Modern Anesthesia Machines: What you should know

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Modern Anesthesia MachinesWhat you should know

• Michael A. Olympio, MD
• Professor of Anesthesiology
• Wake Forest University School of Medicine
• Winston-Salem, North Carolina

ASA 2003 Refresher Course Lecture 194
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Conflict of Interest StatementThis speaker has
received
Educational materials, assistance, and/or courses
from Datex-Ohmeda, Inc., Madison, WI Dräger
Medical, Inc., Teleford, PA Mercury Medical,
Clearwater, FL Siemens-Elema AB, Solna,
Sweden Honoraria from Datex-Ohmeda, Inc.
(totallt2,500) Anesthesia machines and/or
monitors on loan from Datex-Ohmeda, Inc.,
Madison, WI Dräger Medical, Inc., Teleford, PA
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Objectives

• Distinguish conventional vs. modern
• Recognize limitations and safety issues
• Explain how new features operate
• Compare representative machines
• Consider new concerns
• Do not describe every new machine

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Principles of Safety Engineering

• Monitor and warn
• Prevent or attenuate harm
• Provide backup devices for 1 failures
• Prevent misuse of the equipment
• Provide instruction, training, inspection

Schreiber P. Safety Guidelines for Anesthesia
Systems. Drager Medical, Inc. 1985 Eisenkraft JB.
A Commentary on Anesthesia Gas Delivery Equipment
and Adverse Outcomes. Anesthesiology
199787731-3.
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Machine Morbidity and Mortality

• Eichorn JH. (Anesthesiology 198970572-7)
• Hypoventilation in 7 of 11 accidents
• Monitoring could have prevented 100

• Caplan, et.al. (Anesthesiology
  199787741-8)
• Misuse 3-times more than equipment failure
• Monitoring could have prevented 78

• JCAHO. (Sentinel Event Alert 200225) Ventilator
  Deaths/Injury
• Healthcare Risk Control 200341-11 Critical
  Alarms

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Definitions of Conventional and Modern

• Conventional (no feedback modulation)
• Ohmeda
• Modulus series and Excel
• North American Dräger
• Narkomed and GS
• Modern (feedback modulation)
• Datex-Ohmeda
• Aestiva/5 (with 7900 ventilator)
• Anesthesia Delivery Unit (S/5)
• Dräger Medical
• Julian
• Narkomed 6400
• Fabius GS v1.3

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Ten LimitationsofConventional Machines
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1. Numerous External ConnectionsRealize the
consequences.
Cooper JB, et.al., Analysis of Major Equipment
Failures Anesthesiology 19846034-42

• Breathing circuit/ventilator 43/115
• Leaks, mis- or dis- connections most frequent
  critical incident (94/507)
• Human error and failure to check were most likely
  associated factors

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Minimal External ConnectionsConsider the
advantages.
Dräger Julian
Datex-Ohmeda Aestiva/5
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J. Clin Anesth 19891(6)452-6 Potential for
barotrauma or hypoventilation with the Drager
AV-E ventilator. Eisenkraft JB
Revised Dräger AV2
New Dräger Fabius GS
Anesth. Analg 2003 97492-3. Inadvertent
Positive End-Expiratory Pressure Caused by a
Malfunctioning Ventilator Relief Valve. Bourke
DL, Tolentino D
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2. Inaccurate Tidal Volume
Gas Analyzer
Respirometer
Settings
Compression
Leaks
Hose Compliance
Contributes to VT DONT FLUSH
Operating Principles of Narkomed Anesthesia
Systems 1998, Cicman et. al., Dräger Medical,
Telford, PA. With Permission.
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Magnitude of VT Discrepancy
VT400, R10, FGF1.8 l/min, IE12, PIP20 cmH2O

• System compliance (5ml/cm) x (20cm)
  100ml lost
• Hose compliance (2ml/cm) x (20cm)
  40ml lost
• Leaks/gas analyzer (4 3 ml/sec) x (2sec)
  14ml lost

• Compression 3 x 400ml
  12ml lost
• Fresh Gas Flow (30ml/sec) x (2sec)
  60ml gained
• Summation VT400-100-40-14-1260

Desired VT400ml Delivered VT294ml Reported
VT334ml
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Methods for Accurate Delivery

• Electronic flow measurement/control
• Compliance compensation
• Fresh gas decoupling
• Return sampled gas
• Single-step initiation of mechanical vent
• Aestiva/5
• S5/ADU

• Leak measurement
• Reported
• Never corrected
• Electronic settings
• Adjustment to flow sensor data
• Fabius GS v1.3
• Narkomed 6400

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Flow Sensor Technology Anemometer

• Constant temperature
• Variable current
• Thermal conductivity adjustment for Desflurane
• Low resistance to flow
• Not reverse flow
• Caution ignition source

Dräger Spirolog
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Fire in the Breathing Manifold

• Xylocaine pump spray (AstraZeneca, London, UK)
• Ethanol is explosive at 3.5-15 in AIR _at_ 363 C
• 100 Oxygen was in use
• Platinum wire 140-900 C
• Ceramic expiratory disc valve destroyed
• Flame of burning ethanol drawn backwards to ETT
• Instruction manual prohibited use with flammable
  agent

A Combustive Destruction of Expiration Valve in
an Anesthetic Circuit. Kanno TA, Aso C, Saito S,
Yoshikawa D, Goto F. Anesthesiology 200398577-9
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Flow Sensor Technology Ultrasound

• Flow alters time of flight
• Up or downstream
• Reverse flow detected
• Independent of gas mixture or density
• No moving parts
• Resolution /- 20ml

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Flow Sensor Technology Pitot tube
Datex-Ohmeda D-Lite Sensor

• Frontal v. back pressure
• Pressure differential proportional to (flow)2

• Directional flow
• Need density and viscosity corrections

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Flow Sensor Technology Variable Resistor

• Turbulent flow
• Pressure differential
• Flow is inversely proportional to the square root
  of density

• He ltlt O2, N2, N2O, CO2
• Determines direction
• Resolution /- 20ml

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Humidity Problems Resolved

• Tubing of nondistensible, narrow diameter
• Not humidity, but condensed water
• False positive Exp. Reverse Flow alarm
• Use HME instead of heated humidifiers
• Redesigned flow sensor

Ventilatory Failures with the Datex-Ohmeda 7900
SmartVent. Cantillo J, Domsky R, Gratz I,
Goldberg M. Anesthesiology 200296766-8. In
Reply Mitton M, Datex-Ohmeda, North America.
Anesthesiology 2002 96768. Ambietn O.R.
Temperatures and Datex-Ohmeda 7900 SmartVent
Malfunction. Blinder JL. Anesthesiology 2002
971645. In Reply Cantillo J, Gratz I, Domsky
R, Goldberg ME. Anesthesiology 2002 971645.
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Fresh Gas Flow SensorsPneumotachometer (Fleish)

• Measures energy loss through a resistor
• Pressure differential
• Laminar flow
• Only viscosity matters

• Independent of density
• Integrate flow vs time
• Known, constant gas
• Hagen-Poiseuille Law
• Heated and re-zeroed

Image from Raemer DB, Monitoring Ventilation, in
Anesthesia Equipment 1993 Mosby, Ehrenwerth and
Eisenkraft, Eds. With permission.
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Management of Fresh Gas Flow
Initiate Measure Report Backup
Aestiva/5 Needle valve Rotameter Visual
S/5 ADU Needle valve Fleish Digital Combined rotameter
Julian Electronic Fleish Digital None
Fabius GS Needle valve Fleish Digital Combined rotameter
Narkomed 6400 Needle Valve Rotameter Fleish Visual Digital
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S/5 ADU Electronic Gas Flow Display
Measured / Calculated gas flows, concentration
Desired concentration
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S/5 ADU Monitoring Display
All Measured
Mixed
Photo courtesy of Datex-Ohmeda, Inc., Madison,
WI., with permission.
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Failures of O2/N2O Flow Controls

• Broken chain (Ohmeda Link 25)
• freewheeling nitrous dial hypoxic mixture
• Faulty set screw (Ohmeda Link 25)
• turning on the oxygen dial caused the delivery of
  nitrous oxide only! (loose set screw)
• turning the oxygen dial dragged nitrous along
  (set screw too tight)
• Faulty stop pins (Narkomed)
• oxygen could not be turned on

Paine GF, Kochan JJ. Failure of the Chain-Link
Mechanism of the Ohmeda Excel 210 Anesthesia
Machine. Anesth Analg 2002 941365-76
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S/5 ADU O2/N2O Ratio Controller

• O2 and N2O flow measured
• Ratio is calculated
• N2O is limited by the proportional valve, if
  necessary
• N2O further limited by volatile
• 100 ml oxygen before N2O
• N2O cut-off if no O2 pressure

Diagram courtesy of Datex-Ohmeda, Inc., Madison,
WI., with permission.
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Julian Electronic FGF Control

• User sets FiO2 and 2nd gas
• User sets total flow

• Unit meters ratio
• Unit controls FGF valve

Diagram courtesy of Rob Clark, Dräger Medical,
Telford, PA., with permission.
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FGF Interruption Caused Vaporizer Malfunction

• Datex-Ohmeda D-Tec Plus desflurane vaporizer
• NOT the original Tec-6
• Dräger Julian Anesthesia Machine
  (VCV only, not PCV)
• No Output warning was accurate
• Proper response to alarms emphasized
• Software modified to prevent problem

With Technology Comes Responsibility
Intraoperative Failure of an Anesthetic
Vaporizer. Kimatian SJ. Anesthesiology 2002
961533-34. In Reply Feldman JM, Draeger
Medical, Inc. Anesthesiology 2002 961534. In
Reply Mitton M. Datex-Ohmeda, NA.
Anesthesiology 2002 961534-5.
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Reporting Gas Consumption
S/5 ADU calculates fresh gas and volatile agent
consumption.
Narkomed 6400 calculates fresh gas consumption.
Offers alarms.
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Compliance Compensation

• System compliance of 6 ml/cm Set VT 600ml
• First cycle Pplat 20 cm Total comp 30 ml/cm
• Next cycle adds 6 ml/cm x 20 cm 120 ml
• Thus 720 _at_ 24 Then 744 _at_ 24.8 749 _at_ 24.9

Dräger Julian Diagram courtesy of Dräger Medical,
Telford, PA.
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3. Excess Volume Delivery

• FRESH GAS DECOUPLING a mechanism which
  compensates for, or prevents fresh gas flow
  contribution to tidal volume
• Types offered
• Feedback adjustment Aestiva/5
• Pre-emptive adjustment S/5 ADU
• Intermittent FGF Julian
• FGF re-direction Narkomed 6400 Fabius GS

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Conventional mechanical ventilation.
(Representing Dräger Narkomed AV2)
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Servo-controlled volume ventilation Electronic
PEEP.
(Representing Datex-Ohmeda Aestiva/5)
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Decending bellows and fresh gas
decoupling Intermittent fresh gas
flow. Compliance compensation.
FIGURE 13
(Representing Dräger Julian)
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Fresh gas distal to I-valve preemptive
decoupling. Compliance compensation.
FIGURE 5
Representing Datex-Ohmeda S/5 ADU.
Higuchi H, et. Al. Carbon Dioxide Absorption
Capacity. Anesth Analg 200193221-5.
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Addition of a piston ventilator Relocation of
the reservoir bag.
FIGURE 7
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Fresh gas decoupled through reservoir bag Piston
ventilation. Exhalation mode.
FIGURE 9
A
M/S-E
(Representing Dräger Narkomed 6400)
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FIGURE 11
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Clamped Fabius GS PEEP/Pmax
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Advantages of a Piston Ventilator

• No unintentional PEEP
• Non-compliant
• top dead center in VCV
• Universal size
• Mechanical precision
• 10 ml x 80 bpm
• No gas consumption
• Isolated or exposed to patient gas

Narkomed 6400 Divan Ventilator Bellows
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PCV Comparisons for Infant ExtremesNAD 6000 v.
Aestiva 3000 v. Servo 900C
PCV-30/60 PEEP-0/10/15 I/E-13/11, R-10/20/40
C1-3ml/cm (severe)

• Aestiva lowest Vt (?P), flows most accurate set
  P and PEEP (above mandatory)
• NAD highest flow most accurate Vt measurement
  (13, after adjustment)
• Servo pressure overshoot

Stayer SA, et. al. Anesth Analg 2000911145-50
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VCV Comparisons in InfantsNAD 6000 v. Servo 900C
SET Vt 21 RR 25 PEEP 3.6 IE 12

• Randomized crossover in 20 infants lt5kg
• NAD improved ventilation, higher flow
• pCO2 43 v. 47 mmHg
• ETCO2 34 v. 37 mmHg
• Vt (actual) 12.9 v. 11.3 ml
• Vt (reported) 20.0 v. 19.0 ml
• NAD higher MAP
• MAP 9.7 v. 8.6 cmH2O

Stayer SA, et. al. Anesth Analg 20019276-9
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4. Excess Airway Pressure

• Location of pressure sensor
• Inverse ratio ventilation (IRV)
• APL valves
• Pressure controlled ventilation
• Electronically controlled PEEP
• Open scavenger systems (without valves)
• Preset/electronic inspiratory pressure limiters
• Protection from O2 flush during CMV

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Spirometry

• Pressure/Volume Flow/Volume Loops
• Compliance
• Leaks
• Obstructions
• PEEP
• Resistance
• Trending

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5. Advanced Ventilation Features
ACTUAL patient values
(Aestiva/5)
MAP Increased by IRV
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Same patient. ACTUAL values
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Inspiratory Flow Adjustment in PCV
Is selection of Inspiratory Rise consistent
with PCV? Default to Fast in the USA, Medium in
Europe.
Courtesy of Datex-Ohmeda, Inc., Madison, WI.,
with permission.
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Limitations of Mechanical PEEP

• Mechanical/magnetic system
• Several moving parts
• Susceptible to friction
• PEEP adjustment monitored only during exhalation
• Takes time to adjust

Operating Principles of Narkomed Anesthesia
Systems. Second Edition, 1998. Cicman, et. al.,
eds., North American Drager, Telford, PA., with
permission.
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Conventional Variable Resistor APL Valve
Operating Principles of Narkomed Anesthesia
Systems. Second Edition, 1998. Cicman, et. al.,
eds., North American Drager, Telford, PA., with
permission.
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CPAP During Spontaneous Ventilation
Circuit pressure is directly related to flow,
because APL is a resistor. E I x R
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Modern Dräger APL valves are regulators.
They have an instantaneous pressure-release
feature. (Datex-Ohmeda APL Valves are also
regulators)
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Clinician distracted.

• Manual ventilation
• APL is closed
• Quick-release indicated!

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Without a doubt the most neglected safety device
of the anesthesia machine is the scavenger.
Petty C. Scavenger is Often a Neglected Safety
Device. APSF Newsletter Fall 1992 p.28
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Automation of Pressure Limiters
Operating Principles of Narkomed Anesthesia
Systems, 1998. Cicman, et. al., North American
Drager, Telford, PA. With Permission.
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Protection From O2 Flush During CMV

• Pressure limited
• Narkomed AV2
• Julian _at_ P-max

• Inspiratory abort
• Aestiva/5 _at_ P-limit
• S/5 ADU _at_ P-release

True decoupling Fabius GS, Narkomed 6400
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SIMV (S/5 ADU)
Courtesy of Datex-Ohmeda, Inc., Madison, WI.,
with permission.
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Mechanical Ventilation Comparisons
Minimum Volume Frequency Range Pmax (Drive) PEEP Range IE ratio Range
Aestiva/5 20 4-100 60 30 4-30 18 21
Narkomed 6400 10 3-80 70 2-20 15 51
Julian 50 6-60 70 0-20 14 21
Fabius GS 20 4-60 70 0-20 14 - 41
S/5 ADU 20 2-60 40 20 2-20 14.5 21
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6. Consumption of Compressed Gas

• Metered gas volume
• All Datex-Ohmeda Julian
• Additional drive gas flow
• Exhalation valve/PEEP Aestiva
• Inspiratory pause Narkomed (conventional)
• Venturi entrainment volume
• Narkomed (conventional)
• No gas consumption
• Fabius GS piston
• Divan piston (minimal membrane gas)

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Line Pressure Variations
Aestiva ADU Julian Fabius 6400
Oxygen Regulator 100 psi (some) Electronic Leave open
Failsafe On Air No No No No Yes
Propor- tionator Elec-tronic Electronic Same as f/s Pneumatic Same as f/s
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7. Low Flow Capability

• Smaller circuit volumes (2.5 v. 6 liters)
• Less circuit leakage (35 v. 300 ml/min)
• Return of sampled gas to circuit
• Heated circuit manifold
• Fresh gas decoupling
• Subatmospheric pressure prevention
• Piston relief valve
• Ventilator abort
• Scavenger system modifications

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Compact Breathing Manifolds

• Fewer connections
• Very tight, no leaks
• Small volume
• Incorporates all valves
• Heated metal
• Internal connections

Dräger Narkomed 6400
Photo courtesy of Dräger Medical Inc., Telford,
PA.
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8. Problems with Anesthetic Vaporizers

• Crossfilling
• Overfilling
• Underfilling
• Calibrating

• Locking
• Tilting
• Leaking
• Indicating

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Incomplete Protection Against Crossfilling
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Incomplete Protection Against Tilting
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Electronic VaporizationDatex-Ohmeda AS/3 ADU
Aladin Cassette
Photo courtesy of the Datex-Ohmeda Corporation,
Madison, WI.
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Aladin Electronic Vaporizer

• Measures bypass
• Measures output
• Adds it together
• Reports total flow
• Regulates agent proportion valve
• Feedback to 3 CPUs
• To regulate nitrous
• To adjust vent drive gas
• To calculate FiO2
• Minimum 200 ml FGF

Diagram courtesy of the Datex-Ohmeda Corporation,
Madison, WI, with permission.
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Overfill Protection with Aladin

• Key-filled
• Within 7 of level
• Air outflow into bottle ceases when full
• Excess liquid will close liquid flow prevention
  valve
• Then, vapor output ceases, and alarm sounds
• Dumps liquid to scavenger

Diagram courtesy of the Datex-Ohmeda Corporation,
Madison, WI, with permission.
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The ADU Vaporizing Unit A New VaporizerHendrickx
JFA, et. al. Anesth Analg 2001 93391-5

• High FGF all outputs decreased
• Inadequate heat transfer? Duration significant.
• Desflurane most pronounced
• Carrier gas variable effects because
• Viscosity N2O lt O2 (resistor effects) (Anesth
  Analg 199479548-52)
• Solubility N2O gt O2 (absorption effects) (Anesth
  Analg 19866588-90)
• Effects not overcome despite flow
  measurement/algorithms
• Dial settings
• Higher setting lower output
• Agent
• Changed the effects of carrier gas, dial setting
• Perhaps related to amount of liquid vaporized

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Unique Aberrations Without Electricity
Datex-Ohmeda ADU
Dräger Julian

• No volatile agent
• No nitrous oxide

• Must actuate safety oxygen
• No nitrous oxide
• No air
• Cant see FGF

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9. Machine Checkout Procedures

• Manual ventilation bag !!!
• Software checks
• Interactive components of automated test
• Calibration of sensors
• Leaks and Compliance
• Automated valve functions
• Ventilator or piston excursion and compression
• Compressed gas measurement (Julian, ADU)

Cicero EM ECRI Testing. Health Devices January
1998
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Detection by Automated Checkout
Olympio MA, et.al. Instructional Review Improves
Performance of Anesthesia Apparatus Checkout
Procedures. Anesth Analg 199683618-22.
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Draeger Narkomed 6000 Poses Patient Safety Risks
Gross JB. Anesthesiology 2001 95567. In Reply
Feldman JM, Draeger Medical, Inc. Anesthesiology
2001 95567-8.

• Machine must be used in ON position
• Pneumatic (NOT electrical) systems enable manual
  ventilation
• Manual ventilation not possible during self test
• Cancel self test (standby key) to enable
• Leave machine ON for automatic standby
• Ventilator override is NOT intended to be used
  to bypass the start-up process

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10. Communication with AIMS

• Fully integrated systems can export data more
  efficiently
• Combined hemodynamic, volume, pressure, gas, and
  metabolic outputs
• Reporting of digital FGF
• Automatically included on record
• Reporting of volatile agent consumption
• Pharmacy billing
• Conservation of resources

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Summary of New and Potentially Protective Features

• Fewer user-accessible connections
• More accurate tidal volume delivery
• Prevention of excess volume delivery
• Limitation of excess airway pressure
• Advanced ventilation features
• Lower fresh gas consumption
• Low flow enhancements
• New vaporizer technologies
• Automated checkout systems
• Enhanced communication with AIMS
• Sophisticated alarms (not discussed)

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Educational Programs

• The Virtual Anesthesia Machine
• Anesthesia Patient Safety Foundation
• Sem Lampotang, Ph.D., Project Coordinator
• http//www.anest.ufl.edu/eduweb/vam/
• The Dräger Fabius GS
• Dräger Medical, Inc.
• http//www.simanest.org/
• Explore! The Anesthesia System. Aestiva/5
• Datex-Ohmeda, Inc.

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www.simanest.org