Understanding Anesthesiology - The Global Regional Anesthesia ...

cording to lung compliance). The ventilator moves the
gas mixture through the common gas outlet and into
the anesthetic circuit, the tubing that connects to the
patient’s airway. The vast majority of general anesthetics
today are delivered through a circle system. The circle
circuit has a CO2 absorber, a canister containing a
hydroxide mixture (soda lime) that absorbs CO2. The
absorption of CO2 allows the expired gas to be recycled,
thus minimizing the excessive cost and pollution
that would otherwise result. There are several other
types of circuits which are useful in specific clinical
situations or are of historical interest. The origin and
pathways of gas flow that applies to most anesthetic
machines is depicted in schematic form in Figure 9.
It is imperative that all anesthesia equipment undergo
regular checks and maintenance. It is the responsibility
of the anesthesiologist to ensure that the equipment is
in functioning condition prior to the administration of
every anesthetic. The pre-operative checklist can be
found on every anesthetic machine.
Figure 9 Pathway of gas flow in anesthetic machine
The shaded shapes represent (from left to right): volatile anesthetic vapourizer,
ventilator and bag used for bag-mask ventilation. Image by
Wikimedia user TwoOneTwo, available under the Creative Commons
Attribution-Share Alike 3.0 Licence. Image modified by Emma Kolesar.
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