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gtown nur641 > Gas Systems & Scavenging > Flashcards

Gas Systems & Scavenging Flashcards

Carter/maggie+ bowman

1
Q

link 25 proportioning system in newer machines is

A

internalized. As dials are electric, you cannot turn on nitrous oxide without oxygen flowing.

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2
Q

color of helium cylinder

A

brown

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3
Q

Full E sized oxygen cylinders have ___ volume and ___ pressure

A

625-700 L at 2000 - 2200 PSI

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4
Q

Full E sized air cylinders have ___ volume and ___ pressure

A

~625 L at 1900 PSI

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5
Q

In air and oxygen cylinders, pressure falls in

A

proportion to the volume remaining in the tank

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6
Q

Full E sized N2O cylinders have ____ volume and ____ pressure

A

1590 L and 745 PSI

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7
Q

purity of medical gases is specified and enforced by

A

Specified us US Pharmacopeia or national formulary

Enforced by FDA

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8
Q

Cylinder Label

A

each cylinder must have a label or decal on the side or on the shoulder. But not covering any permanent markings.

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9
Q

Cylinder Label shows (3)

A

the compressed gas association marking system.

Diamond shape,
 name of gas, 
signal word with statements of hazards and measured to be taken. 
Hazard Status
Caution words
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10
Q

DOT permanent markings on cylinders (6)

A 
Include: 
cylinder type, 
working PSI 
serial number 
date of manufacture
neck rick identification 
restest markings
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11
Q

7 safe handling procedures for cylinders

A
  1. Never stand a cylinder upright without support
  2. Never leave empty cylinders on the machine
  3. Never leave the plastic tape on the port while installing the cylinder
  4. Never rely on the cylinders color for identification of its contents
  5. Never oil valves
  6. Before any fitting is applied to the cylinder valve, particulates of dust, metal shavings, and other foreign matter should be cleared from the outlet by slowly and briefly cracking the valve a way from you and/or other personnel
  7. The valve should always be fully open when a cylinder is in use. Marginal opening may result in failure to deliver adequate gas.
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12
Q

vapor pressure sevoflurane

A

160 mmHg

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13
Q

vapor pressure enflurane

A

172 mmHg

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14
Q

vapor pressure isoflurane

A

240 mmHg

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15
Q

vapor pressure halothane

A

244 mmHg

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16
Q

vapor pressure desflurane

A

669 mmHg

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17
Q

Tec 6 vaporizer maintains

A

a temp of 39 and atm of 2 for desflurane, constant temp/pressure

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18
Q

Gas-vapor blender =

A

tec 6 vaporizer

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19
Q

pressure regulating valve in Tec 6

A

down regulates the desflurane to 1.1 atm

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20
Q

Aladdin cassettes are

A

computer controlled variable by pass vaporizers

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21
Q

Copper Kettle is unique in that it (4)

A

has its own dedicated flow meter

is out of the circuit

non-agent specific

bubble through

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22
Q

Steps of gas through copper kettle (~4 steps)

A

Air flows from dedicated flow meter into copper kettle, into loving cup,

loving cup forces it back down,

then bubbles through the gas diffuser disk that is filled with anesthetic of your choice,

is laden with anesthetic gases, flows out o f copper kettle as a very highly concentrated anesthetic, joins rest of gas flow.

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23
Q

copper kettle calculation

A

(Carrier Gas x Vapor Pressure) / Barometric Pressure - Vapor Pressure = Vapor output in mL/min

then! [Vapor Output] in mL/min / [total gas] flow in mL/min

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24
Q

variables you can change in copper kettle calculation

A

Carrier gas and total gas flow

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25
Q

If you accidentally put an anesthetic with high vapor pressure in a low vapor pressure vaporizer

A

High- low -> High

higher concentration than set

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26
Q

If you accidentally put an anesthetic with low vapor pressure in a high vapor pressure vaporizer

A

Low - high ->

Lower concentrations than set

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27
Q

Definition of scavenging

A

COLLECTION of excess gases from equipment used in administering anesthesia or exhaled by patients and REMOVAL of these excess gases to an appropriate place of discharge outside the working environment.

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28
Q

NIOSH recommended levels of anesthetic gases in OR

A

volatile halogenated anesthetic alone = 2 ppm

nitrous oxide = 25 ppm

volatile anesthetic with nitrous oxide = 0.5 ppm

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29
Q

Basic Components of Scavenge (5)

A
  1. Gas collecting assembly
  2. Transfer means
  3. Scavenging interface
  4. Gas disposal tubing
  5. Gas disposal assembly
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30
Q

Size of connections in scavenging system is important so that

A

it is unable to connect to other components of the breathing system

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31
Q

Gas Collecting Assembly (Does)

A

captures excess gasses at the site of emission and delivers them to transfer tubing

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32
Q

Gas Collecting Assembly connection is usually

A

30 mm (19mm) in older machines and male fitting.

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33
Q

Transfer means of scavenge system

  • also called:
  • function
A

Also called exhausted tubing or transfer system.

function: conveys gas from the collecting assembly to the interface

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34
Q

Transfer means of scavenge system details (5)

A

usually a tube with female fitting connectors on both ends

tubing is short with a large diameter to carry a high flow of gas w/o a significant increase in pressure

must be kink resistance

must be different from breathing tubes

color coded yellow and stiffer plastic

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35
Q

problem with NIOSH recommended levels

A

“Theres no safe level of gas exposure and its questionable where these numbers came from”

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36
Q

Scavenging interface function (3)

A

prevents pressure increases or decreases the scavenging system from being transmitted to the breathing system

also called the balancing valve or balancing device

interface limits pressures immediately downstream of the gas collecting assembly to between -0.5 to 3.5 cmH2O.

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37
Q

Scavenging interface details

A

inlet should be 30 mm male connector

should be situated as close to gas-collecting assembly as possible

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38
Q

3 basic components of the scavenging interface

A

positive pressure relief - protects pts and equipment in case of occlusion in system

negative pressure relief - limit sub atmospheric pressure

reservoir capacity - matches the intermittent gas flows rom gas collecting assembly to the continuous flow of disposal system

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39
Q

2 types of scavenging interfaces

A

open

closed

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40
Q

Open interface scavenging system

A

No valves!
Is open to the atmosphere via “relief ports” in reservoir, avoiding build up of positive and negative pressure

  • must have high vacuum flow to prevent pollution of OR.

requires reservoir and vacuum

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41
Q

Positive Pressure Relief only closed scavenge system

A

Only positive pressure relief valve

Disposal is passive, no vacuum, pressure comes from expiration

Gas vents to a non circulating HVAC or a window,

No reservoir bag needed

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42
Q

Positive+ Negative relief closed scavenge system (5)

A

used with active disposal (vacuum)

has a reservoir bag

gas is vented to the atmosphere if pressure is over +5cmH2O

Room air is entrained if pressure is below -0.5cmH2O

BACKUP negative pressure valve at -1.8cmH2O if first one becomes occluded

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43
Q

In positive+negative relief closed scavenge system, adjust the vacuum control valve so that

A

the reservoir bag is appropriately inflated

i.e. neither overly distended or completely deflated

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44
Q

Reservoirs in scavenging systems should match the

A

intermittent volume from pt expiration/gas collecting assembly to the continuous flow of the disposal system

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45
Q

Gas disposal tubing that is connected to an active gas disposal system requires

A

a DISS

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46
Q

Gas disposal tubing for passive systems should be

A

short and wide (decrease resistance, increase flow)

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47
Q

Gas disposal tubing to ensure no kinks should be

A

running overheard to prevent accidental obstruction (stepping) or kinking

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48
Q

Gas Disposal Assembly consists of

A

Components used to remove waste gases from OR . Two types, active and passive

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49
Q

Active Disposal Assembly advantages/disadvantages

A

Vacuum! Connected from breathing system to hospital vacuum via an interface controlled by needle valve

advantage: convenient in large hospitals where many different machines are used in different locations
disadvantage: expensive to have network, needle valve may need continual readjustment

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50
Q

Passive Disposal Assembly advantages/disadvantages

A

Waste gas is directed out of building via open window, pipe passing to outside wall, fan to outside

advantage: Cheap! simple
disadvantage: may be impractical in some buildings

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51
Q

Scavenging System Check (3)

A
  1. Ensure proper connections between scavenging system and both APL VALVE and VENTILATOR RELIEF VALVE to waste gas vacuum
  2. Fully open APL valve and occlude Y-Piece, with minimal O2 flow collapse scavenger bag and ensure it reads 0 and not negative pressure (appropriate vacuum)
  3. Fully open APL valve and occlude Y-piece ,with high gas flow allow reservoir bag to distend and ensure that pressure does not rise to greater than 10 cmH2O.
52
Q

Capnometry vs Capnography

A

Capnometry: quantification of carbon dioxide concentration

Capnography: actual graph of capnometry values over time

53
Q

“Purposes” of capnograhy (8)

A
  1. gold standard to determine if patient is being ventilated, critical, life-saving monitor
  2. used to confirm ETT/LMA placement
  3. Without an airway, helps determine if pt is adequately exchanging air/oxygen
  4. Guide ventilator settings (avoids too much or too little ventilation )
  5. Detect circuit disconnections
  6. Detect CIRCULATORY abnormalities - (PE, occult hemorrhage/hypotension)
  7. Detect excessive aerobic metabolism (Malignant hyperthermia)
  8. Standard for VAE detection
54
Q

contraindications to capnography

A

there are none

55
Q

“Clinical uses” of capnography (2)

A

May be used as ESTIMATE of PaCo2

Used as an evaluation of dead space

56
Q

EtCO2 compared to PaCo2

A

PaCo2 > EtCo2 by approx 2-5 mmHg

57
Q

Methods of Measuring CO2 in Expired gases

A
  1. colorimetric

2. infrared absorption spectrophotometry (most common)

58
Q

Colorimetric co2 detector uses

A

metacresol purple paper (turns color with present of carbonic acid)

59
Q

Infrared Absorption Spectrophotometry works

A
  • by analyzing the gas mixture
  • determination by proportion of gas contents
  • each gas in mixture absorbs infrared radiation at different wave lengths, amount of CO2 is measured by detecting its absorbable at specific wavelengths and filtering the absorbance related to other gases
60
Q

measurement techniques of etco2 include (2)

A

main stream and side stream capnography

61
Q

mainstream capnography

advantages
disavtanges

A

advantages: Less time delay

disadvantages: potential for burns r/t heated circuit,
increases dead space
heavy -> can kink ETT.

62
Q

Side stream capnography works by

A

aspirating a fixed amount of gas/minute to analyze in the sampling cell via tubing

63
Q

side stream capnography should be

A

as close to ETT as possible

64
Q

Potential problems with side stream capnography

A

time delay
potential disconnect
water vapor condensation, traps/filters used

65
Q

capnogram =

A

Pco2 vs time

has 4 phases

66
Q

Phase 1 of capnogram (4)

A

Should have no CO2 reading,

represents inspiration and beginning of expiration.

Dead space gas exhaled.

Inspiratory baseline

67
Q

Phase 2 of capnogram (3)

A

An expiratory upstroke!

Sharp upstroke represents rising CO2 level in sample

mixture of dead space and alveolar gas

68
Q

Slope of line in phase 2 of capnogram represents (~3)

A

evenness of alveolar emptying

straight = healthy, no air trapping

sloped = air trapping

69
Q

Phase 3 of capnogram (5)

A

Alveolar plateau

Constant or slight upstroke

Longest phase

Alveolar gas is sampled

Peak at the end of plateau is where reading is taken

70
Q

Reading of ETCO2 is taken at

A

peak of phase 3 (alveolar plateau)

71
Q

Phase 4 of capnogram (2)

A

Beginning of inspiration

co2 concentration has rapid decline to inspired value

72
Q

5 characteristics of capnogram

A 
frequency 
height 
rhythm 
baseline
shape
73
Q

Primary use of capnogram is to

A

verify ETT placement in the trachea vs esophagus

74
Q

Indications of tracheal intubation on capnogram

A

presence of stable CO2 waveforms for 3 breaths >30mmHG

75
Q

Causes of rebreathing = (3)

A

equipment dead space
exhausted CO2 absorber
inadequate FGF

76
Q

Contributors to rising CO2 when ventilation unchanged (6)

A
  1. malignant hyperthermia
  2. release of tourniquet
  3. release of aortic/major vessel clamp
  4. IV bicarb administration
  5. insufflation of CO2 into peritoneal cavity
  6. equipment defects, (expiratory valve stuck CO2 exhausted)
77
Q

Gradual Decrease in ETCO2

A

likely hyperventilation, reflects increased minute ventilation

78
Q

Rapid decrease in ETCO2

A
  • PE, V/Q mismatch
  • Cardiac arrest
    ? Sampling error
79
Q

Sampling errors in ETCO2

A

disconnects, high sampling rate with elevated FGF

80
Q

Capnogram pattern in obstructive lung disease

A

COPD/Asthma/Bronchoconstriction/Acute obstruction

  • slow rate of rise in Phase ii
  • steep upslope of phase iii (in extreme cases may not see phase iii)
81
Q

Spontaneous ventilation/recovery from neuromuscular blockade on a capnogram

A

tugging the middle of plateau

82
Q

Carbon dioxide absorber works by (~5)

A 
chemical neutralization of cO2 
Base neutralizes an acid
acid:carbonic acid (formed by CO2/H2O)
base: some hydroxide (alkali or alkaline earth metal)
end product: water, a carbonate, heat
83
Q

Older CO2 absorbers (2 canisters) were a problem because (2)

A
  1. couldn’t change during the case because disturbs circle system integrity
  2. common sources of leaks
84
Q

Modern single canister models have

A

bypass feature so you can change during case

85
Q

4 common absorbents

A
  1. soda lime (sodium hydroxide lime)
  2. amsorb plus (calcium hydroxide lime)
  3. baralyme
  4. litholyme (lithium hydroxide)
86
Q

Soda lime contains %

A

Sodium Hydroxide Lime

4% sodium hydroxide 
1% potassium hydroxide 
15% H2O
0.2% silica 
80% calcium hydroxide
87
Q

Characteristics of soda lime

A

silica added for hardness to prevent dust
capable of absorbing 26 L of CO2 for 100 g of absorbent granules
water is present as thin film on granule surface
MOISTURE IS ESSENTIAL reaction makes place between ions that only exist in presence of water
a pound of CaOH can absorb 0.59 lb of CO2

88
Q

Soda Lime Reaction

formula

A

CO2+H2O H2CO3 + 2NAOH(KOH) NA2CO3(K2CO3) + 2H2O + HEAT
^predominant reaction b/c faster^

slower reaction:
CO2 + Ca(OH)2 CaCo3 + h2o + heat

89
Q

Soda Lime Rxn in words

A

“Carbon dioxide combines with water to form carbonic acid, carbonic acid reacts with the hydroxides to form sodium (or potassium) carbonate, water, and heat.

Some carbon dioxide reacts CaOh2 but this reaction is much slower.

90
Q

Amsorb Plus (Calicum Hydroxide Lime) contains

A

80% calcium hydroxide
16% water
1 -4 % calcium chloride

91
Q

Characteristics of calcium hydroxide lime/Amsorb Plus (2)

A
  1. calcium sulfate and polyvinlyprrolidine added hardness to prevent dust
  2. capable of absorbing 10L of CO2/100g of absorbent granules
92
Q

Calcium Hydroxide Lime/Amsorb Plus Reaction Formula

A

CO2 + H2O H2CO3 + Ca(OH)2 CaCO3 + 2H20 + heat

93
Q

Calcium hydroxide rxn in words

A

carbonic acid + calcium hydroxide calcium carbonate + water + heat

94
Q

Baralyme was voluntarily pulled from market b/c of

A

risk of fire

95
Q

Baralyme (Barium Hydroxide) consists of

A

20% Barium Hydroxide

80% Calcium Hydroxide

96
Q

Characterstics of Baralyme (7)

A

Small amounts of sodium/potassium hydroxide may be added

Granules are 4-8 mesh

No hardening agent is needed

It is slightly less efficient than Soda lime but is less likely to dry out

No water

Implicated in fires

Absorptive capacity similar to soda lime of 26 L co2 / 100 g granules

97
Q

Baralyme Reaction formula

A

BaOH + 2(8H2O) + CO2 -> BaCO3+ 9H2O + heat.
9h2o + co2 -> 9H2CO3
9H2CO3 + 9Ca(OH)2 -> 9CaCO3 + 18H2O + heat

98
Q

Litholyme (Lithium Hydroxide Monohydrate) components

A

75% lithium hydroxide (LiOH)
12-19% H2O
<3% lithium chloride

99
Q

Characteristics of litholyme

A

also comes in anhydrous form

1 pound of LiOH absorbs 0.91 lb of CO2

100
Q

Litholyme reaction formula

A

2LiOH + H2O + CO2 Li2CO2 + 3H2O - heat

101
Q

Indicators (5 things to know)

A
  1. An acid or base whose colors depends on pH
  2. Color conversion signals absorber exhaustion
  3. Replace absorbent with 50 - 70% color change
  4. Color reverts back with rest, especially in NaOH containing formulas
  5. Ethyl violet - most common, critical pH 10.3
102
Q

Phenolphthalein

A

fresh; white

used; pink

103
Q

Ethyl Violet

A

fresh; white

used; purple

104
Q

Clayton Yellow

A

fresh; red

used; yellow

105
Q

Ethyl Orange

A

fresh; orange

used ; yellow

106
Q

mimosa 2

A

fresh; red

used; white

107
Q

Size of absorbent granules (4)

A

4-8 mesh in size

irregular shape -> increased surface area

small granules increase resistance but also provide greater surface area

blend of large and small minimize resistance with little sacrifice in absorbent capacity

108
Q

Granule hardness (3)

A

Not enough hardness = excessive powder which can lead to channeling and caking

Hardness is tested with steel ball bearings and screen pan
& of original remaining = hardness number,

hardness number should be >75

109
Q

Silica in soda lime

A

is to increase hardness

110
Q

Channeling results from

A

loosely packed granules

111
Q

Some manufactures may now use

A

a polymer to bind the granules in pre-formed channels to prevent channeling

112
Q

Air space in the co2 absorber occupies

A

48 to 55%

113
Q

Strong bases capable of degrading volatile gases

A

absorbents containing KOH and also NaOH

114
Q

Compound A has been found

A

to cause nephrotoxic effects In rats

115
Q

To prevent theoretical formation of compound A

A

Manufactures recommend not more than 2 MAC hours at flow rates <2 L/min

116
Q

Carbon monoxide has been known to accumulate

A

in desiccated (Dry) NaOH and KOH containing absorbents when they are not used for 24 to 48 hours.

117
Q

With dried out absorbents a slow

A

reaction occurs with the volatile agents and absorbents that produces carbon monoxide, can result in critically high levels of carboxyhemoglobin in exposed patients .

118
Q

Desflurane is associated with

A

highest accumulation of carbon monoxide

119
Q

Anesthesia Safety Foundation Recommendation on Safe Use of Carbon Dioxide Absorbents (6)

A
  1. Turn of all gas flow when the machine is not in use
  2. Change absorbent regularly
  3. Change absorbent whenever the color change indicates exhaustion
  4. Change all absorbent not just one canister
  5. Change absorbent when uncertain of the state of hydration, such as if FGF
  6. Low flows preserve humidity in granules
120
Q

DISS and PISS are required

A

for all anesthesia machines

121
Q

KISS

A

key index safety system, part of vaporizer

122
Q

At altitude, you need to increase concentration of

A

tec-6 vaporizer, desflurane.

because tec 6 will heat des to 39 / 2 atm regardless of ambient temperature to deliver a constant percentage that will be lower at 350 mmHG thats 750 mmHg

123
Q

Vaporizers are made of metals with

A

high specific heats and high thermal conductivity to maintain uniform internal temp

124
Q

Most vaporizers are (3)

A

temperature compensated
agent specific
variable by-pass

125
Q

Potential Vaporizer Hazards (7)

A

Wrong agent in the vaporizer
(high - low high or low - high - low)

Contamination (leaving it open)

Tipping

Overfilling

Simultaneous administration of vapors

leaks

pumping effect
(alternating pressure in pipeline that ends up giving more gas than expected)

126
Q

Not enough hardness =

A

Not enough hardness = excessive powder which can lead to channeling and caking

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