Module 2C: anesthesia; the machines

Question 1

What are the 2 principal functions of anaesthesia machine?

Answer 1

Delivers gases to the patient (oxygen, medical air,
nitrous oxide and volatile anaesthetic agents)
 Provides a means to manually ventilate the patient
under positive pressure (via a connected bag
and/or an integrated automatic ventilator)

Question 2

What are the basic parts of the machine?

Answer 2

Gas supplies under pressure(central supply + backup supply)

Gas flow controls(flow meters and rotameters)

Vaporisers (convert volatile anaesthetic agents into gaseous form)

Breathing circuit(connects machine to airway of patient)

Ventilation systems (reservoir bag+ automatic ventilator)

Question 3

In what form is oxygen stored as and where?

Answer 3

stored as liquid form in giant external tanks, hospitals have central backup.

Oxygen piping is white and cylinders are black with white shoulder

Question 4

Give the characteristics of NO2 (function, storage location, colour)

Answer 4

Carrier gas to augment anaesthesia

Stored in large NO2 cylinders piped to theatre

Colour is royal blue

Question 5

What gas is found in black lines?

Answer 5

clean medical air (21% oxygen in nitrogen)

Question 6

How do flowmeters work?

Answer 6

Gas enters the machine under HIGH pressure.

Stepped down by valves

There are individual flow controls for each gas

Safety interlink prevents N2O from being given alone

O2 is usually mixed with mixed air or N2O

Question 7

What are vaporisers

Answer 7

Convert volatiles anaesthetics from liquid into gas form-> delivered

Each volatile agent has own vaporizer

Question 8

What colour is halothane

Answer 8

red

Question 9

What colour is isoflurane

Answer 9

Purple

Question 10

what colour is sevoflurane

Answer 10

yellow

Question 11

what colour is desflurane

Answer 11

blue

Question 12

What are vaporiser fillers?

Answer 12

metal/plastic keyed fillers(top) or funnel-filler adapters(bottom)

colour coded for each agent

one side fits in bottle, other on correct vaporiser

Question 13

what is the breathing circuit?

Answer 13

circle system consisting of piping with unidirectional valves where machine puts gas into inspiratory limb and patient exhales into expiratory limb.

Circuit contains a CO2 absorption system

Question 14

What is the name of the CO2 absorption system and how does it work?

Answer 14

Soda-lime system granules-> absorb CO2 to form heat and moisture preventing dry air.

Has indicator that changes colour when exhausted

Question 15

What is Ayre’s T-piece

Answer 15

lightweight breathing circuit, ideal for INDUCTION IN PAEDIATRICS

Valve free, resevoir bag OPEN

NO CO2 ABSORPTION SO MINIMUM GAS FLOW TO WASH OUT CO2

Question 16

What are heat moisture exchange filters

Answer 16

warm and humidify gases delivered to patient

square/circular shaped

single use

placed at end of ETT/Mask

Question 17

What is a resevoir bag?

Answer 17

manual ventilation by closing adjustable valve

Can provide PEEP

If valve is fully open=spontaneous breathing

Used to check for circuit leaks

Question 18

What is a self-inflating resuscitator/ambubag

Answer 18

part of essential equipment, used as backup ventilation in case of MACHINE FAILURE OR LEAKS

Used to transport patients

Question 19

What is the function of a ventilator

Answer 19

provides automatic positive pressure ventilation, most use gas driven bellows, others pistons

Question 20

What are the 2 general modes on ventilators

Answer 20

Volume control ventilation (VCV)
Pressure control ventilation (PCV)

Question 21

What adjustable setting does a ventilator have?

Answer 21

Tidal volume (VCV)
Airway pressure (if PCV)
Resp rate, PEEP, inspiratory/expiratory ratio

Question 22

What are some important features of anaesthesia machine

Answer 22

oxygen flush
oxygen failure alarm
oxygen analysers