Anesthesia Machines
rev Jan 11 dmcmahon
First actual use of ether - March 1842,by Dr Crawford Long in Georgia.
First public use of ether - Oct 1846, by Dr Morton
Diethyl ether -- first inhaled anesthetic
Chloroform used for Queen Victoriain childbirth, 1847.
Anesthesia can be –> Local, often Local with Monitoring (“LMAC”)
> Regional
- spinal
- epidural
- nerve block specific
> General, which includes: - lack of awareness
- lack of sensation
- amnesia
- uneventful post-op recovery
- Usually obtained by inhaled agent thru a tracheal tube,
or can be by a drug infused IV (eg propofol)
Inhaled Anesthetic Agents –
> Many are ethers (general formula R – O – R’)
> First was diethyl ether
> First vaporizer-delivered agent was halothane (1960’s)
> Followed by several others (1970’s – 1990’s)
> Vast majority of general anesthetics now given with
- isoflurane (“Forane”, Zeneca Labs)
- sevoflurane (“Ultane”, Abbott Labs & Baxter)
Propofol - first injectable non-opioid general anesthetic
GE / Datex / Ohmeda:
Aisys
Aespire 100
North American Drager:
Fabius GS
Apollo
Drager:
Fabius MRI
The bare essentials of anesthesia delivery:
> Oxygen-carrying gas mixture
- could be room air
> Anesthetic agent vapor
- metered-out very precisely
> Ability to create positive airway pressure
- necessary for respiratory exchange
Three machine hazards and their solutions:
1: Oxygen supply failure, leaving anoxic gas supply
- the “Fail-Safe Valve” or Oxygen Failure Protection Device (OFPD)
Shuts off all gas flows if the oxygen fails
2: Hypoxic or anoxic mixtures from the flowmeters
- the “Hypoxic Guard” or Oxygen Ratio Monitor-Controller (ORMC)
Assures that at least 25% oxygen is delivered
3: More than one agent vaporizer turned-on
- vaporizer lock-out mechanism; Allows only one vaporizer to be enabled
Pressure Regulator
Basic manometer (pressure meter)
Bourdon tube
Gas Supply Check Valve
Gas Pressure-Actuated Power Switch
Flowmeter Needle Valve
Flowmeter Tubes in Series
Digital flowmeters - Drager Fabius GS
Typical screen - Drager Fabius GS
O2 failure shutoff valve (“FailSafe Valve”)
Oxygen ratio controller
Basic Anesthetic Vaporizer
Basic Anesthetic Vaporizer
Delivering the volatile anesthetic –
Modern Vaporizer, Closed
Modern Vaporizer, Open
Vaporizer Lock-Out Mechanism(Drager Co.)
Vaporizer Lock-Out Mechanism(Drager Co.)
Essential Monitors of the Anesthesia Machine:
> Delivered oxygen percentage
> Airway pressure
> Airway gas flow
(These monitor the machine, not the patient)
CO2 Absorber Assembly - schematic
From machine
Patient’s lungs
CO2 absorbent:
> Chemically removes CO2 from the patient’s respiratory gases.
> Consists of NaOH, KOH, and Ca(OH)2, which react with CO2 to form carbonates and water in two separate reactions.
> Includes a dye which changes to purple when the CO2-absorbing capacity is exhausted.
> Major brands:
SodaSorb©, Baralyme©, Amsorb©
CO2 Absorber Assembly - Drager Co
CO2 Absorber Assembly w/ VentilatorDrager Co.
Aneroid Manometer for Airway Pressure
Adjustable Pressure Limiting (APL) Valve
Manual Ventilation:
Manual Ventilation:
Mechanical Ventilation:
Mechanical Ventilation:
Scavenging of
Waste Anesthesia Gas (WAG) :
> Required by NIOSH / OSHA
> NIOSH allows < 25 ppm of N2O (8-hour average)
> Gases must be actively drawn out of the local air
> Scavenging is integrated into the anesthesia machine
> Testing should be done at least annually
> Can be done with dosimeters from a commercial lab,
or with an IR detector made for air testing.
Scavenging Relief Valve
Virtual Anesthesia Machine: http://vam.anest.ufl.edu
> Univ of Florida, Dept of Anesthesiology
> From the Home Page, click on the Simulation & Workbook tab
> Requires one-time free registration (Annual fee for educators’ version)
March 2009: APSF Newsletter
Most common troubleshooting issues:
> Leaks in the absorber circuit and/or patient circuit
> Inadequate volume delivered from ventilator
> Water accumulated in ventilator tubing
> Flow meter inaccuracy or failure
Be pro-active:Get the owner’s book out and know the troubleshooting tables.
Know how to do a pre-op machine checkout.
Get factory service training
> North American Drager
> GE-Datex-Ohmeda
Minor Players:
Major Players in Anesthesia Machines:
> Spacelabs (Blease from the UK)> DRE, Oceanic (compact types)
Samurai
Origami
Fuji-Maximus
K Takaoka anesthesia machines –
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