Anesthesia Workstation Flashcards
Government agency
Oversees the machine 2 bodies:
ASTM: in charge and oversees all machines and equipment out on the market since 2000.
ASTM: American Society for Testing and Material
ANSI: all machines prior to year 2000.
ANSI: American National Standards Institute
Common manifold
All the flow meters are housed: Green = oxygen Blue = nitrous oxide Yellow = air Deliver oxygen alone or other substituents
Vaporizers
Oxygen to flow meter
Purpose of Oxygen in Anesthesia Machine
1) Flow to the fresh gas flowmeters
2) Powers the oxygen flush valve
3) Activates the fail-safe mechanisms
4) Activates oxygen low pressure alarm
5) Compresses the bellows of the Ventilator
Oxygen Flush Valve
Automatically delivers 35-75L directly from the pipeline to the common outlet. Only for anesthesia machine check and circuit or fill the bellow. Delivers that much oxygen = cause barotrauma.
Pneumatic System
Air Pressure System
1) High Pressure
2) Intermediate Pressure
3) Low Pressure
High Pressure System
The High-pressure circuit consists of those parts which receive gas at cylinder pressure:
o hanger yoke (including filter and unidirectional valve)
o yoke block
o cylinder pressure gauge
o cylinder pressure regulators
Intermediate Pressure System
The Intermediate pressure circuit receives gases at low, relatively constant pressures (37-55 psi, which is pipeline pressure, or the pressure downstream of a cylinder regulator):
o pipeline inlets and pressure gauges
o ventilator power inlet
o Pressure regulators
o Oxygen pressure-failure device (fail-safe) and alarm
o flow meter valves
o oxygen and nitrous oxide second-stage regulators
o oxygen flush valve
Low Pressure System
The Low-pressure circuit includes components distal to the flowmeter needle o valves o flow meter tubes o vaporizers o check valves (if present) = unidirectional valves o common gas outlet o Hypoxia prevention safety device o Pressure relief valves
DISS: Diameter Index Safety System
Provides non interchangeable connections for the medical gas lines
Connection consists of body, nipple and nut combination
Only properly mated parts will fit together and allow the threads to engage
Required for every anesthesia machine
Oxygen Pressure Failure Device
Only works off as pressure and not FiO2. Still deliver a low oxygen mixture. Yes.
Oxygen Flush Valve
Special ring around them and prevent activation. O2 + symbol for the oxygen flush valve
Flow Meter Tubes
Hypoxia prevention safety device. Chain that connects oxygen and nitrous so that if you try to deliver oxygen at less than 25% it won’t turn nitrous on
Oxygen and nitrous = chain link
When you try to decrease oxygen and increase nitrous, it won’t allow you to deliver less than 25% while oxygen is on board
O2 Pressure Sensor Shut-Off Valve
A safety valve located downstream from the N2O supply source.
Purpose: shuts off N2O or proportionally decrease the supply of N2O allowed into the machine, if O2 supply pressure decreases to a pre-determined threshold value: 25 psi
Pressure Sensor Shut-Off
Oxygen enters the machine and flows to pressure-sensor shut off valve and oxygen supply failure alarm system
Pressures sensor: less than 20, pistons start to close.
Oxygen supply greater than > 20 psi = N2O flows
Oxygen supply less than <20 psi = N2O flow stops
Oxygen Supply Source
#1 Pipeline Source: 50-55 psi from the wall supply with check valve = goes through second stage regulator. #2 Cylinder Supply: 2200 - 2000 psi. Goes through cylinder pressure regulator
Cylinder Size
Department of Transportation regulates this.
Pressure from the cylinder needs to be less than pipeline: 45 psi
Cylinder size of G and H: only source of oxygen
Cylinder: back up source and attached to hanger yoke and pin index safety to prevent misconnection
PISS
Each gas has their certain configuration Green = oxygen = PISS: 2, 5 Blue = nitrous oxide = PISS: 3,5 Yellow = air = PISS: 1,5 Each cylinder has 2 pins that correspond
Tank Capacity for Oxygen
E cylinder oxygen are considered full at 2000 - 2200 psi and approximately 625 - 700 L of O2.
O2 is used from the cylinder, pressure falls in proportion to the amount of gas left in the tank.
Oxygen Pressure
Oxygen pressure on the cylinder gauge reflects volume of contents of the E-sized cylinder O2 stored as GAS
Nitrous Oxide
Only way to figure out the amount of nitrous oxide left is to weigh it
Nitrous is stored as liquid
Pressure Regulators
Reduce cylinder pressure
O2: 2000-2200 psi
N2O: 745 psi
Second Stage Regulators: not found in all machines will reduce psi to be more compatible with the machines
Flow Meters
Measure gas flow to the common gas outlet
Thorpe Tubes vs. Electronic flow sensors:
Gas is specifically color coded
O2 flow knob:
Distinctly fluted
Projects beyond the control knob for other gases
Larger in diameter
Oxygen flow meter positioned downstream from nitrous prevents a hypoxic mixture if leak is present but this not fail proof!
Order: air, nitrous, oxygen and vaporizer
O2 next to vaporizer to prevent back-flow
Fail-Safe Mechanism
Oxygen is located downstream position. However, if leak is in O2 flow meter, you can still have hypoxic mixture
O2 Flush
Flow 35-75 L/min Delivery directly to machine Outlet to patient circuit Use with caution: barotrauma Reasonable use: Aid in machine check Help fill bellow on EXPIRATORY phase of respiration Bellows not filling = don't have mask on face correctly
Proportional Link System
Second-stage N2O regulator: > 26 psi
Second stage O2 regulator: 14 psi
Bicycle chain: turn on oxygen no problem
Turn on nitrous the chain system is engaged; oxygen automatically turns on
Anesthesia Machine Check
Two checks
1) Complete and thorough daily check
2) Circuit check is performed before each new case
Monitors
EKG Systemic blood pressure Body temperature Arterial hemoglobin saturation with oxygen Carbon Dioxide Anesthetic gas and vapors Alarm system
Monitors
ETCO2 = capnography is best for revealing a disconnect
Oxygen analyzer: most important monitor on the machine. Calibrate at 21% O2 = room air
SpO2 = provides ongoing monitoring of exchange
Anesthesia Machine Check
Gas Line connectors Ventilator check Flow meter controls Vaporizer levels Oxygen analyzer Low pressure circuit leak test Circle system test Workstation Self-tests
Oxygen Analyzer
The most important monitor on your machine
The only monitor that detects problems downstream from the flow control valves
General procedure entails exposing O2 sensor to room air (21%) for a given amount of time
Detects FiO2 = detects downstream
Upstream from O2 analyzer: failure, proportional link and fail safe
After the common gas outlet = only downstream regulator
Low Pressure Circuit Test
Checks the integrity of the machine from the flow control valves to the common gas outlet
Components in the low pressure circuits are most vulnerable to breakage
Flow control to common gas outlet
Low Pressure Leak Test
Master machine switch, flow control valves and vaporizers to be in OFF position
Performed using a suction bulb to the common gas outlet
Suction bulb is squeezed several times, fully collapsed, creating a vacuum in the low pressure circuit.
If the bulb remains collapsed for at least 10 seconds, the machine is leak free.
Circle System Check
Purpose: Evaluates the integrity of the circle breathing system
The circle breathing system extends from the common gas outlet to the Y piece.
Leak Test: occlude the Y Piece, close APL valve, pressurize the circuit to 30 cm of water using the O2 flush valve.
Flow Test: attach breathing bag to Y Piece, turn on ventilator and assess integrity of unidirectional valves
Simple Circle System
Expiratory phase
Expiratory breathing tube
Through the expiratory limb one way valve
In and out of the reservoir bag
Excess gas is vented out through the pop-off (APL) valve to the scavenger system
Inspiratory phase
Through the absorber canister flow from top to bottom; where CO2 is removed
Back towards the patient
Fresh gas enters the circle from the common gas outlet of the anesthetic machine
Flows through the inspiratory limb one way valve
Then flows through the inspiratory breathing tube
