Critical illness is a continuum with different phases and trajectories. The “Intensive Care Unit (ICU) without walls” concept refers to a model whereby care is adjusted in response to the patient’s needs, priorities, and preferences at each stage from detection, escalation, early decision making, treatment and organ support, followed by recovery and rehabilitation, within which all healthcare staff, and the patient are equal partners. The rapid response system incorporates monitoring and alerting tools, a multidisciplinary critical care outreach team and care bundles, supported with education and training, analytical and governance functions, which combine to optimise outcomes of critically ill patients, independent of location.