This paper explores the design collaboration between designers and expert users in the specific case of new surgical instrument design. To this end, two design evaluation meetings were studied. Decision and interaction analysis methods were applied to compare the effectiveness of the design team on discussing and solving design issues with and without active participation of the expert user. The observations showed that, in the absence of the user, the designers were unable to make decisions about technical solutions relating to usability issues, and the expert user's comments during the subsequent meeting significantly altered their decisions. These two observations indicate that the use of a support tool could have a significant role to help asynchronous communication in such a design process.