Medical

Modern iron lung designed to address ventilator shortage

Modern iron lung designed to a...
Rendering of the exovent in use
Rendering of the exovent in use
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Rendering of the exovent in use
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Rendering of the exovent in use
The exovent works on the same principle as the iron lung
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The exovent works on the same principle as the iron lung

British engineers are developing a modern version of the Negative Pressure Ventilator (NPV), more popularly known as the "iron lung," to provide COVID-19 patients under the care of the NHS with a simple, inexpensive alternative to ventilators.

One of the resources that is in critically short supply for treating COVID-19 patients in need of respiratory support is ventilators. They help to support breathing in people whose lungs have been heavily affected by the virus, but these machines face a number of problems.

The most obvious difficulty is that ventilators are in short supply across the world as health authorities scramble to secure enough to meet the current and estimated demand as the pandemic spreads. They are also complex, expensive, require monitoring by trained personnel, and are dangerous to use on even healthy people because they require the patient to be intubated and sedated, and sometimes even paralyzed.

Such Intermittent Positive Pressure Ventilators (IPPV), as they are formally known, work by means of positive pressure. That is, they pump air or oxygen directly into the lungs as a way to help a patient breathe. The iron lung is essentially the opposite.

First suggested in the 17th century, an iron lung, in its classic form, is a large, airtight cylindrical chamber big enough to hold a person, whose head sticks out at one end through a special collar. Inside the chamber is a diaphragm hooked to an electric motor. As the motor turns, it operates a crank that causes the diaphragm to expand and contract. As it does so, the volume inside the chamber becomes larger and smaller, causing the air pressure to rise and fall. This causes the patient's chest to expand and contract, allowing them to breathe even if they are totally paralyzed.

The exovent works on the same principle as the iron lung
The exovent works on the same principle as the iron lung

Such iron lungs were a common sight in hospitals and even private homes during the height of the polio epidemics of the 20th century, though they have since been superseded by more sophisticated machines. But COVID-19 might give them a new lease on life.

The product of the University of Warwick, Marshall Aerospace & Defence Group, the Imperial NHS Trust, the Royal National Throat Nose and Ear hospital, and teams of citizen scientists, medical clinicians, academics, manufacturers, and engineers, the new NPV device, called the "exovent," has already reached the prototype stage and will be tested at two intensive care clinics in the UK.

Unlike ventilators, the exovent doesn't require intubation and is much simpler in design and operation. According to the consortium responsible for its design, patients can remain awake, take medications, eat and drink, and talk to their loved ones on the phone. In addition, the machine improves heart efficiency by 25 percent over conventional ventilators, which can adversely affect cardiac functions.

The developers also say that the exovent can be used in regular wards, which frees up ICU beds for more serious cases. Enclosing only the thorax, the machine does not use compressed air or oxygen, has only a few moving parts, and the components are readily available. The design is also adaptable for individual patients.

It's estimated that, once approved, 5,000 exovents could be manufactured a week in the UK.

"We are delighted to be working with exovent to help scale up their non-invasive ventilator from prototype to volume manufacturing," says Margot James, Executive Chair, Warwick Manufacturing Group (WMG), University of Warwick. "Our engineers and researchers are collaborating with the exovent team on the design, engineering, component sourcing and assembly of the ventilator. I am extremely proud of the unstinting and dedicated efforts of our research team, led by Archie MacPherson at WMG, and glad that we are able to apply our expertise to this important project."

Sources: University of Warwick, Marshall Aerospace & Defence Group

10 comments
ChairmanLMAO
What the heck is with all these ancient techniques? Maybe all this stuff they are teaching is just money grabbing? Blood transfusions of recovered coronavirus just seems on the verge of pseudoscience. Wait, that was pseudoscience.
Grumps
https://www.nbcnews.com/health/60-years-iron-lung-us-polio-survivor-worries-about-new-2D11641456
Martha Ann Lillard, now 65, has spent most of the past six decades inside an 800-pound machine that helps her breathe.
Lillard owns her iron lung, which was built in the 1940s and runs on a fan belt motor that friends help patch together with car parts when it breaks.
“It feels wonderful, actually, if you’re not breathing well,” says Lillard. “When I was first put into it, it was such a relief. It makes all the difference when you’re not breathing.”
Lillard taught herself with great effort to walk again and she’s able to leave the respirator — but she often doesn’t want to. She says she has tried the portable positive pressure ventilators that most polio survivors use. Those devices force air into the lungs, often through a tube in the throat.
But Lillard says the harsh air from those devices causes “tremendous amounts” of inflammation and worsens asthma caused by post-polio syndrome, a debilitating condition common among many polio survivors. The devices are also difficult to keep clean and could introduce life-threatening bacteria into her vulnerable system, says Lillard, who is 4-foot-9 and weighs just over 100 pounds.
“If I use the positive pressure vent, I’m not as well rested,” she says. “Some people have said I’d rather die than leave my iron lung, and it makes it sound like I’m not trying to be modern, and it’s not like that at all.”

Could be better than a ventilator if they are causing damage to lungs?

No microchips....even better.
Mat fink
I hope they left the smiley face on the Henry Hoover after giving it that black paint job.
paul314
Every little bit helps. There are supposedly some things positive pressure can do that negative pressure might not be able to do (such as keeping all the tiniest lung passages inflated), but even if all that the negative-pressure versions can do is to relieve ICU beds that will be a huge thing.
Christopher Smith
I began using large Drinker-Collins Iron Lungs (and what was know as the “Cuirass”, an abbreviated version) in 1968. They were in storage after the widespread Polio Virus epidemics and we would occasionally put them to use on Adults and adolescents (dependending on the physical size of the device) who required ventilatory Life Support, but not Intubation. Oxygen was administered by Venturi Mask or either external nasal cannula or we’d lube then droop a straight plastic Nasal Cannula through a nostril down into the nasal pharynx, before sighting it at just above the Uvula (if with a mouth open and you could see the tip, you’d retract) - taping it externally to the cheek or nose to set it’s correct depth. Oxygen was titrated through a Flowmeter attached to an oxygen source, air/oxygen mix box or O2 Blender, a somewhat inexact proportioning device, depending on how fancy you got or how much time “in your “Extra time” sprinting between emergencies you attended. We used graphs, tables formulas and gas analyzers to estimate and measure O2 Concentration which you sampled while hand-pumping a rubber bulb often (the Beckman Analyzer).. It was an Art and rather laborious with many separate operations. It took years to learn the Craft. I was an Operator and continued so for 35 years.

But I digress. The Iron Lung’s set pressure was adjusted opening or marginally closing leak flaps set into the total body enclosing chamber, set by twisting knurled thumbscrews altering flap leakage. The floor device that looks and for all intentsI iS an older style vacuum cleaner, pulled ambient Air through a hose from within the body enclosing chamber generating a (-) Negative atmosheric pressure. This pulled Air through the mouth and nose. The rate, or speed of breathing was adjusted by electronics either on the floor mount vacuum generator or at the box seen mounted outside the Thorax enclosing chamber in the New Atlas article. You could twist a dial controlling an interrupting pressure valve at variable lengths of time - you set the rate using a wall clock or with your wrist watch. The size, or Volume of each breath was measured using a small handheld “Wright” Spirometer using either a mouthpiece placed to a Patient’s mouth or with a resuscitation mask attached to the Spirometer if they were unconscious or sedated.

So constant pressure was nessesarily interrupted along the pattern of a normal respiratory rate, the depth of each breathe by variably managed body or thorax chamber‘s air leakage and the size of each breathe directly measured by handheld Spirometer, which would set you off to “nudge” an air flap open or closed - ever so marginally.

The later developed smaller Cuirass Neg Pressure ventilator only enclosed Thorax and not Abdomin, which was perceived as an improvement over the massive Iron Lungs (aka “Iron Maidens”) we also used. Compression of abdominal contents was eliminated, and patient access was facilitated, simpifiying I.V. placements and toiilet and bed linen changes as well and could be rapidly removed in dire extremis for CPR.. The arms and legs were outside the “Turtle-like” shell. Negative Pressure (vacuum) was likewise conveyed through a hose to the chest shell (similar to a Turtle shell) from a floor rolling “Bendix”-style Canister vacuum cleaner. Wired atop the “Vacuum cleaner” were controls to adjust the respiratory rate’s speed - this is pre-integrated printed circuits, everything was hard-wired.

The Cuirass was a simplification over the Iron Lung, both complexity, design and cost.

These devices were superseded by the development iof the Mechanical Ventilator, both Volume or Pressure generating Devices and the expanded use of Endotracheal tubes.

An interesting historical note, pre-existing the Iron Lung, as a measure to save lives during the widespread paralytic Polio Virus Epidemics, Pulmonary Ward rooms were constructed. Under a floor was attached a great Piston that could be adjusted to move a room’s entire Floor up and down to alternate the ambient pressure (both negative and positive pressure) within the room. All Patient’s beds moved up and down vertically, say 12-15 times/minute! Air was let in and out of the room through Windows - and all bedded Patient’s lungs, as well as all Caregivers and Visitors, in unison. Everyone was forced to breathe AND speak in together, a curious sensation! As you might imagine, as was the case, Birds and Bees (etc) were sucked in and out through the Windows necessitating the placement of Window screens.

Now, as in the past, when there are no more Ventilators, searching through the Storerooms for previous Ventilation devices, (or in archives for designs) you must build your own. If nothing else you may find Birds flying about on Patient Rounds.
ljaques
In 3rd world countries everywhere, cardboard boxes and shop vacs are quickly being repurposed into ventilators to keep their loved ones alive during the COVID-19 crisis, I'll bet. Bravo to them!
Tony Morris
I don't understand the "Pulmonary Ward Room". Where is the pressure differential when the entire patient including mouth and nose, is subjected to the pressure fluctuations?
vince
How will this work with deaf people? Will they be able to move their arms to talk with their family (American Sign Language). Will they be able to text on a phone to talk with their family and to read books on an ereader or tablet PC to do banking, etc while stuck in the machine?
Once again
Christopher Smith. lol!
"An interesting historical note," ... please cite your source on the birds and the bees in and out of the windows. I would love to read about this!
Gadget
So an NPV is a great idea, but we are in 2020 folks and we have better tech at our disposal, often almost instantly available. How about 3D scanning patients on diagnosis of the Covid-19 / SARS-CoV-2 version. Then print up a fully encasing hard plastic chest mold at say 20% greater than actual body size. Seals top and bottom, side locking seams for easy removal for treatment interventions and small pressure pump / valve systems. Self inflating airbed ones might work well enough. Chest units would be low cost per person and disposable / recyclable after the patient is released. Handles on the side to make it easy for nursing staff to turn them over. Come on Elon Musk this is right up your alley.