esctaic 20051 evaluation of graphical symbols used in icu comprehension among users in germany and...

FachhochschuleMünster University of

Applied SciencesCenter for Ergonomics and Usability Engineering

Z F ECenter for Ergonomics and Usability Engineering

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1ESCTAIC 2005

Evaluation of Graphical Symbols Used in ICU

Comprehension among Users in Germany and in China

Long Liu, Uvo Hoelscher Muenster University of Applied Sciences




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Muenster University of Applied Sciences

10.000 students 12 faculties Faculty of Engineering Physics

– Biomedical Engineering Group

– Centre of Ergonomics and Process Design in Healthcare

Use-Lab GmbH

Affiliated institutes– USA

– China

– Japan

Cooperations Projects




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Motivation of the project

Symbols are widely used due to their advantages:– They transfer information without language barrier

– They occupy less space on devices

– They provide information more quickly and direct than text

Problems with symbol application:– Too many symbols may cause confusion

– Some symbols may be difficult to learn, remember or understand

– Even standardized symbols may be misunderstood

– How are symbols validated before use

– Medical personnel complains about symbols

– Misunderstanding of safety-related symbols may result in additional risk




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According to ISO 14971 and EN 60601-1-6, all use-related risks should be analyzed and controlled

Although many efforts (e.g. standardization) have been exerted to improve symbol application on medical devices, there are examples where users obviously are confused and add descriptions

Symbol application on medical devices




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Purpose of the study

Comprehension of some frequently used IEC 60878 symbols

Influencing factors on symbol comprehension

Intercultural aspects on symbol comprehension, e.g. China, Germany and Canada / USA

Evaluation method (e.g. influence of context information, etc.)




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Criteria for effective symbol application

Noticeability If a symbols can be noticed by target users

LegibilityIf a symbol is legible (under all context conditions, for all target users)

Comprehensibility If a symbol can be comprehended correctly by target users

Learnability If a symbol can be learnt easily




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Methods to evaluate symbol comprehension

Typical tasks that the participants conduct: – Matching a symbol to a specified meaning (matching test)

– Choosing a correct meaning of a symbol (multiple choice)

– Freely guessing the meaning of a symbol (open-ended free “definition”)

Presentation ways: – Symbol presentation using electrical media or on paper

– Symbol presentation with or without time limit

– Symbol presentation without any context, or with context in form of text, drawn picture, photos, etc.

Evaluation criteria:– The correct responses and the incorrect responses of the participants

– Execution time

– Subjective valuation like response certainty or user satisfaction




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Methods suggested by ISO 9186:2001

The comprehensibility judgment test is NOT a test to evaluate the comprehension of the symbols but a test to evaluate the judged comprehensibility of the symbols. In the test a concept and a symbol are presented to the participants. They are asked to judge the percentage of the target population which would understand the meaning of the given symbol without problems.

The comprehension test is a test to evaluate the comprehension rate of the participants of the symbols. In the test the participants are presented with some symbols and are required to express the meaning (the response) of these symbols.




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Method used in the study

Open-ended comprehension test

– Free answer while global context is presented by photo. Global context shows the general workplace where a device with the symbol is typically used

– Free answer while global and fine context are presented by photo. Fine context shows a device with the symbol




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Evaluation criteria (ISO 9186: 2001)

Each response is assigned into one of 7 categories:1. Correct understanding of the symbol is certain (estimated probability of

correct understanding over 80%)

2. Correct understanding of the symbol is very probable (estimated probability of correct understanding between 66% and 80%)

3. Correct understanding of the symbol is probable (estimated probability of correct understanding between 50% and 65%)

4. The stated meaning is the opposite to the assigned

5. Any other response except: “Don’t know”

6. Response: “Don’t know”

7. No response




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Evaluation criteria: scoring

Method suggested by ISO 9186:2001

Final score for the comprehensibility of a symbol:

100 % of category 1 (correct understanding certain)

+ 75 % of category 2 (correct understanding very probable)

+ 50 % of category 3 (correct understanding probable)

- 100 % of category 4 (stated meaning opposite)

--------------------------------------

= Final Score




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Test

Symbols tested – 13 from IEC 60878– 3 from frequently used medical products

Participants were doctors or nurses. Participants had extensive experience with medical devices being marked with the such symbols.

Test has been conducted in their working locations

Participants in Germany– 20 from intensive care department / OR

Participants in China– 13 from intensive care department / OR




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Selected symbols

Number Symbol Intended Meaning Number Symbol Intended Meaning

1 Date of manufacture 9 Trend information

2 Person identification 10 Bell cancel

3* Bellow connection 11 Do not re-use

4 Manual control 12 Nurse

5 Power plug 13* Infusion status

6 Display transfer 14 Locking (locked status)

7 Type BF applied part 15 Zero-point adjustment

8 Stand-by 16* Blood pressure measurement

Symbols with * are from manufacturers, the others are from IEC 60878




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Pictorial Abstract

ICU

/OR

G

ener

alCategory of symbols




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Test material - Symbol with context

answer: Fine context

answer: Global context

Global context

Fine context




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Results – ICU / OR (Germany)

Mean (with global context) = 42,7%

Mean (with fine context) = 52,3%




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Results – ICU / OR (China)

Mean (with global context) = 32,2%

Mean (with fine context) = 48,2%




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Conclusions - 1

Average comprehension of symbols is poor in both countries– RISK ASSESSMENT for symbols used to establish an ESSENTIAL

REQUIREMENT is recommended

Some symbols may be evident for designers but may not evident for users

Fine context is essential for comprehension of those symbols that have lower comprehensibility




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Results - Germany vs. China (ICU)

Special symbols with fine and global context

0,0%

20,0%

40,0%

60,0%

80,0%

100,0%

1 2 3 4 5 6 7 8

General symbols with fine and global context (China)

0,0%

20,0%

40,0%

60,0%

80,0%

100,0%

1 2 3 4 5 6 7 8

General symbols with fine and global context

0,0%

20,0%

40,0%

60,0%

80,0%

100,0%

1 2 3 4 5 6 7 8

Special symbols with fine and global context (China)

0,0%

20,0%

40,0%

60,0%

80,0%

100,0%

1 2 3 4 5 6 7 8

Global context

Fine context

General symbols Specialized symbols

Germany

China




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Results - Germany vs. China (ICU)

Abstract symbols with fine and global context (China)

0,0%

20,0%

40,0%

60,0%

80,0%

100,0%

1 2 3 4 5 6 7 8

Global context

Fine context

Abstract symbols Pictorial symbols

Germany

China

Abstrat symbols with fine and global context

0,0%

20,0%

40,0%

60,0%

80,0%

100,0%

1 2 3 4 5 6 7 8

Pictorial symbols with fine and global context

0,0%

20,0%

40,0%

60,0%

80,0%

100,0%

1 2 3 4 5 6 7 8

Pictorial symbols with fine and global context (China)

0,0%

20,0%

40,0%

60,0%

80,0%

100,0%

1 2 3 4 5 6 7 8




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Conclusions - 2

Differences in comprehension performance in Germany and China are not significant

Work experience has more influence on comprehension performance than cultural difference (general symbols are more frequently used, so they are better comprehended)

Pictorial symbols are much better comprehended than abstract symbols




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Symbol evaluation by ISO 9186:2001

Rather subjective;

Difficulties to exactly assign responses to category 1-3;

The assignment between category 3 and 5 is not always clear;

The formula for the final scores should consider category 5

The formula for the final scores should checked

Evaluation process is not efficient.

esctaic 20051 evaluation of graphical symbols used in icu comprehension among users in germany and...

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