Breathing Systems Lecture 2 Flashcards
(87 cards)
1
Q
How are Mapleson circuit different from other breathing circuits?
A
Only one limb (no separate exp/insp limbs)
2
Q
What are the components of a Mapleson Circuit?
A
- Reservoir bag
- Corrugated tubing
- APL valve
- Fresh gas inlet
- Patient connection
3
Q
Position of the _____________ on the Mapleson circuit will determine the type of Mapleson performance and classification
A
Fresh gas inlet
4
Q
What type of circuit is this?
A
Mapleson A (Magill’s system)
5
Q
Where does FGF enter in a Mapleson A circuit?
A
Near reservoir bag (back of circuit opposite of patient)
6
Q
Where is APL located in a mapleson A circuit?
A
Near the patient
7
Q
What is the Mapleson A circuit the most efficient circuit for?
A
Spontaneous ventilation
8
Q
What is the Mapleson A circuit the worst at?
A
Controlled ventilation
9
Q
Why does rebreathing typically occur during controlled ventilation with Mapleson A circuit?
A
Rebreathing occurs unless minute ventilation is VERY high (>20L/min)
10
Q
What type of circuit is this?
A
Mapleson B
11
Q
Where are APL, FGF, and reservoir bag on mapleson B circuit?
A
- APL and FGF: Near patient
- Reservoir bag: at end of system
12
Q
What should the rate of FGF be to prevent rebreathing during spontaneous/controlled ventilation with a mapleson B circuit?
A
FGF should be 2X minute volume during spontaneous and controlled ventilation to prevent rebreathing
13
Q
Which Mapleson circuit is identical to mapleson B, but doent have the tubing?
A
Mapleson C
14
Q
What circuit is this?
A
Mapleson C
15
Q
When is mapleson C used?
A
Used in emergency resuscitation (almost as efficient as mapleson A)
FGF 2x minute vent
16
Q
What type of circuit is this?
A
Mapleson D
17
Q
What is the most efficient system for controlled ventilation?
A
Mapleson D
18
Q
Which system has a 3 way T piece and what is it connecting?
A
- Mapleson D
- connecting patient mask, fresh gas inlet, and corrugated tubing
19
Q
Where is the APL in Mapleson D circuit?
A
At the end near reservoir (Can add PEEP valves)
20
Q
What is the Bain modification of the mapleson D circuit?
A
Fresh gas flow coaxial inside the tubing
21
Q
What type of circuit is this?
A
Bain (modification of mapleson D)
22
Q
What FGF is required to prevent rebreathing in a bain circuit?
A
- 200-300 mL/kg/min with spontaneous breathing (2x Vm)
- 70 mL/kg/min with controlled ventilation
Clinically proven FGF should be at least 1.5-2X pt minute ventilation in order to minimize rebreathing
23
Q
What factors influence the composition of the inspired mixture?
A
- FGF (only factor that can be manipulated in a spontaneously breathing pt)
- Resp rate
- Exp rate
- VT
- CO2 production in the body
24
Q
What are advantages of the Bain system?
A
- Warming the fresh gas inflow by surrounding exhaled gases (counter current exchange)
- Improved humidification with partial rebreathing
- Ease of scavenging waste
- Overflow/pressure valves (APL)
- Disposable/sterile
25
What are disadvantages of the bain circuit?
- Unrecognized disconnection
- Kinking of inner fresh gas flow tubing
- Requires high flows
- Not easily converted to portable when commercially used anesthesia machine adapter bain circuit used
26
What is a unique hazard of the Bain circuit?
Disconnection or kinking of the inner hose (fresh gas delivery hose)
27
What is the Pethick's test for the Bain circuit?
- Occlude the patients end of the circuit (at elbow)
- Close the APL valve
- Fill the circuit, using the oxygen flush valve
- Release the occlusion at the elbow and flush
- Venturi effect flattens the reservoir bag if the inner tube is patent (sucks the air out)
*Tests patency of inner hose*
28
What is another name for Mapleson E?
Ayre's T piece
29
What is this circuit?
Mapleson E
30
What is different about the "reservoir" of the mapleson E circuit?
- Corrugated tubing attached to the T-piece functions as a reservoir
- No reservoir bag/No APL
- Used in spontaneous breathing pts to give O2
31
What is another name for the mapleson F circuit?
Jackson-Rees
32
What is the Jackson Rees circuit (mapleson F) a modification of?
Modification of mapleson E circuit→ just has reservoir bag added
33
Why is excessive pressure less likely to develop in a Jackson Rees circuit?
No APL valve
34
Which circuit is common to use with pedi patients?
Jackson Rees
35
Which circuit is this?
Mapleson F (Jackson Rees)
36
What allows for improved rebreathing efficiency of the mapleson circuits?
Location of the pop-off valve relative to FGF
37
Which mapleson circuits have significant amount of fresh gas vented through pop-off at end expiration?
Mapleson B and C
38
Which mapleson systems have fresh gas flow that drives exhaled alveolar gas away from the patient?
Mapleson D, E, and F
39
Which mapleson is most efficient with spontaneous ventilation?
[A] > [D, E, F] > [C, B]
40
Which mapleson system is most efficient with controlled ventilation?
[D, E, F] > [B. C] > [A]
41
What are advantages of Mapleson systems?
- Simple, inexpensive, light weight
- Changes in FGF composition result in rapid changes in circuit
- Low resistance to gas flow
- No toxic products d/t lack of CO2 absorbents
- No degradation with volatiles
42
What are the disadvantages of mapleson systems?
- Require high FGF
- Less efficient conservation of heat/humidity
- Scavenging challenge (except mapleson D)
- Not suitable for patients with MH (couldnt increase FGF enough to remove excess CO2)
43
What allows for unidirectional flow in a circle system?
Unidirectional valves
44
Which system is dependent on FGF to determine extent of rebreathing and conservation of exhaled gases?
Circle system→ higher FGF = less rebreathing and greater waste gas
45
What are rules to prevent rebreathing from a circle system?
- Unidirectional valves located between pt and reservoir bag on inspiratory AND expiratory limbs
- Fresh gas inflow cannot enter circuit between patient and expiratory valve
- APL valve cannot be located between patient and inspiratory valve
46
Where does some waste flow go in a semi close circle system?
Partial rebreathing but some waste flow is vented through APL or waste gas valve of ventilator
47
How much of expired gas is rebreathed during low flow anesthesia (FGF less than Vm) through a semi-closed circle system?
50% of expired gas is rebreathed after CO2 removal
48
What type of system are ICU vents and scuba gear?
Semi-open circle system (non rebreathing systems with higher FGF)
49
What is a downside of semi-open circle systems
Wasted gas from high flow rates
50
Which system function with complete rebreathing where rate of O2 inflow matches metabolic demand?
Closed circle system
51
Where is waste gas vented in a closed circle system?
TRICK! there is no waste gas to be vented (rebreathing everything)
52
How are volatile anesthetics added to a closed circle system?
Added to circuit in liquid form in precise amounts through vaporizer
53
Is it common to use closed circle systems?
Impractical for use and rarely done (low-minimal flow anesthesia)
54
What are advantages of low flow anesthesia?
- Decreases use of volatiles
- Improves temp and humidity control
- Reduced environmental pollution
55
What are disadvantages of low flow anesthesia?
- Hard to adjust depth rapidly
- Possible unwanted exhaled gases (CO, Acetone, methane)
- Volatile degradation byproducts (CO, compound A)
56
What are advantages of the circle system?
- Can use low FGF
- Elimination of CO2
- Stable inspired gas concentration
- Conservation of moisture/heat/gases
- Prevents OR pollution
57
What are disadvantages of circle system?
- Complex design
- CO/compound A (Low flow)
- May compromise Vt during controlled vent
- ASA closed claims project (misconnections/disconnections)
58
What are the components of a self inflating manual resuscitator?
- Self expanding bag
- T shaped non rebreather valve
- Bag inlet valve
- Pop-off valve
- Excess O2 venting valve
- O2 reservoir
59
Why is it hard for someone to try to spontaneously breathe with self inflating manual resuscitators?
Take more effort for them to breath spontaneously because the bag is stiff (you musty squeeze for them to get O2)
60
What are uses for self inflating manual resuscitators?
- Hand ventilate in absence of O2 or air source
- Pt transport
- CPR
- Emergency back up
61
What are potential hazards to self inflating BMV?
- Barotrauma
- Gastric insufflation
- Significant variation of Vt, PIP, and PEEP
- Nonrebreathing valves generate resistance
62
What is the function of bacterial filters? Which limb do you place the filter on?
- Prevent contamination of anesthesia machine from airborne diseases
- Placed on expiratory limb
63
What is an issue with the bacterial filters? What specific populations might this impact?
Adds more pressure to circuit→ worry about barotrauma for pedi pts or pts with pulm issue (may need to take filter off)
64
Why are some bacterial filters hydrophobic? How does this impact resistance and efficiency?
- Hydrophobic to prevent water penetration
- Increases resistance and decreases efficiency
65
Where are combination (filter + HME) bacterial filter placed on the circuit?
- Placed at the y piece
- Creates inspiratory and expiratory barrier
66
What are complications from bacterial filters?
- Obstruction (sputum, edema, NEBs, mispositioned)
- Leakage
67
Amount of water vapor in a gas:
Humidity
68
Mass of water vapor present in gas in mg H2O/L of gas:
Absolute humidity
69
Percent saturation; amount of water vapor at a particular temp:
Relative humidity
70
Pressure exerted by water vapor in a gas mixture:
Water vapor pressure
71
At what point in the airway of a normal person has humidification occured?
By mid trachea (38 mg/L absolute humidity)→ as gas travels distally it is heated to body temp (44 mg/L)
72
What is the isothermic saturation boundary?
The point in the respiratory tract where inhaled air becomes fully saturated with water vapor (100% relative humidity) and reaches body temperature (37°C or 98.6°F)
73
________ inspired gas may trigger bronchospasm
Cool
74
What can happen to a patient if inspired gases are underhumidifed?
- Damage to resp tract (thick secretions, ciliary function decreases, surfactant impaired, mucosa susceptible to injury)
- Body heat loss
- Tracheal tube obstruction (increased resistance and WOB from thick secretions)
75
What are potential consequences of overhumidification?
- Water in the airway
- Reduced mucus viscosity and risk of water intoxication
- Inefficient mucociliary transport
- Airway resistance (risk of pulm infection, surfactant dilution, atelectasis, V/Q mismatch)
- Obstruction to sensors
76
What is the function of heat and moisure exchangers (HMEs)?
- Conserves some exhaled heat and water and returns to pt
- Bacterial/viral filtration
- Disposable
77
Where are HMEs placed?
Between Y piece and proximal end of ETT/LMA
78
What are down sides of HMEs?
- Low ETCO2 readings
- Increases resistance and dead space in circuit
- Efficiency may be reduced with large Vt (hydrophobic models)
79
What are the 2 types of HMEs?
- Hygroscopic→paper or fiber barrier coated with moisture retaining chemicals
- Hydrophobic→Pleated hydrophobic membrane with small pores
80
How do hygroscopic HMEs affect inspiration and expiration?
- Increase inspiratory and expiratory resistance when saturated
- Absorb water with exhalation, release water with inspiration
- Efficient in retaining heat/moisture when not saturated
81
Which filters are the most efficient for pathogens and more commonly used in anesthesia?
Hydrophobic HME filters
82
What is a downside of hygroscopic HMEs?
Become saturated quickly which makes it hard to ventilate (more commonly used in ICU)
83
Where on the circuit are humidifiers placed?
Inspiratory limb downstream of unidirectional valve
84
What are different mechanisms for humidifiers to pass a stream of gas?
- Bubble or cascade
- Pass-over
- Counter flow
- Inline
*can be heated or unheated→ used to increase humidity in inspired O2*
85
Which patients would benefit from a humidifier on the circuit?
- Neonates
- Pts with difficult respiratory secretions
- Hypothermic patients
86
What are advantages of humidifiers?
- Can deliver saturated gas at body temp or higher
- More effective than HME
87
What are disadvantages of humidifiers?
- Bulky
- Potential electrical malfunction or thermal injury
- Contamination, cleaning issues
- Higher cost than HME
- Water aspiration risk
