Week 1: Anesthesia Machine Flashcards
Defined as a gas that does not liquefy at ambient temperatures, regardless of the pressure applied.
Non-liquified, compressed gas
Examples of non-liquified, compressed gas
Oxygen (O2)
Nitrogen
Air
Helium
A gas that is a liquid at ambient temperatures and pressures between 25 - 1500 psi.
Liquified, compressed gas
Example of liquified, compressed gas:
Nitrous Oxide (N2O) - Liquid at room air.
Enforce the purity of medical gases
FDA - Food and Drug Administration
They publish requirements for the manufacturing, marking, labeling, filling, qualification, transportation, storage, handling, maintenance, and disposition of medical gases.
Department of Transportation (DOT)
Regulate matters affecting the safety and health of employees
Department of Labor (DOL)
&
Occupational Safety and Health Administration (OSHA)
Published standards that are voluntary
National Fire Protection Association (NFPA)
And
Compressed Gas Association (CGA)
Cylinders range in sizes from ____ to ______
A to H
Cylinders ____ to _____ utilize a pin-index safety system (PISS) to decrease chances of misconnections and delivery of hypoxic mixtures
A to E
(All cylinders are also color-coded as a safety measure).
The ______ marking indicates aluminum. * this cylinder is used in the MRI environment.
3AL
The ______ marking on a cylinder indicates steel
3AA
*most tanks are constructed of steel
The _____ of a cylinder attaches to the valve. It contains the: 1.____ 2._____
NECK
- Pressure regulators 2. Flow-metering device
This is where cylinders are filled and discharged.
The VALVE
- made of bronze or brass
- attached to the neck
Where the gas exits from the cylinder.
The Port.
*it should be covered in transit.
* do not mistaken the port for the depression on the other side of the valve.
Rotated to open or close the valve. When turned counterclockwise it ______ the valve and clockwise it _________ the valve.
The Stem
Opens ; closes
When the valve is open, the stem moves ________ allowing gas to flow to the port.
Upward
On a cylinder: When the handle is turned clockwise it pushes the _______ downward and closes the seat. This prevents leakage of the gas.
Upon opening the valve, the upward force of the spring opens the seat.
Diaphragm
- The diaphragm valve is preferred in the cylinders because no leaks can be allowed with flammable gases.
Packed valve
Prevents leakage of the gas.
*small cylinders: stem sealed with teflon.
*large cylinders: force is transmitted by means of a driver square capable of withstanding high pressures.
Usually attached to the anesthesia machine. Used to close or open the cylinder valve:
The Handle
*It causes the stem to turn allowing gas to flow out of the port.
What do Pressure Relief Devices do?
They will vent the cylinder contents to the atmosphere if the temperature of the enclosed gas increases to a dangerous level.
Types of pressure relief devices:
Rupture disc, Fusible plug, and Pressure Relief Valve.
It protects against excess pressure as a result of high temperature or overfilling. When a predetermined pressure is reached, the _________ breaks and allows ALL the contents inside cylinder to be released.
The Rupture Disc
- follows the Gay-Lussac’s Law: Increase in Temp = Increase in Pressure.
*a metal disk designed to break off at high internal pressure
(AKA - frangible disk assembly).
This pressure relief device will only protect from excessive pressure caused by a high temperature. It is thermally operated.
Fusible Plug
* has low melting point, will melt in a fire and allows all the gas to escape.
A spring-loaded device that will close once once normal pressure has been restored in the cylinder
Pressure relief valve
AKA - safety relief valve.
*the set pressure at which a cylinder will discharge is marked on the valve.
*found on air, helium, oxygen, nitrogen, and carbon dioxide cylinder. (- NOT on N2O)
Relies on two stainless steel pins on the cylinder yoke connector just below the fitting for the valve outlet port. These pins fit exactly into the corresponding holes in the cylinder valve positioned in an arc.
Pin Index Safety System (PISS)
*designed to ensure that the correct gas is connected to its corresponding CYLINDER yoke.
*7 combinations are possible.
NON-INTERCHANGEABLE SYSTEM.
PISS connections for
AIR:
OXYGEN:
NITROUS OXIDE:
Nitrogen:
Air: 1, 5
Oxygen: 2, 5
Nitrous Oxide: 3, 5
Nitrogen: 1,4
Tank color of gases:
Air -
O2 -
N2O-
Helium-
CO2-
Nitrogen-
- Suction * -
Air - yellow
O2 - green
N2O- blue
Helium- brown
CO2- gray
Nitrogen- black
Suction- white or purple
How much pressure should oxygen tank should have least before starting a case?
1000 psi (Half-filled tank)
The most common size cylinder used in anesthesia.
Size E
*A is the smallest and H the largest.
*volume and pressure of a gas in a particular size cylinder may vary.
O2 gas E- cylinder psi and liters:
2000 psi
660 L
Nitrous Oxide (N2O) E- cylinder psi and liters.
1590 Liters
745 psi
Air E- cylinder psi and liters:
625 L
1900 psi
Can you know how much volume is left based on the pressure O2 tank?
Yes, the pressure in an oxygen tank is proportional to the volume of oxygen in the cylinder.
Ex. 500 psi = 1/4 of the total volume (660L) = about 155L
Can you know how much volume is left based on the pressure of N2O?
No, the pressure depends on the vapor pressure of the liquid and is not an indication of the amount of gas remaining in the cylinder.
The pressure gauge remains at 745 psi as long as there is some liquid in it.
When all liquid is evaporated, the pressure will decline.
How can the volume of an N2O tank be determined?
By weighting the actual cylinder.
At the point where the liquid in an N2O cylinder and the pressure gauge drops the container is more than ________ empty.
3/4 (75% empty = so about 400L. Full tank is 1590L).
When calculating how long the O2 will last, the calculation refers only to requirements at the __________ and assumes ___________.
Flowmeters; manual ventilation
The tanks are permanently stamped on the __________ of the cylinder. And the test _______ should also be placed on the cylinder.
Shoulder ; Date
The diamond-shaped figure on a cylinder denotes the:
Hazard class (flammable or non-flammable).
Each cylinder should have a white label with:
- The name of gas
- Hazard class
- Expiration date
- Name and address of expiration.
Each cylinder should have a tag that indicates:
FULL, IN USE, or EMPTY
What is an oxidizing gas?
Ones that has oxygen in it. O2 and N2O are both oxidizing gases. They are flammable
Cylinder Hazards
- incorrect cylinder
- incorrect contents
- incorrect valve
- incorrect color
- incorrect labeling
- damaged valve : may cause cylinder to have leak
- Fires: occurs if oxidizing agent present
- Explosion: a cylinder that it is incorrectly filled may not have the proper pressure relief device.
- projectile rocket: if a cylinder falls and the valve breaks. Small should be placed in rack and large should be chained to wall.
- N2O theft: people use it for substance abuse.
- Thermal injury : frost bite from people who use it recreationally.
-Blocked flow meter: if integrated, O2 will not flow.
A pressure regulator in the central supply, normally pipes the gases in at ____ to _____ psi into the anesthesia machine.
50 to 55
The anesthesia machines pull the gas from the _______ pressure source.
Highest
- close O2 tank because pipeline pressure may fluctuate and machine will take the gas from the tank.
Oxygen is stored in the central supply as ________, below its ________, where the potential for ignition is decreased.
Liquid; Boiling point.
Boiling point of Oxygen (O2)
- 297.3 F (-182.9C)
N2O is stored as _______. The problem with N2O cylinders is that the regulator may become so cold it freezes. A warning sign where these are stored should be place because it could create a ____________.
LIQUID ; Hypoxic mixture.
Safety system used in the PIPELINE system to prevent improper connection of supply hoses. *DOES NOT PREVENT HYPOXIC GAS MIXTURE from being delivered to patient.
Diameter Index Safety System (DISS)
- Connection points are gas specific, NON-interchangeable.
- This system is always on the anesthesia machine for pipelines.
DISS connector consist of:
Body, nipple and nut combination.
The 2 most important things you need when changing out a cylinder tank:
A washer (Bodok seal) - prevent leaks
And the handle ( to open/ close tank).
Quick-coupler WALL connections for pipelines have:
Two- prominences on the hose
In the event of pipeline crossover, two actions must be taken:
- The back up oxygen must be turned on (since it’s always off).
- The pipeline supply sources must be disconnected. MANDATORY because the machine will preferentially use the 50 psi pipeline supply source instead of the lower-pressure 45 psi.
Do not let someone plug a ___________ in your anesthesia machine.
Bair Hugger
Basic Components of the Anesthesia Workstation:
- Gas inlets (back of machine)
- Pressure regulators
- Oxygen- pressure failure devices
- Flow-control valves and flowmeters
- Vaporizers
- Fresh gas outlet
- Spirometers
- Breathing circuit
- Pressure gauge
- Ventilator
- Scavenger
- Oxygen analyzer
Consist of those parts that receive gas at cylinder pressure (45 to 2000 psi), this includes cylinder gas down regulated by a first stage regulator.
High Pressure System
High pressure system consist of:
Hanger yoke
Hanger yoke check valve
Cylinder pressure regulator (first-stage)
Cylinder pressure gauge
Receives gases at relatively low and constant pressures of 30 - 55 psi (pipeline pressures)
Intermediate pressure system
Intermediate pressure system includes
- pipeline inlets and pressure gauges
- ventilator power outlet accessory
- O2 flush valve
- Supply failure alarm system
- Oxygen failure safety valve
- Second stage pressure regulator
- Flowmeter VALVES
All parts receiving gas from either a pipeline or cylinder air 15 - 30 psi. The second stage regulator drops pressures from intermediate to low pressures to low pressures, and allows for SAFE DELIVERY OF GASES TO PATIENTS.
Low pressure System (LPC)
Low pressure system includes:
- Flowmeter TUBES
- Vaporizers
- Temperature compensating bypass valve
- Common gas outlet
The LPC leak test checks the integrity of the anesthesia machine from the ______________ to the ______________.
Flow control valves to the common gas outlet.
The most delicate pneumatic component of the anesthesia machine:
Flow tubes
*they can crack or break
Leaks in the LPC can cause:
Hypoxia or subanesthetic mixture;
*leading to a hypoxia injury or patient awareness
The LPC is the most _________ area of the anesthesia workstation
Vulnerable
- most subject to breakages and leaks. Also most likely to go unrecognized if an LPC leak test is not done.
The leak test should be done :
Each day or when a vaporizer is changed.
If a machine has a one-way check valve (outlet check valve) should a positive or negative leak test be done?
Negative- pressure leak test should be done.
*a positive- pressure test will not detect leaks in the LPC of machines with an outlet check valve.
The LPC evaluates the portion of the machine downstream from all safety devices except the:
Oxygen analyzer
Usually made of steel, but made be made of aluminum
Body of cylinder
Attached to the neck of the cylinder, used for filling and discharging, may be made of bronze or brass, and regulates pressure down.
The cylinder valve
Point of exit for gas, usually covered until cracked.
The cylinder port
Within the valve, closes the valve by sealing against the seat, and when opened, it moves it upward and away from the seat.
The Stem of the cylinder
Cylinders are tested every 5 years unless exempted for :
10 years.
Cylinder Hanger Yoke
the attachment on the anesthesia machine where the cylinders are set into place.
The cylinder hanger yoke contains:
Body retaining screw
Nipple
PISS
Washer
Check valve (to prevent back flow into the cylinders).
High pressure cylinder gauges measure:
Measures pressures within a given cylinder
*Bourdon type gauge
The Bourdon Gauge consist of a closed coiled tube connected to the cylinder in which pressured is to be sensed. As the pressure increases the tube will ________, while a reduced pressure will allow tube to ____________. This motion is transferred through a link to a gear connected to an indicating needle.
UNCOIL when pressure up.
COIL more tightly when pressure down.
Controls the variable pressure inside a cylinder. Reduce the high pressure in a cylinder to ~ 45 psi.
High pressure regulator
When you connect the oxygen source (either tank or pipeline) to the anesthesia machine, 5 immediate functions occur or are activated:
- The power outlet accessory
- O2 flush valve is activated
- Pressure sensor shut-off valve (fail-safe valve)
- Supply failure alarm system
- Second stage pressure regulator
Provides pressure to the ventilator
Power outlet accessory
*usually powered by oxygen coming from pipeline.
O2 flush valve delivers oxygen at what pressure and L/min?
At ~50 psi and 35-75L/min
*NEVER USE THIS WHEN CIRCUIT CONNECTED TO A PATIENT
- Bypasses second-stage regulator
How those the pressure sensor shut-off valve work? (Fail-safe valve)
When O2 supplied at ~50 psi, this valve remains in the open position allowing N2O to flow to the Flowmeter
It remains open as long as PSI remains >25. If it falls below 25 psi, then N2O flow is shut-off.
**ONLY RESPONDS TO PRESSURE.
Activated when O2 falls below 28 psi.
Second stage pressure regulator
*Alarm sounds before 25 psi, the point at which N2O flow will cease.
Gas pressure is decreased by a ____________ to a CONSTANT pressure of 16 psi because the flow from the wall (pipeline) varies at times between 40 - 50 psi.
Second stage pressure regulator (12-19 psi in Barash).
*after passing 2nd stage pressure regulator, the gas sits in “stand by” at flow control valve.
Include all parts of the machine which receive gases at reduced pressure from cylinders (35-45 psi)
Intermediate pressure system
**Starts after the first stage regulator when cylinder gases used.
** includes pipeline gas inlets and pressure gauges (deliver gas at 50psi), oxygen failure safety valve and oxygen supply failure alarm, flow VALVES, and oxygen flush valve.
Oxygen failure cutoff valves do not prevent delivery of hypoxic mixture. (T or F)
True. Delivery of hypoxic gas may still occur.
All open or all closed system
O2 pressure-sensor shut off
Oxygen proportioning device creates a minimum FIO2 of ________. A N2O (26 psi) : O2 (14 psi) ratio of _______.
25%.
Ration of 3:1
- it ensures that nitrous oxide can only be delivered in the presence of O2 to the patient.
Turning N2O will make O2 follow. If O2 is decreased - N2O will follow.
* If N2O is turned off - O2 will not necessarily follow.
The anesthesia machine is always running O2 anywhere from _______ to _______, even when machine is completely off.
200 - 300 ml/min (Anesthesia machine book)
50 - 150 ml/min (on PowerPoint)
(Cross said: 0.1 - 0.25 L/min )
The oxygen knob is _______, versus “________,” larger than the other, and protrudes further out.
FLUTED ; gnarled.
*OXYGEN LOCATED ALWAYS furthest to the RIGHT.
Oxygen flush valve bypasses flow meters and vaporizers and goes directly into the CGO at _______ psi and _________ L/min.
35- 75 L/min
~ 45 to 55 psi.
O2 flush valve used for:
- used to rapidly refill or flush the breathing circuit
**NEVER while pt connected. - may cause barotrauma.
Variable-orifice flowmeters are _______ pressure and use an indicator ball (or bobbin) which displays the flow of gas through a ______ tube.
Constant-Pressure ; Thorpe tube
*tube is narrow at the bottom and low flow raises the marker. As the flows increase and the marker rises in the widened tube, greater flows pass around it and reach the CGO.
*may be single or double tube design.
