Anesthesia Machine - Quiz 1 Flashcards
Non Electric Devices
- Mechanical flowmeter,
- Scavenging
- Laryngoscope
- Variable Bypass Vaporizer
- Tec 4, 5, 7, Vapor 19, Vapor 2000
Electric Devices
- Vent
- Monitors
- Lights
- Digital Flowmeter
- Air warming blankets
- Gas/Vapor blenders
- Suprane Tec 6
- Aladin Cassettes in ADU or Aisys
PSI of High Pressure System
750 - 2200 PSI
What are the high pressure systems on the AGM?
- Cylinders
- Hanger Yoke
- Yoke block with check valves
- Cylinder pressure gauge
- Cylinder pressure regulator
When are the cylinder supplies opened or used?
When they are checked, when pipeline supply is unavailable, and in emergency situations
PSI of oxygen cylinder
1900-2200 PSI
Capacity of oxygen cylinder
660L
PSI of nitrous oxide cylinder
745 PSI
State of nitrous oxide in cylinder
Gas and Liquid
Nitrous oxide cylinder capacity
1600 L
PSI of air cylinder
1800 PSI
Capacity of air cylinder
600 L
What is the Pin Index Safety System
- Unique arrangement of pins on each cylinder that matches to its inteded contents.
- Pin arrangement matches yoke holes where cylinders attach to the AGM
- Prevents misconnections
- Not 100% if pins are missing or more than 1 washer used
Most fragile part of cylinder supply
Cylinder Valve
Strutures of the Cylinder Valve
- Body
- Gas exit port
- Conical depression for securing screw
- PISS pins
- Safety relief devices
Function of safety relief device on a cylinder valve
Release cylinder contents in a controlled fashion
Safety Relief Device
- Frangible disk that bursts under pressure
- Valve that opens under extreme pressure
- Fusible plug made of Wood’s metal
Functions of Hanger Yoke
- Orients cylinder
- Provides gas tight seal
- Ensures unidirectional flow
- Contains Standard Filter
- Check valve to minimize transfilling
PSI of Intermediate System
40 - 50 PSI
What are Intermediate Pressure systems on the AGM
- Vent power inlet
- Pipeline inlet
- Check valves
- Pressure gauges
- Flow meter valves
- Oxygen pressure-failure device
- Oxygen second stage regulator
- Flush valve
Production, delivery, and storage of pipeline oxygen
Oxygen is produced by fractional distillation of liquid air.
Delivered to hospital and stored as liquid at 184 C
PSI of pipeline oxygen
50 PSI
(344 kPa)
How to interrupt pipeline supply or isolate leaks in case of fire
Shutoff valves in OR
Problems with Pipeline Supply
- Pressure loss/Excess pressure
- Cross-connection of pipelines
- contamination
- Leaks
- Theft of Nitrous Oxide
How is loss of pipeline oxygen pressure indicated and what happens?
- Pressure loss indicated by pipeline pressure gauge
- Oxygen low-pressure alarm sounds
- Fail-safe valves stop delivery of all other gases
Guideline for Oxygen Pipeline Failure
- Trust oxygen analyzer, don’t try to fix
- Turn on backup oxygen cylinder fully and disconnect pipeline
- Bag mask if inspire oxygen doesn’t increase
- Use low flow oxygen
- Turn off vent and bag manually
- Call for help, calculate remaining time on cylinder
- Find out details of problem and how long
- DO NOT reconnect patient to pipeline until tested
- Vent with oxygen source or room air via bag valve mask
Tasks of Oxygen in the AGM
- Proceeds to fresh gas flowmeter
- Powers oxygen flush
- Activates fail safe device
- Activates oxygen low-pressure alarm
- Compresses bellows of mechanical vent
Primary Valves of the AGM
- Free floating valve
- Ball and Spring valve
- Diaphragm valve
Free Floating Valves
- Moves in direction of gas flow (push)
- Prevents gas leakage out of system
- Found in DISS and dual hanger yoke systems
Ball and Spring Vavles
- YOU supply energy - may cause barotrauma
- Permits gas flow after connection is made
- (Plugging pipeline into wall)
- Oxygen flush
Diaphragm Valves
- Reduces pressure
- First stage regulator
- Second stage regulator
First stage regulator
One of two diaphragm regulators that reduce cylinder pressure to 40-50 PSI
Second stage regulator
One of two diaphragm vavles that reduce pressures from 40-50 PSI to 16 PSI
PSI of Low Pressure System
16 PSI
What are the Low Pressure systems on the AGM
- Flow meter tube
- Vaporizers
- Check Valves
- Common gas outlet
What supplies gas to High Pressure system?
Cylinders
What supplies gas to Intermediate Pressure System
Hospital Pipeline or Cylinder after First stage regulator
What supplies gas Low Pressure system?
Flow after Second stage regulator
Proportioning System
Hypoxic Gaurd - chain that conects nitrous oxide and oxygen that prevent the delivery of a hypoxic mixture
What concentration of gas do modern anesthesia gas vaporizers deliver?
Constant concentration regardless of temperature change or flow
Open Breathing System
- No mask
- No dead space
- Anesthetic to patient by insufflation
- Dilution due to room air
- No rebreathing or reservoir bag
- No valves
Semi-Open Breathing System
- Mask on face
- Pt. inhales anesthetic and room air (open drop technique)
- Reservoir bag, no rebreathing
- Room pollution
- High gas flows
- Unidirectional valve
- increase resistance
- vavle may malfunction
Bain’s Circuit
- Semi-Open System
- Mapleson Class: D
- Spontaneous: 2-3 x minute ventilation
- Controlled: 1-2 x minute ventilation
- Coaxial Mod: fresh gas tube inside breathing tube
What is a unique hazard of the Bain circuit?
- Occult disconnection of inner fresh gas delivery hose
- Entire circuit becomes dead space
- Respiratory acidosis unresponsive to increased minute ventilation
Pethick Test for Bain Circuit
- Occlude patient’s end (at elbow)
- Close APL valve
- Fill cuircit with oxygen flush valve
- Release occlusion and flush
- Venturi effect flattens reservoir bag if inner tube patent
Semi-Closed System
- Mask on face
- Anesthetic gas remains in system
- No room air inspired
- Expired gas exits to scavenging system
- Gases are in delivered flow to inspiratory site
- Unidirectional valves, one inspiratory/one expiratory
- Reservoir bag with 6 L/min capacity
- Conserves moisture and heat
- Fresh gas flow can be less than patient’s minute volume
- Pop off valve and 22mm Corrugated tubing
Process of Neutralizing Carbon Dioxide
- CO2 combines to water to form carbonic acid
- Soda lime neutralizes carbonic acid
- End products: heat, water, calcium carbonate
Color of Soda Lime and its absorbent capacity
Fresh: White
Exhausted: Purple
Capacity: 14-23 L
What is produced if inhaled anesthetis are degraded?
Carbon monoxide, compound A, fire, and extreme heat in breathing system
Steps to prevent CO2 absorbent dessication
- Turn off all gas flow when machine not in use
- Change absorbent regularly
- Change absorbent when color shows exhausted
- Change all absorbent canisters of scavenging system
- Change absorbent if unsure of its freshness
- Consider changing more frequently if canisters are small
Advantages of Heat/Moisture Exchangers
- No need for water or electric power
- No hyperthermia risk
- No overhydration risk
- No burn risk
- No electric shock risk
Function of Heat and Moisture Exchanger (HME)
Act as large particle filter and may serve as bacterial and viral filter
Disadvantages of Heat/Moisture Exchanger
- **Not as effective at heating/humidifying airway as water-based, electrical devices**
- Increase dead space and work of breathing
- Obstructions can occur (fluid, blood, secretions, nebs)
- Trouble shooting peak pressures requires more work with HMEs
Types of Heat/Moisture Exchanger
Hydrophobic and Hygroscopic
Hydrophobic HMEs
- Hydrophobic membrane with small pores; pleated for more surface area
- High ambient temperature may decrease effectiveness
- More effective at preventing spread of Hep C
Hygroscopic HMEs
- Contain wool/foam/paper material coated with moisture retaining chemical
- If wet, it loses ability to filter airborn pathogens and substantial airway resistance may occur
- More effective at preserving heat and humidity
Closed System
- Mask on face
- Anesthetics contained in system and not vented
- Rebreathing of all gases - pop off closed (less pollution)
- CO2 absorber in system
- Unidirectional valves
- Flow 150-500 mL/min for physiologic requirements
- Flow 150-250 mL/min under anesthesia
- Unknown gas concentrations
Design of Anesthesia Ventilator
- Automates process of manual ventialtion
- Manual switch - directs gas flow to bag or ventilator
- Bellows separate drive gas from patient gas
- Pneumatic powered - regulated, high pressure supply gas move bellows
- Produces desired inhalation and expiration
Gas Driven Bellows Ventilator
- Double circuit
- Force of compressed gas (air or O2) is driving mechanism to compress bellows
- Bellows contain gas inspired/expired by patient
- Leaks in bellow may dilute gas with driving gas
- Hypoxia, Loss of agent
- Electronically controlled - needs electricity, backup battery
- Volume/Pressure limited
Ventilator Relief Valve
- Spill valve or overflow valve
- Remains open on expiration
- Prevent buildup of volume and pressure in circuit
- During inspiration, driving gas closes relief valve, preventing gas in bellows from exiting to scavenger
- During early expiration, relief valve held closed by a weight until bellows have filled
- creates small amount of PEEP inherent to bellow design (2-3 cmH2O)
Ascending (Standing) Bellows
- Ascend on expiration
- Safer
- Will not fill if total disconnection occurs
Descending (Hanging) Bellows
- Descend on expiration
- Weighted
- Continues upward and downward despite patient disconnect
- Requires CO2/Apnea alarm
Potential Ventilator Problems
- Excessive Positive Pressure
- Wrong setting, malfunction, O2 flush during inspiration
- Tidal volume differences b/t set and delivered
- Circuit compliance, PIP is 20, compression loss, TV of 500
- Ventilator-Fresh Gas Flow Coupling
- Fresh gas volume will add to tidal volume delivered
Piston Driven Ventilator
- Electric motor compresses gas in rigid piston during inspiration
- No need for driving gas
- No depletion of O2 cylinder in case of pipeline failure
- Safe and effective
- Out of field of view
- Built in positive and negative pressure release valves
Advantages of Piston Vent
- Quiet
- No PEEP
- TV Precision
- System controlled leak and compliance compensation
- Fresh gas Decoupling
Disadvantages of Piston Ventilator
- Loss of visibililty
- Quiet
- Cant easily accomdate non-rebreathing systems
- Potential for NEEP
- Potential to dilute gas concentration with room air
Fresh Gas Decoupling
- Piston vent tidal volume accuracy improved
- Fresh gas flow on Inspiration is diverted to manual breathing bag
- remains in circuit and not added to delivered tidal volume
- Ensures set and delivered tidal volumes are equal
What happens if there’s insufficient evacuation flow from scavenger?
Positive pressure relief valve opens and waste gas escapes from system to OR
What levels are the waste anesthetic gas in an OR with scavenging?
Halothane: 1 ppm
N2O: 60 ppm
Avoiding Waste Gas Exposure
- Good mask fit
- Avoid unscavenable techniques
- Prevent flow from system to room air
- only turn on gas after mask is on face, and turn off before suctioning
- Washout anesthetics at the end
- Dont spill liquid
- Use low flows
- Used cuff ETT when possible
- Check machine for leaks
- Disconnect nitrous oxide pipeline at day’s end
- Total IV anesthesia
Function of inspiration and expiration check valves
Permits unidirectional gas flow to and from patient
Function of the Pop off valve
Adjust the limit of pressure in patient circuit and rebreathing bag
What is the pressure limit in the breathing circuit?
12.5 kPa (125 cm water)
What stops the delivery of all other gases when the oxygen supply is diminished?
Fail-Safe Valve
Why disconnect quick connect fitting when there is an oxygen pipeline failure?
Cross-Contamination - loss of pipeline failure is followed by flow of contaminated content to oxygen pipeline
Why will the pipeline pressure override the cylinder pressure?
Pipeline pressure is set at 50 PSI and cylinder regulator is set at 45 PSI
Oxygen cylinder PIN position
2-5
Nitrous oxide cylinder PIN position
3-5
Air cylinder PIN Position
1-5
What are cylinders made of and which can go into MRI?
Quarter-inch thick steel. Only nonferrous (aluminum) cylinders can go into MRI
Formula for calculating remaining volume
V1/P1 = V2/P2
What are the different content of gases in compressed air?
Oxygen - 21%
Nitrogen - 78%
Argon - 1%
Minute amount of CO2
What happens when you remove N2O at at least 4 L/min
Frost/Freezing of the valve
Where is the problem if high circuit pressure is sustained during manual ventilation
Scavenger
- Obstruction
- Failed relief valve
- Disconnect scavenger and use ambu bag
What is the compliance measurement used to calculate?
How much additional volume must be added to each breath to deliver set volume
How much O2 is delivered when using O2 flush
35-75L/min
Where does gas flow from through the Soda Lime
Directly from the common gas outlet and from the rebreathing bag
DISS, Location, Function
- Diameter Index Safety System
- Back of AGM
- Gas Hoses
- Ball and Spring Valve
- Free Floating Valve
What type of cylinders do Single Hanger Yokes fit into?
E Cylinders
What type of valve is the Single Hanger Yoke?
Free floating valve - opens with pressure and closes with pressure
In a dual hanger yoke system what prevents one cylinder from emptying into the other?
The FREE FLOATING VALVE
