Anesthesia Equipment Flashcards
Functions of anesthesia machine
- Deliver O2 to patient
- Delivery anesthetic gas
- Assist in ventilation
- Remove exhaled CO2 from patient
Components of anesthetic machine
**divided into high and low pressure part
- Medical gas source
- Regulator
- Flowmeter
- Vaporizer
- Fresh gas outlet
- Breathing system
Flow in machine
- O2 tank
- Reduction of pressure (also includes pressure reducing valve
- Flows through flowmeter and vaporizer (picks up inhalation drug)
- Rebreathing or Non-rebreathing circuit
Oxygen
- compressed gas
-Either in: - E cylinder: 2200 psi, 700L (Half at 1100 psi, 350L)
- H cylinder (7000L)
**pipeline pressure is 50-60 psi
- Liquid O2 (very low -180 degrees)
Medical Air
-compressed medical air is formed by drawing ambient air into compressor
-considered clean (filtered and separators to remove water, oil, other impurities)
Oxygen concentrator
-Filters and extracts room air to produce oxygen for medical use
>Removes N2 and uses compressor to store O2 in pressure tank
-need electrical supply
-delivers up to 92-95% O2
-2 zeolite molecular sieves in parallel (retains N2, Argon, unwanted components)
-5-10L/min
Safety system
-Colour coding (O2= white or green)
-Pin index safety: pins match with certain gas
-Diameter Index safety system for Connectors (H-cylinders): body, nut, stem system
Regulators
Convert variable high pressure to a constant working pressure (50-60psi)
- E tanks: 1 stage regulator on anesthetic machine (2200 down to 50-55 psi
- Pipeline supply: 2 stage regulators at O2 source
-Set to 50-55psi
Flow meters
Control rate of gas delivery to low pressure area (Fresh gas flow)
-specific to gas
-colour coded
-L/min
-operated by needle valve; precision instrument
-Ball (center) vs. bobbin (top))
Vaporizer
Vaporizes anesthetic agent and delivers at set concentrations
-agent specific
-temperatures compensated, and bi-metallic strip adjusts ratio
**Two streams: some gas enters, some continues. The gas that enters will eventually join back up.
Vaporizer safety
-colour coding (sevo=yellow, iso=purple)
-key indexed filler systems
-lock on dial
-do not overfill
-do not tip vaporizer
Anesthetic breathing systems
Deliver O2 and anesthetic gases to patient
-allows CO2 elimination
-allows ventilation of lungs
-different types based on CO2 removal
CO2 removal types
- non rebreathing: use high gas flow to flush out CO2
- rebreathing: use chemical rxn to remove CO2 with absorber
Reservoir bags
6-10 times tidal volume
-reservoir of gases during inspiration
-allows monitoring of resp movements
-ventilates lungs
Breathing tube/hose
-provides connection and reservoir for gases
-**Apparatus dead space: potential area for CO2 collection
Rebreathing system
-allow rebreathing and conservation of exhaled
-used on animals larger than 10kg
-CO2 removal is depends on passage of gases through CO2 absorber (chemical rxn)
-allow low/min flow of anesthesia
Advantages of rebreathing sys
-decreased use of volatile anesthetics
-improved temperature and humidity control
-reduced environmental pollution
Disadvantages of rebreathing sys
difficult to adjust anesthetic depth
Rebreathing sys components
-inspiratory one way valve and breathing tube
-y piece
-expiratory tube and one way valve
-reservoir bag
-CO2 absorber
Breathing tubes of rebreathing system
-flexible, low resistance between Y piece and one way
-corrugated to reduce obstruction
-increase resistance by adding length
10-30 ml/kg/min
**low: 4-10 ml/kg/min
F circuit
Co-axial system (inspiratory inside expiratory)
Less dead space! and helps with warming up gases!
Y piece
unites ET tube connector to inspiratory and expiratory breathing tubes
-contributes to dead space
-septum may be present to decrease dead space
Denitrogenization in rebreathing system
Needed for all rebreathing systems
-Air 21% O2, 79% N2
-body and machine equalize levels
-N2 moves down partial pressure gradient from body into breathing system (takes 20mins)
-High fresh gas flow used for first 20mins to flush N2 and to reduce risk of inhaling hypoxic mixtures
One way valves of rebreathing components
-prevents the rebreathing of exhaled gas
-enter below, raising disk
-allow gas to pass in one direction but does add resistance
**when increased resistance, harder for smaller animals
CO2 absorber
-contains chemical absorbent for removing CO2 from exhaled gases
*exothermic rxn , produces water
*pH increases = colour change!! white to Purple
Non rebreathing system
CO2 removal is dependent on fresh gas flow during expiratory pause
-150-300 ml/kg/min
Advantages to non rebreathing
-less resistance to breathing
-less mechanical dead space
-rapid manipulation of anesthetic depth
Disadvantages to non- rebreathing
-higher waste of both carrier gas
-high flow of dry cool gas (heat and humidity loss)
Failure to remove CO2
Non rebreathing sys:
-inadequate fresh gas flow
-kinked tube
-hidden tears or disconnections in coaxial systems
Rebreathing sys:
-stuck 1 way valve
-exhausted CO2 absorber in rebreathing system
Circuit pressure gage (Manometer)
-Corresponds with pressure generated in patient breathing circuit
-guide for positive pressure ventilation in lungs and leak tests
-not greater than 10-25 cm H2O
-highest number= peak inspiratory pressure reached
**also check animals chest expansion
Scavenging system
-conducts waste anesthetic gases away from workspace
>passive
-active
**pink coloured hoses
Adjustable pressure limiting valve
Allow excess gas within breathing system to be vented into a waste gas scavenging system
-always leave open during spontaneous breathing
-only closed during ventilation and leak test
*mechanical ventilation
O2 flush
Allows Oxygen to bypass flowmeters and vaporizers
-O2 delivered at high flow and pressure
-Used with circle systems to flush out anesthetic in emergency. and for leak tests
-Never use with non-rebreathing circuit attached to patient
Ventilators
Used to provide intermittent positive pressure ventilation
-person can also ventilate mechanically
When not to use ventilators?
-open thorax
-neuromuscular blockade (skeletal muscle paralysis)
