An Intensive Care Unit (ICU) is a specialized hospital department providing the highest level of continuous care and monitoring for critically ill patients. ICUs are equipped with advanced life-support equipment, monitoring devices, and staffed with specially trained intensive care physicians, nurses, and respiratory therapists. Patients in ICU may require mechanical ventilation, continuous cardiac monitoring, medication infusions requiring precise control, or treatment for life-threatening conditions like severe infections, heart attacks, or major surgery recovery. The patient-to-nurse ratio is much lower than regular wards, typically one-to-one or one-to-two, enabling constant observation. ICU beds are expensive hospital resources, and capacity limits became prominent during the COVID-19 pandemic. Specialized ICUs exist for neonatal patients (NICU), cardiac patients (CCU), and other populations. ICU admission criteria, discharge decisions, and care protocols aim to match this scarce resource to patients who most need and can benefit from intensive care.