We initialised this piece of research in order to explore methods that could humanise the implementation of NPM principles and make changes in hospital environments socially more acceptable. When one considers the number of reforms that public hospitals have had to face (pricing, new governing schemes, provisional management of professions and skills…), one could presume that they are used to change - but it is not the case at all. In such a context and with such pluralistic organisations as public hospitals, it is much more realistic to accept that introducing change is more than a challenge. Compatible with a polyphonic management, favourable to change when people with different values and opposing interests have to cooperate around one same issue, Actor Network sociology became an obvious assessment matrix for a change process that we have been observing on the one hand, and conducting on the other hand, via two projects that aim to retain staff: professionalising integration programmes and undertaking and promoting a 'well-being at work' scheme. Lead in a transformative approach, our research and intervention is based on two similar casestudies undertaken in public hospitals that have to face chronic shortages in nursing staff in psychiatric wards. Our ethnographic connection with the field was possible thanks to a CIFRE. It enabled us to obtain all kinds of rich and diversified data (documents, questionnaires, individual and group interviews, observation). We thereby brought our contribution to identifying what determines the initial intentions of psychiatric nursing staff in France, thanks to the organisation of multi-disciplinary workshops. During the second part of the implementation of our projects, thought-out in total collaboration with the actors on the field, we determined the actual obstacles to change as well as change-facilitators. Main obstacles include work rhythms and timescales that are incompatible between the various actors, absence of debate, falsely participatory attitudes during meetings, the multiplication of contingent projects, insufficient management and strategic coordination skills at a corporate level and, finally, insufficiently legitimate HR projects, enforced by work that goes totally un-noticed. However, we have come to the conclusion that implementing a project in a hospital environment is made easier by a series of facilitating conditions: the actor network expert's neutrality, goodwill and methodological skills, the co-development of a diagnosis as well as the implementation of the project on a pilot-site in order to favour its deployment, the fine definition of the role that each person is expected to play in such an unusual multidisciplinary collaboration, optimal communication along the whole project, including concerning small changes being made, and finally, good integration and comprehension of an innovative culture based on good-practice sharing.