The document summarizes the components and gas flows of an anesthesia machine. It describes: 1) The high pressure system that receives gases from cylinders and reduces pressures before entering the machine. It consists of a hanger yolk, check valve, pressure gauge, and regulator. 2) The intermediate flow system that receives gases from the regulator or hospital pipeline at pressures of 40-55 psig. 3) A second-stage reducing device located before the flow control valves that further reduces gas pressures to 26 psig for N2O and 14 psig for O2.

1. The Anesthesia Machine gas lows
D EMAD MOHAMMED

4. The Anesthesia Machine
FLOW
High Intermediate Low Pressure Circuit

5. High Pressure System
 Receives gasses from the high pressure E
cylinders attached to the back of the ane
sthesia machine (2200 psig for O2, 745 ps
ig for N2O)
 Consists of:
Hanger Yolk (reserve gas cylinder holder)
Check valve (prevent reverse flow of gas)
Cylinder Pressure Indicator (Gauge)
Pressure Reducing Device (Regulator)
 Usually not used, unless pipeline gas sup
ply is off

6. E Size Compressed Gas Cy
linders
Cylinder Characteri
stics
Oxygen Nitrous Oxide Carbon Dioxide Air
Color White
(green)
Blue Gray Black/White
(yellow)
State Gas Liquid and gas Liquid and gas Gas
Contents (L) 625 1590 1590 625
Empty Weight (kg) 5.90 5.90 5.90 5.90
Full Weight (kg) 6.76 8.80 8.90
Pressure Full (psig) 2000 750 838 1800

7. Hanger Yolk
 Hanger Yolk: orients and
supports the cylinder, pr
oviding a gas-tight seal a
nd ensuring a unidirectio
nal gas flow into the mac
hine
 Index pins: Pin Index Safe
ty System (PISS) is gas sp
ecificprevents accident
al rearrangement of cylin
ders (e.g.. switching O2 a
nd N2O)

8. Pressure Reducing Device
 Reduces the high and variable pressures found in a
cylinder to a lower and more constant pressure fou
nd in the anesthesia machine (45 psig)
 Reducing devices are preset so that the machine us
es only gas from the pipeline (wall gas), when the p
ipeline inlet pressure is 50 psig.
This prevents gas use from the cylinder even if the
cylinder is left open (i.e. saves the cylinder for back
up if the wall gas pipeline fails)

9. Pressure Reducing Device
 Cylinders should be kept closed routin
ely. Otherwise, if the wall gas fails, the
machine will automatically switch to th
e cylinder supply without the anestheti
st being aware that the wall supply ha
s failed (until the cylinder is empty to
o).

10. Intermediate FLOW Syste
m
 Receives gasses from
the regulator or the h
ospital pipeline at pre
ssures of 40-55 psig.

11. Limitations of Fail-Safe D
evices/Alarms
 These devices prevent hypoxia from some p
roblems occurring upstream in the machine
circuitry (disconnected oxygen hose, low ox
ygen pressure in the pipeline and depletion
of the oxygen cylinder)
 Equipment problems that occur downstream
(for example leaks or partial closure of the o
xygen flow control valve) are not prevented
by these devices.

12. Second-Stage Reducing D
evice
 Located just upstream of the flow cont
rol valves
 Receives gas from the pipeline inlet or
the cylinder reducing device and reduc
es it further to 26 psig for N2O and 14
psig for O2

13. The end