This is a prospective, non-randomized, multicenter, observational national study, involving centers with different working shift organizations.

Participating centers are 24 French adult intensive care units with different working shift organizations (12-hours shift vs. less than 12-hours shift) in public hospitals.

Caregivers (doctors, nurses and assistant nurses) constitute the population of the study.

The duration of the study is 13 months.

The aim of this study is to evaluate the impact of the working shift organizations on:

• The intensive care units operation;
• The use of outside staff;
• The caregivers' quality of life at work;
• The caregivers' satisfaction at work;
• The nursing work environment;
• Psychosocial and organisational work constraints
• The performance of the intensive care units;
• The costs and efficiency of the working shift organizations.

The critical review of the scientific literature leads us to conclude that there are heterogeneous, and sometimes discordant, results about the impact of a 12-hours working shift organizations on caregivers, hospitals and unit operation, compared with less than 12-hours working shift organizations. This variety and ambiguity of the results could stem from lack of documentation and/or lack of quality of the studies' methodology, the choice of the outcomes, a too short time period for analysis after an organizational change.

In addition, the sociologist analysis is rarely developed. Finally, quite a few studies are declarative, therefore, whatsoever objective outcome is measured.

The determinants of the choice of working shift organization in health facilities are interlinked with multiple factors. Individual and economic factors are considered, as well as clinical risk management, continuity of care and continuity of public services. To the best of our knowledge, no study have evaluated the capacity to maintain a continuity of public health services using 12-hours working shift organization, in particular in French intensive care units subjected to a regulation on nursing and assistant nursing workforce per patient. Besides, there is no data about the impact of 12-hours working shift organization on the performance of intensive care units regarding clinical risk management.

Our hypothesis is that a 12-hours working shift organization may result in a more important number of hours during which the French standard ratio of 1 nurse for 2.5 patients is observed or during which the intensive care beds are not closed, compared with a less than 12-hours working shift organization, with similar caregivers quality of life and performance of intensive care units.

First month of the study: self-administered questionnaires used in order to evaluate nursing work environment (Practice Environment Scale of the Nursing Work Index PES-NWI), caregivers quality of life at work (Nottingham Health Profile NHP, Perceived Stress Scale PSS10 and Hospital Anxiety and Depression Scale HADS) caregivers satisfaction at work (Minnesota Satisfaction Questionnaire MSQ) and psychosocial and organisational work constraints (NWI-EO) will be completed by caregivers (doctors, nurses and assistant nurses).

During the study a sociologist will carry semi-structured interviews on a subset of caregivers from different participating centers.

Eleventh month: self-administered questionnaires used during the first month of the study will be completed again by all caregivers under the same conditions.

One year study period: human resources, activity and performance data will be collected from the beginning to the end of the study.

Inclusion Criteria:

• assistant nurses, nurses, doctors
• working in an hospital intensive care unit

Exclusion Criteria:

- opposition to use data

volunteer caregivers: health care staff of 24 intensive care units will be included in the study: doctors, nurses and assistant nurses