Tag Archives: breathing

What are ‘iron lungs’, and could this old tech still be useful today?

Although they’re relatively old technology in this day and age, there is renewed interest in iron lungs today against the backdrop of the coronavirus pandemic.

An iron lung device. Image credits The B’s / Flickr.

Few devices can boast having as terrifying — and cool — a name as the iron lung. These somewhat outdated medical devices were the earliest devices designed to help patients breathe. Compared to modern breathing aides, these devices were huge and quite scary-looking.

Still, iron lungs were a very important development at their time. In the aftermath of the COVID-19 epidemic, there has also been renewed interest in these devices as they can be used as an alternative to modern ventilators.

So let’s take a look at exactly what iron lungs are, and how they came to be.

So what are they?

Iron lungs are quite aptly named; unlike other modern ventilators, they function using the same mechanisms as our own lungs.

An iron lung is a type of negative pressure ventilator. This means that it creates an area of low-pressure or vacuum to move and draw air into a patient’s chest cavity. In very broad lines, this is the exact mechanism our bodies employ, via movements of the diaphragm, to let us breathe.

The concept behind these devices is quite simple. The main component of an iron lung is a chamber, usually a metal tube (hence the ‘iron’ part in its name) that can fit the body of a patient from the neck down. This acts as an enclosed space in which pressure can be modified to help patients breathe. The other main component of the device is mobile and actually changes the pressure inside the tube. Usually, this comes in the form of a rubber diaphragm connected to an electrical motor, although other sources of power have been used, including manual labor.

Patients are placed inside an iron lung, with only their head and part of their neck (from their voice box upwards) left outside the cylinder. A membrane is placed around their neck to ensure that the cylinder is sealed. Afterward, the diaphragm is repeatedly retracted and contracted to cycle between low and high pressure inside the chamber. Because the patient’s head and airways are left outside of the cylinder, when pressure is low inside it, air moves inside the patient’s lungs. When pressure increases inside the cylinder, the air is pushed back out.

The whole process mirrors the way our bodies handle breathing. Our diaphragm muscles draw on the lungs, increasing their internal volume, which pulls air in from the outside. To breathe out, the diaphragm muscle squeezes on the lungs, pushing air out. Iron lungs work much the same way, but they expand and contract the lungs alongside the rest of the chest cavity from outside the body.

This process is known as negative pressure breathing; low (‘negative’) pressure is generated in the lungs in order to draw in air. Most modern ventilators work via positive pressure: they generate high pressure inside the device to push air into the patient’s lungs.

One advantage of such ventilators is that patients can use them without being sedated or intubated. On the one hand this eases the pressure on medical supplies each patient requires; on the other, it slashes the risks associated with the use of anesthetics — such as allergic reactions or overdoses — and the risk of mechanical lesions following intubation.

Epidemics, pandemics

An opened iron lung device at the Science Museum, London. Image credits Stefan Kühn / Wikimedia.

“The desperate requests for ventilators in today’s treatment of patients in the grasp of the coronavirus brought to mind my encounter with breathing machines in the early 1950s polio epidemic, when I signed up as a volunteer to manually pump iron lungs in case of power failure at Vancouver’s George Pearson Centre,” recounts George Szasz, CM, MD, in a post for the British Columbia Medical Journal.

Iron lungs saw their greatest levels of use in developed countries during the poliomyelitis outbreaks of the 1940s and 1950s. One of the deadliest symptoms of polio is muscle paralysis, which can make it impossible for patients to breathe. The worst cases would see patients requiring ventilation for up to several weeks. Back then, iron lungs were the only available option for mechanical ventilation, and they saved innumerable lives.

As technology progressed, however, iron lungs fell out of use. They were bulky and intimidating machines, hard to transport and store despite their reliability and mechanical simplicity. With more compact ventilators, the advent of widespread intubation, and techniques such as tracheostomies, such devices quickly dwindled in number and use. From an estimated height of around 1,200 iron lung devices in the U.S. during the ’40s and ’50s, less than 30 are estimated to still be in use today

There are obvious parallels between those polio epidemics of old and today’s COVID-19 pandemic in regards to the need for ventilation. Machines such as the iron lung have been suggested as a possible treatment option for COVID-19 patients due to this. For most cases, such devices can help, but not for all.

In cases of severe COVID-19 infections, the tissues of the lungs themselves are heavily affected. A buildup of fluid in the lungs can physically prevent air from reaching the alveoli (the structures in the lung where gases are exchanged between the blood and the environment). While iron lungs can perform the motions required to breathe even for patients who are incapable of doing it themselves, they cannot generate enough pressure to push air through the tissues affected by a COVID-19 infection.

“Iron lungs will not work for patients suffering from severe COVID-19 infections,” explains Douglas Gardenhire, a Clinical Associate Professor and Chair of Respiratory Therapy at the Georgia State University (GSU) Department of Respiratory Therapy. “Polio interrupted the connection between brain and diaphragm and while some polio patients did have pneumonia, it was not the principal issue. For the most part, the lungs themselves did not have any change in their dynamic characteristics.”

“COVID-19 pneumonia physically changes the composition of the lungs,” adds Robert Murray, a Clinical Assistant Professor at the GSU. “The consolidation of fluid in the lungs will not respond with low pressure generated by the iron lung. The lungs of a COVID-19 patient will be a heterogenous mix of normal and consolidated lung tissue making mechanical ventilation very difficult.”

Still an alternative

Although patients with severe COVID-19 infections might not benefit from the iron lung, there are cases in which the device can prove useful. One paper (Chandrasekaranm, Shaji, 2021) explains that there still is a need for negative pressure ventilators in modern hospitals, especially for patients who have experienced ventilator-induced lung injuries. The use of negative pressure ventilators, especially in concert with an oxygen helmet, may also play a part in reducing the number of infections by limiting the spread of viruses through contaminated materials in cases where resources are stretched thin, the team adds.

While the concept is being retained, however, the actual devices are getting an upgrade. One example is the device produced by UK charity Exovent, which aims to be a more portable iron lung. Exovent’s end goal is to provide a life-saving device that will impose fewer limits on what activities patients can undertake. A seemingly-simple but still dramatic improvement, for example, is that patients can use their hands to touch their faces even while the Exovent device is in operation. Eating or drinking while using the device is also possible.

Exovent’s ventilator was designed before the coronavirus outbreak to help the millions of people suffering from respiratory issues including pneumonia worldwide. However, its designers are confident that, in conjunction with oxygen helmets, it can help patients who are recovering from a coronavirus infection — a process that leaves them with breathing difficulties for months.

All things considered, iron lungs have made a huge difference for the lives of countless patients in the past, and they continue to serve many. Although most of them today look like archaic devices, engineers are working to update and spruce them up for the modern day. And, amid modern ventilators, there still seems to be a role — and a need — for devices such as iron lungs.


Mosquitoes hunt first by smell, then by eyesight

Smelling is key if you’re a hungry female mosquito, a new study reports.


Image via Pixabay.

A team of researchers led by members from the University of Washington has looked at the brains of female mosquitoes in real-time to understand how they identify, track, and home in on their next meal. The process integrates information from the visual and olfactory sensory systems, they report. The insect’s olfactory system catches the scent of its target and triggers chemical changes in the brain of the female mosquito that makes her visually scan her surroundings for specific types of shapes and fly toward them.

Smell first, find targets later

“Our breath is just loaded with CO2,” said corresponding author Jeffrey Riffell, a UW professor of biology. “It’s a long-range attractant, which mosquitoes use to locate a potential host that could be more than 100 feet away.”

Only female mosquitoes feed on blood — the guys dine on pollen. However, this also means that only female mosquitoes bite people and spread diseases such as malaria. The present research comes as an effort from the team to better understand how the insects find their prey (or ‘hosts’) to bite, which could help develop new methods to control and reduce the spread of mosquito-borne diseases.

The olfactory cue that triggers the hunting behavior in female mosquitoes is carbon dioxide (CO2), Riffell’s prior research has shown. For the insects, smelling CO2 is a telltale sign that a potential meal is nearby, “priming” their visual systems to hunt for a host — so the team focused their study on this gas. They analyzed the changes triggered by CO2 in mosquito flight behavior and recorded how it impacts the brain activity in the olfactory and visual centers.

Data was collected from roughly 250 individual mosquitoes during behavioral trials conducted in a small circular arena, about 7 inches in diameter. The arena was fitted with a 360-degree LED display frame, and each mosquito was tethered in the middle of the rig using a tungsten wire. The mosquito’s wings were monitored from below with an optical sensor, while the LED display showed different types of visual stimuli and odors were fed into the area using an air inlet and vacuum line. What the team wanted to see was how the tethered Aedes aegypti mosquitoes responded to visual stimuli and puffs of air rich in CO2.

The researchers report that one-second-long puffs of air with 5% CO2 — for comparison, we exhale air containing 4.5% CO2 — made the mosquitoes beat their wings faster. Certain visual elements (a fast-moving starfield for example) didn’t much influence their behavior. Other elements (the team used a horizontally moving bar)  caused the mosquitoes to beat their wings faster and attempt to steer in the direction of the bar. This response was more pronounced if researchers introduced a puff of CO2 before showing the bar.

“We found that CO2 influences the mosquito’s ability to turn toward an object that isn’t directly in their flight path,” said Riffell. “When they smell the CO2, they essentially turn toward the object in their visual field faster and more readily than they would without CO2.”

The team also repeated the experiment with a genetically modified Aedes aegypti strain created by Riffell and co-author Omar Akbari, an assistant professor at the University of California, San Diego. The neurons in this strain’s central nervous system were engineered to glow fluorescent green when active.  The team could cut a small portion of the mosquito’s skull and use a microscope to record its neuronal activity in 59 areas in the lobula (part of the optic lobe) in real time.

When the mosquitoes were shown a horizontal bar, two-thirds of those regions lit up, the team reports, suggesting a response to the visual stimulus. When exposed to a puff of CO2 before being shown the bar, 23% of the regions had even higher activity than before. This indicates that the CO2 primed the areas of the brain that control vision to elicit a stronger response to the bar. The authors report that the reverse — a horizontal bar triggering increased activity in the parts of the mosquito brain that control smell — didn’t happen.

“Smell triggers vision, but vision does not trigger the sense of smell,” Riffell concludes.

“Olfaction is a long-range sense for mosquitoes, while vision is for intermediate-range tracking. So, it makes sense that we see an odor — in this case CO2 — affecting parts of the mosquito brain that control vision, and not the reverse.”

Mosquitoes can pick up scents over 100 feet away, the authors explain in their paper. Their eyesight, however, is most effective at distances of between 15 to 20 feet.

The paper “Visual-Olfactory Integration in the Human Disease Vector Mosquito Aedes aegypti” has been published in the journal  Current Biology.

Mistletoe exhibits unique, stunning biological property

Mistletoe — a plant whose long history intertwines with druids, Vikings, and more recently, Christmas kissing — has been cast in a dramatic light by a new study. Researchers were surprised to see that a key piece of machinery essential for aerobic respiration in animals and plants is, well, missing.

Mistletoe is essentially a parasitic organism, deriving much its nutritional requirements from its host. Parasitic plants have modified roots which penetrate the host, allowing it to extract its water and nutrients, but over the years, mistletoe seems to have developed another intriguing adaptation.

All known multicellular life, both plants and animals, use an enzyme called Complex I to breathe, but that component is missing in European mistletoe (Viscum album). It seems that over millions of years of evolution, the European mistletoe found another way to produce energy for breathing — its alternative energy pathways include glycolysis which generates energy in a different part of the cell.

Dr. Andrew Maclean, a PhD student at the John Innes Centre and lead author of the study, explains:

“We were following up earlier studies that had shown genes responsible for producing Complex I were missing, but we thought they may have relocated to other parts of the genome. We were stunned to discover that mistletoe has managed to dispense with this piece of metabolic machinery that was thought to be essential for all multicellular organisms.”

Image credits: Andrew Davis / John Innes Centre.

The scientists don’t know for sure why and how this happened, but it’s likely got something to do with the mistletoe’s parasitic nature. The plant probably compensates its breathing by leeching off its host.

“But maybe because mistletoe is a parasite and it gets lots of nutrition from its host then it doesn’t need a high capacity for respiration.”

This offers an exciting, unique glimpse into the evolution of a parasitic plant, but it’s not clear if other plants may have developed a similar mechanism. Mistletoe isn’t the most dangerous of parasites, but some of its relatives can be devastating, and understanding their biochemical mechanisms could one day help us better protect crops.

Mistletoe is a hemiparasite, meaning it can perform photosynthesis and produce some sugars for energy production, but other parasites are more damaging and extract everything they can from the host,” adds Maclean.

Mistletoes are often considered as pests that kill trees and devalue natural habitats, but recently, some species have been recognized as ecological keystone species, having a disproportionately positive impact on their ecosystems. For instance, a study of mistletoe in junipers found that more juniper berries sprout where mistletoe is present, as the mistletoe attracts berry-eating birds, which also eat some of the juniper berries. This counter-intuitive interaction means that although the mistletoe technically parasitizes the juniper, it also helps it spread more and contributes to a richer overall biodiversity.

“Absence of Complex I Is Associated with Diminished Respiratory Chain Function in European Mistletoe” was published in Current Biology.

Dusty air.

Researchers identify main factors of home indoor air pollution: marijuana surprisingly plays a big role

A new study led by San Diego State University researchers has identified the most important factors that go into home indoor air pollution. Tobacco and marijuana smoking turned out to be some of the biggest offender — marking the first time the drug was found to play such a role.

Dusty air.

The researcher’s main goal was to understand what behaviors lead to an increase in airborne particle densities in homes, leading to unhealthy or even hazardous environments for kids. So the team, led by SDSU environmental health scientist and lead author Neil Klepeis, worked with almost 300 families living in San Diego which had at least one child aged 14 or younger and one or more smokers.

Each home had a pair of air particle monitors installed — one as close to the area where the families reported smoking as possible while still being indoors, and one in the child’s bedroom. These sensors could pick up particles between 0.5 and 0.25 micrometers in size, the diameter that includes dust, spores, combustion byproducts as well as auto exhaust. These particles can have a nasty effect on health since they’re small enough to reach deep into the lungs and can cause a wide range of lung and cardiovascular issues.

Out of the total, 44 (22.8%) of families reported at least one household member smoking at least one cigarette indoors in the 7-days prior to the interview. Homes without indoor cigarette smoking reported indoor smoking of cigars (1.3%), hookah (0.8%), electronic cigarettes (14.1%), marijuana (10.1%), and other drugs (0.7%). Nearly all families reported opening a window (95.3%) or opening a door (96.9%) for ventilation purposes. Most homes (60.1%) reported using an exhaust fan in their kitchen and 8.3% of homes used an air purifier. No significant differences in ventilation activities were seen between homes with indoor and outdoor smoking, except the use of central air conditioning which was higher among homes without indoor cigarette smoking (25.5% vs. 6.8%).

On average, the homes had 2.6 bedrooms, 1.6 bathrooms and were mostly one story.  The team notes that “with the exception of the number of doors leading outside, none of the home characteristics of families with and without self-reported indoor cigarette smoking differed significantly.”

Up in smoke


The monitors worked continuously for three months, feeding air quality data to the researchers.The team also carried out two sessions of interviews with each family to ask about their schedule to get an idea of what activities were likely to occur in the house at various times, especially cooking, cleaning, and smoking, as these tend to generate said particles.

Families that reported smoking cigarettes indoors had an average particle level almost double that of non-indoor-smoking families. These particles included nicotine and combustion byproducts, both linked to health issues especially for children. Surprisingly enough, marijuana smoking contributed to in-home air pollution about as much as tobacco smoking. Burning candles or incense, frying food in oil, and spraying cleaning products also led to an increase in the number of fine particles.

“The aim of our research is, ultimately, to find effective ways to promote smoke-free homes and also to find good strategies, in general, for reducing exposure to household pollution,” Klepeis said in a press release. “The findings from our work will allow for better education and feedback to families.”

The team plans to expand on the marijuana findings to see whether the rise in indoor pollution resulting from its use translates into increased exposure to combustion byproducts and cannabinoids in nonsmokers living in the house.

In the meantime, if you’re worried about the quality of air in your home or simply want to tidy it up a bit, here’s a handy guide by NASA to decide what plants to get. They also look pretty, and green, and will make you feel better. Win-win-win!

The full paper “Fine particles in homes of predominantly low-income families with children and smokers: Key physical and behavioral determinants to inform indoor-air-quality interventions” has been published in the journal PLOS One.

Naked mole rats.

The African naked mole-rat can keep its brain alive for more than 5 hours with no oxygen

No oxygen? No problem — when faced with a lack of oxygen, African naked mole-rats take a cue from plants and start metabolizing fructose to survive, a new paper reports.

Naked mole rats.

There’s no metabolic tweak that would make them less ugly though.
Image credits Thomas Park / UIC.

You know what would really ruin your day? A lack of oxygen.

But that’s only because we’re humans and not the awesome Heterocephalus glaber or African naked mole-rat. Individuals of this species are used to living jam-packed with hundreds of their kin in small, poorly-ventilated burrows — where the oxygen-o-meter often falls below breathable levels. So the hairless critters have evolved to counteract this by copying a part of the plant metabolism. Understanding how their bodies do this could open the way to treatments for patients suffering crises of oxygen deprivation, as in heart attacks and strokes.

“This is just the latest remarkable discovery about the naked mole-rat — a cold-blooded mammal that lives decades longer than other rodents, rarely gets cancer, and doesn’t feel many types of pain,” says Thomas Park, professor of biological sciences at the University of Illinois at Chicagoand lead author of the study.

The team exposed naked mole-rats to low oxygen conditions in lab settings, and subsequently found high concentrations of fructose in their bloodstream. This compound was shuttled to neurons via molecular fructose pumps which are only used in the intestine walls of all other mammal species. Park’s team reports that when oxygen levels fall, the naked mole-rats’ brain cells begin metabolizing fructose, a process which releases energy without needing any oxygen. Up to now, this metabolic pathway was only documented in plants — so finding it in the moles was a big surprise.

Fructose metabolism allows the moles to live more than five hours through oxygen levels low enough to kill a human in minutes. Since only their brains are kept at full power by the compound, the moles enter a state of suspended animation in which they exhibit drastically reduced movement and a much lower pulse and breathing rate to save up on energy. It’s the only mammal known to use a suspended-animation state to power through oxygen deprivation.

They’re also seemingly immune to pulmonary edemas — the buildup of fluid which clogs the lungs of mammals in low-oxygen environments, such as climbers at high altitude.

“The naked mole-rat has simply rearranged some basic building-blocks of metabolism to make it super-tolerant to low oxygen conditions,” park adds.

The full paper “Fructose-driven glycolysis supports anoxia resistance in the naked mole-rat” has been published in the journal Science.


This is how the brain makes you sigh every 5 minutes

Sighing is a fundamental biological reflex that’s a lot more important than most people care to think. We don’t just sigh when we’re in a position of weariness or relief, but quite regularly for no particular reason — about 12 times an hour. Sighing opens up the lungs, and is thus  vital to life. Now, researchers say they’ve found the neural pathways thatgovern the reflex. Those who suffer from breathing problems as well as compulsive sighers will benefit the most from the findings.


When we sigh, the million of tiny sacks inside the lungs called the alveoli inflate causing oxygen to enter and carbon dioxide to leave. Sometimes these sacks collapse and it takes a sigh to open them which is typically two breaths in for one breath out. If we didn’t sigh, we’d be dead in under an hour.

Joining forces, researchers from labs at  UCLA and Stanford sought to unravel the neural mechanism that leads to sighing. The researchers screen some 19,000 mouse genes that are involved in brain cells. They singled out 200 neurons in the brain stem that produce  one of two neuropeptides — small protein-like molecules (peptides) used by neurons to communicate with each other — but couldn’t tell at this point which were involved in sighing.

Later they found some peptides triggered a second set of 200 neurons, some of whom were already involved in controlling breathing. A handful of neurons were found to activate the mouse’s breathing muscles to produce a sigh — roughly 40 times an hour. When one of the peptides was blocked, the sighing rate was cut in half. Silencing both peptides halted sighing completely, the researchers reported in Nature.

“Sighing appears to be regulated by the fewest number of neurons we have seen linked to a fundamental human behavior,” explained Jack Feldman, a professor of neurobiology at the David Geffen School of Medicine at UCLA and a member of the UCLA Brain Research Institute. “One of the holy grails in neuroscience is figuring out how the brain controls behavior. Our finding gives us insights into mechanisms that may underlie much more complex behaviors.”

“Unlike a pacemaker that regulates only how fast we breathe, the brain’s breathing center also controls the type of breath we take,” Mark Krasnow, a professor of biochemistry and Howard Hughes Medical Institute Investigator at the Stanford University School of Medicine said. “It’s made up of small numbers of different kinds of neurons. Each functions like a button that turns on a different type of breath. One button programs regular breaths, another sighs, and the others could be for yawns, sniffs, coughs and maybe even laughs and cries.”

Drugs could be designed that target these peptides to either suppress or enhance their generation on a case by case basis. For instance, there are anxiety disorders and other psychiatric conditions where sighing grows debilitating. Conversely, in some cases poor breathing is caused by a poor sighing reflex. As for conscious sighing triggered by emotional states, this is still a subject for debate among scientists.

“There is certainly a component of sighing that relates to an emotional state. When you are stressed, for example, you sigh more,” Feldman said. “It may be that neurons in the brain areas that process emotion are triggering the release of the sigh neuropeptides — but we don’t know that.”


Brilliant GIF shows how Humans, Birds and Insects Breathe

Three different ways to breathe:

Mammals, birds and insects breathe in different ways, as exemplified above. Humans, as mammals, inhale by moving the diaphragm to lower the air pressure in the chest cavity and pull air into the lungs. The human chest cavity is always at a lower pressure than the outside environment.

Birds on the other hand, have air sacs that reach into the bones, and have no diaphragm, respiratory infections can spread to the abdominal cavity and bones. Bird lungs do not expand or contract like the lungs of mammals. Unlike in mammals, air flows only in one direction and this allows birds to take in oxygen even as they exhale.

Insects have no lungs. Instead of lungs, insects breathe with a network of tiny tubes called tracheae. Air enters the tubes through a row of holes along an insect’s abdomen. The air then diffuses down the blind-ended tracheae. Since the biggest bugs have the longest tracheae, they should need the most oxygen to be able to breathe. Grasshoppers use different breathing methods when they are resting, alert, hopping or flying. Here, an alert grasshopper is depicted.

Credits: Eleanor Lutz