The process of health care delivery in Intensive Care Units (ICUs) is subject to significant workload fluctuations and unpredictable events. Medical and nursing staff, while relying on protocols, must adjust to these "out of the routine" disturbances by displaying initiative and innovation. The aim is to maintain the ratio risk-performance in admissible margins for the institution despite severe disruptions of operation. The assumption is that this resilience ability may be intentionally built by a specific work organization. The theoretical framework of "resilience engineering" described here could be a powerful tool in organizational designing suited to the ICUs.