The iron lung, a device that might seem archaic today, played a crucial role in saving lives during the polio epidemics of the 20th century. To understand How Does An Iron Lung Work, it’s essential to delve into the principles of negative pressure ventilation it employs. This mechanical respirator, invented to aid breathing when muscle control was lost, became a symbol of hope for many afflicted by poliomyelitis.
The core mechanism of an iron lung revolves around creating intermittent negative pressure around the patient’s chest. Imagine a large, airtight metal box, or tank, in which a patient would be placed, with only their head protruding. A tight seal around the neck ensured the chamber remained airtight. Attached to this chamber were bellows, or pumps, which would rhythmically alter the air pressure within the tank.
When the bellows drew air out of the tank, it created a negative pressure, or a vacuum, around the patient’s body. This negative pressure caused the chest to expand, mimicking the natural process of inhalation. As the chest expanded, air was drawn into the lungs, allowing the patient to breathe in. Conversely, when air was pumped back into the tank, the pressure inside increased, returning to normal atmospheric levels. This released the negative pressure, allowing the chest to recoil and air to be expelled from the lungs, simulating exhalation. This cycle of creating negative and positive pressure allowed for mechanical respiration, effectively breathing for individuals who had lost the ability to control their respiratory muscles due to polio or other conditions.
The invention of the first iron lung is credited to Philip Drinker and Louis Agassiz Shaw at the Harvard School of Public Health. Faced with the devastating polio epidemics, they developed this “Drinker respirator” in 1928, a large metal box with bellows designed to mechanically assist breathing. While mechanical breathing devices weren’t entirely novel, the urgency of the polio crisis spurred the development of such large-scale devices.
Over time, improvements were made to the original Drinker design. John Haven Emerson, in 1931, created a modified respirator that offered better patient access. Emerson’s version featured a sliding bed, allowing patients to be moved in and out of the machine more easily, and incorporated portholes for medical staff to access the patient without disrupting the air pressure. Despite these advancements, Drinker and Harvard University initiated a patent infringement lawsuit against Emerson, arguing his respirator was too similar to their original design. However, the court ruled in favor of Emerson, invalidating Drinker’s patents by demonstrating that the underlying technologies were already in the public domain. The judge notably emphasized that life-saving technology should be accessible to everyone.
Later, necessity drove further innovation. During a polio outbreak in Australia in 1937, the high cost and logistical challenges of importing Drinker respirators from America led the South Australian Health Department to seek a local, more affordable solution. Biomedical engineer Edward Both responded by designing the “Both respirator.” Constructed from plywood, it was significantly cheaper, easier to build, and transportable. The Both respirator could be produced rapidly, sometimes being operational within an hour of completion. Lord Nuffield, impressed by its design and practicality, facilitated the production of approximately 1,700 Both respirators at his UK car factory, donating them to hospitals globally.
In conclusion, the iron lung’s operation is based on the simple yet effective principle of negative pressure ventilation. By rhythmically altering air pressure around the body, it mechanically induces breathing, providing crucial respiratory support during the polio epidemics. From the Drinker respirator to the Emerson and Both innovations, the iron lung’s history is a testament to the ingenuity and collaborative efforts to combat a devastating disease and provide a lifeline to those in need.
