UVI stands for "unidad de vigilancia intensiva" which means intensive observation unit, UCI stands for "unidad de cuidados intensivos" which means intensive care unit. Patients in the UCI are those who need continuous care to stay alive (like being intubated for example). Patients in the UVI are those who do not need that continuous care but are at risk of needing immediate medical assistance.
Used in US as well
"He just got out of the UCI but they are keeping him in the UVI for now, just in case"