Anesthesia Machine Flashcards
Which breathing system has only 1 valve?
Nonrebreathing Systems
Bain system
No unidirectional valves and no CO2 absorber
What kind of system is a Bain?
Modified Mapleson D -In mapleson D, APL is close to bag and FGF is close to patient after tubing.
In Bain, APL is close to reservoir bag and FGF is before the tubing.
Fresh gas hose enters the single corrugated tubing and travels through inside lumen. Expiratory gases flow around the fresh gas hose inside the corrugated tubing
CO2 removal is dependent on the fresh gas flow, tidal volume, and pattern of breathing
Traditional circle system has 3 valves:
Inspiratory limb one-way valve
Expiratory limb one-way valve
Pop off valve/APL (adjustable pressure limiting valve)
Purpose of valves is to supply unidirectional flow
What safety relief device melts at 157-175 degress F?
Fusible (Melting) Plug - Style #2
Made of Wood’s Metal - BLTC (bismuth, lead, tin, cadmium,)
All or none phenomenon - plug melts and is gone
What is the flow of the O2 flush valve (oxygen flush button)
35-75 L flow
Direct connection from oxygen source (PISS/DISS)
What style valve is the Oxygen Flush Valve
Type III
Consists of a button and stem connected to pin and ball
What style valve open at extreme temperatures and is a spring loaded device that recloses and prevents gas escape once conditions return to normal?
III - Pressure Relief Valve
What type of gauge is used on the high-pressure side of the machine?
Bourdon gauge
copper piece inside that’s hollow and straightens as there is more pressure
PISS system protects machine from?
Interchangeability of cylinders on the cylinder yoke
Link 25 proportioning system - recognize picture of it and know what it is:
Prevents hypoxic mixture of O2/N2O.
Link 25 chain connects nitrous sprocket and oxygen sprocket.
Mechanically link N2O and O2 flows to prevent final inspired oxygen concentration less than 25%.
Consists of pneumatic and mechanical controls
Hypoxic guard system - know and recognize:
GE: Link 25 Proportioning
Drager: Oxygen Ratio Monitor/Controller and Sensitive Oxygen Ratio Controller
Oxygen Ratio Controller: shuts off n2o when o2 pressure is less than 10 psi
Sensitive Oxygen Ratio Controller: fail safe and proportioning system
Fail safe - when o2 flow is <200 ml, n2o shuts off
Proportioning - limits n2o concentration in the fresh gas so that o2 concentration does not fall below 21%
Can permit hypoxic mixtures when:
Pipeline crossover or wrong gas supply in cylinder
Pneumatic or mechanical components are defective
Leaks exist downstream of flow control valves
If theres a double hangar yoke, 1 tank is empty, the other has 2000 psi, what prevents flow from more full tank to the empty tank?
Floating check valve
Cylinders don’t get transfilled based on pressures
Allow change of cylinders
Minimize leaks to atmosphere if a yoke is empty
What type of valve is the 1st stage regulator?
Diaphragm style valve that serves both hangar yokes
Reduces pressure to 40-50 psig
Sevo and Iso utilize supplied heat?
False, Des does
Recognize traditional circle breathing system:
Utilizes valves to ensure unidirectional flow
Reservoir bag
Carbon dioxide absorption - allows rebreathing of exhaled gas
Giveaway for inspiratory side of the system:
Fresh gas hose
Recognize expiratory side of breathing system
Reservoir bag is an expiratory reserve bag, it holds an expiratory reserve volume
From patient through expiratory breathing tube
Through expiratory one way valve
APL valve
Absorbent canister
Flow meters
Thorpe tube design is the traditional design for flowmeter tubes
Variable orifice: Wider at top and narrow at bottom
Distance between the bobbin/float and side of the tube is the annular opening
The higher the ball in the tube (the higher the flow) the more turbulent the flow
What’s required for soda lime reaction:
Water + CO2
Results in: CaCO3, Na2CO3, H2O
Classic soda lime is made up of Ca(OH)2, H2O, NaOH, and KOH
Ascending bellows:
Are preferred
Will collapse to the bottom in the event of a disconnect, does not keep cycling
Attached to the BASE of the assembly
Compress downward during inspiration
Expand upward during expiration
Descending bellows
Attached at the top of the system
Compress upward during inspiration
Expland down during expiration
Will drop even if there is a disconnect because of the weight
Why does the CO2 absorber get warm?
The CO2 + H2O reaction is Exothermic - creates heat
Releases 13,700 kcal for every 22.2 liters (1 mole) of CO2 absorbed
Temperatures within the sodalime can reach 45-50 degrees C
Know allowed parts per million for gases and nitrous in OR, dentist office, etc.
Halogenated agent alone: 2 ppm (in an 8-hour time-weighted sample)
N2O alone: 25 ppm in 8 hours
Halogenated agent + N2O = 0.5 ppm (in 8 hours)
Dental facilities N2O alone = 50
What is the indicator dye that is added to the absorbent to signify absorbent exhaustion?
Ethyl Violet
Most complex portion of the scavenging system:
Interface - Provides positive pressure or negative pressure relief and may provide reservoir capacity
Everything else is just tubes and hoses
All Active scavenging interfaces have:
Suction
Active = Suction
All passive interfaces have:
no suction
True or False: All open systems have to be passive.
FALSE - they are all active
Open must have suction
True or False: All closed systems have to be active
FALSE - they can be active or passive
Active Scavenging =
Suction. Closed with bag is also active system.
What makes a steel cylinder vs an aluminum cylinder?
Aluminum has AL or ALMon them
Where do you read the flowmeter float/bobbin?
Ball: Dead center
Everything else is read at the top - non-rotating, plumb bob, skirted, H-type
O2 flow meters are located at the far RIGHT of anesthesia machine, why?
In case of a crack - will take path of least resistance
Closest to the common gas outlet/patient
What are the wall pressures coming out of DISS?
50 psi
What is the pressure after the 1 stage regulator?
45 psi
Which feature of the machine allows one of the safety features to work and knocks pressure down from 45 to 16 psi
Second stage regulator - In a GE machine
What protects the anesthesia machine from accepting the wrong pipeline gas?
Diameter Index Safety System (DISS)
Prevents interchangeability of hoses
GE pressure sensor shut off:
Shuts off gases (nitrous) in the presence of insufficient oxygen pressure
Makes sure that o2 is the last gas to go to the patients
If o2 is low (<20 psi), Nitrous and Air shut off
When O2 pressure is >20 psi, the valve gets pushed open and other gases can flow
Know 3 pin index safety systems
(There are 10 possible combinations of the 6, now 7, positions of pins and holes)
O2 - 2,5
Nitrous - 3,5
Air - 1,5
How do I make oxygen and nitrous oxide
O2 is manufactured via Fractional distillation of liquified air - MOST COMMON
N2O is commercially manufactured by the thermal decompensation of ammonium nitrate
Who regulates purity?
Pharmacopia of the United States (USP) specifies
Enforced by the FDA (us food and drug administration)
Calculate how much time you have left in a tank
Full tank of O2 has 660 liters and 2000 psi
It is all pressurized gas
Tank displays 1000 psi, you’re running at 6L/min, how many minutes of o2 remain?
1000 psi = 330 L»_space; 330/6 = 55 minutes left in tank
How much liquid anestetic does a vaporizer use per hour?
Formula:
3 x fresh gas flow L/min x vol% = mL liquid used per hour
2L O2 + 2L N2O + Sevo control dial = 2%
3(constant) x 4(total liter flow per min) x 2(sevo concentration) = 24 ml
Which gas is liquid form in the tank?
Nitrous oxide
Carbon dioxide
How do I know how much gas is left in a tank?
Tank gauge
How do I check how much nitrous is left in the tank?
Weigh it
1600 L = 745 psig - pressure remains constant if the temp remains constant until all the liquid has evaporated
Full tank weighs 8.8 kg
How is N2O commercially manufactured?
Thermal decomposition of ammonium nitrate
What size are the soda lime granules?
4-8 mesh
What’s in the high pressure side of anesthesia machine? - know the picture and whats on each side
Consists of those parts which receive gas at cylinder pressure
Hangar yoke
Yoke block
Retaining screw
Pin Index Safety System
Check valve assembly
Cylinder pressure gauge - Reflects cylinder pressure aka psi in tank
Cylinder pressure regulator
First stage regulator
What’s in the low pressure side of the machine? - what is found on each side?
Flowmeter tubes
Vaporizers
Check valves
Common gas outlet
Distal to flowmeter needle valves to common gas outlet
Where do most leaks occur?
Low pressure side of the machine
In the event machine is running with 5L o2 all weekend
change co absorber - because of desiccation
Desiccation means the granules are dried out
Pick out ascending vs descending bellow:
Ascending is attached to bottom and expands upward during exhalation
Descending is attached at the top and expands downward during exhalation
What is the hospital pipeline made out of?
Wrought copper - seamless or standard weight copper
How often do you check/test cylinders?
Every 5 years
Every 10 years with special permission
1 stage regulator utilizes:
Diaphragm (NOT floating check valve)
What happens if the inside of the tubing is retracted?
Anything from site of disconnection or site of break down (there to patient) is going to be dead space
3 features of desflurane vaporizer
2 separate systems (liquid and vapor side)
electrically heated
Pressurized
central processing unit in it (computer chip)
dual circuit design
Diaphragm
Ga/vapor blender - head produces vapor which is injected into fresh gas flow
What is des liquid heated to?
39 degrees
If you turn retaining screw on side of hangar yoke and you hear hissing, what is the likely cause?
Smashed gasket washer. They are only meant for 1 time use. An old crushed washer can cause friction from a small leak and increase risk for fire
Colors in US for 3 gases and what do they change it to internationally
USA:
O2 = Green
N2O = Light Blue
Air = Yellow
ISO (WHO)
O2 = White
N2O = Light Blue
Air = Black and White
Passive scavenging systems are:
No suction
What size are tanks on the side of machine?
E cylinder (M24) - usually steel unless for MRI
Vaporizer Style #1:
Nondesflurane
Variable bypass - a stream of gas passes over the surface of a volatile liquid and sweeps away vapor. Vaporizer determines carrier gas split.
Flow over wick
Temperature compensated - automatic
Splitting ratio:
1st intersection of carrier gas
Flow Over Wick Design:
Increases surface area
Allows more molecules to be up higher in the vaporizing chamber
Spreads out molecules more evenly in the chamber
Bimetallic strip
Adjusts to temperature
Application of heat causes the equilibrium to shift so that more molecules enter the vapor phase. Lowering the temperature causes a shift toward liquid phase and a decrease in vapor pressure
Strip allows more or less gas flow in depending on the temperature
Dictates how much gas goes down inside the vaporizing chamber
When colder, strip moves to the ?
When hotter, strip moves to the ?
What would happen with a higher mesh size granule?
The higher the mesh number = the smaller the absorbent particle
Higher mesh size will have less air space between particles and result in greater resistance
What holds the cylinder to work station?
Hangar yoke
Who is responsible for marking, labeling, filling, qualification, transport, maintenance, and disposition of cylinders containing compressed gas? Who is responsible for investigating when cylinders fall off a truck?
Dept of Transportation (DOT or motor safety division of DOT)
Walk through CO2 reaction - what goes in and comes out?
The end products are Sodium Carbonate, Calcium Carbonate, and water
CO2 + H2O = H2CO3
H2CO3 is a weak acid and dissociates into its ion
Sodium hydroxide (NaOH) and calcium hydroxide (Ca(OH)2) are dissociated into their ions
Sodium and calcium ions combine with carbonate ions, forming end products sodium carbonate and calcium carbonate and water
CaCO3, Na2CO3, H2O
Check valve on high pressure side is
Floating check valve
Intermediate Pressure Side
Pipeline inlets
Check valves
Pressure gauges
Ventilator power inlet
Oxygen pressure failure device
Oxygen second stage regulator if present
Flush valve
What type of flowmeter is the most accurate
Electronic, 5-10 times more accurate than glass
True or False: All anesthesia machines have a common gas outlet
False
Sodalime moisture content
Between 10% and 22%
