Renaissance in Anesthesia Machine Safety

The Modern Anesthesia Machine (Workstation) & Anesthesia Delivery Unit (ADU): Improved Safety Features

Charles G. McCombs, Jr. CRNA, BSA

Morton’s Ether Inhaler (1846)

Wm. T. G. Morton

Civil War Era Anesthesia

Chisholm Chloroform Inhaler Ether Cone

1860’s

Pioneers1903 – Charles K. Teter, DDS Jay Heidbrink DDS Samuel S. White DDS 1917 - Dr. Henry Edmund Gaskin Boyle

First Anesthesia Machine (Boyle Machine)

The Teter Anesthesia Machine (1903)

The Boyle Machine (1917)

Ohio Medical (1966)

No. American Drager 2A (c1986)

1979 American National Standards Institute (ANSI)

ANSI Z-79 Committee Machine Standards

Failsafe Valve & Alarm

Vaporizer Lockout

DISS Connections

PISS Connections

Active Regulators

Legible & Visible Gauges

1988 American Society For Testing and Materials (ASTM)

ASTM F-29 Committee

ASTM F1850-00

Preuse Checkout Procedures

Proportioning Device

Concentration Calibrated Vaporizers

Integral O2 Analyzer

Master Switch Enabled Alarms

Hierarchical Alarm Prioritization

The Modern Anesthesia Workstation

No. American DragerJulian

Datex Ohmeda (GE Health Care)

Aestiva 5

The Modern Anesthesia Workstation

GE Health CareADU/5

ADU/5 Aladin Cassette Vaporizers

“Brain Damage & Death Related to Anesthesia Machines” (Caplan, 1997)

RA Caplan (1997) - Study of 3791 Closed Anesthesia Claims (1962 – 1991) 72 claims related gas delivery system Claim frequency decreased from 2.2% to

1.2% from 1985 – 1991 Pure equipment failures were rare Rate of equipment misuse, 3 x higher than

pure failures 76% of claims – Death or Brain Damage 78% of injuries could have been prevented

by better monitoring Caplan,RA, Visica, MF, Posner, KL, Cheney, FW Adverse anesthetic outcomes arising from gas delivery equipment; a close claims analysis. Anesthesiology 1997;87:741-8

Specific Damaging Events (Caplan, 1997)

Breathing Circuit (39%) - The #1 Culprit Caused 70% of the incidence of death & Brain

Damage Most Frequent Circuit Event – Disconnects or

misconnects leading to hypoventilation or barotrauma

Vaporizers (21%) Overdose or awareness Gas analysis or cerebral monitoring may have

prevented

Ventilators (17%) Improper activation or excessive Vt /Inspiratory

pressure

Specific Damaging Events (Caplan, 1997)

High Pressure Gas Supplies (11%) – direct connection to respiratory system w/o proper decompression

Human Error – 3 times more common than failure of equipment Failure to precheck Unfamiliarity with equipment Lack of Vigilance Unauthorized repair or “jury rigging”

Caplan,RA, Visica, MF, Posner, KL, Cheney, FW Adverse anesthetic outcomes arising from gas delivery equipment; a close claims analysis. Anesthesiology 1997;87:741-8

Conventional Machines Modern Machines

North American Drager - Narkomed Series (2A, 2B, 3, 4, & GS)

Ohmeda - Modulus & Excel

Drager Medical – Fabius GS v1.3, Julian, Apollo, Narkomed 6400

Datex-Ohmeda – Aestiva/5 (assuming 7900 ventilator),

Anesthesia Delivery Unit (ADU) (assuming S/5 monitor system)

Conventional v.s. Modern Anesthesia Machines

Limitations of the Conventional Machine

Numerous External ConnectionsBarotrauma Protection (Manually Set

Pressure Limiters)Vaporizer RisksLack of Advanced Ventilator FeaturesInaccurate Delivery of Set Tidal Volumes (Vt)Manual Preuse Checkout ProceduresLack of Integrated Information SystemsPoor Low-Flow AdaptationCompressed Gas Consumption

The Modern Machine Addresses Limitations

Reduced External ConnectionsInternal Modular

Design (Aestiva/5) or Manifold Components (Julian)

Electronically Controlled PEEP and Open Reservoir Scavenging

Electronic Vaporizer Cassettes

ADU, Aladin Cassettes (GE Healthcare)

Electronically Control & Measure Vaporization

Eliminates need for multiple vaporizers

Color Coded, magnetically labeled

Agent delivery reported to Information Management System (IMS).

Overfill protection

Automatically leak tested

Check valve protection for bypass circuit

Piston Driven Ventilators (Drager Medical)Fabius GS Narkomed 6400 Divan

Modern Ventilators“Conventional” Dual Circuit, Pneumatic

Drive 7900 “SmartVent” (GE Healthcare)Single Circuit Electronic Piston Drive

Divan or Fabius GS (Drager Medical)Allows Flexibility in ventilation

Pressure Control Ventilation (PCV)Volume Control Ventilation (VCV)Pressure Support Ventilation (PSV)Synchronized Intermittent Mandatory

Ventilation (SIMV-Vol & SIMV-PC)

Modern VentilatorsMethods to Assure Accuracy in Delivery of

set Tidal Volumes (Vt)Fresh Gas Decoupling (FGD)Compliance Testing and CompensationLeak Testing/Measurement and ReportingLocation and Electronic Activation of PEEP Electronic Settings Reduce Operator ErrorOne-step activation of Control Mode Ventilation

(CMV)

Automated Checkout Procedures and Monitoring

User cannot Circumvent Multitude of Surveillance Alarms Critical Systems Checked

Computer Circuit Loops Flow Meters Pressure Sensors Piston Drive Gears Coordination /operation of Valves Compliance Compensation Fresh Gas Control Display of Ventilation & Airway

Pressures

Information Management Systems (IMS)

Integrated Systems exceed ASTM Standards

Integrated Physiological and Respiratory Monitoring Data

Digital Fresh Gas & Volatile Agent Flow Data (Inspired & Expired Concentration)

Data Exported to Anesthetic Record Data MAY be Exported to other

Demographic and Financial Records

New Machines; New ConcernsOperator Learning Curve - even less

understanding of machine functions)Over reliance on Technology – Are you sure it

will tell you all that fails?Dependence on Electricity - How does your

machine function in a power failure?Piston Ventilators – quiet, hidden – Will you

know if the piston fails to move?

New Machines; New ConcernsCan a machine have a clinically significant

failure after passing an automated checkout?The new machines still do not warn of oxygen

consumption from open cylinders if wall pressures drop

New Solutions to Old Problems Raises New Questions!!!