Rarely Seen: Our Curator Discusses the Iron Lung
Guest Post by Mütter Museum Curator Anna Dhody
Rarely Seen offers visitors a glimpse of objects from the storage rooms of the Mütter Museum. Several items have not been displayed for decades and some are recent acquisitions that have never been exhibited. Some of the instruments represent the pinnacle of medical knowledge for their time while others had mixed and sometimes detrimental medical results.
Many people remember when the threat of polio was omnipresent. Public pools and movie theaters were closed and parents lived in fear that their children could be struck down at any moment, unable to move or breathe. No one was safe: while the poliomyelitis virus affected mainly children, adults were also susceptible. The iron lung became one of the most iconic objects of the polio scourge, a symbol of the epidemics of the 1940s and 50s.
"Emerson Negative Pressure Ventilator." This machine goes by many names including “artificial respirator,” but it is more popularly known as the iron lung. Industrial hygienist Phillip Drinker and physician Louis Agassiz Shaw invented the first version, known as the Drinker Respirator, which was first used in 1928 at Children’s Hospital, Boston. In 1931, John Haven "Jack" Emerson, an inventor of medical devices, debuted his version of the machine which improved upon the Drinker design. Emerson’s proved more efficient, lighter, quieter, and was less than half as expensive at $1000 (the equivalent of over $12,000 in today’s currency). Drinker immediately sued Emerson, an act which proved unwise as the courts determined that all of the individual technical elements of Drinker’s machine were already patented by others, a decision that rendered Drinker’s patent invalid.
Both Drinker and Emerson’s iron lungs worked upon the principle of negative pressure. This principle governs how humans and most mammals breathe. In normal respiration, the rib cage expands while the diaphragm contracts downwards. This act expands the chest cavity and causes the pressure in the cavity to decrease. The lungs expand to fill the empty space which causes the air pressure inside them to fall and become negative. Air then flows into the lungs resulting in inhalation. When the chest cavity is contracted, the process reverses and results in exhalation.
When a person contracts the poliomyelitis virus, the resulting infection can cause motor paralysis and disrupt the normally involuntary act of breathing. Machines such as Emerson’s create a microenvironment that mimics the pressurization (and de-pressurization) that normally occurs in a healthy body. Artificial ventilation proved to be less invasive, the rate and depth of respiration could be regulated, and the machine could fit all body shapes and sizes, from children to adults. In the iron lung, the patient lies on his or her back on a removable bed. The head rests on a stand outside the machine with a rubber collar around the neck to provide the seal necessary to maintain the pressurized environment. The patient can be removed from the machine for short intervals by removing the end with the head and sliding the bed out.
While many people consigned to the iron lungs were eventually able to recover and breathe on their own, some suffered permanent damage and had to remain in the machines. According to Post-Polio Health International, as of 2008 there were approximately 30 patients in the United States still using an iron lung.
UPDATE: As of October 13, 2010, Rarely Seen is open! If you're near Philadelphia, come to the Mütter Museum to see the exhibit. We'll post next week on Dr. Robert Austrian's bacterial incubator, which is also featured in the exhibit. This incubator was an important piece of equipment in Dr. Austrian's pneumococcal researches.