What is an iron lung, and is it useful for people with polio?

It is a primitive negative pressure ventilator. It is basically cylinder-like rigid metal box where the patient lies so that his or her head sticks out. A vacuum pump creates a variable negative pressure inside the cylinder so that the patient’s thorax and abdomen mimic the natural breathing rhythm.

Iron lung was the first functional perpetual respirator. It was used for artificial breathing in cases, where the patient was unable to breathe on his or her own, such as respiratory paralysis, muscular dystrophy, drug overdose, poisoning etc. But being large, cumbersone and claustrophobic, it was a technological dead end.

Poliomyelitis is a virus disease where the virus attacks the motor neurones of the frontal lobe of spinal cord. By killing those neurones (nerve cells), it can cause paralysis. Polio did not only kill, it also crippled for life.

On 0.1% of all polio cases, the paralysis can spread to the bulbous medulla oblongata and the nerves which control the muscles for breathing and swallowing. If those got paralyzed, the result would be death by asphyxiation.

Iron lung was used to treat those polio patients who had it really bad and who had the disease spreading to the respiratory organs and who thus needed artificial breathing. (Another disease in which iron lung was used was ALS or Lou Gehrig’s Disease.)

Some 80% to 90% of the polio patients who were put to iron lung, died in the acute phase of the disease. They usually drowned in their own saliva because the swallowing muscles had been paralyzed, choked on carbon dioxide buildup due to clogged airways, or died from acidosis due to buildup of CO2 in bloodstream. For them, the iron lung was nothing but a terrifying and claustrophobic death chamber.

But some did survive, and they usually recovered when the surviving neurons began to re-grow axons to the muscles and began to reconnect. Yet for 1 in 10,000 the paralysis was left permanent.

Iron lung seems to be a peculiarly American contraption. They were not used much in Europe; the Europeans invented something better. Positive pressure ventilators eventually superseded iron lungs in Europe since 1952, when Björn Ibsen from Blegdamshospitalet, Copenhagen, Denmark, successfully performed tracheotomy and used positive pressure ventilation for 12-year-old Vivi Ebert, saving her life. He built a prototype using the German “Pulmotor” device and WW2 aviator respirators as the model, and he never patented it, to make it and its design spread as fast as possible.

Positive pressure ventilators had several advantages over iron lungs: they were way cheaper, easier to manufacture, easier to use, easier to maintain, more reliable, less claustrophobic, smaller, and did not require as much space. Moreover, they freed the patient to bed and the patient could be seated in semi-sitting position so that the saliva would drip in the stomach and the airways could be cleansed. The fatality rate by using positive pressure ventilation fell from 80% to 11% in the 1952 epidemic in Denmark.

There is one polio survivor from the 1950s epidemics still in Finland with respiratory paralysis alive. She uses a positive pressure ventilator integrated on her electric wheelchair.