Troubleshooting

Gas Machines and Monitors

Robert D. Elliott, MD
Ottawa Hospital - General Site and University of Ottawa

Objectives:

  1. To put in perspective the role of equipment faults and misuse in causing critical incidents.
  2. To develop a logical preoperative checkout method for anaesthetic apparatus and to review possible faults which might be discovered.
  3. To develop a logical approach to solving intraoperative equipment problems.

Link to: Anesthesia Apparatus Checkout Procedure

Equipment Failure vs. Human Error

The anaesthetic literature is replete with anecdotal descriptions of equipment mishaps and failures, many of which have resulted in patient injury. Historically, anaesthetic machines were often a cobbled-together piece of piping and canisters, waiting for accidents to happen. Much has been done in the past 20 years to standardize and implement safety measures. The challenge today remains, however, even with the introduction of computerization. The truth is that the apparatus has become more complex than ever, despite the sophisticated monitoring and alarm sensors.

The ground-breaking work by Cooper1,2 and associates in the early 1980's analyzed the etiology of critical incidents. The dominant factor was human error (82%) while overt equipment failure accounted for just 14% of the incidents. However, 22% of the instances of human error involved anaesthesia machine use in some way and another 11% were related to breathing circuit and ventilation. When all associated factors were examined in detail, inadequate familiarity with equipment/device and failure to perform a normal check represented 14% of the total. With respect to primary causes of negative outcome, equipment failure by itself accounted for only 4% while 90% was attributed to human error .

The work of Cooper et al has been supported by other investigators in Australia3, Great Britain and Canada4. The conclusion concerning adverse events during anaesthesia is that, "Human failure [is] more frequently responsible than equipment failure, and failure to perform a normal check [is] the factor most frequently associated."5

Types of Equipment Problems

The following table summarizes data collected by the ECRI regarding the role of equipment in anaesthesia incidents. In analyzing these data, Spooner and Kirby6 suggest once again that the mishaps were often a combination of occasional overt device failure along with a large component of various types of human error.

Elements of Incident

%

Part of anaesthesia system implicated
  • Scavenging system
  • Vaporizer
  • Breathing circuit
  • Absorber/pop-off/directional valve
  • Ventilator
  • Flow control and meter
  • Gas system/fail-safe/flush valve

29
21
18
8
8
8
7

Type of problem discussed
  • Failure to function properly
  • Inadequacy or lack of component
  • Leaks and disconnects
  • Improper use
  • Misassembly
  • Sepsis

31
30
17
12
11
1

Resulting Hazard
  • Hypoxia
  • Pollution of operating room
  • Arrhythmia or cardiac arrest
  • Barotrauma
  • Lightened anaesthesia
  • Infection
  • Explosion

34
27
17
16
6
1
1

Adapted from Spooner RB, Kirby RR: Int Anesth Clin 22(2):133-147, 1984

 

How Well are Equipment Faults Discovered or Recognized?

In the early 1980's, 190 attendees at a major anaesthesia meeting were invited to identify deliberate faults in a standard gas machine within 10 minutes.7 Of the five intentionally created faults, the average discovered was only 2.2; only 3.4% found all five and 7.3% of participants found none. The five faults were as follows:

  1. Discs removed from both inspiratory and expiratory unidirectional valves
  2. Pins removed from Pin Index which allowed a switch of nitrous oxide and oxygen cylinders
  3. Oxygen-failure shut-off valve was bypassed so that nitrous oxide continued to flow when oxygen source pressure fell to zero
  4. Cyclopropane and oxygen flowmeter tubes interchanged, reducing oxygen flow to 10% of indicated
  5. Halothane vaporizer filled with methoxyflurane


Checklists for ensuring proper gas machine function prior to the start of an anaesthetic have been advocated by many groups, including the CAS, the ASA and the APSF (American Patient Safety Foundation). In 1986, the US FDA along with the ASA introduced a generic apparatus checklist. To assess the value of the FDA checklist, March and Crowley8 rigged machines with four faults which should have been detected if the FDA checklist was used properly. Study participants were then instructed to use their own method of machine checkout and then were given the FDA checklist to use. No attempt was made to instruct the participants on use of the FDA checklist. Results of the study revealed that the practitioners' own checkout found the four faults only 25.8% of the time and using the FDA checklist improved performance to only 29.9%! Clearly, a checklist can improve patient safety only if it is used knowledgeably.

The 1986 FDA checklist is extensive and, if followed religiously, the full first-of-the-day procedure took almost 25 minutes and subsequent before-each-case check took 6 to 8 minutes. Although a good teaching tool, it was felt that the checklist was too extensive to be practical. Informal studies showed that the checklist was not widely adopted or utilized. In fact, a 1990 FDA study9 of 125 hospitals showed that although 77% had some sort of checkout procedure mandated, only about 27% were actually using it daily.

In 1993 the FDA published a revised version of the checklist to attempt to simplify matters. It is unknown whether this has been widely adopted or not and whether actual daily use has increased. I would think that the situation has changed very little.

The problem is that a busy practitioner is not motivated to spend more than 8 to 10 minutes to check out the anaesthetic apparatus at the beginning of each day. The challenge is to show that a very comprehensive check is possible in that time frame if it is logical, organized and sequential. In addition, the practitioner must know what faults might be discovered at each step of the checklist and to be able to recognize them.

The following is a composite checklist, incorporating the 1993 FDA checklist with additions from the 1986 checklist and some modifications based on a literature search. The procedure requires practice and my hope is to develop a computer simulation which allows anaesthetists to hone their fault-finding skills in a practical and fun manner.

Link to: Anesthesia Apparatus Checkout Procedure

References

  1. Cooper JB, Newbower RS, Kitz RJ: An analysis of major errors and equipment failures in anesthesia management: considerations for prevention and detection. Anesthesiology 60:34-42, 1984
  2. Cooper JB, Newbower RS, Long CD, et al: Preventable anesthesia mishaps: a study of human factors. Anesthesiology 49:399-406, 1978
  3. Webb RK, et al: Equipment Failure: an analysis of 2000 incident reports. Anaesth Int Care 21:???-???, 1993
  4. Webb RK, Davies JM: Editorial. Adverse events in anaesthesia: the role of equipment. Can J Anaesth 40:987-992, 1993
  5. Craig J, Wilson ME: A survey of anaesthetic misadventures. Anaesthesia 36:933-936, 1981
  6. Spooner RB, Kirby RR: Equipment-related anesthetic mishaps. In Pierce EC, Cooper JB editors: Analysis of Anesthetic Mishaps Int Anesth Clin 22(2):133-147, 1984
  7. Buffington CW, Ramanathan S, Turndorf H: Detection of anesthesia machine faults, Anesth Analg 63:79-82, 1984
  8. March MG, Crowley JJ: An evaluation of anesthesiologists' present checkout methods and a test of the validity of the FDA checklist for use by anesthesiologists. Anesthesiology 73:A1020, 1990 (abstract)
  9. FDA Medical Devices Bulletin. 7:1-2, 1990 - cited by Eichhorn JH: Ch. 22 - Anesthesia Equipment: Checkout and Quality Assurance. In Eichhorn JH, Eisenkraft JB, editors: Anesthesia Equipment.