Design for HCI can be more complex than for other fields of engineering. This is because it is inherently interdisciplinary and involves aspects relating to user and usage that may not lend themselves to analysis. Although there are resources that allow developers to take into account the interaction between users, the tools that they use and the environments in which they live and work, there may be challenges integrating them with existing development practice. There may be questions regarding suitability for safety critical purposes. We report on an interview study involving professionals from major manufacturers of medical devices, to better understand their development practices and the external forces that shape those practices. For example, manufacturers will provide devices engineered to meet a generic need, however it is impossible to anticipate all combinations of user and usage. Results are divided into six themes. These are: collaborative working practices; understanding the user and their situation; providing adequate justification for the adoption of a user-centred approach; provision of clear guidance and support; communication of mandatory controls and industry wide standardisation. We will provide examples of potential interventions and highlight the importance of ensuring that techniques are adequately justified, applied at the correct time, aligned with the development lifecycle and easy to adopt..