Anaesthesia Machines - Basics
| What does "Anaesthesia" mean? |
an = without aesthesia = sensation |
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| What does it do? |
The anaesthesia machine mixes the correct concentrations of
gas and drugs to be inhaled and exhaled by the patient so they
lose consciousness. They are held unconscious and have no sensation
while being operated on, then regain consciousness after the
operation. |
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| Physiology |
Anaesthetic gas affects the nervous system, resulting in a
numbing of the nerve pathways. The patient becomes unconscious,
unaware of what is happening, has no pain, is immobile (may
need breathing support) and free from memory while under the
influence of the anaesthetic agent. |
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| How it works
|
Air, Oxygen, and Nitrous Oxide are supplied from wall outlets
or cylinders. The pressures are reduced by pressure regulators
then pass through an O2 failure alarm. The flow of
gas is controlled by flowmeters. The gas is mixed and passed
over a vaporiser containing the anaesthetic agent. An Anti-hypoxic
device ensures that the flowmeters deliver a minimum of 25%
O2 to the agent vaporiser. The gas then goes
through an over pressure relief valve and back flow valve, then
to the common gas outlet (CGO), ready to be given to the patient.
There is an emergency O2 flush valve connected to give 100% O2 if required. The gas then enters a patient circuit and ventilator. Expired gas can be stripped of CO2 in a soda-lime filter and recirculated, or scavenged out of the room. |
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| Units of measurement |
Flow: L/min, Pressure: kPa and cmH2O |
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| Typical values
|
Dependant on patient size, rate and strength of breathing, circulation and solubility of the anaesthetic. | ||||
| Pictures of equipment | |||||
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