Artificial respiration – from the iron lung to the respirator

HISTORY OF TECHNOLOGY. It started with an awkward drawer connected to two standard vacuum cleaners. Today, the Swedish-developed respirator is used in hospitals all over the world. The iron lung and its substitutes have saved lives for almost 100 years, and changed our view of death.

The American industrial researcher Philip Drinker was young, ambitious and completely focused on air pollution in factories and power plants. That his invention came to save the lives of tens of thousands of children and adults during the great polio epidemics of the 20th century was almost a coincidence.

As a senior lecturer in industrial ventilation at Harvard, he experimented in the early 1920s with various techniques for artificial respiration. Among other things, he placed an anesthetized cat, with the respiratory system paralyzed by curare, in an airtight box connected to a manometer. Drinks managed to keep the animal alive for several hours by manually pumping air into and out of the box with a cannula.

The principle was simple: the negative pressure created in the box when the air was pumped out caused the cat’s chest to dilate and air to be drawn down into the lungs. When air was pumped into the box and the negative pressure disappeared, an artificial exhalation was achieved.

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With $ 500 in funding from a New York gas company, Philip Drinker and a Harvard colleague, Louis Shaw, a professor of physiology, began to further develop the technology on a human scale. The goal was an apparatus for treating people poisoned by industrial gases.

In parallel, the ventilation expert Drinker was hired by Boston Children’s Hospital, who wanted him to develop a safe and hygienic air conditioning system for their neonatal ward. But the initial inspection of the children’s hospital’s premises was a shocking experience:

Phil saw children slowly dying of suffocation, caused by polio; he could not forget the little blue faces and their terrible gasping for air, ”his sister Catherine Drinker Bowen would later write in her memoir Family Portrait.

Artificial respiration could come in handy

Before effective vaccines were developed, polio was one of the world’s most feared diseases, infecting hundreds of thousands of people every year. The disease, also known as polio, is caused by a highly contagious virus which in most cases is harmless. However, in about one percent of those infected, the virus attacks the spinal cord, and can then cause varying degrees of paralysis. In the worst case, the infection leads to life-threatening paralysis of the respiratory system.

Philip Drinker and Louis Shaw realized that their technology concept for artificial respiration could be useful in polio care. They built a prototype consisting of a rectangular box, internally clad with ordinary sofa cushions, where the patient lay with only his head outside. The neck is enclosed by an airtight collar, made of the inner tube from a car tire. For the alternating air flow into and out of the box, which alternately created overpressure and underpressure, two modified household vacuum cleaners responded.

Drinker and Shaw tested the invention on themselves, and in the fall of 1928, they placed it on the children’s hospital’s polio ward for further development on site. They did not yet consider the device ready for clinical trials, but soon a hurried doctor called Philip Drinker: an eight-year-old girl had stopped breathing, and for lack of other alternatives, she had been placed in the strange sandwich. What do we do now?

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“When Phil arrived at the hospital, the girl was unconscious, but the medical staff had not dared to turn on the machine. He started it, and after less than a minute she woke up to life. Phil stood there and just cried “, Catherine writes in the memoirs.

The dying girl’s miraculous recovery gave enormous attention to the new treatment method. Already in the same year, an improved, cylindrical version of the device began to be mass-produced under the name Drinker & Shaw Tank – but popularly, the mechanical breathing machine was called “iron lung”, or the iron lung.

Even the first versions of the device were remarkably effective. Patients with paralyzed diaphragm, which was previously considered a death sentence, could in most cases be kept alive until their ability to breathe returned after a couple of weeks.

But the spread to other countries was hampered by high production costs, and by the fact that the 350-kilo machine had to be returned to the United States every time it needed service and maintenance. Cheaper and more flexible variants soon began to be launched in several places.

The engine was powered by hydropower

The Danish physiologist and Nobel laureate August Krogh designed a model where the engine was powered by hydropower from Copenhagen’s main pipeline network – probably to secure operation in the event of a power outage. He also designed an infant-sized iron lung.

John Haven Emerson, a young innovator in New York, developed a model in which fans and valves are replaced by an elastic diaphragm at the foot end of the cylinder. Overpressure and underpressure are achieved by alternately pulling out the diaphragm and returning it by a mechanical arm, which was both quieter and more efficient than the humming fan motors used by Drinker and Shaw. Emerson’s iron lung also had sliding patient beds and glass doors in the sides, so that the hospital staff could see if blankets and heating pads needed to be adjusted.

Real mass production, however, did not come until 1937, when the Australian inventor Edward Both launched his “Both portable cabinet respirator”. The metal casing had been replaced by plywood, which made the machine so light that it could be placed on wheels and become movable. It was so simply designed that the hospital staff could assemble it from a kit, and replace spare parts themselves if necessary.

The price was one twentieth of what a Drinker & Shaw Tank cost. Now the technology spread around the world, saving countless lives.

But even in the more sophisticated machines, it happened that patients died, even though the air flowed through their lungs. One who thought about this problem was the Swedish infection doctor Carl Gunnar Engström.

He had cracked the Air Force extra by measuring the gas levels in the blood of fighter pilots, and that was the key to his insight: the deaths in the iron lung were due to elevated carbon dioxide levels. This was caused by the limitations of the external suppression principle. With it, it was not possible to calibrate how much air the patients got in and out, with the result that the body did not always exhale enough carbon dioxide.

The solution was the so-called Engström respirator, whose first prototype was completed in 1950. The respirator’s principle was the opposite of the iron lung: with overpressure through a tube in the trachea, air is forced into the lungs, and when the device releases the overpressure, the lung’s elasticity pushes the air out again.

An obvious disadvantage was, of course, that the patient could not talk or eat with a tube in his throat. But by transferring the air from the respirator’s mechanical piston to a separate system, where you could set the breathing volume and frequency, you could regulate the patient’s air flow with much greater precision than the iron lung could.

The Stockholm company Mivab began mass-producing the Engström respirator in 1951, and when Sweden suffered a major polio outbreak a couple of years later, it made a big impact. More than 3,000 people suffered from paralysis during this last polio epidemic in our country, and about 5 percent of them died. Without Engström’s invention, the deaths would probably have been many more.

Soon, the area of ​​use was broadened, and the respirator became standard equipment in operations and other procedures where the patient had to be anesthetized. Over time, Mivab became part of the giant international conglomerate General Electric Health Care.

Our view of death changed

The technology continued to be further developed and improved, and in the 1970s a significant technological leap was taken at Siemens-Elema in Sweden. In collaboration with physiology professor Björn Jonson, engineers Sven-Gunnar Olsson and Georgios Psaros developed the so-called Servo ventilator, which not only supports breathing but also provides measurement values ​​that can be used to diagnose breathing problems.

This contributed to the development of specialized intensive care units, and thanks to the Servo-Ventilator’s improved sensors, pressure, volume and flow could be regulated with increased precision. This made it possible to start ventilating even very small children, even premature babies who were so small that they could not be saved before.

Another change that came with the respirator was that over time, even severely brain-damaged people could be kept alive. This led to a change in our view of death: during the 1980s, brain death became the clinical criterion for death in most western countries, including Sweden, which was of great importance for organ donations and transplants. Nowadays, organs can be taken from a donor where the heart is still beating, which was impossible as long as the heartbeat itself meant that a person was defined as alive.

With a few exceptions, the respirator has long competed with the iron lung. But by 2020, British engineers have begun developing a modernized iron lung called Exovent. The reason: in the ravages of the global covid pandemic, it is feared that the respirator, and the specially trained healthcare staff it requires, will become in short supply.

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