Spotlight Case October 2004

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Spotlight Case October 2004

• Thin Air

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Source and Credits

• This presentation is based on the Oct. 2004 AHRQ
  WebMM Spotlight Case in Medicine
• See the full article at http//webmm.ahrq.gov
• CME credit is available through the Web site
• Commentary by David M. Gaba, MD, Stanford
  University School of Medicine
• Editor, AHRQ WebMM Robert Wachter, MD
• Spotlight Editor Tracy Minichiello, MD
• Managing Editor Erin Hartman, MS

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Objectives

• At the conclusion of this educational activity,
  participants should be able to
• Identify the gas-specific non-interchangeable
  connectors used for bulk gas supply outlets in
  hospitals
• Define forcing function, both in engineered
  safety devices and in human procedures
• Review strategies to prevent delivery of wrong
  gas to hospitalized patients

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Case Thin Air

• A 73-year-old woman was admitted with fever and
  back pain. She was diagnosed with pyelonephritis.
  The morning after admission, she became
  hypotensive and short of breath. Her oxygen
  saturations were 70. She was placed on high-flow
  oxygen with little benefit. A chest x-ray showed
  diffuse pulmonary infiltrates consistent with
  acute respiratory distress syndrome (ARDS).

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Case (cont.) Thin Air

• The patient was intubated for hypoxemic
  respiratory failure. Shortly thereafter, the
  respiratory therapist arrived and noticed that
  the patient was being treated with compressed
  airnot oxygen.

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Oxygen and Air Flowmeters With Correct Adapters
Green, thin adapter on green O2 flowmeter
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Air and Oxygen Flowmeters With Adapters Swapped
Green adapter placed incorrectly on yellow
compressed air flowmeter
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What Went Wrong in This Case

• Tubing connected to green Christmas tree adapter
  which was inadvertently connected to the air port
  instead of oxygen port
• OR
• Tubing connected to yellow Christmas tree
  adapter (instead of green Christmas tree adapter)
  which was connected to air port

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The Scope of the Problem

• The frequency of tubing/flowmeter swaps is
  unknown, but it is often enough that a Patient
  Safety Advisory was issued by the Veterans Health
  Administration Warning System in March 2002
• Probably more common that oxygen tubing becomes
  disconnected from a correct flowmeter during a
  resuscitation

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Case (cont.) Thin Air

• The patient was transferred to intensive care
  and died the next day of overwhelming sepsis and
  systemic inflammatory response syndrome (SIRS).

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Human Factors Engineering Approach

• Rely on improving design of artifacts in the
  world rather than relying on instructions,
  training, labels, or the usual admonition to be
  more careful
• Forcing functions
• Engineered safety devices
• Procedural forcing functions

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Engineered Safety Devices

• Engineered Safety Device a physical arrangement
  that precludes the wrong action
• Examples include
• Diameter Index Safety System (DISS)physically
  impossible to insert oxygen hose or flowmeter
  into any other port, or to attach anything
  inappropriate to oxygen port

Norman D. The psychology of everyday things. 1988.
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Engineered Safety Devices (cont.)

• Pin Index Systemeach cylinder has specific
  pattern of holes into which matching pins from
  appropriate regulator must fit
• Oxygen proportion limiting control system
  physically prevents selecting an oxygen
  concentration of less than 25
• Mechanical vaporizer lockprevents activating
  more than one vaporizer delivering a volatile
  anesthetic gas at a time

Petty C. The anesthesia machine. 1987 In
Ehrenwerth J, et al, eds. Anesthesia equipment.
1993 In Miller RD, ed. Anesthesia. 2000.
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Diameter Index Safety System (DISS)
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Yet Mistakes Still Happen

• The threaded output of the flowmeter is one size
  fits all and fits yellow, green, and clear
  color-coded Christmas tree adapters
• Oxygen tubing fits non-oxygen flowmeters

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Implementing Engineered Safety Devices

• Extend the diameter index system to flowmeter
  output port or have Christmas tree adapters
  molded into device
• Create gas-specific non-interchangeable fitting
  for low pressure oxygen tubing

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Procedural Forcing Functions

• Standard procedures call for personnel to verify
  certain conditions before proceeding
• Verification of blood products prior to
  transfusion
• Timeout prior to surgical incision to decrease
  incidence of wrong site surgery
• Procedural forcing functions limited due to
  psychological factors such as haste, complacency,
  and social shirking

Heimann C. Acceptable risks politics, policy,
and risky technologies. 1997.
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Take-Home Points

• Consider strategies to reduce the likelihood of
  connecting oxygen tubing to the wrong gas
• Eliminate air flowmeters
• Permanently fix Christmas tree adapters to the
  correct flowmeter
• Use clear Christmas tree adapters rather than
  color-coded ones that way, the adapter conveys
  no information and forces the user to look at the
  flowmeter to identify the gas

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Take-Home Points

• Consider the possibility that the wrong gas (or
  no gas) is being administered when a patient does
  not respond to treatment with supplemental
  oxygen double check the flowmeter and tubing
  connections
• Implement engineered safety devices when possible
  rather than procedural forcing functions