Module 2C: anesthesia; the machines Flashcards
What are the 2 principal functions of anaesthesia machine?
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)
What are the basic parts of the machine?
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)
In what form is oxygen stored as and where?
stored as liquid form in giant external tanks, hospitals have central backup.
Oxygen piping is white and cylinders are black with white shoulder
Give the characteristics of NO2 (function, storage location, colour)
Carrier gas to augment anaesthesia
Stored in large NO2 cylinders piped to theatre
Colour is royal blue
What gas is found in black lines?
clean medical air (21% oxygen in nitrogen)
How do flowmeters work?
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
What are vaporisers
Convert volatiles anaesthetics from liquid into gas form-> delivered
Each volatile agent has own vaporizer
What colour is halothane
red
What colour is isoflurane
Purple
what colour is sevoflurane
yellow
what colour is desflurane
blue
What are vaporiser fillers?
metal/plastic keyed fillers(top) or funnel-filler adapters(bottom)
colour coded for each agent
one side fits in bottle, other on correct vaporiser
what is the breathing circuit?
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
What is the name of the CO2 absorption system and how does it work?
Soda-lime system granules-> absorb CO2 to form heat and moisture preventing dry air.
Has indicator that changes colour when exhausted
What is Ayre’s T-piece
lightweight breathing circuit, ideal for INDUCTION IN PAEDIATRICS
Valve free, resevoir bag OPEN
NO CO2 ABSORPTION SO MINIMUM GAS FLOW TO WASH OUT CO2
What are heat moisture exchange filters
warm and humidify gases delivered to patient
square/circular shaped
single use
placed at end of ETT/Mask
What is a resevoir bag?
manual ventilation by closing adjustable valve
Can provide PEEP
If valve is fully open=spontaneous breathing
Used to check for circuit leaks
What is a self-inflating resuscitator/ambubag
part of essential equipment, used as backup ventilation in case of MACHINE FAILURE OR LEAKS
Used to transport patients
What is the function of a ventilator
provides automatic positive pressure ventilation, most use gas driven bellows, others pistons
What are the 2 general modes on ventilators
Volume control ventilation (VCV)
Pressure control ventilation (PCV)
What adjustable setting does a ventilator have?
Tidal volume (VCV)
Airway pressure (if PCV)
Resp rate, PEEP, inspiratory/expiratory ratio
What are some important features of anaesthesia machine
oxygen flush
oxygen failure alarm
oxygen analysers
