• Karin Garmer, Erik Liljegren, Anna-Lisa Osvalder, and Sven Dahlman.
• Department of Human Factors Engineering, Chalmers University of Technology, Göteborg, Sweden. garmer@hfe.chalmers.se
• J Clin Monit Comput. 2002 Feb 1; 17 (2): 105-14.

ObjectiveThere is a need to develop adequate methods for use by the manufacturers of medical equipment when specifying requirements for their development and in order for hospitals to critically assess their usability qualities before purchase. A Human Factors approach was used to determine requirements for the redesign of an existing volumetric infusion pump. With these requirements as a starting point, a new user interface for an infusion pump was designed. Usability tests were carried out to verify whether the new interface had better usability than the existing interface or whether further improvements were needed. This paper has two aims: 1) to compare the nature of the requirements derived from a Human Factors approach and from usability tests and 2) to evaluate the use of usability tests on existing medical equipment as a basis for redesign and for evaluating the redesign.MethodThe user requirements derived from the Human Factors approach were compared with the user requirements derived from the usability tests.ResultsThe results show that the requirements derived from the Human Factors approach adequately covered contextual aspects of use. However, to derive requirements for a specific and operational level, usability tests must be conducted on existing equipment and prototypes. This study indicates that usability tests on existing medical equipment as a basis for redesign give a better understanding of problems with existing equipment. Moreover it is important to carry out usability tests to evaluate a redesign and find a satisfying solution. Expert users of the equipment had the experience, competence and confidence to be critical and suggest improvements based on their practical knowledge. The novice users on the other hand were important test users as they uncovered most of the serious handling problems and also committed most errors.ConclusionThe requirements derived from the Human Factors approach and the usability tests are important for the development of a new and improved user interface. The requirements derived from the Human Factors approach can be attributed to contextual requirements. The requirements derived from the usability tests have a higher degree of concreteness, are more specific and focus more on design solutions compared to the requirements derived from the Human Factors approach. It is important to consider intended user groups when carrying out usability tests, as the nature of the information from the different groups can be different.

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