Ventilators form the last line of defence against COVID-19.
Misha Friedman/Getty

Coronavirus ventilators: Why one machine is pivotal in the battle against COVID-19

As health authorities scramble to get the coronavirus pandemic under control, one device has become a symbol of hope and fear.

If it wasn't so macabre it would be almost poetic: An illness that aggressively attacks the lungs, caused by a newly discovered coronavirus, has spread so rapidly and completely that we've barely had time to stop and catch our breath.

The coronavirus responsible -- SARS-CoV-2 -- hijacks the cells of the throat and the lungs, causing the illness now dubbed COVID-19. Some people develop a fever and dry cough, others find themselves unable to breathe. Doctors can only manage the symptoms of infection. For mild cases, that requires rest and increased fluid intake, or perhaps painkillers for those feeling worse for wear.

But in the most severe cases, one biomedical device becomes indispensable: the ventilator. 

"The ventilator is the difference between life or death for people with severe COVID-19," says Brian Oliver, a respiratory disease researcher at University of Technology Sydney in Australia.

In critical COVID-19 infections, a patient's lungs become so damaged they can no longer breathe. To remedy this, doctors pass a tube down the windpipe, connecting it to an instrument that resembles a standing desk with tentacles. The machine, replete with knobs, switches, buttons and a digital screen, takes control of breathing. It mixes oxygen with air, warming the gas and pushing it into the lungs. Its static, mechanical thrums count out each breath. 

With confirmed cases of COVID-19 approaching 1 million, the enormous scale of the crisis has cast the device as the most necessary armament in the fight against a new, insidious foe. "Ventilators are to this war what missiles were to World War II," New York governor Andrew Cuomo said at a recent press conference. 

Global estimates suggest that around 5% of COVID-19 patients will require intensive care involving a ventilator. That might seem like a small figure, but physicians and doctors around the world have been warning of health care systems overrun with patients. Ventilator shortages in the worst-hit nations, such as Italy, have already forced health care workers to choose who gets to live. 

As the coronavirus continues its grim march across the global battlefield, nations are quickly finding out they don't have enough missiles. And so the pandemic is inspiring a wave of innovation and rapid development of new and improved ventilation devices that could be key to keeping the coronavirus in check until a vaccine or effective, standardized treatment comes along.

A handful of newly designed, cutting-edge ventilators may be on the way from the likes of tech giant Dyson , , MIT and a British consortium led by Airbus. But significant regulatory hurdles and engineering problems may keep them from getting to the hospitals that need them most quickly enough to stem the deluge. 

The ventilator has become a symbol of both the hopes and fears of health care workers across the globe as they struggle to get the pandemic under control. Indefatigable in its mission to keep lungs filling and emptying, the device has been a constant, silent force inside hospitals for over 60 years. 

Now it's being called on for its toughest mission yet.

Just breathe

Around 2 billion years ago, an evolutionary hiccup changed life on Earth: Ancient bacteria evolved the ability to convert carbon dioxide to oxygen, slowly changing the planet's atmosphere. The microorganisms that took advantage of this new air spurred an evolutionary cascade eventually resulting in the two spongy sacks in your chest: lungs.

Human lungs are full of branching passages that end in clusters of hollowed sacs known as alveoli, like a bunch of blueberries hanging from a bush. And there are millions of them. "Everyone has around 300 million of these alveoli," says Elena Schneider, a lung health expert at the University of Melbourne, Australia, "and each one is surrounded by really tiny blood vessels." The blood vessels are where gases are exchanged.

When you breathe in air, the alveoli fill up "like a balloon," says Schneider. The oxygen passes into the blood vessels and is carried throughout the body, while carbon dioxide present in the blood flows into the sacs before being exhaled.

For all this to occur, the body has to create a difference in pressure. When you breathe in, muscles in your chest and abdomen contract, decreasing the pressure inside, and allowing the lungs to expand and fill. The opposite occurs when you breathe out. Muscles relax, pressure increases and the lungs are squeezed, pushing carbon dioxide out.

In COVID-19, this process is disrupted. The virus infects and injures the alveoli, causing the body to ask for help from the immune system. Sometimes, that process can go into overdrive. "The immune response is sometimes so strong it can also damage the tissue," explains Oliver. 

Damaged tissue leads to a leakage of fluid and cells, which fill up the alveoli like so many water balloons, decreasing the amount of oxygen they can carry. This is the condition we call pneumonia, and it can be fatal. 

"When a person has pneumonia, fluid and pus in their lungs is what makes it difficult to breathe," says Oliver. In the most critical cases of COVID-19, patients experience a severe inflammation of the lungs. A ventilator becomes the only way to move oxygen into parts of the lung that aren't badly damaged by the virus.

The coronavirus pandemic has placed a spotlight on the devices as a last line of defense, a final effort to keep patients breathing. But the story of the ventilator begins much earlier -- around a century ago -- when another virus plagued the planet. 

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Heavy lungs

In the early 20th century, polio outbreaks haunted cities around the world, coming in waves and forcing sporadic shutdowns. Polio, like COVID-19, is caused by a virus. Shaped like a 20-sided-die, the virus sneaks into the nervous system and wreaks havoc. Damaged nerves result in paralysis, freezing up the muscles necessary to breathe. Patients with polio have healthy lungs -- but they can't draw a breath.

The virus, in the late 1920s, inspired the invention of the iron lung -- giant, cylindrical tanks with enough room for patients to lie flat on their back. At one end, the patient's head protrudes through a small opening. The iron lung was a "negative pressure ventilation" device that worked by altering the pressure inside the tank. This pressure difference helped the lungs fill and empty.

But when polio ripped through Copenhagen in the 1950s, a more efficient ventilation method was required. An anesthesiologist named Bjorn Ibsen instated a new protocol at his overcrowded hospital: Around 1,500 medical students ventilated polio patients with an inflatable bag, standing by each bedside, hand pumping air into their lungs.


The iron lung was first developed in the 1920s. Only a handful are still in use today.

CDC/GHO/Mary Hilpertshauser

"Mortality from paralytic polio was about 80%," says Arthur Slutsky, a mechanical ventilation expert and clinician at St. Michael's Hospital in Toronto. "Once mechanical ventilation was started, it went down to 40% overnight."

This form of ventilation -- "positive pressure ventilation" -- changed assisted breathing forever. Before the end of the 1950s, Forrest Bird, an eccentric American inventor, created the first reliable, mass-manufactured ventilator using the same principles. The semi-transparent, green ventilator was about the size of a shoebox, small enough to fit by a hospital bed. "His contribution was tremendous," Slutsky notes. Bird's invention has saved millions of lives. 

The ventilators fighting the COVID-19 pandemic aren't all that different from the green, transparent box Bird first tinkered with in the early 1950s: They pump air in and out of the lungs. Their core mission is the same. 

"What you're doing with a ventilator, in general, is to try and buy time so the body can heal itself," says Slutsky. 

That mission is made easier because today's devices have benefited from significant technological upgrades. A city of wires, electronic sensors and circuits sprawls out from the units seen in hospitals and theaters. Schneider says they can be individualized to make the process "much more tolerable and comfortable." And built-in alarms alert health care workers to the slightest breathing abnormalities. 

"It's like comparing a mobile phone from the 1980s to the latest phones," Oliver says.

Plugging the gap

Under normal circumstances, health care services would have a healthy supply of ventilators on hand. The coronavirus pandemic is anything but normal. 

Genetic mutations in the virus' genome have allowed it to spread faster and farther than any coronavirus before it. Although the lowest estimates suggest that only 5% of patients with a critical COVID-19 infection will need mechanical ventilation, the expansive reach of the coronavirus means we simply don't have enough devices to keep that percentage of people breathing

In Italy, where COVID-19 has killed over 10,000 people and overwhelmed the health care system, doctors have had to ration ventilators. The weight of choosing who receives life-saving ventilation and who, by default, will likely die, has left health care workers weeping in hospital hallways

Sparked by the urgent need for more, some of the world's biggest manufacturers have turned their attention from vehicles and vacuums to ventilators. 

Elon Musk , CEO of electric vehicle giant Tesla , shipped over 1,000 devices to California in late March and has committed to converting Tesla's New York facility into a ventilator production line. General Motors has partnered with ventilator company Ventec Life Systems to ramp up production in Indiana. British tech giant Dyson, a company mostly known for its vacuums and hand dryers, has an order with the UK's National Health Service for 10,000 of its newly designed "CoVent" systems. A team at MIT has prototyped an inexpensive ventilation device out of a small bag and mechanical paddles.

Health agencies, including the US Food and Drug Administration, Australia's Therapeutic Goods Administration and the UK's Department of Health and Social Care, have all signaled their intent to look at alternative ventilator strategies that could plug any gaps

The ventilator is not an overly complicated device to build. The number of manufacturers putting their hand up to remedy the expected shortfall in North America might even suggest creating such a device is easy. But there are engineering problems to overcome.

"There are some subtleties in making a ventilator," Slutsky says. He's been working with engineers, physicists and even a Nobel Laureate over the last few weeks, answering "simple" questions about design, how valves work and how to build a machine lung. "They're actually a little more complicated than people think." 

One big issue is distribution. Even if a company were to design and scale up production exponentially, as GM and Ventec are trying to do, how do they get ventilators from the factory to the hospitals where they're most needed? Slutsky sees inexpensive designs, which can be downloaded and manufactured by local engineering firms, as a way to quickly scale up production. 

"The idea here is to have a ventilator [but] keep it open-source so anybody can build it," he says.


Over 1,500 medical students hand-pumped air into the lungs of polio patients in the early 1950s.

Taechit Taechamanodom/Getty

Unintended long-term effects

The difference between medicine and poison is in the dose.  

"The ventilator, like any therapy we have, saves lives," says Slutsky. "It can also cause injury."

Severe COVID-19 infections and patients experiencing respiratory distress will require intubation -- the process of physically passing a tube down the windpipe. 

"An invasive intubation is something that you would only want if you really need it," says Schneider. Intubation can be prone to bacterial infection and may harm parts of the windpipe. 

More recent advances in ventilator research have focused on how machines themselves may damage the lungs. No matter how well you do it, positive pressure ventilation is intrinsically harmful because it exposes lungs to higher-than-normal pressure. If airflow is not carefully managed, lungs can overinflate. Slutsky has studied this problem for decades and compares it to blowing up a balloon. "If you blow it up too big, it's gonna pop," he says. 

Overinflation can cause a cascade of negative effects as lung cells stretch and withdraw. During the process, they release molecules that find their way into the bloodstream and travel to other organs, causing further complications. Patients with COVID-19 in critical care units may have to confront the reality of these unintended long-term effects somewhere down the line -- but in many cases, mechanical ventilation is the only option.

Slutsky suggests some patients may have long-term side effects, but there will also be "plenty" of people whose lung function returns to normal.

"I don't want the message to be, 'if you get on a ventilator, for sure your lungs are gonna be shredded,'" he says.

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If necessity is the mother of invention, the coronavirus pandemic should inspire a ventilator renaissance. 

The parallels with the polio epidemics of the 20th century are unavoidable: Those crises stimulated the invention of the iron lung and the emergence of positive pressure ventilation. Ventilators formed the last line of defense against death. They saved lives. They bought time for patients to heal and for doctors to develop new methods of treatment. 

Such a parallel inspires hope and fear. 

Ventilator shortages are widespread. In the US, President Donald Trump invoked the Defense Production Act -- a relic of the Korean War that enables and encourages widespread production of critical medical equipment -- to compel General Motors to speed up ventilator manufacturing. But new machines could still be a month away, and health authorities are pleading for them right now.

The situation has become so dire we're able to watch ingenuity and innovation take place in real time. 

In the UK, Formula One teams have collaborated on improving another type of breathing aid that might keep COVID-19 patients off ventilators altogether. Across the Atlantic in New York, doctors have taken to jury-rigging one ventilator to two patients to keep them breathing. One group suggests resources could be stretched even further, using a single ventilator for seven patients. And though medical associations have cautioned against such arrangements, soon there may be no other choice.

As the last line of defense, there are no guarantees mechanical ventilation will keep a patient alive. They're not a cure. But they form a critical component in COVID-19 health care. They buy time.

The ultimate goal is the same as it was during the polio epidemics: building a reliable, safe vaccine. "It was nice to have a ventilator that saved some people's lives," Slutsky says, "but the real thing that saved us was the polio vaccine." Vaccine development has progressed at great speed and dozens of potential candidates have been identified, but experts caution it's unlikely we'll see one until at least mid-2021. 

Until then, frontline health care workers will turn to a machine they've been using for over 60 years, holding out until the pandemic ends and we can, finally, breathe easily again. 

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Originally published March 2, 5 a.m. PT
Update March 7: Removed reference to acute distress