Especially during COVID-19, ventilators have become incredibly important. These useful tools are needed when the body’s respiratory system stops working properly. The respiratory system normally works when the diaphragm contracts and relaxes. When you inhale, the diaphragm contracts which expands the chest cavity. Air is allowed to be inhaled, and this inflates the alveoli, which are like tiny balloons in the lungs. These balloons are surrounded by capillaries. Blood in the capillaries absorbs the oxygen and leaves behind CO2 and any other gases. These gases are all exhaled when the diaphragm relaxes.

The first idea for the ventilator came in the 1500s. A doctor named Andreas Vesalius theorized that an animal that was suffocating could be kept alive by putting a tube into its trachea and blowing air in to inflate the animal’s lungs. This is recognized as the first description of mechanical ventilation.

There are two ways ventilators get oxygen into the body when the lungs can’t: negative pressure ventilation and positive pressure ventilation. Negative pressure ventilation allows air to be passively let in, and was heavily used throughout the 19th and 20th centuries. This was initially used because it is very similar to natural breathing. Doctors would enclose patients in tight and slowly let air out of the chamber to allow the chest cavity to easily expand. In 1928, pumps powered by electric ventilation called the Iron Lung became a fixture in hospitals. However,negative pressure designs restricted patient movement and made it difficult for caregiver analysis.

In the 1960s, there was a shift towards studying positive pressure, where air was actively pumped into the lungs. This can be done noninvasively for minor cases. Severe cases need a device to completely take over the process. A tube is inserted into the trachea with valves and pipes forming a circuit for inhaled and exhaled air.