Spotlight Case October 2004

Thin Air

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Source and Credits• This presentation is based on the Oct. 2004

AHRQ WebM&M 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 WebM&M: 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 air—not 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 System”—each 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 lock—prevents 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