Transcript ANESTHESIA MACHINE

Parts of the
Anesthetic Machine
Purpose of the Anesthetic Machine
A liquid inhalant anesthetic is vaporized into a carrier
gas, and delivered to the patient via a breathing circuit.
Oxygen
is delivered at a controlled rate (L/min)

Isoflurane is converted to a gas and given at a
specific percentage
Gases
exhaled from the patient are scavenged OR
can be re-circulated once CO2 has been removed
*Can also be used to deliver just oxygen
during recovery or in an emergency*
Components of the Anesthetic Machine
1. Compressed gas supply
 Gas
tanks, their pressure gauges, pressure reducing valves,
flow meter
2. Anesthetic vaporizer
 Precision,
out-of-circuit vaporizer is ideal (what we use)
 Located near the fresh gas outlet
3. Breathing circuit
 Unidirectional
valves, breathing tubes, reservoir bag,
pop-off valve, CO2 canister, pressure manometer,
negative pressure relief valve
4. Scavenging System
 Disposes
of excess and waste anesthetic gases
PART 1: Compressed Gas Supply
Gas Cylinders
Most
It
commonly used carrier gas is oxygen
comes compressed in a metal cylinder and
held under pressure- up to 2200 psi
Available
in various sizes
 “E”
tanks hold 660 L of oxygen and are attached to
the anesthesia machine
 “H”
tanks hold 6900 L of oxygen and stand separate
from the machine
Tanks
are delivered and picked up by the
oxygen supply company as needed
Gas Cylinders
Tanks
are color coded for safety and recognition
 Oxygen
tanks: green, white (Canada)
 Nitrous
oxide tanks: blue
 Carbon
dioxide tanks: gray
E
tanks/cylinders, attach to the
machine via a yoke.
H
anesthetic
tanks/cylinders, are attached via hoses or
pipes. Gas lines may be used to bring the gas into
the surgical area from another room.
Gas Cylinders- Safety
In
addition to color-coded tanks, the yokes are gasspecific.


The valve on the oxygen tank matches the
connecter on the yoke specific to oxygen

An oxygen yoke has two pins below the outlet
port
The yoke is connected to a
pressure regulator to control the
amount of gas released.
*May or may not be able to
see this component
Gas Cylinders- Safety
Combustible
If

gases- avoid flames and sparks!
dropped, has the potential to act as a torpedo
Never leave a cylinder unattended!
Tank Pressure Gauge
Display
of the pressure of oxygen currently in the
tank.

Only displays when the tank is open/on

To open tank: use key

Only open once tank has
been connected to a yoke!
Gauge
reads zero when tank is empty AND when
tank is turned off/closed
 What
about gas left in the machine?
*Turn on O2 and check this gauge BEFORE every
anesthetic procedure
Tank Pressure Gauge
Replace
with new tank when the pressure is 100 psi
 Some
clinics will require tanks to be changed
much earlier!
 Refill
Gauge
line is at 500 psi (red zone)
gives you the amount of O2 in
psi but you set your flow rate in
liters/minute…how can you tell how
much time you have left until empty?
Calculating Oxygen Volume in Liters
Total
volume of oxygen left in your tank can be
calculated by multiplying the pressure by:
0.3 for E tanks and 3 for H tanks
Example: Gauge reads 1100 psi on E tank
1100 psi x 0.3 = 330 L of oxygen
Divide that amount by the flow rate you’re using:
330 L of O2 / 1 L/min = 330 minutes of use (5 ½ hrs)
330 L of O2 / 2 L/min = 165 minutes of use (<3hrs)
Nitrous Oxide

A full E cylinder contains 760 psi.
Nitrous
oxide is present in liquid AND gas forms
inside the tank.
When
the tank is turned on, liquid evaporates
into a gas as other gas leaves the tank.

The pressure of the tank doesn’t change
(because of the constant replacement of the
gas) until all liquid has been volatilized.
*The gauge will not drop until almost empty*
Anesthetist
should change the tank as
soon as 500 psi is reached.
Pressure Reducing Valve
Regulates
the pressure of the gas leaving the
tank to flow through the lines, into the flow meter
of the anesthesia machine.

Reduces the pressure of oxygen that leaves the
tank at 2200 psi to a safer 40-50 psi.
Allows
a constant flow of gas into the machine,
despite pressure changes within the tank


Can be measured with a line pressure gauge
In cases of E tanks and gas lines, the line pressure is
preset at 50 psi, so there is usually no gauge seen
Flow Meter

Allows the flow rate of oxygen traveling through
the machine to be adjusted by the anesthetist.

Reduces the psi AGAIN, from 50 down to 15 psi

Oxygen does not reach the patient unless this is
turned on (neither does the anesthetic gas).
Measured
 Ball
in liters per minute by a ball
rises in height, proportional to gas
*Read at center of ball
Oxygen Flush Valve
Button
that when depressed, rapidly delivers pure
oxygen at a high flow rate (35-75 L/min)
O 2
goes directly from pressure reducing valve to
breathing system
•
Bypasses flow meter AND vaporizer
•
Must be used in short bursts
•
Not to exceed 2 cmH2O on pressure manometer

When would we want to use this?
1.
2.
3.
PART 2: Anesthetic Vaporizer
Next
Now
stop as oxygen travels from the flow meter
that the gas is in the machine, it’s job is to
mix with the liquid anesthetic and be delivered to
the patient.
Vaporizer
Converts
the liquid anesthetic agent (usually
isofluorane or sevofluorane) into a vapor.
Adds
controlled amount of these vapors to the
carrier gas  “fresh gas”
 The
mixture of the anesthetic gas and carrier
gas is known as fresh gas.
The
vaporizer must be on to deliver any
anesthesia to the patient.
 Must
The
press down on safety lock to turn dial
flow meter must be on to supply the
oxygen; otherwise nothing is delivered.
Vaporizer
Amount
of anesthetic liquid left in vaporizer is
visible in the indicator window. Check BEFORE
your surgery to see if it needs refilling!
 Refill
by unscrewing cap of fill port
If
for some reason the vaporizer is tipped over
(usually the whole machine), turn the vaporizer
off and run oxygen only through the machine for
15 minutes to flush it out.
Use
the correct anesthetic with the
correct vaporizer!
 Iso
vs. Sevo
Vaporizer
The
vaporizer has a inlet port and an outlet port
Optional:
 When
Common Gas Outlet aka Fresh Gas Outlet
switching between rebreathing and nonrebreathing systems, this is where you will connect your
breathing tubes
Precision vs. Non Precision
Non-precision
vaporizers are simple, cheaper,
and are typically used for anesthetics with low
vapor pressure such as methoxyfluorane
Non-precision
vaporizers are located within the
breathing circuit (VIC)
 Gas
flows from the flow meter into the
breathing tubes, which contain the vaporizer
*They are no longer commonly used; we will
focus on precision vaporizers
Precision vs. Non Precision
Precision
vaporizers deliver a precise, controlled
amount of anesthetic to the patient
 Expressed
as a % which is chosen based on an
anesthetic’s MAC and the patient’s requirements
 Commonly
used anesthetics can reach concentrations as
high as 30% + if they are not controlled (vapor pressure)
 Precision
vaporizers are located outside of the breathing
circuit (VOC)
 Newer
models compensate for the factors that determine
the concentration of anesthetic delivered (other than
what you set it to).
 Ex.
Temperature, respiratory rate, back pressure
Precision Vaporizer Compensation
Made
to deliver a precise concentration of
anesthetic; non-precision vaporizers do not
Factors that are compensated for:
Temperature
changes: Volatile anesthetics
vaporize more rapidly at high temperatures


If not compensated for: hot room = higher
anesthetic output
Carrier gas flow rates and respiratory rate
effect amount of anesthetic delivered
 If not compensated: high L/min or
tachypnea = higher anesthetic output