Medical Gas Systems/Vaporizers/Scavange/Co2 absorber/Indicators. Flashcards
What are the Characteristics of the Diss Systems
- Provides non-interchangeable connections for the medical gas lines
- Connection consists of a body, nipple, and nut combination
- Only properly mated parts will fit together and allow the threads to engage
- Required for every anesthesia machine
In The Diss System.”As the diameter of the body increases/decreases the matching________________will do so in tanderm.
Nipple
The Diss is used for cylinder or Pipeline
Pipeline
What are the characteristics of the Piss Systems
1.Required for every anesthesia machine
2.Uses a series of pins to connect associated gas cylinders valves with its matching yoke clamp
3.Position of holes on the cylinder valves corresponds with the pins on the yoke attached to the equipment
Each gas has a unique pin configuration
4Prevents connection of the wrong cylinder to a yoke
Piss For Co2
1,6
Piss for Entonox:[nitrous oxygen gas mixture. Laughing gas]
7
Helium gas color is?
Brown
Full Air Cylinder pressure
1900-2000 psi
Full air cylinder Volume
625Liters
Nitrous tank with no liquid in volume weighs?
14.2lbs at 250L
Nitrous tank Empty
12.9LB
What agency enforces the purity of medical gases
FDA
What Do the cylinder markings mean on the tanks
Markings designed to indicate ownership, specification, pressure ratings, and other important data
Date of manufactor, serial numbers, test markings
1. cylinder specification (DOT), cylinder type of material, service/working pressure in psi
2. serial number
3. date of manufacture
4. neck ring identification
5. retest markings
(+ is 10% overfill, star is meets qualifications for a 10yr retest instead of the usual 5)
4 is month, L is facility, 60 is year, then either ’+’ or a star
What Is represented on the cylinder labels
Label shows the Compressed Gas Association (CGA) marking system.
1.Diamond shape denotes hazard class (in this case, non-flammable).
2.To the left is name of contained gas (carbon dioxide). 3.Signal word (Caution) with statements of hazards and measures to be taken to avoid injury is to the right
should not cover permanent markings
What is represented on cylinder tags
Full, In Use, Empty connected by perforations. Denotes the amount of cylinder contents and is not used for identification purposes :
When cylinder is first opened, the full portion of the tag should be removed. When cylinder is empty, you have to remove the in service tag.
Name the Safe handling procedures for Cylinders
Never stand a cylinder upright without support
- Never leave empty cylinders on the machine
- Never leave the plastic tape on the port while installing the cylinder
- Never rely only on the a cylinder’s color for identification of its contents
- Never oil valves
- Before any fitting is applied to the cylinder valve, particles of dust, metal shavings, and other foreign matter should be cleared from the outlet by slowly and briefly “cracking” the valve away from you and/or other personnel. WHY??
- The valve should always be fully open when a cylinder is in use. Marginal opening may result in failure to deliver adequate gas.
What is Vaporization
Vaporization is the conversion of liquid to a gas
Why is Vaporization Important
- The inhalation agents we use today are liquids that must be converted to a vapor to be inhaled
- Anesthetic gases are also referred to as “Volatile Agents” because they are liquids that have a high propensity to vaporize into gas form.
Vaporization depends on what factors
Vapor pressures
Temperature
Amount of carrier gas used
Name the 2 phases that molecules of a volatile agent is distributed between
Liquid and gas phases
What causes increase in Vapour pressure in a mixture of liquid and Gas Interphase
Increase in temperature
How is vapor pressure generated in gas liquid interphase in a container
The gas molecules bombard the surface of the liquid and the walls of the container creating vapor pressure
Vapor pressures of Anesthetic
Sevoflurane = 160mmHg Enflurane = 172mmHg Isoflurane = 240mmHg Halothane = 244mmHg Desflurane = 669mmHg
When a Carrier gas is passed over liquid,which direct ion does the equillibruim shift towards?
Towards Vapor causing the liquid to loose heat and become cold because of a drop in temp after the heat on Vap has been supplied by the liquid.
Define Latent heat of Vaporization
Number of calories required to change 1 gram of liquid into vapor without a temperature change
*note 1g=1mL
Is it preferable to use an outside source for Heat or energy of the liquid itself?
Outside source
Why is it preferable to use an outside source for Heat instead of energy of the liquid.
We need the temperature of the liquid to remain constant
What Will be the result of using energy of the liquid instead of outside source
- The temp of the liquid will decrease during vaporization
2. Rate of Vaporization will decrease
What is Specific Heat?
The number of calories required to increase the temperature of one gram of a substance by one degree centigrade
Name 2 rational for using specific heat
- it indicates how much heat must be supplied to the liquid to maintain a constant temperature when heat is being lost during vaporization.
- Manufacturers select vaporizer component materials that have high specific heat because these materials better resist temperature changes associated with vaporization.
A measure of speed with which heat flows through a substance is called?
Thermal Conductivity
The higher the thermal conductivity, the better the substance conducts heat.T/F
T
Why are vaporizers constructed with metals that have high thermal conductivity?
1.helps them maintain a uniform internal temperature during evaporation by allowing them to absorb envi- ronmental heat more effectively.
Name the Characteristics of Vaporizers
Agent Specific
Temperature Compensated
Variable Bypass
Explain variable bypass Vaporizer
A portion of the gas flow will pass into the vaporizing chamber where it will become saturated with vapor.
This vapor-laden portion then rejoins the gas flow for dilution to deliverable concentrations.
Name some components of the Variable bypass vaporizer
Temperature compensating valve Inlet Wick Concentration control dial Machine outlet check valve.
Why does Desflurane use a TEC 6 or special Vaporizer
Because it is highly volatile and vapor pressure is 669 which is very close to atmospheric pressure and will evaporate too quick to be useful.
In Tec 6 vaporizer …Desflurane is heated to what temp? and at what pressure?
39deg celcius temp and aproxx 2atm pressure.
Which Volatile agent does not need acarrier gas for it to be delivered.
Desflurane
Tec 6 is what kind of vaporizer?
Gas-Vapor blender
In Tec 6 vaporizer,Pressure is regulated from 2atm down to ?
1.1atm.
Alladin casette uses the KISS safety device true or false
True
What is the Copper Kettle Vaporizer made up of?
1.Measured flow, Bubble Through
2Dedicated flowmeter for the kettle (MEASURED FLOW)
3.Gas comes up through central tube inside of the
vaporizer to the LOVING CUP
4Flow of gas is then directed down toward the liquid (BUBBLE THROUGH)
5Highly concentrated vapor then exits the vaporizer and is
6.Diluted into the fresh gas flow
Copper kettle can be described as?
An out of circuit non-agent specific,measured flow,bubble through vaporizer.
Formular for vapor output
CGxVP/BP-VP
Anesthetic concentration
vapor output ml/min/Total gas flow in ml/min
Whats the relationship between Altitude and Atmospheric pressure
Increase in altitude gets a decrease in Barometric Pressure
Decrease in altitude gets an increase in barometric pressure.
Name vaporizer hazards
1Wrong Agent in the vaporizer High – Low – High Low – High - Low 2.Contamination 3.Tipping 4.Overfilling 5.Simultaneous Administration of More than One Vapor 6.Leaks 7.Pumping Effect
Upon filling vaporizers,where at what point should you stop filling
Black fill line.
During change in Altitude,will be the new required dial setting.
Normal dial setting (%) x 760 mmHg/ Ambient pressure (mmHg)
Explain ALtitude effcect in Tec 6 with Desflurane
Effect is that you would have to deliver higher dialed concentration of Des at higher altitude/lower barometric pressure. Conversely, you would alter your concentration dial to decrease output in lower altitude to avoid delivering overdose of anesthetic
Define Scavenging
Collection of excess gases from equipment used in administering anesthesia, or exhaled by patients.
Removal of these excess gases to an appropriate place of discharge outside the working environment.
Niosh Rec levels of Anesthetic gases in the OR
Volatile Halogenated Anesthetic alone = 2 ppm
Nitrous Oxide = 25 ppm
Volatile Anesthetic with Nitrous Oxide = 0.5 ppm
5 basic components of scavenging
- Gas collecting assembly
- Transfer means
- Scavenging interface
- Gas disposal tubing
- Gas disposal assembly
Name the components of the gas collecting assembly in the scavenger system
APL valve
Apl bypass valve
exhaust
Function and characteristics of the gas collecting Assembly in the scavenger system
Captures excess gasses at the site of emission and delivers them to the transfer tubing.
Outlet connection usually 30mm (19mm on older machines) male-fitting.
Size of connections is important so that it doesn’t connect to other components of breathing system.
Characteristics of the Transfer tubing in the Scavenger system
Conveys gas from the collecting assembly to the interface.
- Usually a tube with female-fitting connectors on both ends.
- Tubing is short and large diameter, to carry a high flow of gas w/o a significant increase in pressure.
- Must be kink resistant.
- Must be different from breathing tubes
- Color coded yellow and stiffer plastic
What is the function of the scavenging interface in the Scavenger system(Balancing valve/Balancing device)
- prevents pressure increases or decreases from being transferred to the breathing circuit.
- Interface limits pressures immediately downstream of the gas-collecting assembly to between -0.5_+3.5cm H2O.
What are the components of the Scavenging interface of the scavenging system
- Negative pressure relief valve and positive pressure relief valve.
- 30mm male connector inlet
- Reservoir
- Situated as close to gas collecting assembly as possible.
Characteristics of Open Interface(Scavenging Interface)
- No valves.Open to the atmosphere via relief port in reservoir…this avoids buildup of positive or negative pressure.
- Require use of a central vacuum system and a reservoir (open canister –size should allow for high waste gas flows).
- Gas enters the system at the top of the canister and travels through a narrow inner tube to the base.
- Vacuum control valve can be adjusted – varies the level of suction on the canister/reservoir – must be > excess gas flow rate to prevent OR pollution
Characteristics of Closed Interface(Scavenging Interface)
Two Types:
POSITIVE-PRESSURE RELIEF ONLY
Single positive-pressure relief valve opens when a max. pressure is reached
Passive disposal – no vacuum used, no reservoir bag needed
POSITIVE-PRESSURE AND NEGATIVE-PRESSURE RELIEF
1.Has a positive-pressure relief valve, negative-pressure relief valve, and a reservoir bag.
2.Used with an active disposal systems -Vacuum control valve adjusted so that the reservoir bag is NOT over distended or completely deflated
Gas is vented to the atmosphere if the system pressure exceeds + 5.0 cm H2O
Room air is entrained if the system pressure is less than -0.5 cm H2O.
3.A backup negative-pressure relief valve opens at -1.8 cm H2O if the primary negative-pressure relief valve becomes occluded.
Name the characteristics of the Gas disposal tubing(Scavenging System)
1.Connects the scavenging interface to the disposal assembly.
2.Should be different in size and color from the breathing system.
3.With a passive system the hose should be short and wide.
4.Tubing running overhead ideal to prevent accidental obstruction and kinking
If connected to an active gas disposal system it must be a DISS connector.
5.Tube should be kink resistant
Name the 2 types of gas disposal assembly
- Active-
2. Passive
Characteristics of passive Gas disposal Assembly
The waste gases is directed out of the building via:
1.An open window
2.A pipe passing though an outside wall
3.An extractor fan vented to the outside air.
4.pressure is raised above atmospheric by the patient exhaling.
5.manual squeezing of the reservoir bag or ventilator (needs positive pressure).
Advantages: inexpensive to set up, simple to operate.
Disadvantages: may be impractical in some buildings.
Passive-
Characteristics of an active Gas disposal Assembly
These systems connect the exhaust of the breathing system to the Hospital vacuum system via an interface controlled by a needle valve.a mechanical flow-inducing device moves the gases (produces negative pressure in disposal tubing; must have negative pressure relief)
Advantages: convenient in large hospitals where many machines are in use in different locations.
Disadvantages: vacuum system and pipework is a major expense.Needle valve may need continual adjustment.
Most commonly used in hospitals
what is the Gold standard to verify patient ventilation
Waveform Capnograpy
Purposes of Capnography
- Used to Confirm ETT and LMA placement
- In general anesthesia without an airway, helps determine if patient is adequately exchanging air/oxygen
- Guide ventilator settings- avoid too much or too little ventilation
- Detect circuit disconnections
- Detect circulatory abnormalities- pulm. embolism, occult hemorrhage, hypotension
- Detect excessive aerobic metabolism: Malignant hyperthermia
Clinical Use of Capnography
May be used as estimate of PaCO2,
PaCo2>PEtCO2
Average gradient = 2-5mmHg under GA
Used as an evaluation of dead space
Name 2 ways to measure C02
Colorimetric
Rapid assessment of CO2 presence
Uses metacresol purple impregnated paper (changes color in presence of acid)
CO2 combines with H2O—carbonic acid–paper changes color
Infrared Absorption Spectrophotometry-Most common
Gas mixture analyzed
A determination of the proportion of its contents
Each gas in mixture absorbs infrared radiation at different wavelengths
The amount of CO2 is measured by detecting its absorbance at specific wavelengths and filtering the absorbance related to other gases
Name 2 types of measuring techniques
1.Mainstream and Side stream
Characteristics of MainstreAM capnograph
aka Flow Through Heated infrared measuring device placed in circuit Potential burns Sensor window must be clear of mucous Less time delay Weight- kinks ETT + increase dead space Less of an issue with newer technology
Characteristics of Side stream capnograph
Aspirates fixed amt gas/minute (30-500ml/minute)
Pediatric sampling- lower Vt = dilution
Transport expired gas to sampling cell via tubing
Best location for sampling near ETT
Time delay
Potential disconnect source
Water vapor- condensation- traps/filters used
Characteristics of phase 1 Capnogram
An inspiratory baseline
Should have no CO2 reading
Inspiration and first part of expiration
Dead space gas exhaled
Characteristics of phase 2 capno
An expiratory upstroke
Sharp upstroke represents rising CO2 level in sample
Slope determined by evenness of alveolar emptying
Mixture of dead space and alveolar gas
characteristics of Phase 3 capno
Alveolar Plateau Constant or slight upstroke Longest phase Alveolar gas sampled **Peak at end of plateau is where the reading is taken- End Tidal Partial Pressure of CO2 (PEtCO2) Normal Value = 30-40mmHg Reflection of PACO2 and PaCO2
Characteristics of Phase 4 capno
Beginning of Inspiration
CO2 concentration- rapid decline to inspired value
In a Co2 Capno,what are the 5 curve characteristics to inspect.
Frequency Rythm Height Baseline Shape
What is the primary use of Waveform capno
Verify placement of ETT in the trachea
Presence of stable CO2 waveforms for 3 breaths > 30 mmHg indicates tracheal intubation
The waveform Capno will show what characteristics in the waveform of Obstructive Lung disease.{Copd,asthma,brochoconstriction,acute obstruction}
Slow rate of rise in Phase II
Steep upslope of Phase III (in extreme cases may not see phase III)
How can we tell that rebreathing has occured on a co2 waveform capno
If value remains above baseline at the end of phase 4
Causes of rebreathing are?
Equipment dead space,Exhausted co2 absorber,Inadequate fresh gas flow
Causes of rising co2 when ventilation is adequate
Malignant Hyperthermia
Release of Tourniquet
Release of Aortic/Major Vessel Clamp
IV Bicarb administration
Insufflation of CO2 into peritoneal cavity
Equipment Defects (e.g. expiratory valve stuck, CO2 absorbent exhausted)
What are the causes of decrease in ETco2
- Hyperventilation- gradual decrease reflects increased minute ventilation
- Rapid decrease- PE (thrombus, fat, amniotic fluid, air) V/Q mismatch. Increase in PaCO2-PEtCO2 gradient.
- Cardiac Arrest
- Sampling error- disconnect(s), high sampling rate with elevated fresh gas flow
How does Carbon dioxide absorber work and what are its characteristics
Chemical neutralization of CO2
Base neutralizes an acid
Acid: carbonic acid – formed by reaction of CO2 and H2O
Base: hydroxide of an alkali or alkaline earth metal
End product: water, a carbonate, & heat
Name two disadvantages of the classic co2 absorber
1.Couldn’t change
during the case because disturbs circle system integrity
2.Common source of leaks
ADvantage of new absorber/Morden single canisters
Can change during case has a bypass feature
Name the common absorbers
Soda Lime (Sodium hydroxide lime)
Amsorb Plus(Calcium Hydroxide lime)
Baralyme
Litholyme (Lithium Hydroxide)
What are the chemical Components in Sodalime by %
4% sodium hydroxide 1% potassium hydroxide 15% H2O 0.2% silica 80% calcium hydroxide
Basic characteristics of Soda Lime.
1.Silica added for hardness to prevent dust
2.Capable of absorbing 26 liters of CO2/100g of absorbent granules
3.Water is present as thin film on granule surface
Moisture is essential. Reaction takes place between ions that only exist in presence of water
4.* a pound of CaOH can absorb 0.59lb of carbon dioxide
How does The Reaction of Soda Lime and CO2 happen and the formula.
Carbon dioxide combines with water to form carbonic acid. Carbonic acid reacts with the hydroxides to form sodium (or potassium) carbonate and water and heat.
SODA LIME:
CO2 + H2O—->H2CO3
H2CO3 + 2NaOH (KOH)—> Na2CO3 (K2CO3) + 2H2O + HEAT
Na2CO3 (K2CO3) + Ca(OH)2 (quick reaction)—> CaCO3 + 2NaOH (KOH) + HEAT
Some CO2 may react directly with Ca(OH)2, but this reaction is MUCH slower—> CaCO3 + H2O + HEAT
What are the Chemical components and characteristics of Amsorb(Calcium Hydroxide Lime)
Aka: Amsorb Plus
80 % calcium hydroxide
16% water
1-4% calcium chloride
Calcium sulfate and polyvinlypyrrolidine added hardness
Capable of absorbing 10 liters of CO2/100g of absorbent granules
What is reaction formular for Calcium Hydroxide lime
CO2 + H2O—–>H2CO3
H2CO3 + Ca(OH)2—–>CaCO3 + 2 H2O + HEAT
What are the chemical components and characteristics of Baralyme
Barium Hydroxide Lime Consist of:
20% BaOH and 80% CaOH
Small amounts of NaOH and KOH may be added
Granules are 4-8 mesh
No hardening agent is needed
It is slightly less efficient than soda lime but less likely to dry out
No water
Implicated in fires
Absorptive capacity similar to soda lime 26 liters of CO2 per 100 grams granules
Baralyme reaction and formular
- Ba(OH) + 2(8H2O) + CO2——> BaCO3 + 9H2O + Heat
- 9H2O + 9CO2—–>9H2CO3
- 9H2CO3 + 9Ca(OH)2—->9CaCO3 + 18H2O + Heat
Litholyme(Lithium hydroxide monohydrate) Characteristics and formula
75% lithium hydroxide (LiOH)
12-19% H2O
<3% lithium chloride (LiCl)
Reaction:
2 LiOH * H2O + CO2——>Li2CO2 + 3H2O – HEAT
* 1 pound of LiOH absorbs 0.91 lb of carbon dioxide
What are the characteristics of indicators
An acid or base whose color depends on pH
Color conversion signals absorber exhaustion
Color reverts back with rest (especially in NaOH containing formulations)
Replace absorbent with 50-70% color change
Ethyl violet – most common—critical pH = 10.3
Is Ethyl violet an acid or Base
Base.
Color change that occur in Etyl violet indicator
White—->purple
Color change that occur in Phenophthalein indicator
White to pink
Color change that occur in Clayton yellow indicator
Red to yellow
Color change that occur in Ethyl Orange indicator
Orange to yellow
Color chnage that occur in MImmosa 2
Red to white
What are the characteristics and significance of absorbent granules
- 4-8 mesh (granule size= number of openings per inch in a sieve through which particles can make it through)
- Irregular shape – increased surface area
- Small granules increase resistance
- Provide greater surface area
- Blend of large & small minimize resistance with little sacrifice in absorbent capacity
Which absorbent is the best and less toxic
Litholyme
What are the characteristics of Granule Hardness
Excessive powder——-> channeling resistance & caking
Soda Lime – silica added to increase hardness
Tested with steel ball bearings & screen pan
% of original remaining = hardness number
Hardness number should be > 75
What are the characteristics of channeling
- Preferential passage of exhaled gas flow through 2.absorber via pathways of low resistance
- Results from loosely packed granules
- Air space occupies 48-55% of the volume of the canister
- Absorbent along channels may exhaust
- CO2 may filter through channels not visible
- CO2 monitoring
- Some manufacturers now use a polymer to bind the granules in pre-formed channels to prevent channeling
What absorbent issue is possible when Sev0flurane is used.
SevoFlurane When degraded by a strong base in carbon dioxide absorbents (containing KOH and to a lesser extend NaOH), sevoflurane forms compound A at concentrations which have been demonstrated to be nephrotoxic in rats.
Does not appear to be an issue with absorbents with no KOH/NaOH
How can the Formation of compound A be avoided or minimized when Sevo is used in the setting of CO2 absorber containing KOH and NaoH
Therefore manufacturer recommends not more than 2 MAC hours at flow rates of 1 to <2 L/min.
Most practitioners use at least 2 liters of fresh gas flow with sevo
How does carbon Monoxide formation happen,resulting in Co2 absorbent problem
Carbon monoxide has been known to accumulate in desiccated (dry) NaOH and KOH containing absorbents when they are not used for 24-48 hours
High flow through a system for prolonged time (such as if one forgets to turn down the O2 flow over the weekend) = drys it out
With dried out absorbent, a slow reaction occurs with the volatile agents and absorbents that produces CO
can result in critically high levels of carboxyhemoglobin in exposed patients
Which volatile agent is associated with the highest level of Carbon monoxide production/Accumulation
Desflurane
Fires is caused by which of the absorbents
Baralyme
Anesthesia Safety Foundation Recommendation on Safe Use of Carbon Dioxide Absorbents include
- Turn off all gas flow when the machine is not in use
- .Change absorbent regularly
- Change absorbent whenever the color change indicates exhaustion
- Change all absorbent, not just one canister
- Change absorbent when uncertain of the state of hydration, such as if FGF is high
- Low flows preserve humidity in granules
During which cycle does the FGF go through the absorber
During Inspiration
Name 3 basic elements of the scavenging interface
- Positive pressure relief-protects patient and equipment in case of occlusion of system.
- Negative pressure relief-limit sub-atmospheric pressure.
- Reservoir capacity-matches the intermittent gas flow from gas collecting assembly to the continuous flow of disposal system.
