BT SQ 1.10 Describe the supply of medical gases (bulk supply and cylinder) and features to ensure supply safety.

This is a Lego anaesthetic machine made for the huge American ASA Conference quite a few years ago. Fortunately our real machines have less parts. You need to be quite familiar with all the components of your machine- you don’t necessarily have to be able to deconstruct it, though!

The pin index system means you can connect an oxygen cylinder to any manifold because it has a universal setting T/F

Oxygen cylinders may be coloured white or green or black with white shoulders T/F

A carbon dioxide cylinder contains a mixture of liquid and vapour T/F

A full oxygen cylinder contains gas at over 150 atmospheres of pressure T/F

A full  C size oxygen cylinder on the back of your machine contains about 760 litres of oxygen T/F

BT_SQ 1.16 Describe when a level 1 anaesthesia machine check is required. Refer to College professional document PS31: Recommendations on Checking Anaesthesia Delivery Systems


Latex-free project 111.jpg” by Chrisjw is licensed under CC BY 2.0

Understanding the equipment used in anaesthesia is an important part of anaesthetic training and the primary exam.  Anaesthetic machines (or the more politically correct term – Anaesthetic Delivery Systems) have become increasingly sophisticated and complicated meaning, like cars engines, many of the components are now hidden away and require trained technicians to service and repair.  Gone are the days of owners fixing problems themselves.

The subject of this post is covered by a professional document produced by ANZCA, PS31 can be found here with a background paper here

T/F A level one check is done to verify that the system is functional and complies with the relevant Australian or New Zealand standards

T/F Intravenous and local anaesthesia delivery devices should be included in a level one check

T/F  A level one check should be performed at the start of every anaesthetic list

T/F Documentation of a level one check should include the date, the items checked, the results of the check, and the identity of the person performing the check

T/F Every step in a level one check is done because of a previous adverse event related to a failure of the component being checked

T/F  If a level one check has just been formed then a level two check is not required

2018.1 SAQ 4 Hazards of CO2 absorbents

Outline the hazards associated with the use of CO2 absorbents within a circle breathing system and how the risks can be minimised.

We use a CO2 absorber as part of a circle circuit on a daily basis. It is important to be cognisant of potential hazards associated with its use. The CO2 absorbents are continually evolving to help eliminate some of the absorbent specific risks, but the are a number of general risks that exist regardless of the absorbent used.

Miller’s Anaesthesia Ch 29 covers this topic well, including a discussion of the newer Ca(OH)2 and LiOH based absorbents.

Please note however that there is an error in Miller with regard to soda lime and Compound A production. Compound A production and buildup is favoured by dry soda lime, contrary to what Miller says. I have been in contact with the editor regarding the mistake.

The risks of using desiccated absorbent, especially those containing strong alkalis, are significant and it is important to be mindful of this.

BT_SQ 1.15 Outline how CO2 is absorbed in a circle system and the hazards associated with the use of CO2 absorption

4-8 mesh granules provide the optimal balance between surface area of CO2 absorption and resistance in the circuit  T/F

Ultra low flow anaesthesia (<0.5L/min FGF) increases the risk of carbon monoxide (CO) buildup in the circuit  T/F

Higher fresh gas flows, may increase the rate of CO production by drying the absorbent T/F

The CO2 canister is a common site for a circuit leak T/F

Inspiratory CO2 monitoring is a less reliable measure of detecting expired CO2 absorbent than a pH sensitive dye T/F

The use of sevoflurane or a Ca(OH)2 based absorbent will prevent potential CO poisoning T/F

BT_AM 1.19 Describe different modes of ventilation available on modern ventilators and their physiological consequences

T/F During pressure-cycled ventilation, inspiratory flow is constant

T/F PEEP can decrease left ventricular afterload

T/F PEEP decreases total lung water

T/F CPAP can be achieved by partially closing the APL valve on a circle circuit

T/F PEEP or CPAP can increase left ventricular transmural pressure

T/F PEEP can increase right ventricular volume

T/F During pressure support ventilation, cycling into expiration occurs when the inspiratory flow rate decreases to a pre-set level

Medical Gas Cylinders

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


T / F   nitrous oxide cylinders have a blue body, and blue shoulders

T / F   a medical gas cylinder with a single pin index hole would contain carbon dioxide

T / F   a full C-size oxygen cylinder at 20 degrees C would contain 490 L of oxygen, at 400 kPa

T / F   an Entonox cylinder contains 50% liquid nitrous oxide and 50% gaseous oxygen

T / F   the fitting which couples to the cylinder neck is known as a Schrader valve



BT_SQ 1.5 Describe basic physics applicable to anaesthesia, in particular:
…. principles of humidification and use of humidifiers ….


T / F   during quiet breathing, air reaching the carina is close to 37 degrees C and 100% relative humidity

T / F   at 37 degrees C, air can hold a maximum of 44 mg/L of water vapour

T / F   during expiration, water vapour condenses onto the airway mucosa

T / F   absolute humidity depends upon both the temperature and the atmospheric pressure

T / F   a HME can warm inspired gases to about 30 degrees C, but this takes about 20 minutes

Pressure Regulators

BT_SQ 1.10

O-Series regulator with attached pressure gauge. If you have a particular interest in this regulator, it is described in detail in Russell. You are probably more familiar with the small transport oxygen cylinders with the integrated pressure regulator, flowmeter and pressure gauge.

Integrated Regulator 2

T/F Pressure regulators should be regularly lubricated with a hydrocarbon based grease to prevent sticking.

T/F Pressure regulators for oxygen may be used with air but not nitrous oxide

T/F Adiabatic gas expansion can cause moisture to freeze and jam pressure regulators

T/F Rupture of a regulator diaphragm can cause loss of gas from the anaesthetic circuit to the pipeline.

T/F Pressure regulators convert a constant upstream pressure to a variable downstream pressure


BT_SQ 1.9

Dedicated scavenging pumps. The hospital vacuum is designed to suck up fluids, and usually vents in to the plant room of the hospital. The plant room staff will not thank you for connecting the scavenging to such a system. The anaesthetic gas scavenging system should be vented away from where people will inhale the gases.







T/F A risk of using a scavenging system is excessive positive pressure in the breathing circuit

T/F Active scavenging systems should be capable of developing a high negative pressure

T/F Prolonged exposure to trace concentrations of volatile agents my be teratogenic in the second trimester of pregnancy

T/F Passive scavenging systems should have a flowmeter to measure flow

T/F A closed scavenging interface must be used with an active scavenging system

Color coding of gases

BT_SQ 1.10

For the end of January puzzle: See how many safety and standards violations you can find in this picture!


One of my friends was telling me about an incident at her hospital a while ago, where the patient became hypoxic after being given 100% oxygen. The hospital had done some work on the piping, but hadn’t tested it or notified anyone…

T/F Nitrous oxide hoses should be colour coded light blue

T/F Oxygen hoses should be colour coded green

T/F Air hoses should be colour coded yellow

T/F CO2 hoses should be colour coded gray

T/F Scavenging hoses should be colour coded black and white


Bonus questions:

1. How are the gas pipelines themselves coded so the workmen know which outlet to connect them to.

2. (Non examinable) What qualifications do you have to hold to install a medical gas pipeline in Australia?


Cleaning of Equipment

IT_SQ 1.5

Oxyvir wipesI am sure this is a subject which has you on the edge of your seats.

When I was training one of the hospitals I worked at would heat treat their PVC endotracheal tubes so they could reuse them. The trouble was that after they had been cooked, they had the structural strength of freshly cooked spaghetti. You had to unkink them several times per case. I got into the habit of tearing off the pilot balloon of cuffed tubes so that they couldn’t be re-used…



T/F Laryngoscope blades should be sterilised after use

T/F Single use items may be sterilised if the process complies with AS/NZS 4187

T/F Disinfection involves the inactivation of non-sporing organisms and spores.

T/F Bougies should be disinfected after use.

T/F The surface of the anaesthetic machine should be disinfected between patients