Pipeline Supply Source
The pipeline supply source is the primary gas source for the anesthesia
machine. Most hospitals have a central piping system to deliver medical gases such
as oxygen, nitrous oxide, and air to the operating room. The central piping system
must supply the anesthesia machine with the correct gases at the appropriate pressure
for the anesthesia workstation to function properly. Unfortunately, this does not
always occur.
In a survey of approximately 200 hospitals in 1976, 31% reported
difficulties with pipeline systems.[29]
The most
common problem was inadequate oxygen pressure, followed by excessive pipeline pressures.
The most devastating reported hazard, however, was accidental crossing of oxygen
and nitrous oxide pipelines, which led to several deaths. This problem caused 23
deaths in a newly constructed wing of a general hospital in Sudbury, Ontario, during
a 5-month period.[29]
[30]
In 2002, two additional hypoxic deaths were reported in New Haven, Connecticut.
These deaths resulted from a medical gas system failure in which a damaged oxygen
flow meter was inadvertently connected to a wall supply source for nitrous oxide.
[3]
The operator must take two actions if a pipeline crossover is
suspected. First, the backup oxygen cylinder should be turned on. Second, the pipeline
supply must be disconnected. This step is mandatory because the machine preferentially
uses the inappropriate 50 psig pipeline supply source instead of the lower-pressure
(45 psig) oxygen cylinder source.
Gas enters the anesthesia machine through the pipeline inlet connections
(see Fig. 9-3, arrows
).
The pipeline inlet fittings are gas-specific, Diameter Index Safety System (DISS),
threaded-body fittings. The DISS provides threaded, noninterchangeable connections
for medical gas lines, which minimize the risk of misconnection. A check valve is
located downstream from the inlet. It prevents reverse flow of gases from the machine
to the pipeline or the atmosphere.
