Gas, Breathing systems and Ventilators Flashcards
1
Q
With regard to the Bain System It requires a test of the bag integrity using the Pethick procedure
A
False
The Pethick procedure is used to test for Fracture of the inner fresh gas tube at the common gas outlet
2
Q
With regard to the Bain System It is most efficient in controlled ventilation
A
True
3
Q
With regard to the Bain System It risks failure of safe scavenging if the inner tube fractures at the common gas outlet
A
False
fracture of the inner fresh gas tube at the common gas outlet results in a massive increase in dead space within the system rather than scavenging failure.
4
Q
With regard to the Bain System It is a coaxial variant of the Mapleson D system
A
True
5
Q
With regard to the Bain System It can safely be extended to over 5 m in length with no loss in efficiency
A
True
The length of the system does not affect efficiency and this makes the Bain a useful alternative to the Circle when long systems are required for example in the MRI scanner.
6
Q
The critical temperature of a gas can be correctly defined as ‘The temperature…
A
Above which it cannot be liquefied by pressure alone
7
Q
With regard to Entonox:
It is a 50:50 mix by weight of oxygen and nitrous oxide
A
False
Entonox is oxygen and nitrous oxide 50:50 by volume.
8
Q
With regard to Entonox:
It is supplied in cylinders at a pressure of 137 bar
A
True
9
Q
With regard to Entonox:
It has a pseudo-critical temperature of 5.5 degrees Celsius
A
False
The two components separate below the pseudo-critical temperature of -5.5 Celsius.
10
Q
With regard to Entonox:
Cylinders should be stored upright
A
False
horizontal storage increases the surface area for diffusion of oxygen back into the liquid nitrous oxide to reform the entonox mix more quickly but this is not a normal storage requirement per se.
11
Q
With regard to Entonox:
It exists only in gaseous form in a cylinder
A
True
12
Q
Essential elements of the oxygen VIE include:
A double-skinned steel pressure vessel
A
True
13
Q
Essential elements of the oxygen VIE include:
A secondary outlet to remove additional vapour from the top of the tank in times of high demand
A
False
During high demand or cold temperatures, vapour pressure will fall within the VIE and so liquid must be removed from the bottom of the tank and vapourized to meet demand.
14
Q
Essential elements of the oxygen VIE include:
A bourdon gauge to indicate remaining contents of the vessel
A
False
Because the tank contains predominantly liquid oxygen, contents are primarily measured by weighing scales which form the support base for the tank.
15
Q
Essential elements of the oxygen VIE include:
A system of regulators to reduce supply pressure to 4.1 bar
A
True
16
Q
Essential elements of the oxygen VIE include:
A safety valve to open at 15 bar
A
True
17
Q
With regard to standard medical gas cylinders:
Undergo safety checks every three years
A
False
Cylinders are checked every five years
18
Q
With regard to standard medical gas cylinders:
Have plastic neck rings to signify year of manufacture
A
False
Safety check dates rather than those of manufacture, are indicated by coloured plastic rings around the cylinder neck.
19
Q
With regard to standard medical gas cylinders:
Are made of molybdenum steel
A
True
20
Q
With regard to standard medical gas cylinders:
Can withstand pressures 65-70% above working pressure
A
True
21
Q
With regard to standard medical gas cylinders:
Are safe in MRI scanners
A
False
Standard cylinders are ferromagnetic (molybdenum steel) and are extremely dangerous in MRI scanners – specialist composite or aluminium cylinders are required in this environment.
22
Q
With regard to the Mapleson A System:
It is most efficient when used for controlled ventilation
A
False
The Mapleson A system is most efficient in spontaneous ventilation
23
Q
With regard to the Mapleson A System:
It is available in parallel and coaxial configurations
A
True
24
Q
With regard to the Mapleson A System:
It removes the weight of the APL valve from the patient’s face when used in the Magill configuration
A
False
The Lack modification of the original Magill removes the APL valve from the patient mask to the anaesthestic machine end of the system.
25
With regard to the Mapleson A System:
| It requires a fresh gas flow 1.5-2 x minute volume when used for spontaneous ventilation
False
| spontaneous ventilation requiring a fresh gas flow of approximately 70% minute ventilation.
26
With regard to the Mapleson A System:
| It has an inner expiratory and outer inspiratory tube in the coaxial variants
True
27
With regard to soda lime:
| It is primarily composed of calcium salts
True
28
With regard to soda lime:
| It is the active component of a Cardiff Aldasorber
False
| The Cardiff Aldasorber adsorbs anaesthetic volatile agents onto activated charcoal.
29
With regard to soda lime:
| 1kg will absorb 120 L of carbon dioxide
True
30
With regard to soda lime:
| It will become white when exhausted
False
| Commonly, dyes change granules from white to violet or pink to white when exhausted.
31
With regard to soda lime:
| It is associated with carbon monoxide generation
True
32
With regard to the Circle system:
| It warms and humidifies inspired gases by passing the fresh gas through soda lime
False
| Conventionally, the fresh gas enters the circuit after the soda lime canister.
33
With regard to the Circle system:
| It requires at least one unidirectional valve to prevent rebreathing
False
| The Circle system requires at least two unidirectional valves to prevent rebreathing.
34
With regard to the Circle system:
| It can be used in a fully closed configuration
True
35
With regard to the Circle system:
| Due to the recycling of expired gases does not require a scavenging system
False
While soda lime extracts carbon dioxide, scavenging is still required to prevent pollution of the theatre environment with waste anaesthetic vapours.
36
With regard to the Circle system:
| Inspired and expired oxygen analysers are required for fully closed operation
True
37
With regard to pressure control ventilation:
| It is able to compensate for breathing system leakage
True
38
With regard to pressure control ventilation:
| It is the preferred choice in severe asthma to reduce barotrauma
False
Pressure control ventilation has the principal disadvantages of failing to ventilate those with high airways resistance (acute severe asthma) or low compliance whilst producing very large tidal volumes (potential volutrauma)
39
With regard to pressure control ventilation:
| It is a suitable choice in paediatric anaesthesia
True
40
With regard to pressure control ventilation:
| It utilizes constant inspiratory flow
False
| It uses a constant pressure producing decreasing flow as the lungs inflate.
41
With regard to pressure control ventilation:
| It can maintain ventilation with changes in compliance
False
42
With regard to volume control ventilation
| It utilizes a constant inspiratory flow
True
43
With regard to volume control ventilation
| It is the preferred choice in paediatric anaesthesia
False
Because of the uncuffed endotracheal tubes used in paediatric practice, volume modes are less efficient at maintaining adequate ventilation owing to the airway leak.
44
With regard to volume control ventilation
| It can be combined with positive end-expiratory pressure (PEEP)
True
45
With regard to volume control ventilation
| It is the preferred choice in head injured patients
True
Volume control ventilation maintains much better minute ventilation control providing better PaCO2 control than pressure control modes.
46
With regard to volume control ventilation
| It is a good mode for the final stages of weaning ventilation on the ICU
False
Pressure modes tend to be better tolerated by conscious patients and this makes volume control a less suitable mode for ventilation weaning.
47
Methods of optimising oxygenation include:
| Increasing levels of PEEP
True
48
Methods of optimising oxygenation include:
| Increasing fractional inspiratory oxygen
True
49
Methods of optimising oxygenation include:
| Increasing mean airways pressure
True
50
Methods of optimising oxygenation include:
| Decreasing levels of Expiratory Positive Airways Pressure (EPAP)
False
EPAP increases mean airways pressure in a similar manner to PEEP (Positive End Expiratory Pressure) and so decreasing it may worsen oxygenation.
51
Methods of optimising oxygenation include:
| Moving from supine to semi-recumbent position
True
In the semi-recumbent position, functional residual capacity is increased and atelectasis reduced. For ventilated ICU patients this is also the optimal posture to minimize the risk of gastric regurgitation and pulmonary aspiration.
52
Methods of reducing PaCO2 include
| Increase in respiratory rate
True
Optimal minute ventilation is required to ensure CO2 clearance and this is determined by adequate respiratory rate and tidal volume.
53
Methods of reducing PaCO2 include
| Avoiding high peak airways pressure
False
High peak airways pressure should always be avoided but this will not improve CO2 clearance. Higher CO2 is often permitted in cases of lung injury (ALI/ARDS) to avoid the damaging effects of high peak pressure.
54
Methods of reducing PaCO2 include
| Increasing minute ventilation
True
55
Methods of reducing PaCO2 include
| Increasing fresh gas flow
True
Increasing fresh gas flow when using semi-closed systems (those classified by Mapleson) will reduce the chance of re-breathing alveolar gas.
56
Methods of reducing PaCO2 include
| Decrease in the duration of inspiration to the duration of expiration (I:E ratio)
False
A decrease in the I:E ratio, usually achieved by reducing inspiratory time, will result in decreased respiratory rate (and minute ventilation) unless adjustments are made to maintain constant rate.
57
Concerning cryogenic liquid systems
| recommended on-site storage capacity is 4 days
False
58
Concerning cryogenic liquid systems
| One volume of liquid O2 gives 130x its volume of gas
False
59
Concerning cryogenic liquid systems
| pressure inside vacuum insulated evaporator is 4 bar
False
60
Concerning cryogenic liquid systems
| heating of gaseous oxygen is required at the outlet
False
61
Concerning cryogenic liquid systems
| cylinder back-up is required
True
62
Concerning medical gas cylinders
| Titanium is most often used for making cylinders
False
63
Concerning medical gas cylinders
| in the UK O2 cylinders are colour coded as blue
False
64
Concerning medical gas cylinders
| gauge pressure in a full molydenum steel O2 cylinder should read 137 bar
True
65
Concerning medical gas cylinders
| Nitrous oxide cylinders contain liquid
True
66
Concerning medical gas cylinders
| Size E oxygen cylinders contain 1800 L
False
67
Regarding Piped gas supply
| pipes are made of aluminium alloy
False
68
Regarding Piped gas supply
| pressure in medical air pipe is 7 bar
False
69
Regarding Piped gas supply
| Schrader sockets and probes are used on the back of the anaesthetic machine to prevent inadvertant misconection
False
70
Regarding Piped gas supply
| Schrader probes are of different size for different gases
False
71
Regarding Piped gas supply
| pressure in O2 pipe is the same as in nitrous oxide pipe
True
72
The emergency O2 flush
| bypasses the flowmeter block
True
73
The emergency O2 flush
| should provide a flow of at least 20 L/min
False
74
The emergency O2 flush
| it should be possible to lock it in position
False
75
The emergency O2 flush
| incorporates a pressure limiting valve to prevent barotrauma
False
76
The emergency O2 flush
| use may lead to awareness
True
77
Regarding suction
| can be generated using the venturi system
True
78
Regarding suction
| should be able to generate unrestricted flow >40 L/min
False
79
Regarding suction
| should be able to generate negative pressure of >500 mmHg in 10 sec
True
80
Regarding suction
| tubing should be of a low resistance but high compliance
False
81
Regarding suction
| float controls are essential parts to protect the patient
False
82
Flowmeters on the anaesthetic machine
| are constant pressure, variable orifice devices
True
83
Flowmeters on the anaesthetic machine
| readings are taken from the bottom of the bobbin
False
84
Flowmeters on the anaesthetic machine
| bobbins are universal for all medical gases
False
85
Flowmeters on the anaesthetic machine
| the tube us a cylindrical shape
False
86
Flowmeters on the anaesthetic machine
| the flow control knobs are colour coded
True
87
Regarding plenum vaporisers
| temperature compensation is not required
False
88
Regarding plenum vaporisers
| the output is independant of the gas flow
False
89
Regarding plenum vaporisers
| TEC 6 vaporser is heated to 23.5C
False
90
Regarding plenum vaporisers
| splitting ratio ensures better vaporisation
False
91
Regarding plenum vaporisers
| latent heat of vaporisation reduces agent concentration
True
92
Concerning soda lime
| heat is produced in the process of its action
True
93
Concerning soda lime
| the largest component is sodium hydroxide
False
94
Concerning soda lime
| usually presented as powder
False
95
Concerning soda lime
| may react with sevoflurane to produce carbon monoxide
False
96
Concerning soda lime
| 1kg will absorb about 100L of CO2
False
97
Regarding scavenging
| Maximum recommended concentrations for nitrous oxide in theatre are 100 ppm
True
98
Regarding scavenging
| it is attached to breathing systems with 22mm connection
False
99
Regarding scavenging
| pressure relief valves are incorporated in passive systems to maintain pressure within the -50 to 1000 Pa range
True
100
Regarding scavenging
| Active scavenging systems incorporate a reservoir that is open to the atmosphere
True
101
Regarding scavenging
| Active systems and suction use the same vacuum supply
True
102
Regarding breathing systems
| There is no mapleson classification for the circle system
True
103
Regarding breathing systems
| The circle system has the lowest minimum fresh gas flow requirement of all commonly used systems
True
104
Regarding breathing systems
During spontaneous ventiation, mapleson D and E systems have the same minimum fresh gas flow requirement to prevent rebreathing
True
105
Regarding breathing systems
| Mapleson E system can only be used with spontaneously breathing patients
False
106
Regarding breathing systems
| Mapleson A systems function as a T-piece if the bag is removed
False
107
Concerning Nitrous Oxide cylinders
| The amount of N2O can be calculated using charles's law
False
108
Concerning Nitrous Oxide cylinders
| The amount of N2O can be calculated using boyles law
False
109
Concerning Nitrous Oxide cylinders
| the filling ration in the UK is 0.85
False
110
Concerning Nitrous Oxide cylinders
| the knowledge of molecular weight of N2O is required to calculate the remaining amount
True
111
Concerning Nitrous Oxide cylinders
| The size is determined by the cylinder weight when empty
False
112
The Desflurane Tec 6 vaporiser
| the vaporisation chamber is heated to a temp of 23.5C
False
113
The Desflurane Tec 6 vaporiser
| the vaporisation chamber is pressurised to approx 200 kPa
True
114
The Desflurane Tec 6 vaporiser
| is an example of variable bypass vaporiser
False
115
The Desflurane Tec 6 vaporiser
| fresh gas flow never goes through the vaporising chamber
True
116
The Desflurane Tec 6 vaporiser
| incorporates a differential pressure transducer
True
117
Regarding breathing system components
| The standard adult reservoir bag size is 1 L
False
118
Regarding breathing system components
| Reservoir bags limit the pressure within the breathing system to 40 cm H2O
True
119
Regarding breathing system components
| when fully open, the APL valve requires a presure of 2-5 cm H2O to allow exhalation of gases
False
120
Regarding breathing system components
| the pressure across an APL valve is limited to a maximum of 50 cm H2O
False
121
Regarding breathing system components
| All connections except those for scavenging are 15 or 22mm
True
122
The following are safety features of a modern anaesthetic workstation
emergency O2 flush
True
123
The following are safety features of a modern anaesthetic workstation
NIST connections
True
124
The following are safety features of a modern anaesthetic workstation
colour coded pressure gauges
True
125
The following are safety features of a modern anaesthetic workstation
Ohmeda Link 25 system
True
126
The following are safety features of a modern anaesthetic workstation
colour oded cylinder bodies
False
127
Regarding the oxygen supply failure alarm
| activation is dependant solely on oxygen supply pressure
True
128
Regarding the oxygen supply failure alarm
| it eliminates the possibility of anoxic gas mixtures
False
129
Regarding the oxygen supply failure alarm
| it is coupled to a valve that interrupts the flow of anaesthetic gases
True
130
Regarding the oxygen supply failure alarm
| it requires oxygen in the back-up cylinder as a power source
false
131
Regarding the oxygen supply failure alarm
| requires an electrical power source for its audible component
False
132
Concerning Vacuum insulated evapouriser
| it contains only liquid oxygen
False
133
Concerning Vacuum insulated evapouriser
| the temp inside is -119C
False
134
Concerning Vacuum insulated evapouriser
| the blow-off valve opens at 1000 kPa
False
135
Concerning Vacuum insulated evapouriser
| the pressure inside is less than 100kPa
False
136
Concerning Vacuum insulated evapouriser
| amount of oxygen inside isdetermined by the pressure gauge
False
137
Concerning Mapleson D (Bain Circuit)
| fresh gas flow is delivered via inner tube
True
138
Concerning Mapleson D (Bain Circuit)
| is a type of T-piece system
True
139
Concerning Mapleson D (Bain Circuit) is more efficient for controlled ventilation than spontaneous
True
140
Concerning Mapleson D (Bain Circuit)
| could be used with low-flow anaesthesia
False
141
Concerning Mapleson D (Bain Circuit)
| better for controlled ventilation due to high resistance to breathing
False
142
in a circle system
| a unidirectional valve must be located between the patient and reservoir bag only on the expiratory limb
Flase
143
in a circle system
| fresh gas flow cannot enter between patient and expiratory valve
True
144
in a circle system
| APL valve can be located between patient and inspiratory valve
False
145
in a circle system
| soda lime is always essential for use
False
146
in a circle system
| scavenging is easier compared to jackson rees circuit
True
147
The variable bypass vaporisers currently available
| are based on the principle of dilution of the vapour produced in the vaporising chamber by a bypass gas stream
True
148
The variable bypass vaporisers currently available
| deviate the major part of the gas flow through a channel which bypasses the vaporising chamber
True
149
The variable bypass vaporisers currently available
| completely saturate the carrier gas passing through the vaporising chamber with anaesthetic vapour
True
150
The variable bypass vaporisers currently available
| have comparatively high resistance to flow
True
151
The variable bypass vaporisers currently available
| have a temperature sensitive valve that reduces flow through the vaporiser when cooled
False
152
Regarding anaesthetic machines
| it is recommended that vaporisers be removed from the machine prior to filling them
False
153
Regarding anaesthetic machines
| tilting vaporisers can esult in a delivery of a dangerously high concentration of vapour
True
154
Regarding anaesthetic machines
| The oxygen failure alarm should be checked weekly by disconnection of the O2 hose
True
155
Regarding anaesthetic machines
| the anti-hypoxia device should ensure that when nitrous oxide is used at least 25% O2 also flows
True
156
Regarding anaesthetic machines
| the AAGBI anaesthetic machine checklist includes cheking the scavenging system
True
157
```
The Magill (Mapleson A) breathing system:
Is the most efficient Mapelson system for spontaneously breathing patients
```
True. This system is characteristically efficient for spontaneous ventilation but not controlled ventilation.
158
```
The Magill (Mapleson A) breathing system:
Will work with minimal re-breathing at a fresh gas flow of 70% of minute volume in spontaneous ventilation
```
True
159
```
The Magill (Mapleson A) breathing system:
Makes scavenging of exhaled gases easier
```
False. Scavenging requires an appropriate system to be connected to the APL valve but this is not particularly more or less easy to achieve for the Mapleson A than other systems.
160
```
The Magill (Mapleson A) breathing system:
The co-axial version is the Lack system
```
True
161
```
The Magill (Mapleson A) breathing system:
Is also efficient during controlled ventilation
```
True
162
Breathing (reservoir) bags:
| Have a capacity roughly equating the vital capacity of an 80 Kg adult
False. The reservoir bag for adult use has a volume of approximately 2L.
163
Breathing (reservoir) bags:
| A standard 0.5L bag can be used with a Jackson-Rees system
False. The Jackson-Rees modification to the Mapelson E (making it a Mapelson F) includes a specialised reservoir bag with an opening at the end to allow a controlled leak and variable PEEP.
164
Breathing (reservoir) bags:
| Prevent wastage of fresh gas flow during expiratory pause
True
165
Breathing (reservoir) bags:
| Provide a rough visual assessment of volume of ventilation
True
166
Breathing (reservoir) bags:
Act as a reservoir because the anaesthetic machine can not provide the peak inspiratory flow required in normal respiration
True
167
Regarding breathing systems used in anaesthesia:
The Magill system is most efficient for spontaneously breathing patients even at a fresh gas flow (FGF) of 70% of minute ventilation
True
168
Regarding breathing systems used in anaesthesia:
| D, E and F systems are all T pieces
True
169
Regarding breathing systems used in anaesthesia:
| The Bain system requires a FGF of 50-60 ml/kg during spontaneous breathing
False. The Bain system (a Mapelson D variant) requires a FGF 2-3x minute ventilation to prevent rebreathing.
170
Regarding breathing systems used in anaesthesia:
The rate of change of vapour concentration in circle system depends on circle system volume, the FGF rate and net gas uptake
True
171
Regarding breathing systems used in anaesthesia:
| The Magill system is inefficient during controlled ventilation because much of the gases are vented via pop-off valve
True
172
Concerning absorption of carbon dioxide in breathing systems:
Soda lime granules are size 4-8 mesh
True
173
Concerning absorption of carbon dioxide in breathing systems:
Baralyme contains calcium hydroxide in addition to barium hydroxide
True
174
Concerning absorption of carbon dioxide in breathing systems:
Soda lime produces more compound A during low fresh gas flow
True
175
Concerning absorption of carbon dioxide in breathing systems:
Dry soda lime absorbs more carbon dioxide
False. Water is generated by the overall reaction of CO2 with soda lime but it's presence or absence does not influence performance of the compound.
176
Concerning absorption of carbon dioxide in breathing systems:
Carbon dioxide first reacts with sodium and potassium hydroxide of soda lime
True
177
Regarding anaesthetic breathing systems:
| Re-breathing does not occur in Mapleson D during controlled ventilation
False. Re-breathing can be prevented from occurring in controlled ventilation with the Mapelson D but this is dependent on adequate fresh gas flow.
178
Regarding anaesthetic breathing systems:
With a fresh gas flow (FGF) <1.5 L, volatile concentration in the breathing system may be higher than the dial setting of the vaporiser at steady state
False. The delivered volatile concentration is, in practice, rarely the same as the dial setting but it cannot exceed it except in the few moments after the vapouriser is dramatically turned down or switched off and the system is re-equilibrating.
179
Regarding anaesthetic breathing systems:
| In the circle system with a FGF <1 L (N2O:O2=66:34), FIO2 in the circle may increase over time
False. In low flow operation of the circle, particularly where the oxygen volume supplied falls towards or below metabolic requirements, the FiO2 will steadily fall and the circle will empty; N2O rapidly equilibrates and so uptake of N2O will not exceed that of oxygen so increase in oxygen concentration does not result.
180
Regarding anaesthetic breathing systems:
A FGF of 3 times the minute volume may be needed to prevent re-breathing in Bain's co-axial system during spontaneous ventilation
True
181
Regarding anaesthetic breathing systems:
| Dead space gas is preserved in Magill system during spontaneous ventilation
True
182
Regarding nitrous oxide:
| Has a MAC of 1.05
False. Nitrous oxide has a MAC of 105% and so is not an anaesthetic suitable for use at STP as pure nitrous oxide would neither have a MAC of 1.0 nor deliver any oxygen to the patient.
183
Regarding nitrous oxide:
| Can be safely administered via a Quantiflex mixer
True. It can be safely delivered via a Quantiflex mixer which allows a full range oxygen/nitrous oxide mixtures to be administered from 21-100% oxygen so avoiding accidental hypoxic mixtures.
184
Regarding nitrous oxide:
| Has a pseudocritical temperature of -5.5C
False. A pseudocritical temperature is a property of gas mixtures such as entonox.
185
Regarding nitrous oxide:
| Is an inert gas
False. Nitrous oxide is not an inert gas and in fact with sufficient heat, dissociates to become an avid oxidant.
186
Regarding nitrous oxide:
| Is recognisable by French-blue cylinders and a pin-index of 3 and 5
True
187
The Mapleson A breathing system:
| Is a non-rebreathing system
False. Re-breathing can occur with any Mapelson system if used incorrectly.
188
The Mapleson A breathing system:
| Must have the expiratory valve close to the patient
False. The position of the APL relative to the patient is not the critical factor and the Lack system is a Mapelson A where the APL is removed from the patient end of the system.
189
The Mapleson A breathing system:
| Requires a fresh gas flow equal to the dead space ventilation
False. Fresh gas flow requirements are determined by the ventilation mode - 70% of MV in spontaneous ventilation, 200-300 ml/kg in controlled ventilation.
190
The Mapleson A breathing system:
| Requires a higher fresh gas flow than a Mapleson D system in manual ventilation
True
191
The Mapleson A breathing system:
| Was modified by Magill from Mapleson's original design
False. William Mapelson classified the semi-open breathing systems by functional characteristics, he did not design them.
192
Activated charcoal, as used in the Cardiff Aldasorber:
| Does not absorb nitrous oxide
True
193
Activated charcoal, as used in the Cardiff Aldasorber:
| Is effective in absorbing isoflurane
True
194
Activated charcoal, as used in the Cardiff Aldasorber:
| Increases expiratory resistance significantly
False. The Cardiff Aldasorber is a low resistance device.
195
Activated charcoal, as used in the Cardiff Aldasorber:
| Can be reactivated by heating to remove the absorbed agents
True
196
Activated charcoal, as used in the Cardiff Aldasorber:
| Changes from white to blue when exhausted
False. There is no indicator dye; the only change the device undergoes during use is a small and gradual increase in mass as volatile substances are adsorbed onto the granules.
197
A canister of soda-lime:
| Contains mostly calcium carbonate
False. The principal ingredient in soda-lime is calcium hydroxide with others including sodium hydroxide (3%) and water (20%).
198
A canister of soda-lime:
| Requires water for the absorption process
True
199
A canister of soda-lime:
| Contains 50% by weight of sodium hydroxide
False
200
A canister of soda-lime:
| Will absorb nitrous oxide
False. Nitrous oxide is not absorbed.
201
A canister of soda-lime:
| When packed will be 50% filled with granules
True
202
When using a circle system (with a CO2 absorber) and a vaporiser outside the circle:
A fresh gas flow of at least 2/3 of the minute volume is required
False. Due to the ability to largely recycle gases and a lack of leaks, modern circle systems can sustain very low flows; in a fully closed configuration, total gas flow can be reduced to 100% oxygen at a rate equivalent to the metabolic requirements of the patient (200-300ml/min).
203
When using a circle system (with a CO2 absorber) and a vaporiser outside the circle:
The actual inspired vapour concentration during maintenance may be higher than the vaporiser setting
False. During maintenance (i.e. at steady-state), the inspired volatile agent will eventually reach but never surpass the set concentration on the vapouriser.
204
When using a circle system (with a CO2 absorber) and a vaporiser outside the circle:
The actual inspired oxygen concentration may be lower than that of the fresh gas at low fresh gas flows
True
205
When using a circle system (with a CO2 absorber) and a vaporiser outside the circle:
Sevoflurane is a suitable agent to use
True
206
When using a circle system (with a CO2 absorber) and a vaporiser outside the circle:
The system can only be used for patients breathing spontaneously
False. The circle can be used equally well in spontaneous or controlled ventilation.
