How do ventilators work?

In the 16th century, physician Andreas Vesalius described how a suffocating animal could be kept alive by inserting a tube into its trachea and blowing air to inflate its lungs. Today, Vesalius’s treatise is recognized as the first description of mechanical ventilation— a crucial practice in modern medicine. So how do our modern ventilators work? Alex Gendler explains the life-saving technology.