Changes

==Introduction==

==Introduction==

[[Image:vapouriser.jpg|right|thumb|125px|<small><center>Isoflurane Vapouriser</center></small>]]

[[Image:vapouriser.jpg|right|thumb|125px|<small><center>Isoflurane Vapouriser</center></small>]]

A vapouriser delivers safe and effective concentrations of anaesthetic vapour and are commonly found on the back bar of an anaesthetic machine. As most inhalation agents are stored as liquids at room temperature, there is a requirement for them to be vapourised before reaching the patient. Safe concentrations are achieved by the stream of fresh gas being split as it reaches the vapouriser causing some of it to pass through the vapouriser chamber containing the saturated vapour, while the remaining gas bypasses this meaning that the vapour is diluted down making it safe for the patient to breathe.  

A vaporiser delivers safe and effective concentrations of anaesthetic vapour and are commonly found on the back bar of an anaesthetic machine. As most inhalation agents are stored as liquids at room temperature, there is a requirement for them to be vapourised before reaching the patient. Safe concentrations are achieved by the stream of fresh gas being split as it reaches the vapouriser causing some of it to pass through the vaporiser chamber containing the saturated vapour, while the remaining gas bypasses this meaning that the vapour is diluted down making it safe for the patient to breathe.  

*''Plenum vapourisers'' have the gas flowing through them under positive pressure where the gas is delivered from flowmeters proximal to it on the anaesthetic machine. They are the most common type and fitted to the backbar of the machine.  

*''Plenum vaporisers'' have the gas flowing through them under positive pressure where the gas is delivered from flowmeters proximal to it on the anaesthetic machine. They are the most common type and fitted to the backbar of the machine.  

*''Down-over vapourisers'' have the gas flowing through them under negative pressure developed distal to it, generated by the patient's inspiration. They have low resistance to gas flow and are usually used 'in-circuit'.

*''Down-over vaporisers'' have the gas flowing through them under negative pressure developed distal to it, generated by the patient's inspiration. They have low resistance to gas flow and are usually used 'in-circuit'.

The amount of anaesthetic vapourised depends on a number of factors :-

The amount of anaesthetic vaporised depends on a number of factors :-

*The saturated vapour pressure (SVP) of the agent.

*The saturated vapour pressure (SVP) of the agent.

*Temperature.

*Temperature.

*Gas flow.

*Gas flow.

*Contact between gas and agent.

*Contact between gas and agent.

*Vapouriser dimensions

*Vaporiser dimensions

*Movement of the vapouriser

*Movement of the vapouriser

*Back pressure

*Back pressure

==Plenum Vaporisers==

==Plenum Vaporisers==