p.12
Humidity and Heat Conservation
How does the circle system manage humidity and heat conservation?
Absorbent granules provide heat and moisture, while exhaled gas is saturated with water at body temperature.
p.4
Draw-Over Anesthesia Systems
What are the components that make the draw-over anesthesia system awkward for certain surgeries?
The nonrebreathing valve, PEEP valve, and circuit filter.
p.14
Effects of Hypercapnia
What is one of the dangerous effects of hypercapnia in patients with increased intracranial pressure?
Cerebral blood flow increases proportionately with arterial CO2.
p.4
Draw-Over Anesthesia Systems
What are some disadvantages of insufflation and draw-over systems?
Poor control of inspired gas concentration, mechanical drawbacks during surgeries, and pollution of the operating room.
p.4
Mapleson Circuit Classifications
What does the Mapleson classification address?
The relative location of components in breathing circuits to determine circuit performance.
p.13
Breathing System Efficiency
What role does the intake valve play in a ventilation bag?
It closes during bag compression, permitting positive-pressure ventilation and is refilled by flow through the fresh gas inlet.
p.7
Breathing System Efficiency
What is the function of a reservoir bag in anesthesia?
It serves as a reservoir of anesthetic gas and a method of generating positive-pressure ventilation.
p.4
Draw-Over Anesthesia Systems
What is a key advantage of draw-over systems?
Their simplicity and portability.
p.1
Breathing System Efficiency
What is a limitation of the insufflation technique?
Ventilation cannot be controlled, and the inspired gas contains unpredictable amounts of atmospheric air.
p.8
Breathing System Efficiency
What is the significance of periodic inspection of the inner tubing in the Bain circuit?
To prevent kinking or disconnection that could lead to significant rebreathing of exhaled gas.
p.10
Carbon Dioxide Absorption
What is the significance of the pH indicator dye in absorbents?
It changes color to indicate absorbent exhaustion, signaling when to replace it.
p.2
Insufflation Techniques
How is insufflation particularly beneficial during induction in children?
It helps when children resist the placement of a face mask or intravenous line.
p.7
Breathing System Efficiency
How is breathing-circuit efficiency measured in Mapleson circuits?
By the fresh gas flow required to reduce CO2 rebreathing to a negligible value.
p.13
Breathing System Efficiency
What distinguishes a resuscitator from a Mapleson circuit or a circle system?
A resuscitator contains a nonrebreathing valve.
p.13
Breathing System Efficiency
What is the function of the patient valve in a resuscitator?
It opens during controlled or spontaneous inspiration to allow gas flow from the ventilation bag to the patient.
p.13
Breathing System Efficiency
How is rebreathing prevented in a resuscitator?
By venting exhaled gas to the atmosphere through exhalation ports in the nonrebreathing valve.
p.7
Mapleson Circuit Classifications
What happens to the fresh gas flow in a Mapleson D circuit during controlled ventilation?
Fresh gas flow forces alveolar air away, maintaining negligible circuit pressure.
p.6
Breathing System Efficiency
Why is the diameter of the breathing tubes significant?
A large diameter (22 mm) creates a low-resistance pathway and a potential reservoir for anesthetic gases.
p.11
Circle System Components
What is the purpose of the APL valve in a breathing system?
To conserve absorption capacity and minimize the venting of fresh gas.
p.10
Carbon Dioxide Absorption
How does Amsorb compare to soda lime?
Amsorb has greater inertness, resulting in less degradation of volatile anesthetics.
p.11
Anesthetic Equipment Malfunctions
What can cause valve incompetence in unidirectional valves?
Warped disks or irregularities in the valve seat.
p.8
Carbon Dioxide Absorption
How does the circle system address the issue of rebreathing exhaled gases?
By incorporating a CO2 absorber and additional components to manage gas flow.
p.6
Breathing System Efficiency
What volume of tidal volume can be lost to the circuit in a compliant breathing tube?
For example, 160 mL can be lost if the compliance is 8 mL gas/cm H2O at a pressure of 20 cm H2O.
p.1
Mapleson Circuit Classifications
Why is the Mapleson D circuit efficient during controlled ventilation?
Fresh gas flow forces alveolar air away from the patient and toward the APL valve.
p.1
Carbon Dioxide Absorption
How does the circle system prevent rebreathing of carbon dioxide?
With an absorber, it prevents rebreathing at low fresh gas flows or during closed-system anesthesia.
p.12
Fresh Gas Flow Requirements
What is the effect of high fresh gas flows in the circle system?
Rebreathing is minimal, making a CO2 absorber usually unnecessary.
p.9
Carbon Dioxide Absorption
What are the end products of the reaction between CO2 absorbents and carbonic acid?
Heat, water, and calcium carbonate.
p.7
Breathing System Efficiency
What prevents rebreathing in Mapleson circuits?
Adequate fresh gas flow into the circuit and venting exhaled gas through the APL valve before inspiration.
p.7
Fresh Gas Flow Requirements
What is required to prevent rebreathing during controlled ventilation with a Mapleson A circuit?
Very high fresh gas flows (greater than three times minute ventilation).
p.14
Effects of Hypercapnia
What can extremely high levels of CO2 (> 80 mm Hg) cause?
Unconsciousness related to a fall in cerebrospinal fluid pH.
p.8
Breathing System Efficiency
What is a key advantage of the circle system compared to Mapleson circuits?
It conserves heat and humidity and has better control of anesthetic depth.
p.5
Mapleson Circuit Classifications
What is the required fresh gas flow for Mapleson A?
Equal to minute ventilation (≈ 80 mL/kg/min).
p.7
Breathing System Efficiency
What does the ceiling effect of a reservoir bag provide?
Minimal protection of the patient’s lungs against high airway pressures.
p.11
Circle System Components
What is the function of unidirectional valves?
They act as check valves, allowing forward flow while preventing reverse flow.
p.13
Effects of Hypercapnia
What was the observed response in the 5-year-old girl after induction of anesthesia?
Tachycardia and mild hypertension were noted despite high concentrations of sevoflurane.
p.14
Effects of Hypercapnia
What should be monitored to rule out hypercapnia or hypoxia?
End-tidal CO2 monitoring, pulse oximetry, or arterial blood gas analysis.
p.2
Insufflation Techniques
What is a limitation of the insufflation technique?
Ventilation cannot be controlled, and the inspired gas contains unpredictable amounts of entrained atmospheric air.
p.7
Mapleson Circuit Classifications
What are the main characteristics of Mapleson circuits?
They are lightweight, inexpensive, and simple.
p.12
Breathing System Efficiency
What is dead space in the context of tidal volume?
The part of tidal volume that does not undergo alveolar ventilation.
p.8
Carbon Dioxide Absorption
What is the primary function of the carbon dioxide absorber in the circle system?
To eliminate CO2 from exhaled gas to prevent hypercapnia.
p.11
Effects of Hypercapnia
What can result from a malfunction of unidirectional valves?
Rebreathing of CO2, which can lead to hypercapnia.
p.11
Circle System Components
Where should unidirectional valves be placed in a circle system?
Relatively close to the patient to prevent backflow into the inspiratory limb.
p.12
Breathing System Efficiency
What is the impact of circuit length on dead space in the circle system?
The tube length does not affect dead space due to unidirectional valves.
p.13
Breathing System Efficiency
What is the effect of connecting a reservoir to the intake valve?
It helps prevent the entrainment of room air.
p.1
Breathing System Efficiency
What is a key advantage of insufflation in breathing systems?
It avoids direct patient contact and prevents rebreathing of exhaled gases if the flow is high enough.
p.10
Carbon Dioxide Absorption
What is Compound A?
A by-product of the degradation of sevoflurane by absorbent.
p.3
Draw-Over Anesthesia Systems
How was open-drop anesthesia historically administered?
By dripping a highly volatile anesthetic onto a gauze-covered mask applied to the patient’s face.
p.3
Draw-Over Anesthesia Systems
What effect does vaporization have on the mask temperature during open-drop anesthesia?
It lowers the mask temperature, resulting in moisture condensation.
p.5
Mapleson Circuit Classifications
What is the fresh gas flow requirement for Mapleson D?
2–3 × minute ventilation.
p.1
Carbon Dioxide Absorption
What is the effect of the drier soda lime on volatile anesthetics?
The drier it is, the more likely it will absorb and degrade volatile anesthetics.
p.2
Breathing System Efficiency
Why are traditional classifications of breathing systems often avoided?
They can confuse rather than aid understanding due to the consolidation of functional and physical characteristics.
p.6
Fresh Gas Flow Requirements
What is the function of the fresh gas inlet in a Mapleson circuit?
It allows gases (anesthetics mixed with oxygen or air) to continuously enter the circuit from the anesthesia machine.
p.6
Anesthetic Equipment Malfunctions
What happens if the gas inflow exceeds the uptake of the patient and the circuit?
Pressure will rise, and gases may exit the circuit through the APL valve to control this pressure buildup.
p.6
Breathing System Efficiency
What is the purpose of the Adjustable Pressure-Limiting (APL) valve?
To vent excess gases and control pressure buildup in the breathing circuit.
p.6
Circle System Components
What materials are commonly used for breathing tubes in Mapleson circuits?
Rubber (reusable) or plastic (disposable).
p.11
Fresh Gas Flow Requirements
Why is the fresh gas inlet positioned between the absorber and the inspiratory valve?
To prevent fresh gas from bypassing the patient during exhalation and being wasted.
p.10
Carbon Dioxide Absorption
What is Amsorb?
A CO2 absorbent consisting of calcium hydroxide and calcium chloride, with additives for increased hardness.
p.3
Draw-Over Anesthesia Systems
What type of circuits do draw-over devices use?
Nonrebreathing circuits that use ambient air as the carrier gas.
p.6
Fresh Gas Flow Requirements
What is the minimum volume of gas within the breathing tubes in most Mapleson circuits?
It should be at least as great as the patient’s tidal volume.
p.8
Circle System Components
What does the APL valve do in the circle system?
It allows for the adjustment of pressure within the breathing system.
p.10
Carbon Dioxide Absorption
What factors increase the formation of Compound A?
Higher concentrations of sevoflurane, prolonged exposure, and low-flow anesthetic techniques.
p.1
Anesthetic Equipment Malfunctions
What happens if either unidirectional valve in a circle system malfunctions?
It may allow rebreathing of carbon dioxide, resulting in hypercapnia.
p.1
Resuscitation Breathing Systems
How does the fraction of inspired oxygen (F IO 2 ) relate to the resuscitator breathing system?
It is directly proportional to the oxygen concentration and flow rate, and inversely proportional to the minute ventilation delivered to the patient.
p.12
Breathing System Efficiency
What is a key advantage of the circle system in anesthesia?
It prevents rebreathing of CO2 at reduced fresh gas flows.
p.12
Breathing System Efficiency
What is a disadvantage of the circle system compared to Mapleson circuits?
Greater size and less portability.
p.11
Breathing System Efficiency
What is the role of the inspiratory valve in a breathing system?
It opens during inhalation to allow the patient to breathe a mixture of fresh and exhaled gas that has passed through the CO2 absorber.
p.11
Breathing System Efficiency
What happens during exhalation in a breathing system?
The expiratory valve opens, allowing gas to flow away from the patient, which can be vented through the APL valve or rebreathed after passing through the absorber.
p.8
Circle System Components
What are the components of a circle system?
1) CO2 absorber, 2) fresh gas inlet, 3) inspiratory unidirectional valve, 4) Y-connector, 5) expiratory unidirectional valve, 6) expiratory breathing tube, 7) APL valve, and 8) reservoir.
p.13
Fresh Gas Flow Requirements
What is Fio2 and how is it affected in a resuscitator?
Fio2 is the fraction of inspired oxygen, directly proportional to the oxygen concentration and flow rate of the gas mixture supplied.
p.4
Anesthetic Equipment Malfunctions
What is the function of the valve in a self-inflating bag?
To prevent retrograde gas flow from the self-inflating bag.
p.5
Mapleson Circuit Classifications
What modification improves the efficiency of the Mapleson A system?
The enclosed Magill system.
p.14
Effects of Hypercapnia
What cardiovascular changes should alert the anesthesiologist during general anesthesia?
The combination of tachycardia and hypertension.
p.5
Mapleson Circuit Classifications
What is unique about the Bain circuit configuration?
It has a fresh gas tube inside the breathing tube.
p.14
Anesthetic Equipment Malfunctions
What can soda lime exhaustion lead to during anesthesia?
Rebreathing of CO2 in the presence of low fresh gas flow.
p.5
Mapleson Circuit Classifications
What does the Jackson-Rees modification of Mapleson E allow?
Controlled ventilation and scavenging.
p.2
Insufflation Techniques
What is the primary advantage of insufflation in anesthesia?
It avoids direct patient contact, preventing rebreathing of exhaled gases if the flow is high enough.
p.2
Breathing System Efficiency
What is the relationship between the patient, the breathing system, and the anesthesia machine?
It is crucial for understanding how anesthetic delivery is managed.
p.12
Bacterial Contamination
What is the role of bacterial filters in the circle system?
To reduce the risk of microorganism retention and potential respiratory infections.
p.8
Breathing System Efficiency
What is a disadvantage of the Bain circuit?
The possibility of kinking or disconnection of the fresh gas inlet tubing.
p.8
Breathing System Efficiency
How does the Bain circuit improve upon the conventional Mapleson D circuit?
It incorporates the fresh gas inlet tubing inside the breathing tube, reducing bulk and retaining heat and humidity better.
p.4
Draw-Over Anesthesia Systems
What is the purpose of a self-inflating bag in a draw-over system?
To assist in ventilation when compressed gases are not available.
p.3
Draw-Over Anesthesia Systems
In what situations might draw-over anesthesia be used?
In locations or situations where compressed medical gases are unavailable, such as battlefields.
p.7
Breathing System Efficiency
What are the three distinct phases of reservoir bag filling?
Phase I: nominal capacity, Phase II: rapid pressure rise, Phase III: plateau or slight pressure decrease.
p.11
Carbon Dioxide Absorption
How can absorbent exhaustion be monitored?
By observing the indicator dye color through the absorber's transparent walls.
p.3
Insufflation Techniques
What is the purpose of insufflation in anesthesia?
To maintain arterial oxygenation during brief periods of apnea.
p.1
Breathing System Efficiency
What should be the position of the adjustable pressure-limiting (APL) valve during spontaneous ventilation?
It should be fully open to keep circuit pressure negligible throughout inspiration and expiration.
p.3
Draw-Over Anesthesia Systems
What is the role of the Schimmelbusch mask in open-drop anesthesia?
It allows air to pass through the gauze, vaporizing the liquid anesthetic and delivering it to the patient.
p.2
Insufflation Techniques
What hazard does insufflation help avoid during ophthalmic surgery?
Carbon dioxide accumulation under head and neck draping.
p.14
Anesthetic Equipment Malfunctions
What should be done if an equipment malfunction is suspected during anesthesia?
The patient should be disconnected from the anesthesia machine and ventilated with a resuscitation bag until repairs are possible.
p.4
Draw-Over Anesthesia Systems
What is one example of a draw-over anesthesia system?
Ohmeda Universal Portable Anesthesia Complete (U-PAC).
p.12
Resuscitation Breathing Systems
How does the location of the reservoir bag affect resistance to exhalation in resuscitation systems?
It decreases resistance by being located in the expiratory limb.
p.12
Fresh Gas Flow Requirements
What happens to inspired gas concentrations during low fresh gas flows?
Concentrations can vary markedly between fresh gas and inspired gas.
p.3
Draw-Over Anesthesia Systems
What modern technique utilizes draw-over vaporizers?
Draw-over anesthesia, which depends on the patient’s inspiratory efforts to draw ambient air through a vaporization chamber.
p.14
Effects of Hypercapnia
How does hypercapnia affect cardiac output during general anesthesia?
It usually results in increased cardiac output, elevated arterial blood pressure, and a propensity toward arrhythmias.
p.6
Breathing System Efficiency
How does the compliance of breathing tubes affect gas delivery?
High compliance can increase the difference between the volume of gas delivered and the volume actually delivered to the patient.
p.8
Fresh Gas Flow Requirements
What is the impact of high fresh gas flows in Mapleson circuits?
They result in waste of anesthetic agent, pollution of the operating room environment, and loss of patient heat and humidity.
p.5
Mapleson Circuit Classifications
What is a significant drawback of the Mapleson A circuit during controlled ventilation?
It is a poor choice due to very high and difficult to predict fresh gas flows.
p.14
Effects of Hypercapnia
What is the normal response of awake subjects to a rise in PaCO2?
They increase their minute ventilation by about 2–3 L/min for each mm Hg rise.
p.1
Breathing System Efficiency
How do long breathing tubes with high compliance affect gas delivery?
They increase the difference between the volume of gas delivered to a circuit and the volume actually delivered to the patient.
p.6
Circle System Components
What is compliance in the context of breathing circuits?
Compliance is defined as the change of volume produced by a change in pressure.
p.10
Carbon Dioxide Absorption
What is the effect of dry absorbent on volatile anesthetics?
It can absorb and degrade them, potentially causing carbon monoxide poisoning.
p.10
Carbon Dioxide Absorption
What happens to exhausted granules if rested?
They may revert to their original color, but no significant recovery of absorptive capacity occurs.
p.5
Mapleson Circuit Classifications
What is the fresh gas flow requirement for Mapleson E?
3 × minute ventilation (I:E-1:2).
