What type of valve is the Ambu e valve?
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A double-leaf valve.
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What type of valve is the Ambu e valve?
A double-leaf valve.
What occurs during expiration with the Ambu e valve?
The inspiratory port leaf valve seals while the expiratory port leaf valve opens, allowing exhaled gases to escape.
What is the function of the Reuben valve during positive pressure ventilation?
It closes the expiratory port, allowing fresh gas to enter the patient.
What is the immediate consequence of a disconnection in the breathing circuit if identified rapidly?
There should be no significant consequences.
What is the length and design of the PAFC?
110 cm long, balloon-tipped, flow-directed catheter.
What do the color codes on vaporisers indicate?
Blue for desflurane, yellow for sevoflurane, and purple for isoflurane.
What did NICE recommend in 2012 regarding DOA monitoring?
The use of EEG-based DOA monitoring (BIS, E-Entropy, or Narcotrend-Compact M) for patients at higher risk of awareness or excessive DOA.
What feature do modern vaporisers have to prevent spills?
A non-spill reservoir allowing up to 180° of tilt.
How is cardiac output (CO) calculated using Fick's principle?
CO = V̇O2 / (CaO2 - CvO2), where V̇O2 is oxygen uptake, CaO2 is arterial oxygen content, and CvO2 is mixed venous oxygen content.
What was the outcome of the b-unaware and bag-recall trials regarding awareness risk?
Both trials found no difference in the risk of awareness between bis-guided anaesthesia and protocol with alarms.
What does V̇O2 represent in the Fick's principle equation?
Oxygen uptake.
What pattern of EEG changes is produced by propofol, thiopentone, and volatile anaesthetic agents?
Increasing high-frequency EEG components, low-frequency EEG components, waveform amplitude, regularity of EEG signal, burst suppression, and isoelectric flat line with deep anaesthesia.
What is the purpose of the pressure release valve in the Mapleson A system?
To vent gas and prevent rebreathing.
What is a pulmonary artery flotation catheter (PAFC)?
A device used to measure cardiac filling pressures, pulmonary artery occlusion pressure, central venous oxygen saturations, and core temperature.
What occurs to a ventilated patient after a disconnection?
The patient remains apnoeic and oxygen saturations fall.
What occurs if the fresh gas flow is too low?
The bag will not be filled solely by dead space gas, allowing some alveolar gas to enter the bag, leading to rebreathing.
How is a disconnection incident classified based on its outcome?
It could be classified as a critical incident or a serious incident requiring investigation.
What are the colour codes for oxygen, nitrous oxide, and air gas cylinders?
Oxygen = black body with white shoulder, Nitrous oxide = blue body with blue shoulder, Air = black body with white and black shoulders.
What is the purpose of the balloon at the tip of the PAFC?
To allow the catheter to advance with blood flow and to enable measurement of pulmonary capillary wedge pressure.
Where can disconnections in the breathing circuit occur?
Between the catheter mount and airway device, HME filter and catheter mount, breathing circuit and HME filter, anaesthetic machine and breathing circuit.
How is cardiac output measured using the thermodilution technique?
By injecting ice-cold saline into the right atrium and measuring the temperature change over time.
What are the three phases of the respiratory cycle?
Inspiration, expiration, and the expiratory pause.
What is the initial statement when describing breathing systems?
The patient has just exhaled, the equipment is full of fresh gas and I put the mask over the patient’s face.
In what other settings might a BIS monitor be used?
In intensive care units to monitor burst suppression in patients with head injuries, raised intracranial pressures, or status epilepticus.
What is the most important monitor for detecting disconnection in the breathing circuit?
The vigilant anaesthetist.
What factors must be considered to determine which monitors would alarm during a disconnection?
The location of the disconnection, whether the patient is breathing spontaneously or being ventilated, and the alarm parameters set.
What classification system is commonly used for breathing systems?
The Mapleson classification system.
How does the nICO measure changes in CO2 concentration?
By using intermittent periods of partial rebreathing through a special rebreathing loop.
What occurs if a ventilated patient experiences a disconnection in the breathing circuit?
EtCO2 measurement and trace would be lost, tidal volumes and minute ventilation would fall, and airway pressures would drop, triggering alarms.
What volumetric markers of preload does the PiCCO device measure?
Global end-diastolic volume, intrathoracic blood volume, and extravascular lung water.
How is the dye or indicator dilution technique used to measure cardiac output?
A known quantity of dye or indicator is injected into a central vein and measured distally from a peripheral arterial blood sample.
What risk is associated with the use of the oxygen flush?
Risk of barotrauma and anaesthetic agent dilution.
What contributes to filling the reservoir bag during exhalation?
The fresh gas flow will also contribute to filling the bag.
In what condition is LiDCO calibration not possible?
In the presence of atracurium.
What happens during positive pressure ventilation with the Ambu e valve?
The inspiratory port leaf valve seals the expiratory port, allowing gases to enter the patient.
What issue can arise during low inspiratory gas flow rates with the Ambu e valve?
The inspiratory port leaf valve may not seal well, allowing fresh gas to escape and reducing supply to the patient.
Where should the distal lumen of the PAFC be positioned?
In the pulmonary artery to measure PA pressure and sample mixed venous blood.
What did the National Audit Project (NAP) 5 identify about end-tidal anaesthetic gas monitoring?
It is a reliable method for ensuring the desired concentration of inhalational agent is administered when used with audible alarms.
How do gas cylinders connect to the anaesthetic machine?
Via a pin-indexed system incorporating a bodok seal for a gas-tight connection.
What happens to the alveolar gas during exhalation in the Mapleson D system?
The alveolar gas is vented through the pressure release valve to avoid rebreathing.
What is the purpose of the Ambu 'mushroom' valve?
To control the flow of air during expiration and inspiration.
What is the purpose of Depth of Anaesthesia (DOA) monitoring?
To reduce the risk of accidental awareness during general anaesthesia and to titrate the dose of anaesthetic agent.
What conditions cause PCWP to underestimate left ventricular end-diastolic pressure (LVE DP)?
Conditions causing increased pressure within the left ventricle that the catheter tip cannot detect, such as poorly compliant left ventricle and LVE DP > 25 mmHg.
How is a PCWP of 25 mmHg interpreted?
It is commonly interpreted as hypervolemia with increased left ventricular end-diastolic volume (LVE DV), but can also indicate normal or reduced LVE DV in cases of increased juxtacardiac pressure or reduced ventricular compliance.
What happens to EtCO2 trace if a spontaneously breathing patient has a disconnection proximal to the sampling point?
The EtCO2 trace would still be present, but the patient would not receive fresh gas flow.
What should be done to assist patients with respiratory fatigue using a resuscitation bag?
Gently squeeze the bag when they inspire to help open the valves and reduce resistance.
What is essential to ensure patient safety before using an anaesthetic machine?
A pre-use check to ensure the correct functioning of the machine and equipment.
How does the transcutaneous Doppler technique work?
It uses the Doppler effect to measure blood flow in the pulmonary artery and across the semi-lunar valves, with a probe placed on the supra-sternal notch.
What happens to alveolar gas after dead space gas is exhaled?
It is vented through the APL valve and lost from the system, avoiding rebreathing.
How is cardiac output data acquired using the PAFC?
Through thermodilution methods.
What are the potential consequences of prolonged disconnection for a ventilated patient?
Hypoxia, ECG changes (most likely bradycardia), hypotension, and potentially cardiac arrest.
How does the Reuben valve self-inflate?
It draws in air from the room and oxygen from the reservoir bag.
What risk is associated with a jammed Reuben valve?
It can keep the inspiratory port continuously open, risking hyperinflation of the lungs.
How is the PiCCO device calibrated?
Via a transpulmonary thermodilution technique.
What is the purpose of back-bar pressure relief valves?
To vent off gas mixtures at pressures greater than 35 kPa, preventing barotrauma to flow meters and vaporisers.
What is the Mapleson A system also known as?
The non-co-axial ‘Magill’ system.
What does pulmonary capillary wedge pressure (PCWP) indicate?
Left atrial filling pressure and left ventricular end-diastolic pressure (LVEDP).
What fresh gas flow is required to prevent rebreathing in both Mapleson E and F systems?
Fresh gas flows of 2.5 × MV.
What is the average tidal volume for a 70 kg patient during quiet breathing?
Approximately 500 ml.
What is a consequence of over-ventilating patients in the Bain circuit?
The end-tidal CO2 will not rise despite the patient rebreathing.
How does the LiDCO device track changes in stroke volume?
By tracking the power of the arterial waveform rather than its contour.
What equation is used to calculate cardiac output?
The Stewart–Hamilton equation: q = v (TB – T1)K1 K2 TB(t)dt.
What happens to a spontaneously breathing patient if a disconnection is not identified quickly?
The patient would continue to breathe room air and may wake up.
What is the purpose of the balloon catheter in lower oesophageal contractility monitoring?
To trigger and record oesophageal contractions for generating the oesophageal contractility index.
How does the patient inhale fresh gas in the Mapleson D system?
The patient inhales fresh gas from the supply and from the deflating reservoir bag.
What resistance do the valves offer during inspiration and expiration?
0.8 cm H2O during inspiration and 1 cm H2O during expiration.
What is the efficiency of the Mapleson A system for spontaneous ventilation?
Efficient at 70 ml/kg/min.
What is one of the principal functions of the anaesthetic machine?
To receive compressed gases from their supplies (pipeline or cylinder).
What do pressure regulators do in anaesthetic machines?
They reduce the pressure of cylinder gases to approximately 400 kPa to protect the machine from high gas pressures.
What type of resuscitation bag is found on a cardiac arrest trolley?
A self-inflating bag with a non-rebreathing valve and mask.
What does the BIS monitor measure?
It produces a dimensionless number between 0 and 100 to measure the depth of anaesthesia.
What is the purpose of reservoir bags in breathing systems?
To allow the patient to draw oxygen and gases during deep inspiration.
What monitors are essential for the induction and maintenance of general anaesthesia?
Trained anaesthetist, anaesthetic machine, airway equipment, emergency drugs, ECG, blood pressure, oxygen saturations, FiO2, EtCO2 with capnography, ventilating volumes, airway pressures, temperature monitoring, and depth of anaesthesia monitoring.
What is the purpose of colour-coded gas cylinders in anaesthetic machines?
They act as an emergency source of gases if primary piped gas delivery fails.
In what conditions does PCWP overestimate left ventricular end-diastolic pressure (LVE DP)?
Conditions creating an interfering pressure gradient, such as mitral stenosis, positive end-expiratory pressure (PEEP), and pulmonary hypertension.
What percentage of general anaesthetics in the UK used DOA monitoring according to the National Audit Project 5 in 2014?
2.83%.
How do EEG-based DOA monitors work?
They use electrodes on the forehead to measure EEG activity, which is processed using proprietary algorithms.
What is the purpose of the open-ended reservoir bag in the Mapleson F system?
It allows for the application of CPAP and controlled ventilation.
What does the PiCCO device identify to determine stroke volume (SV)?
The area under the curve (AUC) by recognizing the dicrotic notch on the arterial waveform.
What is meant by 'assumed Fick determination'?
Using an assumed value for oxygen consumption (250 ml/min or 125 ml/min/m²) to calculate cardiac output due to the cumbersome nature of direct measurements.
What are the two types of flowmeters used in anaesthetic machines?
Mechanical (rotameters) and electronic flowmeters.
What is the purpose of the non-rebreathing valve in a self-inflating bag?
To ensure gas flows out of the bag into the patient during inspiration and prevents exhaled gases from re-entering the bag.
What does 'q' represent in the Stewart–Hamilton equation?
Cardiac output.
What does the area under the blood velocity-time waveform represent?
Stroke distance.
What is the purpose of non-interchangeable screw threads in anaesthetic machines?
To ensure gas-specific connections that are permanently fixed.
What does PCWP stand for and what are its pressure values?
Pulmonary Capillary Wedge Pressure (PCWP) values are 4–12 mmHg.
What is the approximate volume of an adult reservoir bag?
Approximately 2600 mL.
What happens to the Ambu valve during expiration?
It closes to prevent atmospheric air from entering.
Why should the Ambu e valve be used cautiously in spontaneously ventilating patients?
Because it offers resistance.
What is FiO2?
Fraction of inspired oxygen.
What happens to the Reuben valve during expiration?
The bobbin shifts to close the inspiratory port, allowing exhaled gases to escape.
Who originally described the isolated forearm technique?
Tunstall, an obstetric anaesthetist, in 1977.
What are the characteristics of the Mapleson E system?
It has no valves or reservoir bag, making it a very low resistance system.
Why is the Mapleson E system suitable for use in pediatrics?
Due to its low resistance.
What modification does the Mapleson F system have?
It includes an open-ended reservoir bag connected to the end of the tubing.
What principle does a non-invasive cardiac output monitor (nICO) apply?
Fick's principle to CO2.
What is the efficiency of the Mapleson D system for controlled ventilation?
It is efficient for controlled ventilation at a flow rate of 70 ml/kg/min.
What fluid is typically used in the thermodilution technique?
10 ml ice-cold 0.9% saline or 5% dextrose.
What is the minute volume (MV) for a 70 kg patient breathing at 20 breaths per minute?
10 l/min.
What is the significance of the 40-60 range in the context of surgical anaesthesia?
It indicates surgical anaesthesia where auditory processing is possible but memory recall is less likely.
What is the colloquial name for the Mapleson C system?
Waters' circuit, although this is technically inaccurate.
What does the nICO system rely on for measurements?
Airway gas measurement.
What is a 'recirculation hump' in the context of dye dilution technique?
A second peak seen on the concentration-time curves due to the recirculation of the dye or indicator, which limits the number of measurements.
What type of gas is exhaled first during expiration?
Gas from the anatomical dead space, which does not contain CO2 and is not depleted of O2.
What is the significance of the Doppler shift in the transoesophageal Doppler technique?
It correlates directly with the speed of blood traveling in the aorta.
Which Mapleson system is represented by Ayre's T-Piece?
Mapleson E.
What features do modern monitors have for alarms?
Prioritised preset alarms with audible and visual components, which can be individualised.
What does Power Spectral Analysis (PSA) analyze?
It analyzes raw EEG data by breaking it down into constituent sine waves.
Are PiCCO and LiDCO devices reliable with arrhythmias?
No, both are not reliable with arrhythmias.
What factors determine the oxygen concentration delivered to the patient?
FiO2, oxygen flow rate, reservoir bag volume, inspiratory flow rate, respiratory rate, and valve type.
What is another name for the Mapleson E system?
Ayre's T-piece.
What is the consequence of high fresh gas flow?
It fills the bag and vents dead space gas along with alveolar gas, which avoids rebreathing but is wasteful and inefficient.
What are the three main objectives of using a breathing system?
To supply O2 to the patient, to allow removal of CO2 from the system and avoid rebreathing, and to supply anaesthetic gases to the patient.
How is the oxygen failure warning device activated?
When the oxygen supply pressure falls below 2 bar.
What is a key safety feature of an anaesthetic machine?
The presence of a trained, competent anaesthetist.
In the co-axial Mapleson D system, how does fresh gas flow?
Fresh gas flows down the inner tubing while exhaled gas enters the outer tubing.
What parameters are measured by sensors in the nICO system?
CO2, air flow, and airway pressures.
What distinguishes Mapleson B and C systems?
Mapleson C has shorter tubing compared to Mapleson B.
What occurs when the patient exhales?
The dead space volume is expelled into the breathing system, passing down the tubing and fills the reservoir bag again.
What flow rate is necessary to avoid rebreathing during controlled ventilation in the Bain circuit?
2.5 × mV, the same as for spontaneous ventilation.
What components make up a non-rebreathing valve?
Inspiratory port, expiratory port, patient port, and one-way valve.
What do high entropy values indicate?
They may indicate that the patient is awake or aware.
What is the purpose of Auditory-evoked potentials (AEP) monitoring?
To assess the patient's awareness during anaesthesia based on auditory responses.
What is the isolated forearm technique?
A method where a tourniquet is applied to the arm to prevent a neuromuscular blocking drug from reaching the muscles of the arm, preserving hand movement.
What are some adverse effects of excessively deep anaesthesia?
Hypotension, impaired cardiac function, increased nausea and vomiting, and delayed recovery.
What does the anaesthetist do during controlled ventilation?
Squeezes the bag to force gas into the patient.
Why should resuscitation bags and valves be used cautiously in patients with respiratory fatigue?
They can significantly increase the work of breathing and impair passive expiration.
What sound level does the oxygen failure alarm produce?
At least 60 dB for a minimum of 7 seconds.
What happens when the patient inhales fresh gas?
The patient inhales fresh gas from the supply and from the reservoir bag, which deflates proportionally.
How can BIS monitoring help in patients who are paralyzed for a long time?
It can be used to reduce awareness in those patients.
Why is the global use of the PAFC falling?
Due to newer, relatively less invasive methods of cardiac output monitoring becoming available.
What principle does transthoracic electrical bioimpedance rely on?
It relies on changes in electrical impedance of the thoracic cavity during blood ejection from the heart, which reflects cardiac output.
What is a theoretical advantage of the LiDCO device?
Reduction of the effect of reflected waves.
What does the transoesophageal Doppler technique measure?
Velocity of blood flow in the descending thoracic aorta.
What types of measurements do modern anaesthetic machine monitors display?
Oxygen, inhalation agent, end-tidal carbon dioxide concentration, gas volume, and airway pressure.
What are the limitations of the transoesophageal Doppler technique?
Not tolerated by awake patients, operator dependent, and risk of oesophageal perforation.
What is the main characteristic of the Mapleson D system for spontaneous ventilation?
It is inefficient for spontaneous ventilation at flow rates of < 2.5 × mV.
What technique does the LiDCO device use for calibration?
Lithium dilution technique.
What are some limitations of EEG-based monitoring of depth of anaesthesia?
Heterogeneity and uncertainty due to individual responses, diverse case mixes, and variations in clinical practice.
What are some non-invasive techniques for cardiac output measurement?
Transcutaneous Doppler and transthoracic electrical bioimpedance.
What dynamic indicators of volume responsiveness does the PiCCO device provide?
Stroke volume variation (SVV), pulse pressure variation (PPV), and systolic pressure variation (SPV).
What happens to cerebrocortical activity with higher-frequency signals?
Cerebrocortical activity increases.
What is the function of the oxygen flush?
Supplies 100% oxygen at rates between 35 and 75 l/min, bypassing flowmeters and vaporisers.
What should be immediately available before commencing any anaesthetic?
A self-inflating bag, an alternative source of oxygen, relevant airway equipment, and emergency drugs.
What is the minimum fresh gas flow for patients under 20 kg in the Mapleson E system?
2.5 × MV (minimum 3 L/min).
What is the purpose of plotting the concentration of dye over time in the dye dilution technique?
To analyze the concentration-time curve and calculate cardiac output based on the area under the curve (AUC).
What are the limitations of transthoracic electrical bioimpedance?
Its reliability decreases in critically ill patients, and it has not gained wide clinical acceptance.
What is the modification of the Mapleson F system?
Jackson-Rees modification.
What is the function of adjustable pressure-relieving (APL) valves in breathing systems?
To vent waste gases and overcome the problem of rebreathing.
What are the pressure values for the right atrium (RA) in the pressure trace?
RA (1–7) mmHg.
Why are indirect autonomic responses unreliable signs of consciousness?
Absence of sympathetic activity does not exclude awareness, and autonomic responses are uncommon in reported accidental awareness cases.
What material are modern gas cylinders made of?
Molybdenum steel, which is lighter and stronger than carbon steel.
What is the main feature of the co-axial Mapleson A system?
It has an inner tube surrounded by an outer one, designed to reduce bulkiness.
What is the significance of the a-v oxygen content difference in Fick's principle?
It is measured to determine cardiac output in the pulmonary circulation.
Why are ketamine, nitrous oxide, and xenon less useful for EEG-derived indices?
They do not produce the same pattern of EEG changes as other anaesthetic agents.
What is the fresh gas flow requirement for spontaneous ventilation in Mapleson A?
70 mL/kg/min.
What is the relationship between cardiac output and AUC?
Cardiac output is inversely related to AUC.
Why must the fresh gas flow rate exceed the patient's minute volume?
To avoid rebreathing.
How do mechanical flowmeters ensure accurate gas flow measurement?
They are produced with anti-static material to prevent the bobbin from sticking.
Which Mapleson system is used on ITU?
Mapleson C (Waters' circuit).
What dynamic indicators of preload does the LiDCO device provide?
Stroke volume variation (SVV), systolic pressure variation (SPV), and pulse pressure variation (PPV).
How is cardiac output calculated using the pulsed heating bursts?
By detecting temperature changes with a thermistor and applying the Stewart–Hamilton method.
What is the function of flow control needle valves?
They govern the transition from high- to low-pressure systems, reducing pressure as gas enters the flowmeter block.
What happens to the ventilator if there is a disconnection in the breathing circuit?
The ventilator would alarm as the bellows would not be able to fill.
What is the capacity of a self-inflating bag for adults?
1500 ml.
What does the b-aware trial published in 2004 compare?
It compares bis-guided anaesthesia with standard care in patients at increased risk of awareness.
What type of battery is present in modern anaesthetic machines?
A back-up, rechargeable battery.
What computer algorithms are used in the dye dilution technique?
Modified Stewart–Hamilton equation to calculate cardiac output.
Can PiCCO and LiDCO devices be used in awake patients?
Yes, they can be used in awake patients.
What physiological changes are assumed to reflect changes in cardiac performance in arterial pulse contour analysis?
Changes in vessel wall diameter.
How is VCO2 calculated in the nICO system?
From minute ventilation including its CO2 content.
What do modern anaesthetic machines have to alert the anaesthetist of a power failure?
Visual and audible indicators.
What does the adjustable pressure-limiting valve do?
Allows excess gas to escape when a preset pressure is exceeded, reducing barotrauma risk.
What is the role of anti-hypoxic mixture devices?
They prevent the inadvertent delivery of a hypoxic-inspired gas mixture.
How is the area under the curve (AUC) related to cardiac output in the dye dilution technique?
Cardiac output is inversely related to the area under the curve (AUC).
What color is the inspiratory port of a non-rebreathing valve?
Often coloured blue ('blue to bag').
What does arterial pulse contour analysis link to cardiac output?
Pulse pressure (PP) and area under the systolic portion of the waveform (AUC).
What is required for arterial pulse contour analysis?
Insertion of an arterial line.
What are the advantages of transthoracic electrical bioimpedance?
It is quick to set up, easy to use, and useful for estimating trends in cardiac output.
What do e-entropy monitors measure?
They measure the irregularity in spontaneous brain and facial muscular activity.
How are gas supplies connected to the anaesthetic machine?
Using colour-coded, flexible hosepipes that connect via a Schrader valve.
What is the target range for the re and se scales in e-entropy monitoring?
The target range is 40-60.
What type of monitoring do both PiCCO and LiDCO devices provide?
Continuous beat-to-beat monitoring.
What is the pressure in the pulmonary artery (PA) according to the pressure trace?
PA (25/10) mmHg.
What is the standard connection size for the common gas outlet?
22 mm male outer diameter/15 mm female internal diameter.
What do vaporizers do in anaesthetic machines?
They convert volatile liquid into vapour and add a controlled amount of volatile to the fresh gas flow.
What color is the expiratory port of a non-rebreathing valve?
Often coloured yellow or gold ('gold for go').
What is required to calculate stroke volume in the transoesophageal Doppler technique?
The product of the cross-sectional area of the aorta and the stroke distance.
What is the capacity of a self-inflating bag for infants?
250 ml.
What is the role of the electric heating coil in modern PAFCs?
It heats up the blood in a semi-random manner to provide continuous cardiac output data.
What does the black, white, and blue color coding represent in gas supplies?
Black = air, white = oxygen, blue = nitrous oxide.
What does the change in blood temperature over time indicate?
It is used to calculate cardiac output.
What is the function of the pressure-relieving valve in a self-inflating bag?
To prevent barotrauma.
What is the purpose of the entrainment valve in a self-inflating bag?
To allow entrainment of air if the oxygen supply does not meet respiratory demands.
What does the P rst scoring system assess?
It provides an objective assessment of sympathetic stimulation.