Aims and objectives. To investigate nurses’ use of a single parameter track and trigger chart to inform implementation of the National Early Warning Scoring tool. To report the characteristics of patients with triggers, the frequency of different triggers, and the time taken to repeat observations. To explore the barriers and facilitators perceived by nursing staff relating to patient monitoring. Background. Sub-optimal care of the deteriorating patient has been described for almost two decades. Organisations have responded by implementing strategies that improve monitoring and facilitate a timely response to patient deterioration. While these systems have been widely adopted the evidence-base to support their use is inconsistent. Design. A mixed method service evaluation was carried out in an acute University hospital. Methods. Physiological triggers (n = 263) and characteristics of triggering patients (n = 74) were recorded from surgical and medical wards. Descriptive statistics were displayed. Questionnaires were distributed (n = 105) to student nurses, health care assistants and registered nurses. Themes and sub-themes were identified from content analysis. Results. Hypotension was the most frequent abnormality. There was variability in the time to repeat observations following a trigger. A high proportion of triggers were identified in older patients, as was a trend of longer time intervals between trigger and repeat observations. Nurses reported a number of barriers and facilitators to monitoring patients including: ‘workload’, ‘equipment’, ‘interactions between staff’ and ‘interactions with patients’. Conclusions. This study identified a number of barriers and facilitators to monitoring and escalation of abnormal vital signs, highlighting the complexity of the process and the need for a system-wide approach to a deteriorating patient. Relevance to clinical practice. The trend of longer delays following a trigger in older patients has not been identified previously and could reflect a knowledge gap of the physiological changes and response to acute illness in older people.