Medical students manually ventilate children with polio at Blegdams Hospital in Copenhagen in 1953.Credit: Medical Museion, Univ. Copenhagen

The number of hospital admissions was more than the staff had ever seen. And people kept coming. Dozens each day. They were dying of respiratory failure. Doctors and nurses stood by, unable to help without sufficient equipment.

It was the polio epidemic of August 1952, at Blegdam Hospital in Copenhagen. This little-known event marked the start of intensive-care medicine and the use of mechanical ventilation outside the operating theatre — the very care that is at the heart of abating the COVID-19 crisis.

In 1952, the iron lung was the main way to treat the paralysis that stopped some people with poliovirus from breathing. Copenhagen was an epicentre of one of the worst polio epidemics that the world had ever seen. The hospital admitted 50 infected people daily, and each day, 6–12 of them developed respiratory failure. The whole city had just one iron lung. In the first few weeks of the epidemic, 87% of those with bulbar or bulbospinal polio, in which the virus attacks the brainstem or nerves that control breathing, died. Around half were children.

Desperate for a solution, the chief physician of Blegdam called a meeting. Asked to attend: Bjørn Ibsen, an anaesthesiologist recently returned from training at the Massachusetts General Hospital in Boston. Ibsen had a radical idea. It changed the course of modern medicine.

Student saviours

The iron lung used negative pressure. It created a vacuum around the body, forcing the ribs, and therefore the lungs, to expand; air would then rush into the trachea and lungs to fill the void. The concept of negative-pressure ventilation had been around for hundreds of years, but the device that became widely used — the ‘Drinker respirator’ — was invented in 1928 by Philip Drinker and Louis Agassiz Shaw, professors at the School of Public Health in Boston, Massachusetts. Others went on to refine it, but the basic mechanism remained the same until 1952.

Iron lungs only partially solved the paralysis problem. Many people with polio placed in one still died. Among the most frequent complications was aspiration — saliva or stomach contents would be sucked from the back of the throat into the lungs when a person was too weak to swallow. There was no protection of the airway.

Ibsen suggested the opposite approach. His idea was to blow air directly into the lungs to make them expand, and then allow the body to passively relax and exhale. He proposed the use of a trachaeostomy: an incision in the neck, through which a tube goes into the windpipe and delivers oxygen to the lungs, and the application of positive-pressure ventilation. At the time, this was often done briefly during surgery, but had rarely been used in a hospital ward.

Ibsen was given permission to try the technique the next day. We even know the name of his first patient: Vivi Ebert, a 12-year-old girl on the brink of death from paralytic polio. Ibsen demonstrated that it worked. The trachaeostomy protected her lungs from aspiration, and by squeezing a bag attached to the tube, Ibsen kept her alive. Ebert went on to survive until 1971, when she ultimately died of infection in the same hospital, almost 20 years later.

The plan was hatched to use this technique on all the patients in Blegdam who needed help to breathe. The only problem? There were no ventilators.

Very early versions of positive-pressure ventilators had been around from about 1900, used for surgery and by rescuers during mining accidents. Further technical developments during the Second World War helped pilots to breathe in the decreased pressures at high altitudes. But modern ventilators, to support a person for hours or days, had yet to be invented.

What followed was one of the most remarkable episodes in health-care history: in six-hour shifts, medical and dental students from the University of Copenhagen sat at the bedside of every person with paralysis and ventilated them by hand. The students squeezed a bag connected to the trachaeostomy tube, forcing air into the lungs. They were instructed in how many breaths to administer each minute, and sat there hour after hour. This went on for weeks, and then months, with hundreds of students rotating on and off. By mid-September, the mortality for patients with polio who had respiratory failure had dropped to 31%. It is estimated that the heroic scheme saved 120 people.

Major insights emerged from the Copenhagen polio epidemic. One was a better understanding of why people died of polio. Until then, it was thought that kidney failure was the cause. Ibsen recognized that inadequate ventilation caused carbon dioxide to build up in the blood, making it very acidic — which caused organs to shut down.

Three further lessons are central today. First, Blegdam demonstrated what can be achieved by a medical community coming together, with remarkable focus and stamina. Second, it proved that keeping people alive for weeks, and months, with positive-pressure ventilation was feasible. And third, it showed that by bringing together all the patients struggling to breathe, it was easier to care for them in one place where the doctors and nurses had expertise in respiratory failure and mechanical ventilation.

So, the concept of an intensive-care unit (ICU) was born. After the first one was set up in Copenhagen the following year, ICUs proliferated. And the use of positive pressure, with ventilators instead of students, became the norm.

In the early years, many of the safety features of modern ventilators did not exist. Doctors who worked in the 1950s and 1960s describe caring for patients without any alarms; if the ventilator accidentally disconnected and the nurse’s back was turned, the person would die. Early ventilators forced people to breathe at a set rate, but modern ones sense when a patient wants to breathe, and then help provide a push of air into the lungs in time with the body. The original apparatus also gathered limited information on how stiff or compliant the lungs were, and gave everyone a set amount of air with each breath; modern machines take many measurements of the lungs, and allow for choices regarding how much air to give with each breath. All of these are refinements of the original ventilators, which were essentially automatic bellows and tubing.

Looming lack

Some anaesthetists and intensive-care doctors, including me, mark 27 August as ‘Bjørn Ibsen day’ — the day Ibsen proposed using positive-pressure ventilation to save lives. Most people have no idea what they owe to this remarkable doctor and his colleagues in Copenhagen. Those of us who live in high-income countries have taken for granted the idea that if we get sick enough to struggle to breathe, from pneumonia, a heart attack or any other cause, we will be placed on a ventilator.

In my day-to-day work, I routinely assess which patients require ventilator support, working with a dedicated team of nurses, pharmacists, respiratory therapists, physical therapists and others, to provide care. Never in more than 20 years of training and practice in the United States and Canada have I had to question whether a ventilator was available.

But I have always known that this possibility loomed. My research focuses on quantifying the availability and nature of ICU beds from country to country, examining the wide variability in provision. Even in ordinary times, demand for ICU beds and ventilators can spike, for instance each year during influenza season. I have been lucky to work in places where such strain in normal times is easily absorbed. In many parts of the world, these facilities do not exist; in some hospitals, particularly in low-income countries, what is considered an ICU bed is simply one that it is equipped to provide supplemental oxygen to a patient, but not with a ventilator.

In the COVID-19 pandemic, the spectre of care without ventilators has reared its head, even in countries that are the best provisioned, such as Germany and the United States. That so many doctors might have no alternative, except to watch patients die, recalls the 1950s and before.

We do not yet know the true COVID-19 mortality rate. This is in part owing to the appalling lack of widespread testing in many nations, which makes it difficult to understand how many have been infected. It is also because, so far, the majority of patients in high-income countries who have needed intensive care and a ventilator have had both.

Comparisons are being made to the 1918 influenza pandemic — eerily, just over a century ago — which had a mortality that might turn out similar. But that outbreak occurred without a ventilator in sight. Is this new disease, in fact, more deadly? Thanks to what my predecessors learnt in Copenhagen almost 70 years ago, we can, in some parts of the world, offset the havoc of COVID-19 with mechanical ventilation and sophisticated intensive care that was not available in 1918. But it is as COVID-19 continues to spread in areas that do not have ICU beds — or not nearly enough of them — that we will, sadly, learn the true natural course of this new virus.