Evaluation of Graphical Symbols Used in ICU Comprehension

Evaluation of Graphical Symbols Used in ICU Comprehension among Users in Germany and in China Long Liu, Uvo Hoelscher Muenster University of Applied Sciences ESCTAIC 2005 1

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 Gmb. H § Affiliated institutes – USA – China – Japan Cooperations ESCTAIC 2005 Projects 2

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 ESCTAIC 2005 3

Symbol application on medical devices § 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 ESCTAIC 2005 4

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. ) ESCTAIC 2005 5

Criteria for effective symbol application § Noticeability If a symbols can be noticed by target users § Legibility If 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 ESCTAIC 2005 6

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 ESCTAIC 2005 7

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. ESCTAIC 2005 8

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 ESCTAIC 2005 9

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 ESCTAIC 2005 10

Evaluation criteria: scoring § Method suggested by ISO 9186: 2001 Final score for the comprehensibility of a symbol: 100 % of category 1 + 75 % of category 2 + 50 % of category 3 100 % of category 4 -------------------= Final Score ESCTAIC 2005 (correct understanding certain) (correct understanding very probable) (correct understanding probable) (stated meaning opposite) 11

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 ESCTAIC 2005 12

Selected symbols Symbols with * are from manufacturers, the others are from IEC 60878 ESCTAIC 2005 13

Category of symbols Abstract ICU/OR General Pictorial ESCTAIC 2005 14

Test material - Symbol with context Global context Fine context answer: Global context answer: Fine context ESCTAIC 2005 15

Results – ICU / OR (Germany) Mean (with global context) = 42, 7% Mean (with fine context) = 52, 3% ESCTAIC 2005 16

Results – ICU / OR (China) Mean (with global context) = 32, 2% Mean (with fine context) = 48, 2% ESCTAIC 2005 17

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 ESCTAIC 2005 18

Results - Germany vs. China (ICU) General symbols Specialized symbols Germany China Global context Fine context ESCTAIC 2005 19

Results - Germany vs. China (ICU) Abstract symbols Pictorial symbols Germany China Global context Fine context ESCTAIC 2005 20

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 ESCTAIC 2005 21

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 2005 22