Severe acute respiratory failure is one of the most frequent causes for patient admission to the intensive care unit (ICU). In the most severe conditions, invasive mechanical ventilation is required life support in these patients. The polio epidemic that occurred in Denmark in 1952 demonstrated how careful airway management and the application of positive-pressure ventilation could dramatically reduce mortality in patients presenting with paralysis of the respiratory muscles. The focus on airway care and ventilator management encouraged the way forward for critical care facilities. Technological advances in the 1960s led to the development of sophisticated, physiological monitoring equipment.