Changes

==Introduction==

==Introduction==

Anaesthetic machines vary between practices as some may be on trolleys while others may be mounted to the wall. However, they are all made up from the same basic components, which when understood make it possible to use any machine presented.  

Anaesthetic machines vary between practices as some may be on trolleys while others may be mounted to the wall. However, they are all made up from the same basic components, which when understood make it possible to use any machine presented.  

*Common gas outlet

*Common gas outlet

*Breathing system

*Breathing system

==Gas supply==

==Gas supply==

A supply of gas to an anaesthetic machine can be either from cylinders or a piped source. Gases that commonly used are oxygen, medical air and nitrous oxide.

A supply of gas to an anaesthetic machine can be either from cylinders or a piped source. Gases that are commonly used are oxygen, medical air and nitrous oxide.

===Cylinders===

===Cylinders===

*Device which extracts oxygen from the air via chemical means, electrically powered.

*Device which extracts oxygen from the air via chemical means, electrically powered.

==Pressure Gauge==

==Pressure Gauge==

Pressure gauges indicate the pressure of gas in the pipeline of cylinders. Depending on the age of the machine they may be found above the cylinder yoke, or on the front panel of the machine. They are colour-coded and calibrated for each gas/vapour. While this oxygen gauge measures the pressure within the cylinder, which is directly related to the contents of the cylinder, the nitrous oxide gauge measures the saturated vapour pressure of the gaseous nitrous oxide and so does not indicate the fullness of the cylinder, and will only start to show a drop in pressure as the liquid nitrous is running low.

Pressure gauges indicate the pressure of gas in the pipeline of cylinders. Depending on the age of the machine they may be found above the cylinder yoke, or on the front panel of the machine. They are colour-coded and calibrated for each gas/vapour. While this oxygen gauge measures the pressure within the cylinder, which is directly related to the contents of the cylinder, the nitrous oxide gauge measures the saturated vapour pressure of the gaseous nitrous oxide and so does not indicate the fullness of the cylinder, and will only start to show a drop in pressure as the liquid nitrous is running low.

==Pressure Reducing Valves==

==Pressure Reducing Valves==

Pressure reducing valves (or pressure regulators) are used to reduce the pressures of the gases being delivered from the cylinder as well as maintaining a constant reduced pressure as the cylinder starts to run low. Machines using cylinders have a reducing valve for each cylinder while pipeline supplies have a regulator at the source. Pressure relief valves are found downstream allowing the escape of gas if the reducing valve is to fail. The final pressure reduction is carried about by control valves which regulate gas flow into the flowmeters via manual adjustment.

Pressure reducing valves (or pressure regulators) are used to reduce the pressures of the gases being delivered from the cylinder as well as maintaining a constant reduced pressure as the cylinder starts to run low. Machines using cylinders have a reducing valve for each cylinder while pipeline supplies have a regulator at the source. Pressure relief valves are found downstream allowing the escape of gas if the reducing valve is to fail. The final pressure reduction is carried about by control valves which regulate gas flow into the flowmeters via manual adjustment.

 

==Flowmeters==

==Flowmeters==

Flowmeters are made up of a transparent tube with either a bobbin or ball, which float in the gas flow. The flow rate is marked on the tubing, and the gas flows around the bobbin or ball, where if the flow increases then the marker will rise indicating a higher flow rate. If a bobbin is present then the flow rate is read from the top of the bobbin whereas if a ball is present then the flow rate is read from the middle point of the ball. Again, flowmeters are often colour coded for the gas that they are controlling, with oxygen commonly being white, while nitrous oxide is blue.

Flowmeters are made up of a transparent tube with either a bobbin or ball, which float in the gas flow. The flow rate is marked on the tubing, and the gas flows around the bobbin or ball, where if the flow increases then the marker will rise indicating a higher flow rate. If a bobbin is present then the flow rate is read from the top of the bobbin whereas if a ball is present then the flow rate is read from the line of the equator. Again, flowmeters are often colour coded for the gas that they are controlling, with oxygen commonly being white, while nitrous oxide is blue.  

 

Flowmeters are supported along with the vapourisers and some other components on the backbar of anaesthetic machines.  

==Common Gas Outlet==

==Common Gas Outlet==

The common gas outlet is where the breathing system is connected to the anaesthetic machine. It is also where a ventilator may be attached here. It can be either fixed or swivelled.

The common gas outlet is where the breathing system is connected to the anaesthetic machine. It is also where a ventilator may be attached here. It can be either fixed or swivelled.

==Oxygen Flush==

==Oxygen Flush==

The emergency oxygen flush receives oxygen directly from the oxygen source and thereby bypassing the vapouriser. It delivers oxygen at a high flowrate and so care should be taken when used e.g. should never be used when connected to a patient.  

The emergency oxygen flush receives oxygen directly from the oxygen source and thereby bypassing the vapouriser. It delivers oxygen at a high flowrate and so care should be taken when used e.g. should never be used when connected to a patient.  

==Oxygen Failure Alarm==

==Oxygen Failure Alarm==

This alarm sounds when oxygen pressures fall, e.g. when a cylinder is empty indicating it's need to be changed over. It should ideally also prevent nitrous oxide delivery also if being used.

This alarm sounds when oxygen pressures fall, e.g. when a cylinder is empty indicating it's need to be changed over. It should ideally also prevent nitrous oxide delivery also if being used.

==Checking an Anaesthetic Machine for Use==

==Checking an Anaesthetic Machine for Use==

#Check the vapouriser is fitted correctly, the dial moves freely (make sure the gas flowmeter is turned off), and check the fluid level on the front of the vapouriser and fill if required.

#Check the vapouriser is fitted correctly, the dial moves freely (make sure the gas flowmeter is turned off), and check the fluid level on the front of the vapouriser and fill if required.

#Check the breathing system for leaks etc.

#Check the breathing system for leaks etc.