Much like the COVID-19 epidemic, in 1952 dozens of people were coming into hospitals and dying of respiratory failure. Doctors and nurses often stood by, desperately wanting to help, but lacking the equipment to do so. It wasn’t coronavirus; it was polio, another viral disease.

The 1952 Copenhagen polio epidemic was one of the worst at the time. The response to the epidemic at Blegdam Hospital isn’t well-known, but it represents the start of intensive care medicine and the use of mechanical ventilation outside operating rooms.

The Blegdam Hospital was dealing with 50 new patients a day, several of whom developed respiratory failure. Doctors used iron lungs to keep these patients alive. Copenhagen had only one iron lung and consequently 87 percent of polio patients that couldn’t breathe on their own died. Sadly, half of those were children. The chief physician of the hospital called a meeting that included Bjørn Ibsen, a Danish anesthesiologist, who had just come back from training at Massachusetts General Hospital.

The iron lung made people breathe by creating negative pressure in an airtight chamber surrounding the body. This forced the ribs and the lungs to expand, pulling air into the trachea and lungs.

People in iron lungs often still died because saliva or stomach contents got into the lungs. Ibsen suggested using positive pressure to introduce air into the lungs, then allow the body to exhale normally. He proposed to use a tracheostomy, during which an incision is made into the base of the neck, a tube is inserted into the windpipe, and then a rubber bag is attached to pump air into the lungs. Tracheostomies were used during surgeries but rarely used on the wards.

Two-hundred medical and dental students were recruited to manually squeeze the air bags attached to the tracheostomy tubes in polio patients. To try and mimic natural breathing, the bag was attached to a tank of 50 percent oxygen in nitrogen along with a soda lime container to remove the carbon dioxide. The students were told how often to squeeze the bag and responded to signs from patients if they needed more. At the peak of the polio epidemic, 70 patients were kept alive this way. This went on for months, and at least 120 people were saved with these heroic methods.

Doctors had thought that polio spread to patients’ brains, but they learned that the lack of oxygen led to increases in blood acidity and eventually organ failure and death. We’ve since learned much more about the physiology of breathing, and we’ve developed more sophisticated mechanical ventilation methods.

Early mechanical ventilators sometimes disconnected, and they lacked alarms and sensors, putting patients at risk. Modern machines gather information to deliver the correct amount of air at the proper pressure with each breath and are vital for those in severe respiratory distress. We hope that countries will stockpile many additional ventilators in anticipation of the next pandemic, and yes, there will be one.

Medical Discovery News is hosted by professors Norbert Herzog at Quinnipiac University, and David Niesel of the University of Texas Medical Branch. Learn more at

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