04 Dec The “iron lung” and the modern “ventilation”
The iron lung is a machine that predated modern respirators, and was frequently used in hospitals to allow patients with respiratory failure to breathe, particularly patients whose respiratory muscles had been paralyzed due to polio. The machine works by creating a depression inside the chamber by means of a bellows, the rib cage expands and produces a depression inside the airways of the patient which then allows air from the atmosphere to flow into the airways and lungs due to the difference in pressure. When the bellows is returned to the starting position, the air flows passively out of the lung. In other words, the iron lung simply reproduces the mechanical act of normal breathing. Invented by American engineer Philip Drinker in 1920, the machine is seldom used today having been replaced by a smaller machine known as a cuirass ventilator. The cuirass is actually a shell which creates a negative pressure only in the rib cage because the shell is adapted to the patient’s body and, together with a flexible seal, creates an air chamber over the chest and abdomen.