Dyson CoVent mockup

We’ll breathe again: engineering responds to the coronavirus crisis

Image credit: Dyson

The Covid-19 pandemic has brought a surge in medical research aimed at slowing, relieving and eventually preventing the disease but one of the more unusual calls to arms in the current situation was the request to engineering companies, including Formula 1 teams and vacuum-cleaner manufacturers, to come to the nation’s aid. In fact, history shows that commercial engineering has always had a place in such crises and has often been pivotal.

For most people who develop Covid-19 it will be no worse than a bad cold or a bout of ’flu, but what makes this virus so dangerous is the 10 per cent of cases where the disease can lead to acute respiratory distress syndrome (ARDS). In these cases, the virus provokes a massive inflammatory over-reaction in the lungs, which can induce severe breathing difficulties, pneumonia and, ultimately, organ failure and death. This is where engineering can and always has stepped in.

When the diaphragm or lungs can’t cope on their own, some form of mechanical ventilation will be needed to keep the patient alive, and this has a long engineering history. Galen in the second century AD had noted that breathing was required to maintain circulation but the mechanics of this only really came under the spotlight in the 16th century when Andreas Versalius first described positive ventilation: “But that life may be restored to the animal, an opening must be attempted in the trunk of the trachea, into which a tube of reed or cane should be put; you will then blow into this, so that the lung may rise again and take air.”

The tools may be a shade more sophisticated now, but this is in effect how positive ventilation is applied to a patient today.

Any engineer can tell you that blowing air into the lungs is not how lungs ordinarily operate. It was a Cornishman, John Mayow, who in 1668 noted the elegant system by which we actually breathe. When the diaphragm is pushed downwards it creates an area of negative pressure in the chest cavity into which air flows to equalise the pressure. When the diaphragm relaxes, the air and any waste gases are expelled. This provided the first clue as to how a person might be artificially respirated.

However, it would be another 160 years before physician John Dalziel built a negative-pressure ventilator in 1838 to assist with breathing. This was a full-body ‘tank’ type ventilator, of the sort that later became known as an ‘iron lung’. It consisted of an airtight box in which the patient sat while air was manually pumped – the negative pressure created by a pair of bellows inside the box, which was worked from the outside by a piston rod and a one-way valve. Windows in the side of the box allowed Dalziel to observe if the patient’s chest was rising and falling. A simple pressure gauge prevented the over-inflation of the lungs. Sadly Dalziel did not publish the results of his tests although his colleague Dr Lewis of Leith noted an experiment where a drowned sailor was bought to Dr Dalziel: “...the effects of air entering into and returning from the lungs were very visible on the cheeks, the lips, and also the nose. A lighted candle was extinguished by being held under one nostril, and again lighted by being placed opposite the other. The dead body was made to breathe in such a manner as to lead the bystanders to suppose that the unfortunate individual was restored to life.”

Throughout the 19th century prototype ventilators appeared, but it was the great polio epidemics of the early 20th century that brought ventilation technology to the fore. In patients whose diaphragm had been paralysed by polio, only an artificial respirator could keep them alive, and in bad outbreaks, thousands might be needed.

The first widely available ‘iron lung’ was the brainchild not of a doctor but an industrial hygienist. Philip Drinker’s background was in engineering rather than medicine and his invention was designed to answer the industrial problem of coal-gas poisoning. Working at Harvard School of Public Health with physiologist Louis Agassiz Shaw they devised a negative pressure tank respirator. This consisted of a ‘whole body’ tank in which the patient lay, with their head protruding from the top via an airtight seal. Previous machines had relied on manual pumping but obviously in cases where a patient might expect to be days, weeks or even months on the machine that was not practical. So Drinker turned to another new invention – the vacuum cleaner – for inspiration. His machine was powered by an electric motor and air pumps from two vacuum cleaners, which changed the pressure inside the sealed box, inflating and deflating the lungs.

Although invented for coal-​gas poisoning, the Drinker respirator first found use, and later fame, in treating polio victims. On 12 October 1928, an eight-year-old girl suffering from the disease became the first person to use a Drinker respirator. She recovered her normal breathing pattern within 60 seconds and the iron lung became an overnight sensation. 

Drinker, Shaw and Harvard University were keen to exploit this breakthrough and, in the face of numerous other medical faculties around the world rushing to make their own negative pressure respirators, they patented the device.

One of those rushing to copy Drinker was American inventor John Haven Emerson. Working from his small machine shop in Boston, he began to work on his own ventilator at the beginning of a polio epidemic in the early 1930s. He improved the Drinker device, adding a flexible diaphragm that more accurately mimicked the natural operation of the lungs, and whose double layer provided a fail-safe should one layer rip. This and various other improvements, including emergency hand operation should the motors fail, and a quick-release system, made the Emerson ventilator (or ‘Old Number One’, as his first machine was called) a valuable tool in the fight against polio. But what was most revolutionary was the cost. At only $1,000 (around $16,000 at 2020 values) it was less than half the price of a Drinker machine, and as thousands would be needed in an epidemic, it rapidly became the machine of choice.

Drinker and Harvard pursued a disastrous patent infringement case against Emerson, who claimed life-saving equipment should be freely available to all. More importantly, in court he demonstrated that there was ‘prior art’ for every aspect of the Drinker machine, so not only did Drinker lose the case but his patents were invalidated.

With the patents removed the floodgates were open, and doctors and engineers in many countries rushed to produce polio respirators. In Britain it was Scottish doctor Robert Henderson who got there first in 1934, although all he received for his efforts was a reprimand from his hospital for using their facilities to build his machine without their permission.

It was in Australia, however, that the story entered its next phase, and in the hands not of a medic but a biomedical engineer, Edward Both – sometimes known as the ‘Edison of Australia’. For Australia the problem with the Drinker machines was twofold. They were heavy to transport, at around 340kg, and expensive. Even the Emerson machine, though cheaper, was expensive to ship to Australia. So the South Australia Health department asked Both and his brother to engineer an Australian iron lung. Their machines, similar in operation to the Drinker and Emerson devices, were made of lightweight plywood, which was cheap to construct and ship across the country. Where a Drinker machine might cost £2,000 to buy and ship to Australia, the Both respirator cost only £100 and could be in use the day it rolled off the production line.

Both travelled the world demonstrating his machine and it was in London in 1938 that he attracted the attention of an unlikely ally. William Morris, British car manufacturer and designer of the iconic ‘Bullnose’ Morris, had recently been ennobled as Viscount Nuffield and endowed the Nuffield Department of Anaethetics at the Radcliffe Infirmary in Oxford. Both lent the hospital a respirator, which appeared in a departmental film that Nuffield saw. In the midst of another debilitating polio epidemic, Nuffield asked why more hospitals were not using the machines and was told the answer was cost.

Realising that Both’s simple, cheap design was suitable for mass production, he turned over part of his Cowley car plant in Oxford to making the machines, which he offered free of charge to any Commonwealth hospital that asked for one.  

When criticised for not waiting until the machine was further developed he replied: “If I had waited for the perfect car, I should be bankrupt now. We must get on with the best possible model available now and improve on it as we go along. It seems a pity to think that some of these respirators will be used as coal scuttles, but it is more tragic still to think of the possibility of a life being lost through the failure on my part to spend £25 or £30.”

Soon, the Morris company was producing Both-Nuffield respirators by the thousand, 1,700 of which were given away.

The sight of rows of iron lungs in hospitals would not last, though. Polio vaccination programmes have largely eradicated the disease, and where artificial ventilation is now needed, positive pressure systems are generally used, where air is blown directly into the patient’s lungs.

The breakthrough came in Copenhagen in 1952, during another polio outbreak. At Blegdams Infectious Disease Hospital anaesthesiologist Bjorn Ibsen realised his patients were dying from respiratory failure, not renal failure as was generally thought. He recommended the simpler and more accessible intubation and positive pressure ventilation, and saw mortality reduced from 87 per cent to 40 per cent. His system was primitive, however, involving 1,500 students manually pumping air into patients for a total of 165,000 hours.

The invention of positive pressure ventilation and the decrease in polio cases also brought a change in emphasis, moving away from ventilation to support paralysis to supporting oxygenation, particularly in cases of ARDS, and this has brought us to our current situation, surprisingly similar to that faced by medics in the 20th century polio epidemics.

On 16 March 2020, the UK government issued an appeal to engineering companies for help in designing and manufacturing the huge quantities of respirators and ventilation aids that would be required in a major outbreak of Covid-19. The brief was challenging – with 8,175 ventilators available in the UK at the start of the outbreak the government was looking to commission another 30,000 machines. These new devices must be able to work continuously for at least 14 consecutive days, be small enough to fit to a hospital bed but strong enough to survive a fall on the floor, offer full and support ventilation, have swappable batteries, clear displays, take no more than 30 minutes to be trained on and sense when a patient stops breathing and intervene. They must also be made of parts that can all be dismantled, swapped out and disinfected.

One of the first to respond to the call was, perhaps not surprisingly, a company that knows all about pumping air – Dyson. The firm’s engineers designed their own ventilator in collaboration with medical technology company The Technology Partnership in Cambridge, shrinking a development schedule that would usually last two to three years down into just a few weeks. Fortunately their Covent system can use readily available vacuum-​cleaner pumps and other commercial parts, just as the early Drinker iron lungs did. With the prototype already in testing, the government has now stood Dyson down in the UK but the company hopes to be able to provide its ventilators elsewhere.

Dyson was not alone. Engineers, anaesthetists and surgeons from Oxford University and King’s College London developed their own Oxvent system, to be mass-​produced by Smith​+Nephew if required, though this didn’t transpire. Oxvent is a stripped-down machine, offering less sophistication, but it is cheap and quick to manufacture – something that John Haven Emerson would undoubtedly have appreciated.

Given the urgency of the need, other groups are looking at mass-producing existing, proven models. The Ventilator Challenge UK consortium comprises two current ventilator manufacturers, Penlon and Smiths, working with Airbus, McLaren, Rolls-Royce and Ford using the manufacturing clout of the big engineering companies and the expertise of a Formula 1 team to simplify fabrication and ramp up production.

McLaren F1 is also working as part of the ‘Pitlane Project’ with other F1 teams on a ‘continuous positive airway pressure’ (CPAP) device that aids breathing without the need for invasive mechanical ventilation. With clinicians at UCL they have been reverse-engineering an existing CPAP for mass production. No doubt Lord Nuffield would have been delighted to see the cutting edge of motor racing technology being put to medical use, just as he turned over his Morris plant at Cowley to making iron lungs.

At the time of writing, many of the ventilators developed in response to the national need are undergoing clinical assessment.

We are still far too early in this worldwide pandemic to see just how these plans will develop and whether, both in the UK and globally, modern ventilation technology will come to the timely rescue of the sick, as it has done in previous epidemics. This work has always gone hand in hand with industry and technology. Necessity is the mother of invention and the engineers working in these companies will play a vital role just as they have done so many times before.

Sign up to the E&T News e-mail to get great stories like this delivered to your inbox every day.

Recent articles