Abstract: Deterioration of hospitalised patients is often missed, misinterpreted, and mismanaged and can eventually result in death. Rapid response systems (RRSs) provide a framework to detect and interpret in-hospital clinical deterioration, to enhance communication between clinicians, and to initiate a response in a timely manner. The main goal of RRSs is to prevent progressing patient deterioration and subsequently to reduce preventable serious adverse events improving the quality of care. A considerable body of research exists studying different aspects and types of RRSs. However, the quality of evidence in relation to patient outcomes is poor and there is no consensus on what the most effective strategy is to prevent serious adverse events. The general aim of this doctoral study is to investigate the effect of a rapid response system on patient outcomes using an evidence-based afferent limb strategy while ensuring an adequate and timely medical response by existing hospital resources. Furthermore, we studied the predictive performance of the national early warning score (NEWS), which is a track-and-trigger system to detect patient deterioration using vital signs. Because of the importance of adequate staffing levels for patient surveillance, we additionally investigated which nurse staffing levels are needed to provide safe care and to minimise patient’s unexpected death. We defined new outcome measures, more sensitive to care processes including nursing practice, to be used in research concerning the deteriorating patient on the general ward. We confirmed an association between higher adherence to a nurse observation protocol and lower patient unexpected death and mortality after cardiopulmonary arrest or unplanned intensive care admission adjusted for patient comorbidity and age. Furthermore, we have shown that an RRS improves nurses’ performance in observing patients without increasing the observation frequency in stable patients. We showed that our intervention increased the mean number of vital signs ...