Anaesthetic Apparatus |
|
Anaesthesia
means loss of feeling or sensation, so that no pain is felt.
In surgery this result is obtained by using an anaesthetic.
A distinction is to be made between general anaesthesia i.e.
total unconsciousness and local anaesthesia i.e. only one
area of the body is deprived sensation.
|
|
The
beginnings of modern anesthetic equipment date back to Morton's
inhalation flagon in 1846. The numerous devices developed
and introduced subsequently can be divided into four groups.
Simple ether and chloroform masks for open inhalation anesthesia,
from Simpson (1847) to Brown (1928). Vapour inhalators according
to the draw over principle of Snow (1847) up to the Oxford
vaporizer (1941). Closed or half-closed inhalation equipment
for ether or chloroform with to and fro breathing, from Clover
(1877) to Ombredanne (1908).
|
|
Equipment
for anaesthesia with nitrous oxide. From 1868 onwards this
led to the incorporation of gas bottles in anaesthetic equipment
and between 1885 and 1890 to the construction of mixing-valves
for nitrous oxide and oxygen. In addition, reducing valves,
flow meters and vaporizers were developed. The first anaesthetic
apparatus with circle system and CO2-absorber was constructed
in 1925 by the Drager factory in Lubeck. Sudeck and Schmidt
introduced this technique of anaesthesia in the university
hospital of Hamburg-Eppendorf between 1920 and 1925.
|
|
General
anaesthesia can be produced in separate ways, including intravenous
injection with thiopental sodium or other agents. The older
and still most widely used method, however is by inhalation
of a gaseous or volatile anaesthetic. Early anaesthetics were
either, nitrous oxide and chloroform.
|
|
At
the present time a range of other agents are available. In
modern surgery, especially for major operations, a combination
of two or more anaesthetic agents may be employed, the gaseous
or volatile anaesthetic being administered by means of a special
apparatus, which enables the various agents to be accurately
proportioned and controlled, so as to minimize the risk of
overdosing.
|
|
A
typical anaesthetic apparatus is shown in the accompanying
illustration. The underlying principle is that the patient’s
breath is circulated through the apparatus, in a closed circuit,
the gas flow rate being controlled by means of valves and
flow meters. The advantage of closed circuit is that loss
of body heat and moisture is prevented. Besides, a considerable
economy in the amount of anaesthetic used is effected.
|
|
|
|
Also
includes in the circuit are a breathing bag, an inlet attachment
for supplying fresh air, an evaporator for volatile anaesthetic
agents e.g., diethyl ether should these be used, and a cartridge
containing an absorbent for the carbon dioxide contained in
the exhaled air. This air may be recycled through the breathing
circuit or may, in other varieties of anaesthetic apparatus,
be discharged from the apparatus.
|
|
The anaesthetic
is managed to the patient either through a face mask or through
a tube introduced into the trachea (windpipe), the latter
method now being considered more safer and more effective.
In apparatus mentioned, the anaesthetic is nitrous oxide gas
used in conjunction with the vapour of a volatile anaesthetic.
Before having this mixture administered to him by inhalation
the patient is usually given a preliminary anaesthetic by
intravenous administration.
|
|
o
DISCLAIMER o
CONTACT US |