiratory and expiratory unidirectional valves
  3. Inspiratory and expiratory limbs/ corrugated tubing
  4. Y-piece connector
  5. Adjustable pressure-limiting valve (APL valve, over-flow valve, or Pop-off valve )
  6. Reservoir bag
  7. CO2 absorber

GOOD TEST QUESTION! AND THEN….name complications……?

31
Q

FGF

A
  • common gas outlet
  • gas inflow incorporated with the inspiratory unidirectional valve or the carbon dioxide–absorbent canister housing
  • preferred fresh gas inflow site is between the carbon dioxide absorber and the inspiratory valve.
32
Q

Unidirectional Valves

A
  • Gas flowing into the valve raises the disc from its seat, then passes through the valve.
  • Reversing the gas flow causes the disc to contact its seat, stopping further retrograde flow.
  • The guide (cage) prevents lateral or vertical displacement of the disc.
  • The transparent dome allows observation of disc movement.

***if worried about a valve issue….INCREASE FGF!

33
Q

Reservoir Bag

A

•Made of neoprene or rubber
•Functions:
1) they serve as a reservoir for anesthetic gases or O2 •optimally sized bag can hold a volume that exceeds the patient’s inspiratory capacity (vary 0.5 L to 6 L)
•3L most common adult size bag
2) visual assessment of SV & rough estimate of the volume
•Visual assessment affected by FGF
3) means for manual ventilation

34
Q

APL Valve

A

• AKA: pressure relief, pop-off, safety-relief valve
• Purpose:
- permits PEEP during SV
- allows for pressure limited controlled respiration
• Releases gases to scavenge or atmosphere exhaust port
• User-adjustable:
- clockwise
- closes valve & increases pressure within system
• Provides control of pressure in system
- pressure gauge on absorber
• Spontaneous Respiration:
- valve fully open
- close partially only if reservoir bag collapses
• Assisted Ventilation:
- valve partially open (based on pt compliance…feel)
- bag squeezed on inspiration
- careful & frequent adjustments necessary
• Mechanical Ventilation- APL left open

35
Q

Breathing Tubes

A

•Large bore, non rigid corrugated tubing
•Clear plastic (historically rubber was used)
•22 mm female fitting w/machine
•Patient end – T piece 22 mm male, 15 mm female coaxial fitting
•Functions:
 Flexible, low resistance, lightweight connection
 Reservoir

***circuit checks for each pt!

36
Q

O2 Flush

A
  • through absorber via common (fresh) gas inlet?
  • through circuit
  • to pt
  • to bag
  • through APL and out?

***see PP slide 44

37
Q

Dead Space in Circle System

A

If the unidirectional valves are working properly, the only dead space in the circle system is the distal limb of the Y-connector and any tube or mask between it and the patient’s airway.

38
Q

Semi-open Circle System

A
  • No re-breathing occurs; very high flow of FGFs (1015L/min) are used and eliminates rebreathing of gases
  • No conservation of wastes gases and heat
  • APL valve is open all the way or ventilator in use
39
Q

Semi-closed Circle System

A

• Most commonly used breathing system in U.S. practice • Allows for some re-breathing of agents and exhaled gases (minus CO2 due to CO2 absorption)
• Uses relatively low flow rates (about 1-3L/min)
• FGF is less than minute ventilation
• Conserves some heat and gases
• APL valve is partially closed and adjusted as needed; or ventilator is in use
***partial closure enough to keep bag inflated

40
Q

Closed Circle System

A

• Used often in long surgical cases and third world countries
***conserves gas
• Inflow gas exactly matches metabolic needs/ O2 consumption of the patient using very low flows (O2 flow rate ~ @ 250 mL/min)
• Total re-breathing of all exhaled gases after absorption of CO2
• APL is closed
• Change in gas concentrations is VERY slow

41
Q

Advantages of the Circle System

A

Relative stability of concentration of inspired gases Conservation of moisture and heat
Low resistance (but not as low as Mapleson)
Can be used for closed-system anesthesia
Can be used with fairly low flows with no rebreathing of CO2
Economy of anesthetics and gases
Can scavenge waste gases
Prevention of OR pollution

42
Q

Disadvantages of Circle System

A

• Complex design
• Has at least 10 connections
- This sets the stage for potential leaks, obstruction, or disconnection
- A third of malpractice claims are related to disconnects or misconnects of the circuit
• Potential of malfunctioning valves
- Stuck open= rebreathing
- Stuck closed= airway obstruction
• Increased resistance to breathing (above Mapleson)
• Less portable and convenient than the Mapleson systems due to its bulkiness
• Increased dead space BUT dead space ends at the Y piece

43
Q

Single-limb Universal F Circuit

A

Similar to Bain system, BUT circle system

44
Q

Increased INSPIRED CO2

A

• CO2 Absorbent Exhaustion
- Temporary fix: increase FGF above minute ventilation
• Incompetent Unidirectional Valve:
- If increasing FGF does not help then it is likely a stuck valve

***EtCO2 wave form and EEP (lack there of)

45
Q

Circle System Check

A

• Leak Test
- 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
- NOTE: This test does not assess integrity of unidirectional valves
• Flow Test
- Attach breathing bag to Y- piece, turn on ventilator, and assess integrity of unidirectional valves

46
Q

Circuit Issues

A
  • misconnections or disconnections
  • leaks
  • valve failure
  • carbon dioxide absorber defect
  • bacterial filter occlusion
47
Q

SLIDE 55!!!

A

STUDY!!!! KNOW!!!!!

NURA 641 Intro to Nurse Anesthesia (8 decks)

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