anesthesia machine Flashcards
Standards of the anesthesia machine are overseen by
American National Standards Institute (ANSI)
- PRIOR TO 2000
American Society for testing and materials (ASTM)
- After 2000
Alt. Associations having something to do with anesthesia machine standards (4)
Internacional Electrochemical Commission (IEC)
Compressed Gas Association (CGA)
Institute of Electrical and Electronic Engineers (IEEE)
Federal Drug Administration (FDA)
Contemporary Components of an anesthesia machine (9 large ones)
electrical supply battery back up alarms required monitors oxygen supply flowmeter oxygen flush valve vaporizers waste gas system
Battery back up must last
at least 30 minutes
Required monitors (6)
Inspired oxygen /co2 expired oxygen/co2 oxygen supply failure hypoxic guard system anesthetic vapor concentration Vital signs oxygen analyzer alarm
Oxygen supply includes
pipeline supply
cylinder
Components of High pressure system (4)
auxiliary E cylinder
Yoke assembly
bordoun gauge
high pressure regulator
High pressure component of the system is exposed to
up to 2000 PSI
Cylinders for MRI are made of
non-ferrous metal; i.e. ALUMINUM
US department of transportation issue regulations (7)
regulate: manufacture marking/labeling filling handling transport storage disposal of cylinders
Associations that have standards for cylinders (3)
compressed gas association
national fire protection association
United States pharmacopecia/national formulary USP/NF
carbon dioxide cylinder color
US/ ISO = grey
Medical air cylinder color
US = yellow ISO = black& white
Nitrogen cylinder color
US/ISO = black
nitrous oxide cylinder color =
US/ISO = blue
oxygen cylinder color =
US = green ISO = white
Vacuum (Suction) color =
US = white ISO = yellow
WAGD/Evac color =
US/ISO = purple
ANSI/ASTM vs FDA
ANSI/ASTM -> regulate what each thing on the machine does.
FDA regulates machine check
most common auxiliary cylinder size
E
United States pharmacopeia/national formulary sets
purity of medical gases
Pressure in cylinders for oxygen/nitrous oxide/air
2000 psig for oxygen/air
750 psig for nitrous oxide
Yoke Assembly (5)
- orient
- gas
- uni
- contains
- some
Orient tanks
Gas tight seal
Unidirectional flow of gases
Contains a filter
Some have check valve
—-> check valve ; Stops leaking into atmosphere
—–>check valve ; Stops transfer between tanks
Yoke Assembly check valve is responsible for : (3)
1 minimizes the transfer of gas from a cylinder at high pressure to one with lower pressure
(2) allows an empty cylinder to be exchanged for a full one while gas flow continues from the other cylinder into the machine
(3) minimizes leakage from an open cylinder to the atmosphere if one cylinder is absent.
PISS oxygen
2, 5
PISS nitrous oxide
3, 5
PISS medical air
1, 5
PISS carbon dioxide
1, 6
PISS entox
7
E cylinder holds volume at
660 L at 1900 PSI
H cylinder holds volume at
6900 L at 2200 PSI
Pressure in a nitrous oxide cylinder will not drop until
75% of the tank is used i.e. about 250 -400 mL remain
Frangible disk
part of cylinder (high pressure system) will burst under extreme pressure
Fusible Plug
part of cylinder ( high pressure system) will melt when exposed to extreme pre-determined temperature
Fusible plug is made of
bismuth, lead, tin, and cadmium
BLT with cheese
High Pressure regulator acts to
reduce the high and variable pressure delivered from a cylinder to a lower and more constant pressure suitable for the anesthesia machine
Pressure regulators are preset at the factory to regulate to
between 40 and 45 PSI
Intermediate pressure system components (6)
hospital supply line (pipeline inlet) oxygen flush valve pneumatic safety systems electrical system auxiliary oxygen flowmeter second stage regulator
Pneumatic safety systems
oxygen supply failure alarms
oxygen failure protection devices
oxygen is typically stored as
a liquid, -184 celcius, cryogenic bank
nitrous typically stored in
H cylinders, liquid
DISS
Diameter index safety system:
ensures only the correct anesthesia gas can be connected
sized and threaded differently
Hospital supply connection includes (4)
DISS
Filter - to stop contaminates
check valve - ensures unidirectional flow
pressure gauge - monitor pipeline pressure
DISS vs quick connections
Quick connections are not uniform across manufactures, thats why we use DISS
When gas cylinders are not in use
They should be closed
Oxygen flush valve
- provides
- enters
- flow rate
Provides 100% oxygen to the anesthesia circuit
Enters the circuit downstream from the vaporizers – directly to common gas outlet
Flow rate between 35 – 75 L/minute
Flow rate of oxygen flush valve
between 35 - 75 L/minute
Hazards of oxygen flush valve
- barotrauma
- anesthetic dilution -> awareness
Pneumatic Safety Systems
Older ohmeda -> oxygen supply failure alarm
fail save devices
fail safe devices are designed to
to prevent the hypoxemia mixture of gas in the event of oxygen supply failure.
- however pneumatic and works based on pressure and not flow.
- either proportional or threshold
Limits of fail-safe devices
does not prevent anesthesia gas from flowing
works even if the wrong gas is supplied
Oxygen Supply Failure Alarm Sensor
Within the oxygen circuit f the intermediate pressure section of the machine
will provide an audible and visible signal if the oxygen pressure drops below manufacturers standards.
oxygen supply failure alarm sensor is a
ASTM requirement of all machines. Cannot be silenced until the full pressure is restored/
Drager! Oxygen Failure Protection Device
Proportional valve, as oxygen pressure decreases, valve will close preventing nitrous oxide from flowing.
Datex-Ohmeda Fail Safe Device
Threshold valve, threshold = 20 PSI
Auxiliary Oxygen Flowmeter
allows for use of low flow oxygen without using the anesthesia circuit.
- not a mandatory requirement but on almost all anesthesia machines
- typically used for monitored care anesthesia
- uses same pipeline or cylinder supply
Second Stage Pressure Regulator (5)
- located
- protects
- supply
- lowers
- ensures
located downstream of intermediate pressure system
- protects against fluctuations off pipeline pressure
supply constant pressure to the flow control valves and proportioning system
lowers the pressure to 14 - 35 PSI
ensures oxygen is the last gas flowing
Typical PSI of oxygen after the second stage regulator
14 PSI
Typical PSI of nitrous oxide after the second stage regulator
26 PSI
Low Pressure System located
located between her low control devices and the common gas outlet.
pressure here is slightly above atmopsheric pressure
pressure is variable in this section
Low Pressure System Components (6)
Flowmeters Hypoxia prevention safety devices Unidirectional valves (info only) Pressure relief devices (info only) Anesthesia vaporizers/vaporizer manifold (info only) Common gas outlet
Flowmeters :
contain flow control valves
flow tubes
- regulate the flow of gases entering the breathing circuit
Flow meters consist of (6)
flow controlled knob a tapered needle valve valve seat valve stops float float stops
Shape of thorpe tube
variable orifice.
narrow at bottom - laminar flow
wider at top - turbulent flow
Each thorpe tube is calibrated
for a specific gas r/t density of gas.
Eger series
places oxygen flowmeter all the way to the right as a fail safe to prevent a hypoxemia mixture.
if it was left and a crack was to the right it would leak
oxygen and nitrous flow valves are
linked mechanically or pneumatically to prevent a hypoxic mixture
Valves of flowmeters are anatomically
the separation of intermediate and low pressure systems
Physical safety features of flow meters
oxygen knob must be larger in size and physically distinguishable
all knobs are color coded and marked permanently with chemical formula of gas
knobs must be recessed or protected to prevent from bumping
Proportiong system is a
pneumatic-mechanical interlock
Drager - SORC
Sensitive oxygen ratio controller system
pneumatic-mechanical interlock
opening oxygen flow creates a back pressure in the chamber opening the nitrous oxide, increasing oxygen will allow you to increase nitrogen.
Drager - SORC maintains a ratio of
minumum 25% oxygen to 75% nitrogen
Datex-Ohmeda Link Proportioning system
Mechanical integration of nitrous oxide and oxygen valve
Increases oxygen when necessary to maintain a 3 to 1 ratio.
Link proportioning system, nitrous oxide sprocket teeth
19
Link proportioning system, oxygen sprocket teeth =
25
SORC vs link proportioning
SORC ; pneumatic-mechanical
Link proportioning; mechanical.
The Link-25 proportioning system can be thought of as a system that increases oxygen flow when necessary to prevent delivery of a fresh gas mixture with an oxygen concentration of less than 25%. In contrast, pneumatic systems such as the SORC work by limiting nitrous oxide flow.
Common Gas Outlet
Receives all the gases and vapors from the machine and delivers the mixture to the breathing circuit
15 mm female slip going fitting.
5 pathways for oxygen in the anesthesia machine
- Flow to the fresh gas flowmeter
- Powers the oxygen flush valve
- Activates the fail-safe valve/mechanism
- Activates the oxygen supply low pressure alarm
- Compresses the bellows of the ventilator
ANSI
American National Standards Institute, managed anesthesia machines prior to 2000
ASTM
American Society for Testing and Means
oversees anesthesia machines since 2000
oxygen flush valve enters the machine at
the common gas outlet, i.e. bypasses the vaporizers
oxygen fail safe valves are
safeguards intended to link the flow of other gases in the gas supply system to the pressure of oxygen
Fail safe valves are either
binary (open/close) = thresshold or
proportional, close proportionally as the oxygen supply pressure decreases
Drager- Proportional Valve
fail safe valve, as pressure of oxygen decreases, the valve will proportionally close the outlet for nitrogen.
Datex Ohmeda fail safe valve
Treshhold, when the oxygen pressure is less than 20 PSI the valve will close. (prevention flow of N2O)
second stage pressure regulator ensures that
oxygen is the last gas flowing
Low pressure system is located
between the flow control devices and the common gas outlet
Pressure in the low pressure system is
slightly above atmospheric pressure
only oxygen safety feature after the flow meter =
the oxygen analyzer which is after the common gas outlet
oxygen supply failure alarm =
low pressure alarm (older ohmeda machine)
flow tubes on newer machines =
depend on electrical power to provide display
must have back up to control and display o2 flows
DISS has
body, nut, nipple
