EQUIPMENT-Anesthesia machine Flashcards
(222 cards)
1
Q
Where does the high-pressure system begin and end on the anesthesia machine
A
Begins = cylinder Ends= cylinder regulators
2
Q
What are the 4 components of the high-pressure system
A
- Hanger yoke
- Yoke block with check valves
- Cylinder pressure gauge
- Cylinder pressure regulators
3
Q
Where does the intermediate-pressure system being and end on the anesthesia machine
A
Begin = at the pipeline End = Flowmeter valves
4
Q
What are the 7 components of the intermediate-pressure system
A
- Pipeline inlets
- Pressure gauges
- O2 pressure failure device
- O2 second stage regulator
- O2 flush valve
- Ventilator power inlet
- Flowmeter valves
5
Q
Where does the low-pressure system begin and end on the anesthesia machine
A
Begins = flowmeter tubes Ends = common gas outlet
6
Q
What are 4 components of the low-pressure system
A
- Flowmeter tubes (Thorpe tubes)
- Vaporizers
- Check valve
- Common gas outlet
7
Q
What does the low-pressure leak test assess
A
The integrity of the low-pressure circuit from the flowmeter valve to the common gas outlet
8
Q
How is a leak test performed
A
By attaching a bulb to the common gas outlet and creating negative pressure (-65 cm H2O)
9
Q
When does a low-pressure system test fail
A
If the bulb reinflates within 10 seconds
10
Q
What 5 things are prerequisites for a low-pressure system test
A
- The fresh gas flow must be off
- If there’s a minimum FGF when machine is on, the machine must be turned off
- The ventilator should be turned off
- The vaporizers should be off first, then test repeated with each one on
- It should be performed before the first case of the day
11
Q
How is a high-pressure leak test performed
A
By closing the APL valve, pressurizing the circuit to 30 cmH2O and observing the airway pressure gauges, which should remain constant
12
Q
What does a high-pressure system assess if the machine has a check valve
A
The breathing circuit and the low-pressure system up to the check valve
It does NOT assess for a leak between the check valve and the rest of the low-pressure system
13
Q
What does a high-pressure system assess if the machine does NOT have a check valve
A
It assesses the breathing circuit and the entire low-pressure system
14
Q
What is the SPDD model
A
Supply
Processing
Delivery
Disposal
It details the path gases flow as they enter the OR, travel through the machine and exit the OR
15
Q
What is the supply component of the SPDD model
Where is this located
A
How the gases enter the anesthesia machine
Location = pipeline to the back of the anesthesia machine
16
Q
What is the processing component of the SPDD model
Where is this located
A
How the machine prepares gases before they are delivered
Location = inside machine to the common gas outlet
17
Q
What is the delivery component of the SPDD model
Where is this located
A
How the prepared gases are brought to the patient
Location = breathing circuit
18
Q
What is the disposal component of the SPDD model
Where is this located
A
How the gases are removed from the breathing circuit
Location = scavenging system
19
Q
What are the 5 tasks of O2 in the SPDD model
A
- O2 pressure failure alarm (intermediate-pressure)
- O2 pressure failure device (failsafe; intermediate-pressure)
- O2 flowmeter (low-pressure)
- O2 flush valve (intermediate-pressure)
- Ventilator drive gas
20
Q
What is the PISS purpose
A
To prevent inadvertent misconnections of gas cylinders
21
Q
What is the pressure change that occurs for O2 E-cylinder upon entering the intermediate system
A
Pressure of 1,900 psi drops to 45 psi ensuring that gas is preferentially pulled from the pipeline if the cylinder is left open
22
Q
What is the PISS configuration for the following e-cylinders
O2
Air
N2O
A
O2 = 2, 5 Air = 1, 5 N2O = 3, 5
23
Q
What is the purpose of DISS
A
Prevents inadvertent misconnections of gas hoses
Each gas hose and connector are sized and threaded for each gas
24
Q
What is the pipeline pressure change that occurs at the DISS connection
A
50 psi, about the same as the intermediate system
25
What setting is are the cylinders on the back of the machine
OFF when not in use. This ensures if the pipeline pressure is lost, the failsafe alarm sounds and the cylinder isn't empty
26
When should the E-cylinder gas be used
If pipeline pressure is lost
27
O2 E-cylinder:
Maximum pressure
Maximum volume
PISS
Maximum pressure = 1,900 psi
Maximum volume = 660 L
PISS = 2, 5
28
Air E-cylinder:
Maximum pressure
Maximum volume
PISS
Maximum pressure = 1,900 psi
Maximum volume = 625 L
PISS = 1, 5
29
```
N2O E-cylinder:
Maximum pressure =
Maximum volume =
PISS =
Full weight =
Empty weight =
```
```
Maximum pressure = 745 psi
Maximum volume = 1,590 L
PISS = 3, 5
Full weight = 20.7 lb
Empty weight = 14.1 lb
```
30
What state does O2 exist inside a cylinder and why
State = gas
| Because its critical temperature is below room temperature (-119*C)
31
Which gas law is used to calculate cylinder gas contents
Boyle's law
32
What is Boyle's law
The pressure inside the cylinder is inversely related to its volume at a constant temperature
P = 1/V
33
How is the remaining gas volume in a cylinder calculated
[Tank capacity (L)] / [Full tank pressure (psi)]
x
[contents remaining (L)]/[gauge pressure (psi)]
34
How is the length of O2 supply calculated
Contents remaining(L)/FGF rate (L/min) = minutes before tank expires
35
The O2 gauge reads 500 psi. If the O2 flow is at 2 L/min, how long will the tank have until empty
87 minutes
36
The O2 gauge reads 600 psi. If the O2 flow is at 5 L/min, how long until the tank is empty
42 minutes
37
The O2 gauge reads 200 psi. If the O2 flow is at 3 L/min, how long until the tank is empty
23 min
38
What state does N2O exist inside a cylinder
Liquid
| UNLESS it's almost empty
39
Why does N2O exist as a liquid in a cylinder
N2O liquifies under high pressure
| Its critical temperature is 36.6*C which is above room temp (20*C)
40
What is critical temperature
The highest temperature where a gas can exist as a liquid
| The temperature above which a gas cannot be liquefied regardless of pressure
41
As N2O is exhausted from the cylinder, what happens to the pressure
It remains constant at 745 psi
42
When does the pressure of a N2O cylinder decrease.
| How full is the tank at this point?
When all the liquid is consumed
| It is 3/4 empty when the pressure is <745 psi
43
How much N2O (L) remains once the psi <745
400 L out of 1,590 L
44
What is the only reliable method to determine the volume of N2O that remains in the tank
Weight
45
What is the most delicate part of a cylinder and what can happen if damaged
The cylinder valve
Damage = missile
46
How should gas cylinders be stored
Upright position and secured
47
When is it acceptable to lay a gas cylinder on its side
Momentarily, when changing the cylinder on the machine
48
When opening a cylinder, a hissing sound is hear. What does this indicate and what are 4 troubleshooting methods
Indicates a leak
1. Tighten connection
2. Replace the washer between the cylinder and hanger yoke is #1 doesn't work
3. Use a different cylinder is #2 doesn't work
4. Do not place more than 1 washer between the cylinder and hanger yoke
49
Why should only 1 washer be used between the cylinder and hanger yoke
Using 2 washers can bypass the PISS and allow the cylinder to be hooked up to the wrong hanger yolk assembly
50
What happens if there is no cylinder or yoke plug present
Gas that should go to the patient will exit the machine
51
What components make up the fire triad
1. Oxidizer
2. Fuel
3. Igniter
52
Where do O2 and N2O fit in the fire triad
They are oxidizers
53
At what temperature is the risk of fire or explosion of gas cylinders
>130*F or 57*C
54
What is the purpose of the safety relief device
It there's a fire, it opens allowing the cylinder to empty its contents slowly
55
What are 3 types of safety relief valves
1. Fusible plug that melts at elevated temps (bismuth, lead, tin, or cadmium)
2. A valve that open at elevated pressure
3. A frangible disk that ruptures under pressure
56
Why is oiling a cylinder valve contraindicated
This increases the risk of fire by combining O2/N2O (oxidizers) with oil (fuel)
57
What is "cracking" a cylinder
The process of slowly opening the cylinder to flush the valve outlet clean of dust and debris
58
What are 4 agencies that mandate anesthesia machine component safety
1. American society for testing and materials (ATSM)
2. Food and drug administration (FDA)
3. Occupational safety and health administration (OSHA)
4. United states department of transportation (DOT)
59
What does the American Society for Testing and Materials monitor
Standards for the components of the anesthesia machine
60
What does the FDA mandate
Anesthesia machine pre-use checkout procedures
61
What standards does OSHA maintain with anesthesia
Sets the standards for acceptable occupational exposure to volatile anesthetics
62
What standards does the US DOT standardize
Standards for compressed gas cylinders
63
How often is a gas cylinder tested
Every 5 years
| 10 years with a special permit
64
What 7 items does the US DOT require on a cylinder label
1. Government agency (DOT)
2. Type of metal used to construct the cylinder
3. Max fill pressure
4. Serial number
5. Manufacturer
6. Owner
7. Date of last inspection
65
What is the purpose of the O2 pressure failure device
To monitor for (and protect against) low O2 PRESSURE in the machine
It will alert if pipeline pressure is lost, disconnected O2 hose, or depleted O2 tank
It does not measure concentration
66
Which pressure system contains the O2 pressure failsafe device
Intermediate-pressure system
67
What are the 2 components of the O2 pressure failsafe device
1. A threshold alarm sounds when the O2 pipeline pressure <28 - 31 PSI
2. A pneumatic device reduces or stops N2O flow when O2 pipeline pressure is < 20 psi
68
How is the O2 pressure not truly a failsafe
1. The failsafe only detects pressure. It would not detect if there was an O2-pipeline crossover and the incorrect hose was connected
2. A leak in the flowmeter is upstream from the failsafe device
69
What does the hypoxia prevention safety device prevent
Prevents the user from setting a hypoxic mixture with flow control valves
70
When N2O is administered, what is the lowest FiO2 it allows
25%
71
What is the maximum ratio of N2O to O2 maintained by the proportioning device
3:1 (N2O:O2)
72
What are 4 situations that the hypoxia prevention safety device will no alarm
1. O2 pipeline crossover
2. Leaks distal to the flowmeter valve
3. Administration of a 2rd gas
4. Defective mechanic or pneumatic components
73
What is the difference between the O2 pressure failure device and the hypoxia prevention safety device
O2 pressure failure device monitors and responds to PRESSURE
Hypoxia prevention safety device prevents hypoxic mixture via proportioning the O2 and N2O
74
In what pressure system does the flowmeter reside
It begins the low-pressure system
75
What does the flowmeter control
The flow of gas that travels toward the vaporizer and common gas outlet
76
What 2 opposing forces determine the position of the flowmeter indicator float
1. Fresh gas flow pushing float up
| 2. Gravity pulling float down
77
What are the 4 types of indicator floats and where is the measurement taken
1. Skirted (top)
2. Plumb bob (top)
3. Nonrotating (top)
4. Ball (middle)
Measurement is taken at the widest part of the float
78
What is the space called that lies between the indicator float and the sidewall of the flowmeter
Annular space
79
Describe the flowmeter internal diameter
Narrowest at base
| Widens at top
80
Why is the geometry of the annular space important
It affects the flow pattern through the space
81
When the annular space is longer than it is wide
Where is the indicator=
What type of flow around float=
Flow dependent on gas=
Where is the indicator= lower in the tube (low flow)
What type of flow= laminar
Flow dependent on gas= viscosity
82
When the annular space is wider than its length
Where is the indicator=
What type of flow around float=
Flow dependent on gas=
Where is the indicator= Higher in tube (high flow)
What type of flow around float= turbulent (orificial)
Flow dependent on gas= density
83
What is Reynolds number for turbulent flow
| Which law is this based on
Re > 4,000
| Graham's law
84
What is Reynolds number for laminar flow
| What principle is this based on
Re <2,000
| Poiseuille equation
85
Why is the order of flowmeters important
O2 must be closest to common gas valve and the patient, so it's all the way to the right
This ensures if there is a crack in any of the other tubes, O2 will not leak causing a hypoxic mixture
86
What happens if there is a leak in the O2 flowmeter tube
A hypoxic mixture can be delivered
87
What is the equation for Reynolds number
(density x diameter x velocity)/viscosity
88
What is the FiO2 delivered if air is 2 L and O2 is 2 L
61%
89
What is the FiO2 delivered if air is 1 L and O2 is 3 L
80%
90
What is the total tidal volume delivered when fresh gas is coupled with tidal volume
Vt set on ventilator + FGF during inspiration - volume lost to compliance
91
```
When FGF is coupled to Vt, how are the following affected with increased FGF
Vt
Vm
PIP
EtCO2
```
```
Vt = increase
Vm = increase
PIP = increase
EtCO2 = decrease
```
92
```
When FGF is coupled to Vt, how are the following affected by a decrease in FGF
Vt
Vm
PIP
EtCO2
```
```
Vt = decrease
Vm = decrease
PIP = decrease
EtCO2 = increase
```
93
Equation for compliance
(change in volume)/(change in pressure)
94
How does circuit compliance affect the Vt a patient receives
During inspiration with PP, gas is lost to circuit expansion. The quantity of gas does not reach the pt
95
Describe the variable bypass vaporizer
Fresh gas enters the vaporizer, some of the gas encounters the liquid anesthetic, the rest bypasses the anesthetic
96
How is the amount of gas encountering the liquid anesthetic vs bypass determined
Setting the vaporizer dial to the desired concentration determines the splitting ratio of bypass gas and gas coming in contact with the anesthetic liquid
97
How is 100% saturation of fresh gas inside the vaporizer chamber ensured
The fresh gas flows over a series of baffles and wicks, which increase surface area and turbulence, ensuring the fresh gas become saturated
98
At what fresh gas flow is vaporizer output reduced
Flow <200 mL/min or > 15 L/min
99
What complication can occur if the vaporizer is tipped over
The liquid anesthetic enters the bypass chamber and can increase vaporizer output. This can lead to anesthetic overdose
100
How much anesthetic vapor does 1 mL of liquid anesthetic produce
~200 mL assuming STP
101
What should you do if the vaporizer is tipped
Run high FGF for 20 - 30 minutes before use with a patient. This ensures the vapor is gone in the bypass chamber
102
Why is temperature compensation necessary in vaporizers
Heat is carried away by vaporized molecules, causing the anesthetic liquid to cool. Cooling decreases vapor pressure and vaporizer output
103
What is the purpose of the temperature compensating valve
Adjusting the ratio of vaporizing chamber flow to bypass flow to guarantee a constant vaporizer output over a wide range of temepratures
104
What is the pumping effect and how is it minimized
Gas and vapor that has already left the vaporizer re-enters the chamber due to PPV or O2 flush valve. Low flow, low gas concentration and low levels of liquid augment the pumping effect
This is minimized by a backflow valve
105
What are 2 causes of vaporizer leak
1. Loose filler cap
| 2. Internal leak in vaporizer
106
When is a vaporizer leak detected
It can only be detected when the vaporizer is turned on
107
What is the equation to calculate how long the agent will last
mL of liquid anesthetic used per hour = Vol% x FGF(L/min) x 3
108
How does the vaporizer for desflurane differ from the variable bypass vaporizer
There is no bypass flow for the des vaporizer
| The des vaporizer injects a precise amount of desflurane directly into the FGF
109
Why is the desflurane vaporizer heated
More volume is required to obtain same depth of anesthesia.
When more volume is carried away, excessive heat is lost causing the remaining liquid to cool and reducing vaporizer output
110
What is the equation to calculate required dial setting for desflurane at elevation to obtain the desired percent delivery
Required dial setting = [Normal dial setting (% x 760 mmHg)] / ambient pressure mmHg
111
What is the set temperature and pressure for a desflurane vaporizer
```
Temp = 39*C
Pressure = 2 atm
```
112
Where is the O2 analyzer
The inspiratory limb of the breathing circuit
113
What is the purpose of the O2 analyzer (3)
1. Monitor O2 concentration
2. Detect an O2 pipeline crossover
3. Detect hypoxic mixture caused by flowmeter leak
114
Why will a pyrexic 70 kg patient become hypoxic with an O2 flow rate of 250 mL/min in a closed-circuit system
Because the flow rate is less than the pts O2 consumption
115
What 2 steps must be performed when a pipeline crossover occurs
1. Turn on O2 cylinder
| 2. Disconnect pipeline O2 supply
116
If a pipeline crossover was assumed to be the reason for the O2 analyzer alarm but the O2 concentration in the breathing circuit isn't increasing following pipeline disconnect, what should be done...
Assume a machine malfunction
Ventilate patient with ambu and O2 tank (do not use machine auxiliary O2 flowmeter which is supplied by pipeline)
Convert to TIVA
117
What is the purpose of the O2 flush valve
Delivery of O2 from the intermediate-pressure system to the breathing circuit
118
What is flow and pressure is the breathing circuit exposed to when pressing the O2 flush valve
```
Flow = 35 - 75 L/min
Pressure = 50 psi
```
119
How can the use of the O2 flush lead to patient awareness
It does not pass through the vaporizer
| Excessive use can dilute the partial pressure of volatile agent and lead to awareness
120
How does O2 flush use lead to barotrauma
Flushing during the inspiratory cycle can lead to barotrauma b/c the ventilator spill valve is closed during inspiration (won't allow the excess pressure to be redirected)
121
How does drive gas compress bellows
1. the drive gas is outside the breathing circuit while the bellows is inside the circuit
2. During inspiration, drive gas increases pressure inside vent chamber creating a pressure gradient the pushes the bellow and fresh gas into the patient
3. On exhalation, the drive gas flow stop and the pressure gradient is reversed
122
How does the spill valve function during inspiration
It is closed, ensuring Vt goes to the patient and not the scavenger
123
How does the spill valve function during exhalation
The exhaled volume refills the bellows first. Once circuit pressure exceeds 3 cmH2O, the spill valve opens and excess gas exits the scavenger
124
How do anesthesia machines minimize risk of barotrauma
1. isolating Vt form flowmeter and O2 flush valve (decoupling)
2. When circuit pressure is greater than a setpoint, the excess gas is vented out the scavenger (APL for ventilator)
125
What 2 functions does the drive gas on a pneumatic ventilator serve
1. Compresses the bellows
| 2. Opens and closes the ventilator spill valve
126
How are bellows classified
By the movement during EXPIRATION
Ascending = RISE during expiration
Descending= FALLS during expiration
127
What occurs when there is a circuit disconnect:
Ascending bellows=
Descending bellows=
Ascending bellows= bellows will not fill
| Descending bellows= can continue to rise and fall
128
What are complications of a leak in the bellows
1. Exposure to high pressure gas to the breathing circuit
2. Barotrauma
3. Increasing FiO2 (if O2 is drive gas)
4. Dilution of anesthetic vapor (risk for awareness)
129
2 ways a piston ventilator differs from the bellows
1. An electric motor compresses the piston that generates positive pressure in the breathing circuit
2. Does no use drive gas
130
What are the 2 pressure relief valves in the piston ventilator
1. Positive pressure valve (guards against excess pressures in breathing circuit >75 cmH2O)
2. The negative pressure valve guards against negative end-expiratory pressure <-8 cmH2O
131
Is the piston vent coupled or decoupled from FGF
Decoupled
132
With a piston ventilator, how does the breathing bag move on inspiration and expiration
```
Inspiration = Inflates
Expiration = deflates
```
133
Describe VCV
Delivery of a preset tidal volume over predetermined time
134
How do inspiratory pressures respond to VCV
They vary as a function of a patients pulmonary compliance
135
What causes increased PIP with VCV
Increased airway resistance
| Decreased lung compliance
136
Describe the inspiratory flow during VCV inspiration
It is held constant
137
Describe PCV
Delivers a preset inspiratory pressure over a predetermined time
138
How does Vt and inspiratory flow respond to PCV
they vary as a function of the patient's pulmonary compliance
139
What factors can decrease Vt with PCV
Increased airway resistance
| Decreased lung compliance
140
How does inspiratory flow function with PCV
It begins high to achieve the set inflation pressure then slows to maintain a constant inflation pressure
141
What are the fixed parameters with VCV
Vt
Inspiratory flow rate
Inspiratory time
142
What are the fixed parameters with PCV
Peak inspiratory pressure
| Inspiratory time
143
What are the variable parameters with VCV
Peak inspiratory pressure
144
What are the variable parameters with PCV
Vt
| Inspiratory flow
145
What are 4 advantages of PCV
1. Delivers larger Vt for given inspiratory pressure
2. Inspiratory flow pattern may improve gas exchange
3. Reduces the risk of ventilator-associated lung injury (VALI)
4. Useful in patients with low compliance
146
What are 2 disadvantages of PCV
1. Increased airway resistance or decreased lung compliance reduce Vt
2. Requires extra attention with conditions that alter pulmonary resistance or compliance (desufflation), causing large Vt changes
147
What compliance factors decrease Vt with PCV
1. Pneumoperitoneum
| 2. T-burg position
148
What 2 resistance factors decrease Vt with PCV
1. Bronchospasm
| 2. Kinked ETT
149
What 2 compliance factors increase Vt with PCV
1. Release of pneumoperitoneum
| 2. T-burg to supine
150
What 2 resistance factors increase Vt with PCV
1. Bronchodilator therapy
| 2. Removing airway secretions
151
What are 3 categories when PCV would be better over VCV
1. Patient has low compliance
2. High PIP would be dangerous
3. Need to compensate for a leak
152
4 examples of patients with low compliance that would benefit from PCV
1. Pregnancy
2. Obesity
3. Laparoscopy
4. ARDS
153
3 examples where PCV is preferred because high PIP would be dangerous
1. LMA
2. Neonate
3. Emphysema
154
2 examples where PCV is beneficial to compensate for a leak
1. LMA
| 2. Uncuffed ETT in children
155
Describe the setting of CMV and what patients are best suited
Mandatory Vt and RR
Does not compensate for patient initiated breaths
Best in apneic patients
156
Risk associated with CMV
patient-ventilator asynchrony
157
Describe the setting of assist control (AC)
Machine initiate breaths with set Vt and RR
| Spontaneous breaths receive same set Vt
158
What complications can be associated with AC ventilation
If patient over breaths they are at risk for hyperventilation and respiratory alkalosis
159
Synchronized intermittent mandatory ventilation
Machine initiated breaths at set Vt and RR
Allows patient to breathe spontaneously
Adjusts timing of breaths if patient initiates
160
How do patient initiated breaths appear of the vent screen
Negative deflection on waveform before inspiration
161
Which vent mode promotes better synchrony between patient and vent
SIMV
162
Describe pressure-control ventilation with volume guarantee (PCV-VG)
Benefits of pressure control ventilation with a guaranteed predetermined Vt while applying minimum pressure to achieve the Vt
163
Pressure-support ventilation (PSV)
Augments spontaneous breaths with pre-set amount of pressure support
No machine initiated breaths
164
Which vent settings are useful for weaning or LMA
PSV
SIMV
PSV-Pro
165
Describe continuous positive airway pressure (CPAP) setting
1. Continuous amount of breath applied to breathing circuit thru respiratory cycle
166
What are 2 benefits of CPAP
1. the pressure augments the patient's spontaneous breath
| 2. Pressure applied reduces airway collapse during expiration
167
How do CPAP and PSV differ
PSV only applied pressure to the circuit when the patient initiates a breath
168
Describe BiPAP
Two levels of pressure are set
P1 = inspiratory positive airway pressure (PSV)
P2 = expiratory positive airway pressure (CPAP)
169
What is airway pressure release ventilation (APRV)
Similar to BiPAP but has a high level of CPAP throughout the respiratory cycle
Periodic release of high level of pressure to facilitate exhalation
Useful in ARDS and with spontaneous ventilation
170
What is inverse ratio ventilation (IRV)
Reverse I:E ratio, allocating more time to inspiration and less to exhalation
171
What is required to perform IRV
Paralysis and sedation
172
In which patients is IRV useful
Patients with small FRC or ARDS
173
What are the risks associated with IRV
dynamic hyperinflation (auto-peep or breath stacking)
174
3 methods of gas transport with high-frequency ventilation
1. molecular diffusion
2. coaxial flow
3. high-velocity flow
175
What are 3 types of high-frequency ventilation
1. high-frequency oscillation
2. high-frequency jet ventilation
3. high-frequency percussive ventilation
176
How do CO2 absorbers remove exhaled CO2 from the breathing circuit
A strong base (NaOH) neutralizes CO2 through a chain of reactions involving H2O and Ca(OH)2
177
What is the first step in CO2 neutralization via soda lime
Co2 + H2O => H2CO3 (carbonic acid)
178
What is the second step in CO2 neutralization via soda lime
H2CO3 + 2NaOH => Na2CO3 + H2O + heat
179
What is the third step in CO2 neutralization via soda lime
Na2CO3 + Ca(OH)2 => CaCO3 + 2NaOH
180
How does the size of the soda lime granule affect absorption and work of breathing
Absorption = more surface area with smaller granules
| Work of breathing = increased with small granules, decreased with large
181
What is the ideal size of soda lime granules to balance absorptive capacity and work of breathing
4 - 8 mesh granules
| between 1/8 to 1/4 inch in diameter
182
What 2 problems with soda lime can lead to complications
1. Exhaustion
| 2. Desiccation
183
What happens to the pH of soda lime as it neutralizes CO2
pH lowers
184
At what pH does the indicator dye signal soda lime exhaustion
pH<10.3
185
What action should be taken if FiCO2 increases and the absorbent can't be changed
Increase FGF
Make circle system semi-open
Prevent rebreathing
186
How can you tell when a CO2 absorber is dessicated
You can't
| There is not indicator
187
What are the risks of desiccated soda lime
Production of CO
188
Which anesthetics produce more CO in the presence of a desiccated soda lime
des > iso >>> sevo
189
What does sevoflurane produce in the presence of a desiccated absorber
Compound A
190
Which anesthetic is the most unstable in the presence of soda lime
Sevo
191
What are 5 methods to minimize the risk of CO and compound A in desiccated soda lime
1. Utilize low FGF to preserve H2O
2. Turn of FGF between cases
3. Change absorbent at one time
4. change canister when indicator is violet
5. Change if unsure about level of hydration (was FGF left on overnight?)
192
How are the irritating effects of NaOH in CO2 absorber addressed
Silica is added to provide hardness and minimize dust production
This decreases chance for bronchial irritation or bronchospasm
193
how does the calcium hydroxide lime differ from soda lime
1. Doesn't contain strong bases
194
What are 3 benefits of calcium hydroxide lime over soda lime
1. No CO production
2. Very little or no compound A production
3. Less fire risk
195
What are 2 disadvantages of the calcium hydroxide lime vs soda lime
1. Absorbs less CO2
| 2. More expensive
196
What is the first step of calcium hydroxide lime CO2 neutralization
CO2 + H2O => H2CO3
197
What is the second step of calcium hydroxide lime CO2 neutralization
H2CO3 + 2Ca(OH)2 => CaCO3 + 2H2O + Heat
198
What are 2 purposes of the scavenging system
1. Removes excess gas from the breathing circuit
| 2. Minimizes environmental exposure to anesthetic gas waste
199
What are the 5 components of the scavenger system
1. Gas collection assembly
2. Transfer tubing
3. Interface (open or closed)
4. Gas disposal tubing
5. Gas disposal system
200
During spontaneous ventilation, what controls the amount of gas released to the scavenger vs in the circuit
The APL valve
201
During mechanical ventilation, what controls the amount of gas in the circuit and what is released to the scavenger
The spill valve
202
What are the 2 types of scavenging systems. Describe the difference
Active = suction used to remove waste gas
Passive = relies of positive pressure of FGF to push gases
203
How is negative pressure generated with the scavenging system
Removal of too much gas creates negative pressure in the circuit
204
How can a scavenging system contribute to barotrauma
If not enough gas is being removed, there is a risk for barotrauma
205
How is gas flow to the scavenging system controlled in the following situations
Spontaneous ventilation
Mechanical ventilation
Spontaneous ventilation = APL valve
| Mechanical ventilation = spill valve
206
How does an open scavenging system function
1. Open to atm
2. Only used with active systems (suction)
3. No need for +/- pressure relief valves
4. The amount of suction determines if waste gas is exhausted to the OR
- Too little suction means the waste gas exits the system to the OR
207
What are 3 benefits of an open scavenging system interface
1. No need for +/- pressure relief valves
2. Removes risk of barotrauma
3. Decreases risk of negative pressure on circuit
208
What are 3 disadvantages of the open scavenging system interface
1. Can only be used with suction
2. Increases possibility of exposure of OR staff to waste gas
3. The amount of suction determines if waste gas goes to the OR vs entraining air into system
209
Describe how the closed scavenging system functions
It communicates with atm via positive and negative pressure valves.
It is a passive system relying on positive pressure for forward flow
210
What are the disadvantages of the closed scavenging system interface
1. Requires pressure relief valves to atm
| 2. Excess FGF is not removed from breathing circuit, increasing risk for barotrauma
211
Most common cause of low pressure alarm
Circuit disconnect
212
What are 5 causes of low pressure in the breathing cicircuit
1. CO2 absorbent canister leak (poor seal or defective canister)
2. Malfunction of bag/vent selector switch
3. Incompetent ventilator spill valve
4. Leaks in breathing circuit
5. Leaks in anesthesia machine
213
What is the second most common cause of circuit leak
CO2 absorbent canister problems
1. Poor seal
2. Defective canister
214
Does the O2 analyzer alert when there is a disconnection?
No, it only reads the O2 concentration in the circuit
215
What should you do if the circuit doesn't hold pressure
Ventilate pt with BVM and O2 tank and convert to TIVA
216
What are 4 ways to detect a circuit disconnect
1. Pressure
2. Volume
3. EtCO2
4. Vigilance
217
What are 9 complications of excessive pressure in the breathing circuit
1. Barotrauma
2. Decreased venous return
3. Decreased CO
4. HoTN
5. CV collapse
6. High PEEP
7. PTX
8. SQ emphysema
9. Death
218
What are 6 causes of high pressure inside the breathing circuit
1. Vent spill valve malfunction
2. CO2 absorbent obstruction
3. Anesthesia mask obstruction
4. Occluded limb of breathing circuit
5. Malfunctioning PEEP valve
6. Malfunctioning expiratory unidirectional valve
219
When a high pressure alarm sounds, what is the first thing that should be assessed
THE PATIENT
| -Ensure pt isn't having bronchospasm
220
What are 11 CRNA related methods to decrease staff exposure to anesthetic gases
1. Ensure good mask fit
2. Tun on gas when mask fit is good
3. Prevent FGF from entering atm
4. Turn off gas before suctioning patient
5. Evacuate anesthetic gases into scavenger at the end of case
6. Use cuffed ETT
7. Vigilance for anesthesia machine leaks
8. Don't spill agents
9. Use TIVA
10. Avoid N2O
11. Low FGF
221
What are 2 environmental factors that decrease exposure to waste gas
1. OR ventilation and air turnover
| 2. Functional anesthesia equipment
222
What is the maximum OSHA recommended exposure to inhaled anesthetics
Halogenated agents=
N2O alone=
Halogenated agents + N2O=
Halogenated agents= <2 ppm
N2O alone= <25 ppm
Halogenated agents + N2O= <0.5 ppm, <25 ppm respectively
