Term
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Definition
-pure gas under P
-volume and P related
i.e. contents of cylinder proportional gas P
~135atm |
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Term
| Nitrous oxide (N2O) cylinders |
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Definition
-gas compressed to liquid
-requires E for liquid to boil to produce gas
-contents of cylinder NOT proportional to gas P
~44atm |
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Term
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Definition
indicate P and so content of cylinders of compressed gas
NB: not N2O! |
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Term
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Definition
| only way to accurate idea of contents is to turn it off and wigh the cylinder |
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Term
| How are cylinders connected to the anaesthetic machine? |
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Definition
| valve of cylinder
yoke of anaesthetic machine |
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Term
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Definition
Ensures incorrect gas cylinder can not be placed in yoke of anaesthetic machine
indents/ holes in neck of valve of cylinder
... correspond with...
pins of yolk of anaesthetic machine |
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Term
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Definition
| prevents leaks between cylinder valve and yoke |
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Term
| Oil or grease use as a seal |
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Definition
| NEVER use oil or grease as a seal - if there is a leak between the cylinder and the yoke a fire will occur |
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Term
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Definition
provides a constant pressure to ensure a steady flow of gas is delivered to the patient (until the cylinder P falls below the output P)
-connected to yoke of anaesthetic machine |
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Term
| How does pressure regulator work? |
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Definition
-uses an internal "diaphragm"
-has a safety valve which releases gas into the environment in case the diaphragm fails (which would result in high P gas being delievered to the patient) |
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Term
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Definition
gas from the regulator to the patient passes over a one-way check valve
-prevents the reverse flow of gas back through the regulator
-important im preventing loss of gas when cylinders are changed on the anaesthetic machine |
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Term
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Definition
aka needle valve
-controls the flow of gas passing through the rotameter/flowmeter and hence to the vaporiser and patient
-gas from the cylinder passes through this after the check valve |
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Term
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Definition
| measures the flow rate of gas in a closed tube
-bobbin within the tube rotates - measure flow of gas from the top of the bobbin |
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Term
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Definition
| for the admin of volatile agent (e.g. isoflurane) to the gas |
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Term
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Definition
indicates the percentage of FGF that is diverted to "pick up" saturated vapour
e.g. 1% isoflurane = 1% of FGF to be delivered to the patient is saturated w. iso. vapour |
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Term
| why must vaporisers be kept upright? |
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Definition
| -if tipped the volatile agent may get into the mixing chamber and may result in a lethal conc. of anaesthetic agent being delieverd to the patient |
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Term
| high pressure relief valve |
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Definition
gas passes through this after the vaporiser
-protects the anaesthetic machine from excess P which may occur is the flow of gas from the machine is restricted
NB: not to protect the patient! |
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Term
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Definition
| the connection between the anaesthetic machine and the patient |
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Term
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Definition
-ratio regulator
-nitrous oxide cut off
-alarm whistles
NB: not all devices are fitted to all machines |
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Term
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Definition
| ensures the proportion of oxygen delivered to the patient is greater than the minimum conc. set (usually 28-35%)
e.g. N2O turned on before O2 flow - O2 flow will automatically be turned on at set min. conc.
-provides a hypoxic guard so patients always receive O2 at safe conc. and so prevent hypoxia |
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Term
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Definition
stope the flow of N2O to the flow control valve in the event of lost supply of O2 to the anaes. machine
NB: does not prevent patient receiving hypoxic mixture |
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Term
| How does the nitrous oxide cut off system work? |
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Definition
-normally the O2 P pushes a plunger up and out of the flow of N2O so the N2O flow can pass
-w/o O2 flow, the plunger is released and blocks the passages of N2O flow |
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Term
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Definition
-activated when P of O2 pipes of anaes. machine reaches a certian preset P
-usually powered by a small cylinder of O2 that is charged when the main cylinder is turned on or the pipeline is connected - when activated the gas in the alarm cylinder is released through a whistle |
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Term
| Sequence of components of anaesthetic machine |
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Definition
Both O2 and N20: gas cylinder -->pressure regulator --> check valve
(O2 cylinder has whistle alarm system attached)
(N2O then passes through nitrous cut off valve)
Both independently--> flow meter control valve and flowmeter
Flow lines combine -->vaporiser --> high P relief valve -->common gas outlet |
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