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6
Circle System
6.1
Design and Description of Performance
© F. Stephan GmbH
The circle system together with the patient forms a closed cycle, into
which fresh gas is fed via the fresh gas pipe line. Excess gas escapes
through the excess gas valve (10)from the cycle and is removed from the
field of activity of the anaesthetist by means of the suction system for
anaesthetic gas (13).During the inspiration phase, the gas contained in the
system is transported to the patients' lungs by effecting pressure,
produced either by the respirator or by manual operation of a respiratory
bag. The consequent PRESSURE RELIEF in the system during the
expiration phase and the increase of pressure in the lungs due to the
elasticity of the thorax makes the gas flow back out of the lungs. Thereby
it is the task of the inspiration valve (1) and the expiration valve (7) to
permit the flow of gas only in one direction and so to establish the cycle.
Prior to reaching the patient again, CO
(2). Humidity and heat given off by the patient are fed back to him in
such a semi-closed system, which prevents desiccation and excessive
cooling of the airways. The fresh gas feeder is located on the lower end of
the holding tube. The adjustability of elevation and the possible
swivelling stand for a good adaptation to the local conditions of the
operating theatre. The respiratory pressure gauge(3), which can be
slipped onto the holding device of the circle system, has a measuring
range from - 10 to 100 mbar. It can be replaced by a blind plug.
As a standard, a mechanic volumeter (9) is installed below the expiration
valve, which measures all expiratory values of respiratory volume. The
measuring of O
-concentration, required
2
in accordance with DGAI, is carried out by means of a polarographic cell
(by Clark) (1) at the head of the inspiration valve. Moreover, the circle
system is provided with connection tapers in accordance with ISO
respectively DIN 13 252, so that corrugated tubes for the ventilation of
adults as well as tube systems for infants can be used. The excess valve
(10) serves to carry off spent respiratory gases. It can be operated in four
different adjustments.
SA-103-0109V1.3-HAO-GB
6
Circle System
is removed in the two absorbers
2
19
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