BT_SQ 1.13 Describe and classify breathing systems used in anaesthesia (episode 2).

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I photographed this little guy in Hong Kong – he’s (or perhaps she’s??) looking bit ragged. Following yesterday’s post I did a bit of research. It tuns out that sea jellies have no breathing system at all. They meet their oxygen requirements through diffusion across their bodies….

Today we will turn our focus to the circle system. This is something most of us use every day. I asked a viva on it in the last exam and was surprised by many of the answers I was given.

The circuit is circular with unidirectional valves – does that mean that gas flows in only one direction throughout the entire system?

BT_SQ 1.13  Describe and classify breathing systems used in anaesthesia. Evaluate their clinical utility and hazards associated with their use

The circle circuit, as commonly used in current anaesthetic practice, is a closed system  TRUE/FALSE

With the standard circle arrangement, fresh gas commonly flows through the CO2 absorber   TRUE/FALSE

Placing the APL valve before the CO2 absorber (on the expiratory limb) helps to conserve the CO2 absorbent  TRUE/FALSE

When running the circle as a closed circuit, minimal gas monitoring is required, as it is a stable system        TRUE/FALSE

A safe circle system requires the fresh gas flow to be placed between the patient and the expiratory valve  TRUE/FALSE

BT_SQ 1.13 Describe and classify breathing systems used in anaesthesia.

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What sort of  breathing system do those guys have? Certainly none of the ones we will be discussing today…

Today I will focus on the Mapleson classification of breathing systems. Here is an article written about them by Mapleson himself. He is still alive and in his 90s. You can read a little more about him here. Textbooks on the ANZCA primary exam reading list generally cover this topic adequately too.

BT_SQ 1.13 Describe and classify breathing systems used in anaesthesia. Evaluate their clinical utility and hazards associated with their use

The Mapleson A circuit is more efficient for a spontaneously ventilating patient compared with Mapleson D    TRUE/FALSE

A Mapleson E circuit is also referred to as classic T-piece     TRUE/FALSE

In the Mapleson D circuit the reservoir bag is located off the expiratory limb    TRUE/FALSE

The Mapleson D circuit is more efficient for controlled ventilation (CV) compared with spontaneous ventilation, due to the longer expiratory phase with CV    TRUE/FALSE

The Mapleson C circuit is the most efficient of these systems for spontaneous ventilation TRUE/FALSE

 

Anaesthetic Machines

Equipment Friday 😃

BT_SQ 1.3 Outline the mandatory safety requirements for anaesthetic machines. Refer to College professional document T3: Minimum Safety Requirements for Anaesthetic Machines for Clinical Practice.

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TRUE/FALSE The oxygen failure alarm shall activate at pressures of less than 410 kPa.

TRUE/FALSE The anaesthetic machine must contain an automatically activated reserve oxygen supply.

TRUE/FALSE The oxygen supply failure alarm must be user cancellable.

TRUE/FALSE The oxygen supply failure alarm must shut off the supply of all other gases in the event of oxygen failure.

TRUE/FALSE The oxygen supply failure alarm must shut off the supply of all other gases in the event of oxygen failure.

TRUE/FALSE If the anaesthetic machine incorporates a gas flowmeter bank, oxygen must be the first gas to enter the common gas manifold at the top of the flowmeter tubes.

 

And a special bonus question:

TRUE/FALSE Equipment is rarely asked in Primary vivas.

 

Pin Index System

BT_SQ 1.10 Describe the supply of medical gases (bulk supply and cylinder) and features to ensure supply safety including pressure valves and regulators and connection systems

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T/F The Bodok seal shown on the right contains latex

T/F The Pin Index System can be defeated by placing two Bodok seals over the nipple

T/F The seal must not be combustible because of the high temperatures achieved when the cylinder is turned on

T/F The Pin Index for Oxygen is a single pin at the 6 o’clock position

T/F The Pin Index system is not used in the main hospital manifold

Have you ever wondered why we only use the pin index system for cylinders and not for gas hoses? The answer was in the recent A&IC History Supplement. If the connection is inserted upside-down, it is possible to fit the wrong coupling into the yoke. This is less of a problem with cylinders for obvious reasons.

Humidifiers

BT_SQ 1.5 “Describe basic physics applicable to anaesthesia in particular:

· Principles of humidification and use of humidifiers

Humidvent

T/F A Heat and Moisture Exchanger (HME) primarily reduces heat loss by warming the inspired gas.

T/F A Heat and Moisture Exchanger (HME) warms inspired gases to a temperature of 35-37°C

T/F At this temperature a Heat and Moisture Exchanger (HME) achieves a humidity of 85-93%

T/F A Heat and Moisture Exchanger (HME) reduces the risk of bacterial and viral cross-infection between patients.

T/F A Heat and Moisture Exchanger (HME) is less effective when using high gas flows in a circle system.

 

Gas Connections & Hoses

BT_SQ 1.10 Describe the supply of medical gases (bulk supply and cylinder) and features to ensure supply safety including pressure valves and regulators and connection systems

Fabius Hoses

With reference to the above diagram:

T/F The colour coding of the nitrous oxide hose is correct

T/F The air hose is white because it uses the American colour coding system

T/F The hoses are connected to the machine using the Sleeve Index System

 

Defeated-SIS-2

With reference to the above diagram:

T/F It would be possible to attach this hose to any gas connector of this type

T/F The standard does not allow hose clamps to be used to attach flexible gas hoses to non-interchangeable gas connectors.

 

BT_SQ 1.12 Describe the principles and safe operation of vaporizers

Q. They are heavy because they are full of liquid.  TRUE/ FALSE

Q. Must be positioned in a particular order if there are two different vaporizers on the machine.  TRUE/ FALSE

Q. All require power to operate correctly.  TRUE/ FALSE

Q. A Desflurane Tec 6 vaporizer does not require adjustment when used at altitude.  TRUE/ FALSE

Q. Should not be laid on their side.  TRUE/ FALSE

2017.1 : SAQ 2

Compare and contrast oxygen delivery via nasal cannulae (nasal prongs/specs), simple face mask (eg Hudson or CIG mask) and Venturi mask.

BT_SQ 1.14

A very practical question, understanding the physics of oxygen delivery by these different means will aid you in appropriate use.

 

Having an end-expiratory pause will affect the performance of the Hudson mask   TRUE/FALSE

Having a high peak inspiratory flow will affect the performance of nasal cannulae   TRUE/FALSE

Low flow rates may lead to an increased inspired pCO2 with the Hudson mask TRUE/FALSE

The Bernoulli effect is relevant for Venturi mask function   TRUE/FALSE

With nasal cannulae the nasopharynx acts as an oxygen reservoir   TRUE/FALSE

 

 

BT_GS 1.52 Explain the principles involved in the electronic monitoring of depth of sedation, including EEG analysis.

Although a unique EEG “neural correlate of consciousness” has not yet been identified, drugs that induce anaesthesia do have characteristic effects on the spontaneous EEG. However, it is important to note that these effects are not the same for different drugs, even though they may produce a similar clinical endpoint. Appreciating these differences is the key to understanding why commercial EEG monitoring devices may give misleading results when certain drugs are used.

 

T / F    The EEG during sevoflurane anaesthesia has less “randomness” than when awake.

T / F    Propofol causes burst-suppression of the EEG at levels which have little effect on spinal reflexes.

T / F    When burst-suppression is induced by propofol, total brain oxygen consumption is reduced by up to 90%.

T / F    Nitrous oxide causes similar changes to the EEG compared to sevoflurane.

T / F    Electrocortical silence cannot be produced with ketamine.

 

 

BT_SQ 1.14 Oxygen delivery systems

Clearly oxygen is a very important element for us as humans and sometimes atmospheric levels of oxygen are insufficient for our patients’ needs.

We are unlikely to find ourselves in the situation of the Apollo 13 astronauts, but it’s important we know how to give supplemental O2…

BT_SQ 1.14 Describe different systems to deliver supplemental oxygen and the advantages and disadvantages of these systems

A non rebreather mask has a one way valve which prevents entrainment of atmospheric air TRUE/FALSE

Venturi oxygen delivery devices make use of the Bernoulli principle TRUE/FALSE

Delivering oxygen at 6L/min via a Hudson mask, a patient with a respiratory rate of 6 breaths per minute (bpm) will recieve a higher FiO2 than a patient with a respiratory rate of 12 bpm TRUE/FALSE

Nasal cannulae are an example of a variable oxygen delivery device TRUE/FALSE

100% oxygen can be delivered to a patient using a Venturi mask with a rating of 1.0 TRUE/FALSE