E2 Flashcards
1
Q
How are compressed gases measured?
A
Psi = pounds per square inch
Psig = pounds per square inch gauge
2
Q
What is the relationship of non-liquefied vs liquefied compressed gases.
A
Relationship btwn pressure and remaining volume and pressure reading on the gauge
3
Q
What are non-liquefied compressed gases and their properties?
A
Gases that don’t liquefy @ room temp regardless of pressure applied
O2
Nitrogen
MEDICAL Air
Helium
b/c boiling point is well below ambient temp
Properties:
Will become liquids at very low temp
volume and Pressure
Non-liquefied gas = pressure ↓ as volume ↓
4
Q
Describe the relationship between pressure and volume of non-liquefied compressed gases.
What law is this?
A
THERE IS A LINEAR RELATIONSHIP btwn PRESSURE & VOLUME FOR THESE GASES
SO P1/V1=P2/V2
Boyles LAW
5
Q
What is liquefied compressed gas, examples and it’s properties?
A
Gas that becomes liquid @ ambient temp and at pressures from 25-1500 psi Liquid at Room temp & Patm N2O CO2 (insufflation)
6
Q
How do non-liquefied gases differ from liquefied gases?
A
Liquefied gases do not follow boyles law
They are liquid at ambient room temp and Patm
7
Q
How is pressure maintained in liquefied compressed gas?
A
WHEN ONE GAS MOLECULE LEAVES TO BE USED then ANOTHER MOLECULE FROM THE LIQUID TAKES ITS PLACE
WILL MAINTAIN PRESSURE UNTIL BASICALLY EMPTY
HAS TO BE OVER 95% EMPTY BEFORE PRESSURE CHANGE ON GAUGE
Liquid pressures = gas pressure
8
Q
When will a pressure change be noted on liquefied compressed gas gauge?
A
HAS TO BE OVER 95% EMPTY BEFORE PRESSURE CHANGE ON GAUGE
9
Q
How is the volume of liquid compressed gas measured?
A
Weight
10
Q
Government regulations of cylinders. FDA, OSHA, DoT
A
FDA = gas purity
Dept of Labor/OSHA = employee safety
DoT = marking, labeling, storing, maintenance, transportation, and disposition
11
Q
What are specific DoT gas regulations? (8)
A
• -Inspected & tested ONCE every 10 years
• -Test date stamped on cylinder
• -Must pass visual inspection & pressure testing
• -Color coded in the US (green)
• but should not be the primary means to identify a gas
• -Diamond shaped label
• identifying fire danger
oxidizer, non-flammable, or flammable
• -Signal word identifying hazard level = CAUTION, WARNING, DANGER
• -Name & address manufacturer & Date of expiration
• -Tag for Full, In USE, Empty to notate gas level
12
Q
Describe the components of medical gas cylinder? (5)
A
Body Steel or steel carbon fiber = 3AA Aluminum = 3AL or 3ALM need in MRI Flat or concave base Neck with screw threads
Valve
Bronze or brass screws into neck
Allows refilling and discharge of gas at stem
Port
Point of exit for gas
Take care not to screw retaining screw into port= damage
Conical depression
Fits the retaining screw on the yoke
Handle Opens/closes cylinder Turns counterclockwise** to open Also called cylinder** wrench Must have one for every machine to be readily use
13
Q
Describe the purpose of the pressure relief device on the cylinder
A
Vents cylinder to atm if pressure within cylinder becomes too high
• PREVENTS EXPLOSION FROM EXCESSIVE PRESSURE
14
Q
What are pressure relief device types
A
Rupture or FRANGIBLE disk
Fusible plug
SAFETY relief
15
Q
Describe the rupture/frangible disk pressure relief device on the cylinder
A
- good for venting in high temp or overfilling
- BUT BREAKS AT HIGHER PRESSURES ALLOWING GAS TO ESCAPE
- non reclosing
16
Q
Describe the fusible plug pressure relief device
A
- WILL MELT w/ HIGH TEMPS AND ALLOW THE ESCAPE OF GAS
* non reclosing
17
Q
Describe the safety relief valve in a cylinder
A
• most common
• SPRING-LOADED MECHANISM TO ALLOW VENTING OF GAS
• IF PRESSURE ↑ IT ALLOWS GAS VENTING
THEN recloses/SEALS after pressure normalized inside cylinder
18
Q
What is the most common type of pressure relief device on a cylinder?
A
- SAFETY relief valve
- most common
- SPRING-LOADED MECHANISM TO ALLOW VENTING OF GAS (normalize to Patm)
- IF PRESSURE ↑ IT ALLOWS GAS VENTING
19
Q
What are the gas cylinder sizes
A
A = smallest
E = most common on gas machines and for pt transport
Volume and pressure will vary in any given cylinder
20
Q
Pressure, volume and color of O2, air and N2O full tanks
A
Full O2 cylinder (GREEN) = 660 L at 1900 psi (some books 625 L @1900 psi)
Full Air cylinder (YELLOW) = 625 L at 1900 psi
Full Nitrous oxide (BLUE) = 1590 L at 745 psi
21
Q
Cylinder safety considerations (8)
A
Valves, regulators, gauges do not come into contact with oil, grease, or lubricants
Temperature regulation
< 130F (54C) & > 20F (-7C))
Keep connections Tight
No adapters should be used to change the size of connections for use of w/ hoses, regulators, or gauges
No alteration of markings and labels
No dropping, dragging, sliding of cylinders
Valve kept closed at all times
Cylinders should always be Properly secured to prevent fall
22
Q
Cylinder storage consideration (8)
A
Storage in Designated secure areas (NOT the OR)
Adequate ventilation
Signage= no smoking, no combustibles in area of cylinders
Not exposed to corrosive chemicals/fumes
N2O secured/locked up to prevent access and abuse
Stored upright in bins or chained to wall
Wrapping and drapes undesirable
Recent jcaho guidelines
• require that empty or partially empty tagged cylinders
• stored separately from partially full and full cylinders w/ proper gauges
23
Q
Considerations for the use of cylinders prior to using it(5)
A
Visible inspection for defects of PISS system, label, regulator
Presence of tamper proof seal around valve (NEW)
must remove prior to attaching to anesthesia machine
Presence of a sealing washer
if absent, you could potentially have a leak
24
Q
Considerations for opening of cylinder (5)
A
Open valve slowly and slightly prior to installation to clean out the valve port Check pressure Open away from patient Face valve away from people Correct leaks
25
Describe the Pin index safety system (PISS)
Two holes on cylinder valve
positioned in an arc = receive pins on the yoke/ pressure regulator
THERE ARE 7 DIFFERENT POSSIBLE PIN POSITIONS
DEPENDING ON THE TYPE OF GAS IN THE CYLINDER
If cylinder valve has no holes = impossible to attach to yoke/regulator with pins
SPECIFIC CONFIGURATIONS BE AWARE OF THIS SAFETY MECHANISM
26
Pipeline supply source guidelines
Must have 2 days supply “banks”
1 primary
1 reserve
each with 2 days supply so 4 days total for both
27
Purpose of pipeline system and gases supplied versus cylinder?
```
Because E- cylinder use is not enough
Used to deliver gases to anesthetizing locations & patient care areas
• O2
• N2O
• MEDICAL Air
```
28
What is included in a pipeline supply system?
central supply system
piping to transport gases to the specific locations
branches and terminal units
29
What is the US pipeline pressure?
| What is the most frequent pipeline problem?
pipeline pressures are 380 kPa or approx. 55 psi
| Low pressure is the most frequently reported problem in pipeline systems
30
Purpose and guidelines of reserve gas supply?
Reserve supply
should be used for emergencies or failure of primary supply.
Ideally in different area with different routing
31
Guidelines for liquid O2 use
Liquid O2 must be in constant use to be cost effective
| Otherwise pressure ↑ as the liquid boils and is then vented in the Patm
32
N2O supply and storage guidelines and regulations
generally supplied by manifold cylinder system
• b/c regulator prone to freezing
Warning signs need to be posted in N2O are warning of asphyxia due to leak
33
Medical air supply storage requirements
use manifolds or compressors
• important for intake locations are free of contaminants
Air systems need to dehumidify to qualify for medical use
34
N2O and medical air storage guidelines
Both systems have a series of valves, pressure regulators, & alarms
to regulate pressure and signify problems
35
What are the components and composition of a pipeline system structure
Main line
• connect gas source to risers
Risers
• vertical pipes connecting mainline w/ branch lines on each level of facility
Branch
• sections supplying a room or group of rooms on one level of the facility
Composition of piping is Copper
36
What are labeling regulations for pipeline systems
Regulation:
Name, pressure, and flow direction
• must be clearly marked every 20 ft and in each room
37
What is the difference in O2 pipeline diameter vs other gases and why?
O2 (1/2 in OD) has different outer diameter than other gases (3/8 in OD) safety mechanism
38
Purpose of pipeline system shut off valve
Allow for certain areas in the piping system to be isolated
for maintenance or problems
ON-OFF, isolation of section or zone
39
2 types of pipeline system shut off valves and their differences.
Where are they located?
“Manual Shut Offs” = visible & accessible at all times
Mandatory locations:
• Main supply into building= turns everything OFF to building
• One at each riser
• One at each branch
• except if branch is to an anesthetizing area or critical care area-Why?
“Service Shut Offs” = locked box- NOT ACCESSIBLE TO US
40
What are 2 types of pipeline alarms and their differences?
Master Alarm System
Must be located in 2 different areas
• 1 panel must be in department responsible for maintaining system
Monitors entire pipeline system
Area Alarm System- check daily, test monthly
In critical care areas- ICUs and ORs
Alarms if the pressure ↑/↓ at 20% from normal line pressure***
May trigger master alarm
41
What are pipeline alarm requirements
Must be audible and visible
Must be labeled for gas and area
Will alarm with a 20% increase or decrease
42
What are terminal units of a pipeline system
Point where piped gas is accessed
by user through hose connections (flow-meter)
i.e. wall connector-hose-station outlet
43
Describe pipeline terminal unit connections
Connection into wall uses quick connectors
Pair of male and female parts
• only connect w/ proper alignment.
Each gas has a specific shape and spacing more prone to leaks vs diss system
44
What is the station outlet of the pipeline terminal unit?
Connection into machine
| uses DISS (diameter index safety system) system
45
Vaporizer definition and additional requirement
Vaporizer = device that changes a liquid anesthetic into a vapor for inhalation
Changes liquid to gas
Must add a controlled amount of vapor to FGF in a breathing system
46
How is the vaporizer calibrated?
Calibrated at sea level
| Affected by barometric pressure changes
47
What are the stages of anesthesia?***
STAGES OF ANESTHESIA
1) ANALGESIA
2) DELIRIUM
3) SURGICAL
4) RESP CESSATION
48
How is the vaporizer affected by pressure and what should the anesthetist do prior to using it?
BMP changes volatile given
READ THE MANUAL FOR THE VAPORIZER AND MACHINE
• PRESSURE MUST BE TAKEN INTO ACCOUNT
49
When considering vapor administration and pressure changes what are the 3 most important considerations for the anesthetists?
GIVE THE PT WHAT THEY NEED
LOOK AT WHOLE PICTURE
MAKE THE CLINICAL DECISION
50
What is the vapor pressure of a liquid
the equilibrium pressure OF the vapor ABOVE ITS LIQUID
51
What is pressure of vapor
RESULTS FROM EVAPORATION OF THE LIQUID
| ABOVE THE LIQUID IN A CLOSED system at a CONSTANT temp**
52
How does temperature relate to VP
increase temp = increase VP
53
How is VP affected by barometric pressure
It is not
| VP is dependent on the liquid and temperature
54
What is VP dependent on?
The liquid and the temperature
55
What is saturated vapor pressure
WHEN THE GAS CONTAINS ALL THE VAPOR IT CAN HOLD AT A GIVEN TEMP
56
What is saturated vapor concentration and important consideration during administration
SVP/atm pressure
THE SVC MUST BE DILUTED BY A BYPASS GAS FLOW
57
What is important to note about each gases VP?
Cannot compare gases by VP
58
What is the best way to compare gas agents
Gas concentration in partial pressure or vol % (MAC)
59
Describe volume percent expression of gas concentration
Concentration of a gas in a mixture
• expressed as percentage of 100% @ 1 ATM
• PP/TP X 100% = volumes %
• MAC is described in terms of volume percent
60
What affects volumes percent and how is it related to anesthetic uptake?
Indirectly relates to patient uptake & anesthetic depth
| • IS INFLUENCED BY BAROMETRIC PRESSURE
61
Describe the partial pressure expression of gas concentration and what is it dependent on?
Pressure exerted by any one gas in a gas mixture on the total gas mixture
• Total pressure of the mixture is a sum of all the PP
* Dependent on temperature
* Not the pressures exerted by total pressure of the gas mixture
62
What affects partial pressure of a gas and how is PP related to anesthetic uptake?
Affected by: temperature
• Not affected by barometric pressure
• SAME POTENCY NO MATTER WHAT THE BAROMETRIC PRESSURE IS
•Directly relates patient uptake and anesthetic depth
63
What is heat of vaporization
The number of calories necessary to convert 1G (or 1ml) of liquid into vapor**
64
How does gas flow affect the heat of vaporization?
As carrier gas flows through the vaporizers
Vapor molecules leave and more liquid is vaporized
As more molecules enter the gas phase, the liquid begins to cool.
65
How does heat flow as gas flows pick up vapor? When is equilibrium established?
The liquid begins to cool
Heat will flow from the surrounding VAPORIZER
To compensate for the loss of heat in the liquid
Heat lost to vaporization = heat supplied by surrounding VAPORIZER
66
What happens to the liquid in the gas state in the vaporizer when the temp drops? Why is this significant?
IT DECREASES:
• IF MY VAPORIZER IS SET AT 1, BUT ITS COOLING
• THERE IS LESS GAS LEAVING THE VAPORIZER
EVEN THOUGH NOTHING HAS CHANGED
67
What happens to the temp as gas leaves the vapor
It cools the whole vaporizer
68
How do manufacturers account for heat of vaporization effects?
MANUFACTURERS MUST ACCOUNT FOR THIS PHENOMENA
INCORPORATE A SYSTEM TO REPLACE AND EQUALIZE LOST HEAT
FOR ACCURATE GAS ADMINISTRATION
• THEY CHOSE CERTAIN METALS TO ACCOMMODATE HOV
• SO WE GET A CONSISTENT ANESTHETIC
69
Specific heat definition
the quantity of heat required to raise the temp of 1gram of a substance 1degree C
70
What is the standard measure of specific heat
H2O is the standard
| • 1cal/gram/1 degree C
71
Specific heat considerations for vaporizers
SH must be considered for maintaining a constant temperature to the vaporizer
Higher SH = temp changes more gradually
72
Thermal conductivity definition
the speed at which heat flows through a substance
73
Thermal conductivity considerations with vaporizers
Higher TC = better conductor of heat
74
Specific heat and thermal conductivity considerations with vaporizers
must be considered in choosing a material/METALS for vaporizer construction
↑ SH=THE HARDER IT IS FOR THE TEMP TO CHANGE-
Higher SH/TC is desirable b/c changes in the the vaporizers are less likely when the gas leaves the vaporizer
75
Vapor concentration calibration and location
Calibrated by agent concentration
Single knob calibrated in volumes percent
Located between flow meter and common gas outlet (PT) - so it isn't flushed with O2
76
Where is the vapor concentration calibration and Why is the location of vapor calibration site important.
Located between flow meter and common gas outlet (CGO)
| So gas isn’t flushed w/ O2
77
How does the vaporizer maintain steady state?
* THE TOTAL VOLUME OF GAS LEAVING THE VAPORIZER IS >> THE TOTAL VOLUME THAT ENTERED
* D/T ADDITIONAL VOLUME ATTRIBUTED TO ANESTHETIC VAPOR AT ITS SVC
78
2 Types of vaporizers**
bypass
| electronic
79
How does vapor pressure and partial pressure of a gas at room temp relate to anesthetic depth?
Why is this important?
Vapor pressure of an anesthetic gas at room temp is GREATER than the partial pressure necessary to achieve anesthesia
so the vaporizer dilutes to a useful concentration
↓ potency of gas w/ mix of vapor and gas flow
80
What is a variable bypass vaporizer?
Vaporizer splits flow
some gas flows into vaporizing chamber
some gas flows into bypass
THIS IS KNOWN AS THE SPLITTING RATIO
Gas that passes through the vaporizing chamber will have volatile agent attached
Both flows are then rejoined before exiting vaporizer
81
Process of the variable bypass vaporizer
Gas flow is split
Portion of gas picks up volatile in vaporizing chamber
Portion of gas bypasses vaporizer chamber
Both flows are rejoined before exiting vaporizer
82
What is splitting ratio dependent upon? (4)
the ANESTHETIC AGENT/CONCENTRATION
size of the adjustable orifice
total gas flow
heat of vaporization
83
How do temperature compensating mechanisms affect variable bypass vaporizers?
THEY DO NOT PRODUCE INSTANTANEOUS RESULTS
| T/F ANTICIPATED CONCENTRATION MAY NOT BE ACCURATE UNTIL COMPENSATION OCCURS
84
What is a bypass vaporizer
NO VOLATILE ATTACHED TO FLOW THROUGH BYPASS CHAMBER VS VAPORIZING CHAMBER
85
How is splitting ratio determined for bypass vaporizer
Splitting ratio = vaporizing/bypass
Higher ratio means
MORE GOES INTO VAPORIZING CHAMBER
t/f MORE GOES TO THE PATIENT
86
What happens to the splitting ratio if the vaporizer is cooled?
How is the problem fixed?
• IT GETS SMALLERSO LESS GOES OUT TO PATIENT
Increase MAC or FGF to increase depth
87
How does an electronic vaporizer work?
```
Computer driven
Calculates either:
volume of CARRIER gas
• to produce the desired concentration
OR
amount of liquid agent needed to be injected into carrier flow
To EQUAL desired concentration
```
88
2 methods of vaporization delivery
Injection
| Flow-over
89
What are the differences between injection and flow-over vapor delivery
Injection
Inject known volume liquid anesthetic into known volume of gas
Flow-over
Carrier gas passes over surface area of a liquid
↑ surface area= ↑ efficiency of vaporization
Most common
90
How is temperature accounted for when delivering volatile gas
Thermocompensation
must maintain constant ANESTHETIC output
Can be mechanical or computer driven
Splitting ratio changes as temp changes
91
How is the splitting ratio affected by temperature
Splitting ratio changes as temp changes
• ↓ TEMP AND ↓ OUTPUT OF GAS/VAPOR
• SPLITTING RATIO WILL ↓ W/O THERMOCOMPENSATION
92
What will happen to splitting ratio w/o thermocompensation
Splitting ratio will decrease
93
Purpose of regulating intermittent back pressure on vaporizers
To limit the change in vaporizer concentration from IBP
| To keep a steady state of volatile delivery
94
Causes of intermittent back pressure
O2+ flush
Positive pressure from inspiration during vent use
95
What can IBP cause during vaporizer use?
| Most common reason?
Can Cause pumping effect or pressurizing effect on vaporizer outputs
Most common: d/t vent and flush valve use
96
Problem of having intermittent back pressure occur
Can cause small changes in the amount of gas delivered
| IBP CAN AFFECT WHAT THE PATIENT IS GETTING
97
How does intermittent back pressure affect delivery of gases
By leading to the pumping or pressurizing effect
98
What is the pumping effect due to and how does it affect volatile delivery?
D/t back pressure during inhalation @ LOW FGF
• Causes INC flow into the vaporizing chamber
• MORE than usual vapor picked up
Effect
= ↑ of vapor output
• COMMON WITH OLDER VAPORIZERS
99
What can lead to pumping effect and how can it be minimized?
More common
• @ LOW FGF
• large pressure fluctuations
• low vaporizer settings
Minimize effect
• Presence of the pressurizing valve
• unidirectional valve
• pressure relief valve
100
How do pressurizing and pumping effect alter gas delivery
pressurizing = not enough vapor output
pumping= too much vapor output
101
What is the pressurizing effect due to and how does it affect volatile delivery?
D/t back pressure at HIGH FGF
• causes INC density into the vaporizing chamber
• LESS than usual vapor picked up
Effect
=↓ of vapor output
102
What can lead to pressurizing effect and how can it be minimized?
```
More common
• at high gas flows
• O2 flush valve use
• large pressure fluctuations
• low vaporizer settings
```
Minimize effects
NEWER, CONTEMPORARY VAPORIZERS
USE VALVES AND OTHER MECHANISMS TO MINIMIZE THESE ISSUES
103
How does FGF affect vaporizer?
It directly affects vaporizer output
104
Definition and effects of high FGF
Flow > pt minute ventilation
Little gas rebreathed
Inspired concentration = vaporizer setting
HIGH FGF >> THAN PATIENT’S MIN VOLUME
• Brand new breath w/ brand new volatile
• NO RECYCLING
• Pt is getting closer to exact gas concentration
• Pt gets what is on the dial
105
Definition and effects of low FGF
```
Flow < pt minute ventilation
Significant rebreathing
Difference btwn vaporizer setting & inspired concentration
• Difference is in bellows or bag
Takes longer to achieve equilibration
```
106
How can equilibration be reached faster with low FGF
increase volatile concentration
Increase flow
107
Difference in high and low FGF monitoring, effects and use?
```
Low FGF
Flow << min ventilation
There's a difference between setting and inspired concentration
Need agent analyzer to get true value
significant rebreathing
Used during maintenance
```
```
High FGF
Flow >> min ventilation
inspired concentration = vaporizer setting
NO rebreathing
useful during induction
```
108
Where is the difference between min volume and flow w/ low FGF use?
In the vent bellows or reservoir bag
109
What is the problem with rebreathing during low FGF use?
Recycling present = patient not necessarily getting dialed concentration
Takes longer to reach equilibrium
110
What are standard regulations for vaporizers? (6)
Average concentration +/- 20% setting
Gas may not pass through more than 1 vaporizer
- SAFETY=to prevent mixing of gases
Output of vaporizer <0.05% in OFF
All control knobs counterclockwise
Filling levels displayed
Cannot overfill when in normal operating position
111
Types of vaporizer mounting systems.
| Which is most common
Permanent
| Detachable = most common
112
Describe the permanent vaporizer mounting system including advantages and disadvantages
```
Tool required
Always filled in upright position
Advantage
• fewer leaks/damage
Disadvantage
• limited mounting locations
• not easily exchanged
```
113
Describe the detachable vaporizer mounting system including advantages and disadvantages
```
Most common
Weight of vaporizer & “O” ring create seal
• O ring damage = can lead to leak
Locking lever on back
Control must be OFF before mounting
Easily removed/replaced
• think MH= machine has to be flushed
Disadvantages:
• Site for leak from
• damaged O ring
• unlocked lever
• Manufacturer compatibility
```
114
Purpose of interlock device on vaporizer
– prevents more than 1 vaporizer being turned ON at a time
Allows only ONE gas to be administered at a one time
Prevents mixture of gases
115
4 vaporizer hazards
Incorrect agent
Tipping
Overfilling
No Vapor output-
116
How is the vaporizer hazard of incorrect agent prevented and how is it fixed if it occurs.
Filling systems agent specific=not likely
• Must have correct/compatible key to fill system
If contaminated filling occurs:
• Must be completely drained
• all liquid discarded
• FGF run until no vapor detected
117
What happens to potency when the incorrect agent is put in the vaporizer?
* Won’t achieve 1 MAC
* Won’t deliver what the pt needs
* dec potency
118
How does the vaporizer hazard of tipping occur, prevented, the effects and how is it fixed if it occurs.
Liquid may get into bypass or outlet
INC concentration of agent
• Bypass carrier flow will pick & deliver more agent
Prevented:
Should be placed in OFF/ travel mode when moved
Newer vaporizers prevent
If tipped:
• High FGF run with low concentration of vapor
• until excessive vapor exhausted
• Until agent analyzer reads concentration that is set on dial
119
How does the vaporizer hazard of overfilling occur, the hazard and what can this lead to
Liquid may enter FG line or cause vaporizer failure
Potential for lethal dose
Can occur during tipping or filling on “ON”
```
Leads to:
• failure to tighten filler cap
• fill valve not closed
• malfunctioning mount/vaporizer
• pollutes OR can probably smell
```
120
Causes of no vapor output
Most common cause = empty
Incorrect mounting
Overfilled = no output because of vaporizer failure
121
What is the anesthesia gas delivery system composed of? (5)
```
anesthesia machine
vaporizers
ventilator
breathing circuit,
scavenging system
```
122
Who sets the standards for anesthesia workstations? When were standards published
American Society for Testing and Materials (ATSM)
starting in 2000
reviewed in 2005
123
What does the term "workstation" include and the basic operations.
include the ventilator & associated monitoring devices used
operations
components have become more technologically advanced (i.e. virtual flowmeters)
124
What should workstations be able to do? (5)
```
Provide:
• accurate & safe gas delivery
• a means for ventilating patients
• electrical outlets
• a housing for monitoring devices like vaporizers
• storage/shelving for other equipment
```
125
How does gas travel through the entire workstation?
Gas source delivers gas to machine
gas delivered to flowmeters & vaporizers
gas mixture goes to common gas outlet (CGO)
then flows to breathing circuit to the pt
gas then leaves the pt through breathing circuit
excess gas exits either via APL valve (spontaneous resp) scavenger or ventilator
(Mech resp)
126
Disadvantages to older workstations
may lack the safety features of newer machines
may be considered obsolete
there are ASA guidelines to consult to determine if this is the case
127
What are workstation system components (19)
- Master switch
- Hanger yoke assembly
- Cylinder pressure indicator/gauges
- Cylinder pressure regulators
- Pipeline inlet connections
- Pipeline pressure indicators/gauges
- Gas pathways
- Machine piping
- Common gas outlet***
- Unidirectional valves
- Pressure relief valve
- Flow adjustment controls
- Flowmeters
- O2 flush valve
- O2 failure protection device
- Hypoxia prevention devices
- O2/N2O linkage
- Auxiliary O2 flowmeter
- Power backup/battery
128
Components of the workstation (16)
```
Master switch (ON/OFF)
Hospital backup/electrical outlets
Hanger yoke assembly
Cylinder pressure gauges/regulators
Pipeline pressure gauges
Gas pathways
Pressure relief valves
Flow controls/flowmeters
Vaporizers
Unidirectional valves (outflow check valve)
Common gas outlet (CGO)
Oxygen flush valve
Oxygen failure protection device (OFPD)
Minimum oxygen flow and ratio
Axilllary oxygen flowmeter
Power failure/battery backup
```
129
What does the workstation master switch activate?
* Pneumatic fxn
* Electrical fxn
* alarms
* safety features
130
When workstation master switch is off, what still function
Electrical components active
• Battery charger
• Electrical outlets
for additional monitors
Pneumatic functions
• Maintained when off
O2 flush valve
auxiliary O2 flowmeter
131
What functions are available when workstation master switch is turned on.
the electronics go through a power ing up protocol
Usually an automated prompt for machine checkout
• The checkout can be overridden in an EMERGENCY***
The pneumatic functions
Permit the delivery of gas
To flow from the flowmeters & vaporizers
132
Requirements for workstation machine and hospital electrical outlets
MACHINE
All contemporary machines
incorporate electrical systems
require a connection to electrical power
Electrical outlets on the machine
intended to power ANESTHESIA monitors only
It is for our use, not the entire ORs
If requirements exceed outlet Circuit breaker will activate
HOSPITAL
***RED OUTLETS*** = Back up generator
Other appliances should be plugged into hospital main!
133
When should a machine checkout occur
1. Before first care of the day
2. If any changes are made to the system
3. Abbreviated check btwn cases (pressures etc)
134
If a machine check is conducted primarily internally by a newer machine, what should still be checked by anesthetist
* O2 sensor calibration
| * high pressure checks
135
How is an abbreviated check of the system performed and why
includes high pressure check
| • To check for pressure problems in the low pressure system
136
How do newer systems perform machine checks
Will display machine checkout results
• On screen upon completion
• May indicate potential problems
• Problem location for correction
137
what is one of the most important steps in a machine checkout that is overlooked
Backup equipment and electrical supply
- O2 cylinder supply
- Ambu bag
138
What are some workstation machine functions
to receive compressed gases from their source
create a gas mixture & flow rate at the CGO to deliver to the pt
Controlling the flow of gases
To prevent admin of a hypoxic gas mixture
139
What is the relation between pressure and flow?
| Which law?
Flow = change in pressure/ resistance
Ohm's law
140
What are the principles of the flow of gases
from high pressure sources (E-Cylinder or Pipeline pressure)
• through the machine
• through the CGO
• at near Patm
141
What is the hanger yoke assembly and it's purpose
```
Orients and supports cylinder
provides a gas-tight seal
Required to have a least
1 yoke for O2
1 yoke for N2O
```
Purpose:
Has check valve assembly to prevent gas from exiting machine when there is no cylinder in yoke
Prevents gas from being transferred from a cylinder w/ higher pressure to one with lower pressure
• if both are in a yoke & ON
• thus prevents the unnecessary depletion of gas
142
Purpose of the cylinder pressure gauge and how it works
Measures pressure of a gas above ambient Patm
Must be present for each gas supplied by cylinders
```
How it works:
Bourdon tubes
curved hollow tubes
inc pressure = straightens curve
Falling pressure = causes curve to redevelop
Motion is transmitted to gauge
```
143
What unit does the cylinder pressure gauge measure in and where is it located?
Units
kilopascals (kPa)
psi
Location
on the front of the anesthesia machine for reading
144
Purpose of the cylinder pressure regulator
device that converts a high, variable input gas pressure into a constant, lower output pressure
Reduces high, variable pressure in cylinders
• to lower constant pressure for machine
• also called reducing valves
Regulator required for EACH gas supplied by cylinder
145
What would occur without the reducing valve (aka pressure regulator)
the anesthetic provider would have to constantly adjust flowmeter to provide constant flow!!!
146
What is the function of the pipeline inlet connection?
| Requirements and connections
Entry point for gases from pipelines to the back of the machine
Connector:
DISS-back of machine
Requirements:
Require O2 & N2O (most have medical air)
Must contain unidirectional check valve to prevent
• gas returning
• flowing back into the pipeline
147
Pipeline pressure gauge requirements and functionality
Requirements:
Indicator required for EACH gas monitored
Indicator must be on pipeline side
Functionality:
Usually found on front of anesthesia machine
Digital or newer machines have LED display
148
Why is the pipeline pressure gauge location important
If gauge is downstream & cylinder valve open
• Getting pressure reading from cylinder
• Not an accurate reading/reflection of pipeline pressure
• Falsely elevated or normal pressure
• adequate pressure reading until cylinder is 0
149
What drives gas flow?
| What is the direction of flow through the system?
Change in pressure from higher to lower
- High pressure system
- First stage regulator
- Intermediate pressure system
- low pressure system
150
What is included in the high pressure system gas pathway
Everything upstream of the cylinder
includes parts upstream of the cylinder pressure regulator
• aka first stage regulator
151
What is included in the first stage regulator gas pathway, pressure range and it's purpose
Includes
• cylinders and pressure regulators with O2 pressures between 45 and 2200 psi
• receives gases from cylinders
```
Purpose:
converts high, variable pressures
from cylinder gases
• to constant, lower pressure of 45 psi for machine use
• aka O2 cylinder pressure regulator
```
152
What is included in the intermediate pressure system gas pathway and purpose
includes
• cylinder pressure regulator and pipeline gas inlet to gas flow control valves (flowmeters)
• going toward flowmeters
Purpose:
• can flow & pressurize gas in multiple directions
• To lower pressure as progress through system
• Pressure goes from higher to lower
153
What is included in the low pressure system gas pathway
```
includes:
• Flowmeters
• Hypoxia prevention devices
• Unidirectional valves
• Pressure relief valves
• Common gas outlet (CGO)
-all parts downstream of the gas flow control valves (FLOWMETERS)
• Extends from flowmeters to CGO
```
154
What are the pressure gauge ranges for the intermediate pressure system
```
Pressure range:
0 psi if master switch off
16 - 55 psi
-50-55 psi for pipeline
40-45 for cylinder
```
155
Describe the deliberate difference in supply pressure of the pipeline vs cylinder O2 and how pressure flows
```
Difference in supply:
the pipeline (50-55 psi) & cylinder oxygen (40-45 psi)
```
How pressure flows:
-From the higher pressure system
-the machine will preferentially receive O2 from the pipeline
d/t higher pressure difference (∆P)
b/c pipeline pressure > cylinder pressure
156
When will the gas pathway system receive O2 from the cylinder over the pipeline
If the pipeline pressure drops below the cylinder pressure
157
After check cylinder pressure what should be done and why
it should be turned off
• to prevent
exhaustion
leakage of gases from cylinders
158
What are the pressures in a low pressure system and what is this dependent on
Pressures normally slightly greater than Patm
pressure is variable
Depends on
flow from flowmeters
and back pressure from breathing circuit
159
3 Requirements for anesthesia machine piping
Connects components inside machine
Must be able to withstand 4x intended pressure
Leaks must not exceed 25 ml/min inside machine
160
What is the CGO and guidelines for use
```
Common Gas Outlet (CGO)
Receives all gases from machine
delivers mixture to breathing system to deliver to the pt
Must be difficult to disconnect
to ensure uninterrupted gas flow
```
161
Why shouldn't the CGO be used for supplemental O2
Should not be used for supplemental oxygen
Such as during a delay in emergencies
Potential delivery of inhalational agents
162
What are the unidirectional valves and where are they located?
Pipeline inlet
Outlet check valve (before CGO)
Pressure relief valve (before outlet check valve)
Various places throughout the system
163
What is the purpose of unidirectional valves
To prevent pipeline backflow
164
Where is and what is the purpose of the outlet check valve do
location:
Located btwn vaporizer & CGO
UPSTREAM from O2 flush valve
```
Purpose:
Prevents/lessens back pressure from O2 flush or breathing circuit
• it prevents reverse gas flow
causing pumping or pressurizing effect
• to ↓ intermittent back pressure!!
```
165
What do unidirectional valve in the pipeline prevent
back pressure
| decreased intermittent back pressure
166
Location and purpose of the pressure relief valve
Prevents the buildup of pressure
Upstream of the outlet check valve
open to atmosphere to vent gas if the preset pressure is exceeded
Limits ability of machine to provide adequate pressure for jet ventilation
-can't get adequate pressures
Location:
- Upstream of the outlet check valve
- Near the CGO and open to atmosphere
167
Purpose of the flow adjustment controls
To Regulate
flow of O2
medical air
other gases
168
Guidelines for flow adjustment controls
Must be only one control for EACH gas
must be adjacent to its flowmeter
• turn in only one direction
• counterclosckwise
169
Guidelines for O2 flow adjustment control
```
O2 flow knob (on flowmeter) must be
fluted
larger than other gases
• looks & feels different
• likely larger & projects out more than other gas knobs
```
170
Flowmeter purpose
```
Indicates
rate that gas is passing through piping (in this order)
• 1st Vaporizer
• into CGO
• then to patient
```
171
Pressures of the O2 supply flowmeter
is regulated to a constant lower pressure by a 2nd stage regulator
• Part of low pressure system
172
Design of flowmeters
```
Thorpe tube used
vertical glass tube
Smallest diameter at bottom
Free floating indicator
A stop at top of tube
A flow scale
```
Must be marked with
appropriate color
chemical symbol of gas
173
How does flowmetered gas flow and the standards
Flowmeter sequence purposeful
allows gas flow from bottom-top & left-right
Standards:
O2 flowmeter on RIGHT side, closest to CGO
174
Where is O2 flowmeter and why is the location important
O2 flowmeter on RIGHT side, closest to CGO
Importance:
• if a leak occurs with other gases then unlikely to result in a hypoxic mixture
• Safety feature= where flowmeter is located
175
What is the O2 flush valve and how is the flow directed
Delivery of high-flow, 100% O2
Receives O2 from
pipeline inlet or
cylinder pressure regulator
Sends high flow O2 to CGO
176
Requirements and design of O2 flush valve (5)
```
MUST be:
Operable with 1 hand
• To deliver O2 to desat pt very quickly
• So you can use it when connected to pt??
Single purpose
Self-closing
Designed to minimize accidental use (innie)
Have flow Btwn 35-75 L/min
```
177
When the O2 flush valve is used what can happen at the CGO. How is the problem prevented.
the pressure could ↑ the supply pressure at the CGO
• w/o the presence of pressure relief valves
• to appropriately regulate it
178
What are the hazards of the O2 flush valve
```
potential sticking of valve
barotrauma
anesthetic awareness
• b/c can dilute or ↓ volatile anesthetic
• receive less vapor gas
```
179
What is the purpose of the O2 failure protection device
```
AKA “Fail Safes” when O2 fails
Shuts off or proportionally ↓ N2O
• to maintain a min 19% O2 flow at CGO
• prevents hypoxic mixtures
Shuts off N2O
May convert to medical air if no O2
```
180
How does the O2 failure protection device work
How it works:
O2 pressurizes when master switch turned on
holds open a pressure sensor shut-off valve
These valves interrupt the supply of other gases to flowmeters except medical air
in the event the O2 supply pressure falls below threshold or to zero
181
Function of the O2 failure alarm
When pressure falls below threshold
• approx. 30 psi
• an alarm sounds w/in 5 sec
182
Purpose and function of hypoxia prevention devices
• prevent a hypoxic gas mixture by maintaining a minimum O2 concentration delivery w/ N2O
Function:
Uses mechanical linkage
• with N2O to limit N2O flow when given in tandem w/ O2
• Link engages when O2 concentration << 25% to
183
Hypoxia prevention device requirements
Requirement of contemporary machines
to avoid the administration of a hypoxic gas mixture
Mandatory Minimum O2 Flow
Min of 50-250 ml/min flow
Activated when master switch is ON
184
Function of the auxiliary O2 flowmeter
Permits O2 flow at 10 L/min (MAX)
can be used w/ non-machine airway devices
• NC, masks, Ambu bag
Similar to the O2 flush valve
the auxiliary O2 flowmeter is active when the master switch is OFF
185
Purpose of the auxiliary O2
Delivers O2 in case of electronic power or system pressure failure by connecting Ambu bag or modified anesthesia circuit in order to ventilate the patient
186
Purpose of workstation power failure/battery
1 backup source for power in the event of power outage
187
Power failure function
Power failure alarm
should be visual & audible
Newer machines
have 1 backup source for all components
188
Backup battery function for workstation.
| Battery life dependent on...
If machine stays plugged in battery backup should be at highest level
• until generator takes over
Duration of backup depends on power usage
manual ventilation uses much less power than ventilator usage
189
What is the mission of the breathing system (5)
1. receives gas mixture from the machine
2. delivers gas to the patient
3. removes CO2
4. allows spontaneous, assisted, or controlled respiration
5. provides gas sampling, measures airway pressure, monitors volume
190
What happens to resistance as it travels through a system
The more pressure it overcomes the more resistance drops
When gas passes through a tube
• The pressure at the outlet is less than the pressure @ the inlet……
The drop in pressure= resistance which was overcome
191
What can alter resistance
* Volume of gas passing through
* Flow types (passing thru tubes) can change resistance
* laminar
* turbulent
192
Describe movement of laminar flow
Flow is smooth and orderly
Particles move parallel to the tube walls
Flow is fastest in the center
• where friction is the least
193
Laminar flow equation
change in P = (L x v x V)/r4
• L = length
• v = viscosity of gas
• V = flow rate
194
How does laminar flow relate to length, viscosity, flow rate and tube diameter
Directly r/t:
length, viscosity, flow rate
```
Inversely r/t
tube diameter (to the 4th power!)
```
195
Describe movement of turbulent flow
Flow lines are not parallel
| • ”Eddies”: particles moving across or opposite
196
Types of turbulent flow
Generalized
• When flow exceeds critical rate
Localized
• Encounters constrictions, curves, valves
197
What is the significance of resistance and breathing
* Parallel changes in work of breathing
| * ETT probably causes more resistance than breathing system
198
How do flow rate and location differ between laminar and turbulent flow
laminar = faster in the middle, straight path
turbulent= same across diameter of tube, occurs @ turns
199
How much is too much resistance in a breathing system
* How much is too much???
* Imposes strain where pt is doing spontaneous work
* No common agreement
* watch flow-volume loops
200
How does turbulent flow affect breathing
It alters work of breathing d/t increased resistance (turbulent?) from tubes
increased resistance = increased WOB
201
Reason flow-volume loop can be altered by increased breathing system resistance?
Changes in the loop d/t:
pt assist less often
pt has Less effort/Vt
pt has Less neg inspiratory pressure
appears as hypoventilation on loop
202
What is compliance and it's significance in respiration
Ratio of ∆ in volume to ∆ in pressure
Measures distensibility (mL/cm H2O)
significance: helps determine Vt
203
Identify turbulent vs laminar flow on slide 8 of breathing system lecture
straight lines are laminar flow
dots are turbulent flow
drawing B = example of turbulent flow exceeding critical rate
204
In regards to breathing systems, what equipment is most distensible
breathing circuit
| reservoir bag
205
What is rebreathing
“To inhale previously inspired gases from which CO2 may or may not have been removed”
206
What influences rebreathing in the breathing systems
* Fresh gas flow
* Dead space
* Breathing system design
207
How does FGF relate to rebreathing and when does it occur
Amt of rebreathing varies
Rebreathing is inversely r/t FGF
↑FGF then ↓ rebreathing
↓FGF then ↑ rebreathing
208
What are fail-safes in the system to prevent rebreathing
insp and exp valve
| separation of insp and exp limbs
209
What can be a benefit of rebreathing
utilizing remain volatile
210
How do FGF and Vm relate to rebreathing
If FGF is =/> Vm rebreathing DOES NOT occur
as long as exhaled gas is vented
If FGF is < Vm rebreathing DOES occurs to meet required Vm
211
How can FGF rate be utilized in induction, maintenance and emergence
FGF rate can help speed or slow induction and emergence
Rebreathing can help with maintenance
212
3 types of dead space
mechanical
anatomic
alveolar
213
What is mechanical dead space and how does this effect rebreathing
aka apparatus dead space
↓ by having INSP and EXP limb separation
• Separation as close to pt as possible
rebreathed gases in breathing system; gases don’t change in composition
214
What is anatomical dead space and how is affected by breathing systems
No gas exchange in pts conducting airways to alveoli
-Adds H2O vapor
Breathing sys effect:
↓ by ETT, tracheostomy (smaller diameter)
↑ by circuits, masks, humidifiers (on pt side of insp/exp limb split)
215
What is alveolar dead space
volume of alveoli ventilated but not perfused (opposite of shunt)
216
Effects of rebreathing
```
Retain Heat and moisture retention (increase vapor)
Altered gas tensions (inc/dec PP)
O2
Inhaled anesthetic agents
• Induction
• Emergence
CO2
```
217
6 desirable characteristics of a breathing system
1. low resistance to gas flow
2. minimal rebreathing
3. removal of CO2 at rate of production
4. rapid changes in delivered gas when required
5. warmed humidification of inspired gas
6. safe disposal of wastes
218
classifications of breathing systems
```
Open (face mask, NC)
No reservoir & no rebreathing
Semi open (mapleson system)
A reservoir but no rebreathing
Semi closed
A reservoir and partial rebreathing
Closed
A reservoir and complete rebreathing… but depends on FGF
```
219
Increased volume delivery with breathing systems concerns
volume of patient or leaks in system
| Modern ventilators designed to eliminate
220
Decreased volume delivery by breathing system concerns
```
Results from
• leaks in circuit
• gas compression
• distention of circuit
Called “wasted ventilation” (increase in container size)
```
221
What are 4 discrepancies in gas concentration in a breathing system
Dilution
Leaks
Uptake by breathing system components
Release by breathing system components
222
How does dilution or leaks in breathing system affect gas concentration
Dilution
FGF < Vt & leaks in system
Room air entrained
Compensate by increasing dial--pt response more important than ##
Leaks
Gas forced out of system
• During positive pressure ventilation
-may not even be able to ventilate pt
223
How does uptake by uptake of gas by system components affect gas concentration in breathing system
May adhere to plastics, rubber, absorbent
Related to time, surface area
minuscule absorbance over time
224
How does release of gas by breathing system components affect breathing system gas concentration
Low output
• even after vaporizer turned off
Inadvertent exposure--think MH -- flush system w/ FGF or use non-volatile machine
Can be released next time used
225
What are the 8 components
```
1. breathing tubing
2. respiratory valves
3. reservoir bag
4. carbon dioxide absorption canister
5. a pop-off valve leading to scavenging
6. a fresh inflow site
7. a Y-piece with mask/tube connectors
8. a facemask, LMA, or ETT
```
226
Fit and design of face mask
```
Must be clear
Inflatable or inflated cuff
Pneumatic cushion that seals to face
Fits between the interpupillary line and in the groove between the mental process and the alveolar ridge
Connect to the Y-piece or connector
with a 22 mm female connection
```
227
Why are face masks clear
to be able to visualize vapor, vomitus, blood
228
Purpose of breathing system connectors/adapters and their benefits
A fitting to joint together 2 or more components
Benefits
Extend distance btwn patient & breathing system
Change angle of connection
Allow more flexibility/less kinking
229
What are the potential negatives to breathing system connectors/adapters
Potential negatives…
↑ resistance
↑ dead space (WHERE?)
↑ locations for disconnects
230
Reservoir bag design (shape, volume, pressures, material etc)
Rubber, plastic, or latex free
Ellipsoidal for 1 hand
3-L traditional for adults
0.5-6 L
Must have 22 mm female connector on neck
When bag extended 4x its size...Pressure 35-60 cm H2O
231
Breathing system reservoir bag function
```
1. Allows gas accumulation
• reservoir for next breath
2. A means of assisted ventilation
3. Visual/tactile monitor of breathing
4. Distensibility
• Protects from excessive airway pressure
```
232
Why is proper facemask fit important
Prevent corneal pressure
| Prevent pressure trauma by "E" hand
233
Female and male connector sizes
Female = 22 mm
| Male =
234
How does adapter/connector angle affect tube
can help prevent kinking
235
How are adapters useful during surgery
can move circuit away from surgical site
Some can allow for passage of bronchoscope or suction
236
What are sources of anesthetic gas contamination
```
APL valve
High and intermediate pressure systems
Low pressure systems
Ventilator
Anesthetic errors
Cryosurgery
```
237
What is the APL purpose
Outlet for anesthetic gases during spontaneous ventilation and assisted ventilation
238
Design and functional design of the APL valve
Depending in FGF
• 5L/min can exit through this valve
• >Vm
Is spring loaded
• only requires minimal positive pressure to open and Allow the exit of waste gas from the circuit
239
Where and how do high/intermediate pressure system leaks occur
```
Location
N2O pipeline
cylinder supply
the machine piping
• that feeds the N2O flowmeters
• common site of leaks are connections
```
How
Leaks in this system can increase waste gas in the OR
• May not be able to hear leak
240
Where can leaks of low pressure system occur
```
Leaks can occur at
CO2 absorber
Due to
• loose seals/connections at valves and circuit
• vaporizer mount,
• scavenger system
```
241
What is included in the low pressure system where gas leaks can occur
```
N2O flowmeter
Vaporizers
fresh gas lines from the machine to the breathing circuit
CO2 absorber
• Ensure it’s seated properly
breathing hoses
unidirectional valves
ventilator
various components of the scavenger system
• bad connections
• system overload
```
242
Why can gas leaks occur at the scavenger system?
Bad connections
| System overload
243
If you suspect a gas leak at the CO2 absorber, what can you do?
Ensure the CO2 absorber is seated properly
244
What can cause leaks in the breathing circuit system
```
High peak pressure
can cause leaks in this system
• even w/ a functioning scavenger system
• can have a 2L/min leak
esp if pressure is greater than what system can handle
```
245
What can be a major source of gas leak
Ventilator
Anesthetic errors
94-99% of waste gas is due to this
246
How can ventilator leak occur, and what's the biggest problem when it happens?
Can leak internally
• causing the mixing of gases
• can’t really determine concentration of delivered gas
247
What issues may occur as a result of ventilator leak
Vent will alarm
• Low Vt
• Alteration in RR
• Issues w/ pressures
248
Causes of anesthesia technique errors
- Insufflation errors of system
- N2O on w/ open circuit
- Poor airway seal
- Uncuffed tracheal tubes
- Post procedure circuit disconnection
- Overfill and gas spillage around vaporizer
- Letting active gases exit open circuit
249
Why do leaks occur with cryosurgery
d/t use of liquid N2O as a tool intraop
to freeze off cells
Gas evaporates intraop and into the OR
250
Requirements and design for breathing tubing in the breathing systems
Large bore, corrugated, plastic, expandable
1 meter in length
400-500 ml/m of length
Low resistance
Flow always turbulent due to corrugation
Somewhat distensible
251
How does breathing tubing affect the dead space. What Type of DS?
Apparatus DS = only from Y piece to patient (after limb split)
• d/t unidirectional gas flow
….longer tubes don’t ↑ DS
252
Purpose of and problems with the unidirectional valves in breathing systems
Purpose:
Ensure gases flow toward pt
In one breathing tube and away in another
Problem:
Failure to seal
Causes a large amount of the circuit into mechanical dead space
253
Manufacturing requirements for unidirectional valves.
```
Requirements:
Arrows or directional words
Hydrophobic so it doesn't stick
Clear dome
Must be placed btwn patient & reservoir bag
• Prevent rebreathing
```
254
APL open/close direction
Clockwise motion = INCREASE pressure (CLOSES valve)
motion ↓↓ pressure
Counterclockwise motion = DECREASE pressure (OPENS valve)
255
Function of the APL in the breathing system
“pop-off” = over pressure pops-off somewhere else
User-adjustable
Controls pressure in breathing system
Releases gases to scavenging system
An arrow must indicate direction to close valve
256
APL position with inspiration and expiration during
Spontaneous resp
Assisted ventilation
Mechanical ventilation
Spontaneous resp:
- insp = OPEN (CPAP partially closed)
- exp= OPEN
Assisted ventilation:
- insp = partially open (excess diverted)
- exp= partially open
Mechanical ventilation:
- insp = bypassed
- exp= bypassed
257
Components of mapleson system
```
Reservoir bag
Corrugated tubing
APL valve
Fresh gas inlet
Patient connection
```
258
What components are not included in the mapleson system
CO2 absorbers
No scavenging
Unidirectional valves (inc rebreathing)
Separate INSP & EXP limbs (rebreathing/DS increased)
259
Where is the respiratory gas monitoring piece located in the breathing system
Between tracheal tube and corrugated tubing
260
Anatomy and problem with Mapleson A system (aka...)
FGF enters opposite of pt end
APL at pt end
Problem:
- FGF would be vented prior to reaching the pt if APL open
- Can waste the FGF
- Could just use a NC
261
What is Mapleson A most efficient for
• Spontaneous, unassisted pts
262
Anatomy, use and problem with mapleson B system
APL and FGF at T piece
Much of FGF is vented
Problem:
inefficient, wasteful
FGF should be double Vm
USE: Obsolete
263
Anatomy and use of mapleson A system
- Identical to mapelson B EXCEPT corrugated tubing omitted
- Lost a lot of DS
- FGF DOUBLE Vm
```
Use:
Emergency resus (Ambu-bag)
```
264
Anatomy and benefits of Mapleson D system
```
Anatomy:
3 way T- piece
• pt connection
• fresh gas
• corrugated tubing
PEEP valves may be added
```
```
Benefits
• Very popular
• most efficient for assisted
• controlled ventilation
• FGF 1.5-3x Vm
```
265
Mapleson D modification
Bain modification
| Made FGF coaxial (exhalation tubing on outside of corrugated tubing for warming)
266
What is not included with mapleson E system
No reservoir bag or APL valve
| along with no CO2 absorber etc
267
Mapleson E system anatomy and use
Corrugated tubing
• attached to the T-piece forms reservoir
Use:
Used in spontaneously breathing pts to deliver O2
• Not used in anesthesia d/t no reservoir and difficulty scavenging gases
268
Anatomy and differences of Mapleson F system (aka...?)
aka Jackson-Rees modification
Mapleson E system PLUS Reservoir bag added
Difficult to scavenge
Excessive pressure less likely to develop
• Occlude vent hole at end of bag
• No APL valve
USE:
Pediatric patients
269
Kane lecture 2:04::14 @ pg 34
Other cards still @ pg 20
270
4 miscellaneous sources of gas leakage
Use of volatiles in CPB (card-pulm bypass) & lack of scavenging
Diffusion of vapor from circuits and from the pt’s surgical wound & skin
Cross-contamination of fresh air & exhaust ducts
Failure to scavenge waste gas appropriately
271
What are two types ventilation systems in the OR ?
| Which is most common?
Nonrecirculating (most common)
| Recirculating
272
What is the setup of the nonrecirculating OR ventilation system
• pumps in air from outside
• removes stale air w/ a variable number of air exchanges/hour
>/= 10/hr is recommended
273
What are considerations for the nonrecirculating OR ventilation system
airflow pattern
workstation location
generation of airflow
274
Why is the type of flow for OR ventilation systems important? What type of flow?
```
Laminar flow in nonrecirculating systems
• optimal
to prevent air mixing
reduce hot spots
• which are heavily contaminated
```
275
What are the advantages and disadvantages of the recirculating OR ventilation system?
Advantages:
More economical
Disadvantage:
Partially recirculates stale air
276
How does air exchange in the recirculating OR ventilation systems?
Where are they most popular and why?
Exchange:
Each air exchange has
• part fresh outside air
• part filtered and conditioned stale air
Not complete removal of gasses/contaminants
Location:
• popular in locations with temp extremes
• more efficient
• air pockets by waste gases
277
What is the recommended air exchange rate for OR ventilation systems.
recommended to have 15-21 air exchanges/hr
| • three must have outside air
278
How much do scavenging systems reduce trace concentration of gases?
90% reduction of waste gases
279
What are the 4 parts of the waste gas scavenging system
```
1. Relief valves
• APL
• ventilator pressure relief
2. tubing to the scavenging interface,
3. interface
4. disposal line
```
280
What is the function of the ventilator pressure relief valve?
How does it work?
Purpose=how waste gases leave the ventilator
• during inspiration
How it works:
• valve is closed d/t positive pressure transmitted from ventilator
281
What is the purpose of the conducting tubing
It moves waste gas from the APL and ventilator pressure relief valve to the scavenging interface
282
What are safety mechanisms incorporated with the scavenging interface
It is equipped w/ relief valves between circuit and vacuum or ventilation system and can have an open or closed reservoir
283
What are two types of scavenging interfaces
Closed
| Open
284
Describe the closed scavenging interface. How it works, what happens if the system fails
How it works:
• includes a bag for waste gas
• then sent to vacuum or ventilation system
```
Failure:
• If the vacuum system fails
• there is excess pressure in the reservoir bag which causes the APL to open
vent waste gases into the room
visual over-distention
```
285
How does the open scavenging system interface function? What is and isn't included?
* It is valveless
* uses continually open relief ports to avoid positive or negative waste gas buildup
Not included:
• NO valves
Includes:
• a flowmeter to show the waste gas being evacuated;
• may incorporate a reservoir bag
286
Pg 21
See Q 269
287
2 types of gas disposal routes. Describe each
may be active or passive
active using a vacuum or evacuation system
passive the OR ventilation system or the wall disposal
288
Newer scavenging systems setup and benefits
consider the use of low flow scavenging systems
• that don’t function when anesthesia is not being given to
• ↓ costs
• ↓ carbon footprint
289
Requirements for active disposal routes
* suction/vacuum systems
| * should be able to vent at least 30 L/min of air
290
What is the optimal setup for scavenging vacuum system
Separate vacuum systems to vent anesthetic gases
291
Scavenging requirement for anesthesia ventilators
Ventilators have a disposal system
| sends waste gases to the scavenger system
292
Problems with older machine and ventilator scavenging
Older machines
may vent waste gases into the air
may not have a scavenging connection
Older ventilator
may have leaks that cause gas mixing
& ↑ amount of gas that must be vented
• may overwhelm the scavenging system
293
Scavenging hazards (6)
Scavenging of the breathing circuit
Excessive positive or negative pressure in the scavenger system
Can cause CV insult or barotrauma
Can cause abnormal pressure in breathing circuit
Ventilator drive gas can be wasted
Large amounts of volatile waste released into atmosphere
294
How can excessive positive and negative pressure in the scavenger system
d/t malfunction
| • can be directed into the breathing circuit
295
Page 22
Page 22
skipped 2nd half of pg 33
296
What are types of absorbents (4)
high-alkali
low-alkali
alkali-free
lithium hydroxide
297
What is the high-alkali absorbent type
* Traditional ie. Soda lime
* High amts of K/NaOH
* When desiccated form CO
* Form Compound A w/ Sevoflurane
* Do not change color if dry
298
What is low-alkali absorbent type
↓decrease amts of K/NaOH
| May produce lesser CO & Compound A
299
What is alkali-free absorbent type
```
Contains calcium hydroxide
No CO formation
No Compound A formation
Changes color if dry
Poorer CO2 absorber
```
300
What is lithium hydroxide absorbent type
```
Reacts w/ CO2 to form carbonate
Does not react w/ anesthetic agents
Expensive
Care with handling
• burns to skin, eyes, lungs
```
301
What are the actual absorbents used shape and size. how are they measured.
```
Pellets or granules
• Smaller granules
• Greater surface area
• Decrease gas channeling
• Increase resistance and caking
Hardening agent used to decrease dust
```
Measured by mesh number
• 4-mesh= 4 openings/sq inch
• 8-mesh= 8 openings/sq inch
302
Absorbent byproducts (3)
1. Haloalkene formation
2. Compound A formation
3. CO
303
What is haloalkene formation
Produce during closed circuit anesthesia w/ halothane
Produces BCDFE
• 2-bromo-2chloro-1,1-difluoroethene
Nephrotoxic in rats
304
What is compound A formation
2-fluoromethoxy-1,1,3,3,3-pentafluoro-1-propene
| Possibly nephrotoxic in humans
305
When can compound A form
```
Occurs with
• Low FGF
• Absorbents containing K or NaOH
• Higher sevo concentrations
• Longer anesthetics
• Dehydrated absorbent
```
306
What contributes to CO production
* Dry absorbent w/ strong alkali
* Many Monday1st case
* Remote locations
307
What type of reaction occurs when CO is formed from the CO2 absorbent
Reaction is exothermic
| • note canister
308
What is the problem with the formation of CO from the CO2 absorbent
Not detected by pulse ox or RGM
Highest levels seen w/ des
309
What are APSF recommendations for CO2 aborbent use
ALL gas flows turned off after each case
Vaporizers turned off when not in use
Absorbent changed at least weekly
Machines rarely used should have fresh absorbent
Packaging intact before use or thrown away
No supplemental O2 through circle system
Temperature of canister monitored (CO=exothermic)
Change when CO2 appears
310
What are manual resuscitator components
```
Self-expanding Bag
Non-rebreathing Valve
Body
Bag Inlet Valve
Pressure-limiting Device
Oxygen-enrichment Device
Reservoir
```
311
Describe the manual resuscitator bag
* Inflated in resting state
* Expands on exhalation
* If O2 delivery source inadequate
* difference is made up by room air
* Rate at which bag reinflates determines Vm
312
How can Vm be estimated when using the manual resuscitator bag
• Rate at which bag reinflates determines Vm
313
Describe the non-rebreathing valve of the manual resuscitators
```
“exhalation valve”
Gas flows out of bag
• into patient on inspiration
Gas flows out
• expiratory port on expiration
```
314
Describe the body of the manual resuscitator
Connector connects to ETT or mask
Swivels
Deflects exhaled gas
Housing is transparent
315
Describe the pressure limiting device of the manual resuscitator
“pop off”
Protects against barotrauma
Helps prevent gas from entering stomach
316
ATSM standards for pressure limiting device of the manual resuscitator
•If pressure limited at 60 cm H2O = must have override
* If override can be locked
* must be apparent
* should have an alarm when override operating
317
What are two locations of O2-enrichment devices on manual resuscitator
Near bag inlet valve
| Directly into bag
318
How do O2-enrichment devices workand concentrate O2 for near bag inlet valve
* O2 concentration d/t air drawn into bag
| * The greater the Vmthe lower the O2 concentration
319
How do O2-enrichment devices work and concentrate O2 directly in bag
* High delivered O2 concentrations
* If flow is less than bag filling rate
* then inlet valve will admit air
320
What are the disadvantages of small or large reservoir bags
Small
• may limit O2 concentration
Large
• Cumbersome
