Anesthesia Machine Flashcards
How can the hypoxic guard fail?
- Crossover
- Leak (crack in FM)
- Defective guard
- Inert gas (ex Helium)
- Use of Air
What are the types of O2 analyzers available?
- Electrochemical/Galvanic fuel cell (Aestiva, Aespire, Fabius)
- Paramagnetic Analyzer (used in most models)
Rate of vaporization depends on what 3 factors?
- Temp
- VP of liquid
- Pressure above evaporating gas
What are some hazards of contemporary vaporizers?
- You can fill with wrong agent
- Tipping/Spills
- Overfilling
- Leaks
- Electronic failures
- Reliance on breath by breath gas analysis rather than preforming regular preventative maintenance)
(Wash-in Time Constant) You have a patient on 5L/min FGF and the circle system is about 10L, in 4min how much of 6% Des will you have given your patient?
- 2nd constant (86%) so 6 x 0.86 = 5% Des
How can resistance in a breathing circuit be minimized?
- Reduce tubing length
- Increase its diameter
- Avoid sharp bends/kinks
- Ensure laminar flow
- Eliminate valves
Advantages of Rebreathing?
- Reduced cost
- Increase tracheal heat and humidity
- Reduce staff exposure
Effects of rebreathing N2O?
- Delayed induction
- Longer to reach agent % concentration
Effects of rebreathing CO2?
- Respiratory acidosis
Where does dead space end?
- Y-piece
Anesthesia gases are considered what and why?
- Dry gases to reduce internal corrosion and bacterial colonization
Describe the types of circle systems?
- SEMI OPEN
- Rebreathing unlikely
- FGF > Ve- SEMI CLOSED
- Rebreathing likely
- FGF < Ve
- CLOSED
- 100% Rebreathing
- FGG <= 1L/min
- SEMI CLOSED
Describe Open circuit? What are some features?
- Mask, NC, or Mapelson models
- Features
- No unidirectional valves
- No CO2 absorber
- FGF determines amount of rebreathing
- Resistance and WOB are low
- Features
When can you use a Mapleson A or D, and what is a modified mapelson D?
- Mapleson A = spontaneously breathing
- Mapelson D = controlled ventilation
- Modified Mapelson D = Bain
Disadvantages of non-rebreathing
- Unrecognized disconnect
- Increased cost
- Increased staff exposure
- Loss of heat from pt
- May require disconnect for assembly and can be reassembled improperly
What is the name of the leak test for a nonrebreathing system like a Bain?
- Pethick Test
What are 2 reasons for inspired CO2
- Exhausted CO2
- Faulty unidirectional valves
Advantages of a Circle System
- Constant inspired concentrations
- Conserve heat & humidity
- Min Staff Exposure
- Low resistance
Disadvantages of Circle System
- Complex
- Misconnection/Disconnection
- Malfunction of unidirectional valve
- Less portable
- Increased dead space
When do you want to use High FGF:
- Smoke inhalation injury
- MHT
- Uncuffed ETT
- Rigid broncoscopy
- Face mask use
- Older equipment
What is the chemical formula of co2 absorbent process?
Where do reactions take place for CO2 absorber?
- On surface
Why are hardeners used in CO2 absorbers?
- To reduce dust and irritation
What is the manufactured water content and size of granules for CO2 absorber?
- Water content 13-20%
- Size of granules is 4-8 Mesh (pass through 4-8 holes/inch)
Clinical Signs of Exhausted CO2 absorbent
- Increased ETCO2
- Resp acidosis
- Hypervent
- Increased bleeding
- Color of CO2 indicator (purple)
- SNS activation
- Late signs: increased HR & BP, dysrhythmias
How do you identify a disconnected Piston Ventilator
- Low pressure alarm
- No ETCO2 waveform
- Movement of manual breathing bag (which should not be in use during vent)
What are the benefits of FGD
- Constant Vt
- Pt safety (reduce barotrauma)
- enhanced control of low flow
Disadvantages of FGD
- Limited effect in some cases
- Technical complexity
- Not suitable for spontaneously breathing pt
When would you want to use FGD
- Low flow anesthesia
- Pt on vent with low compliance (ex. ARDS, COPD, OBESE)
- Pediatric anesthesia
Benefits of Low Flow
- Reduced pollution
- Environmental sustainability
- Reduced cost
- Preserve tracheal heat and moisture
- Prevent CO2 from desiccating
- Preserve body temp
- Electronic peep
Causes of Low Pressure
- Disconnect (Y-piece most common site)
- Poor seal absorbent, defective absorbent (second common site)
- Failure of bag/vent switch
- Leak in corrugated tubing
- Incompetent spill valve
- Gas sampling line preventing manual ventilation
- Ventilator failure due to moisture in flow sensors
How can you tell when there is barotrauma
- Excessive inflow (positive pressure)
- Flutter valve may be stuck closed
- Control assembly problems
What is the primary monitor for a disconnect
- Continuous auscultation (stethoscope) & visual chest rise
What causes high pressure in the circuit
- Spill valve malfunction
- Failure to remove plastic of co2 absorber
- Failure to remove plastic from anesthesia mask
- Occlusion of lumen of circuit
- Malfunctioning PEEP valve
- Malfunction flutter valve or scavenger
What would you do if your machine shoots the High pressure alarms
- Assess pt related causes
- Switch to bag mode and manually vent pt
- Consider disconnect and use ambu bag/TIVA
If high pressure is resolved when you switched to bag mode, what was the most likely cause?
- Spill valve
If high pressure is sustained when you switch to bag mode, what is the most likely cause?
- APL or scavenger
Describe an Active Open Scavenging system
- Suction with canister open to room air
- Too much suction: room air is entrained into system
- Too little suction: scavenged gas released into room
- No need for (+) or (-) pressure relief valves
Describe an Active Closed Scavenging system
- Suction with bag
- Has positive and negative relief valves
- Describe a Passive Closed Scavenging system
- No suction with bag
- Has positive relief valve
- No negative relief valve needed as no suction is applied
5 tasks of O2
Flowmeter
O2 Flush
Drive Gas
Low O2 Pressure Alarm
Fail Safe
Describe the channeling effect
The channeling effect in CO₂ absorbers reduces efficiency by allowing gas to bypass the absorbent, limiting CO₂ removal.
The channeling effect in CO₂ absorbers occurs when the gas follows paths of least resistance, bypassing large portions of the absorbent material. This reduces the absorber’s efficiency, as less CO₂ is removed due to limited interaction with the absorbent. Proper packing, maintenance, and timely replacement of the absorbent help minimize this effect.
OSHA Regulations for Exposure to Waste Anesthetic Gases
- Halothane < 2PPM
- Halothane + N20 < 0.5PPM
- N20 < 25PPM/8hr
Levels in unscavenged anesthetizing locations may be as high as 7000PPMM (0.7%) N2O and 85 PPM (0.008%) Halothane
What does American Society for Testing & Materials (ASTM) set
Sets standards for required components of anesthesia machine via document ASTM F1850
What does FDA regulate
1993 Anesthesia Machine Checkout and requirements for medical gases.
- slide states: equipment/vaporizer/monitor/volatile
What does DOT (dept of transportation) regulate
Manufacturing, handling, transport, storage and disposal for CYLINDERS
What does Compressed Gas Association (CGA) and the National Fire Protection Association (NFPA) regulate
Role in setting cylinder standards
What does US Pharmacopeia (USP) regulate
Requirements of medical gases like FDA
