Scientists hunting for new ways to treat carbon monoxide poisoning are trying a new tactic: hitting blood with bright lights to break the stranglehold of the toxin.
But outside experts say the approach — one of several potential treatments currently being studied — only underscores how complicated it is to stop carbon monoxide from wreaking havoc on the body or to reverse the damage it has already done.
Carbon monoxide poisoning has become far less common in the U.S. in recent decades, thanks to public health campaigns and the introduction of catalytic converters in cars. But it still sends an estimated 50,000 people to the emergency room in the U.S. each year and leads to thousands of deaths each year across the country.
When a person is exposed to carbon monoxide, the gas binds with a protein in the blood called hemoglobin, which is responsible for ferrying oxygen to organs. That displaces the oxygen, making it harder for the body to get as much as it needs. For decades, doctors have treated carbon monoxide poisoning by giving patients pure oxygen, whether through a mask or, in severe cases, in a hyperbaric oxygen chamber. That speeds up the process of clearing carbon monoxide from the bloodstream.
But oxygen treatments fall short in a critical way: Thousands of people who are treated for carbon monoxide poisoning every year go on to have long-term health problems, like cognitive deficits and heart problems. Researchers suspect that’s because oxygen treatments only address the presence of carbon monoxide in hemoglobin — and not other biological effects of carbon monoxide poisoning, such as inflammation or changes to the mitochondria in cells.
The new device, described Wednesday in Science Translational Medicine, works somewhat like oxygen treatments, in that it’s designed to clear the blood of carbon monoxide more quickly than if a patient was just breathing regular air. It relies on an existing device called an ECMO machine, also known as an artificial lung. Artificial lungs pump blood out of a patient through heavy-duty IVs, add oxygen and take out carbon dioxide, and then send the blood back into a patient’s body. They are used to care for people whose lungs or hearts aren’t working well enough to keep them alive.
In the new device, the scientists added another element: red light. In their machine, blood is sent through thin, porous membranes nestled between two sheets of plexiglass. They hit the blood with bright red light, which works to break the bond between carbon monoxide and hemoglobin. At the same time, the artificial lung hits the blood with pure oxygen. As the blood cells release the carbon monoxide, it travels out through the microscopic pores in the device’s channels. Then, the blood travels back into the body.
“You might think of it as breathing. The artificial lung breathes out carbon monoxide,” said study author Dr. Warren Zapol, an anesthesiologist at Massachusetts General Hospital who has studied carbon monoxide poisoning.
In a rat model of carbon monoxide poisoning, Zapol and his colleagues showed that their new device removed carbon monoxide faster from the blood than just giving pure oxygen alone. The light-based treatment was particularly effective in rats with acute lung injury. They’re hoping to test the device next in larger animals.
Outside experts say it’s an interesting idea — but they aren’t convinced it will have a big impact, even if it’s shown to one day work in humans.
“It’s a nice study, but I question whether it’s going to have clinical impact, because it’s not going to deal with other mechanisms of toxicity,” such as the effects on mitochondria, said Dr. Neil Hampson, a pulmonologist at Virginia Mason Medical Center in Washington state who has studied carbon monoxide poisoning. While the researchers did show the device can clear carbon monoxide faster than oxygen alone, it isn’t clear yet whether that acceleration translates to better outcomes.
“Having other therapies available would be novel if they were shown to do more than oxygen,” he added.
Zapol and his colleagues are hopeful the device could one day be used to treat people who have both carbon monoxide poisoning and severe lung injury from inhaling toxins, like firefighters or soldiers exposed to fumes after an explosion. In those cases, oxygen treatment might not work or might lead to other acute health problems.
Another concern: Using an artificial lung, the centerpiece of the system, is often a last resort for doctors.
“The biggest limitation is that ECMO is a very, very invasive procedure [reserved] for the sickest patients,” said Dr. Jason Rose, a pulmonologist and biomedical engineer at the University of Pittsburgh.
Rose and his colleagues are experimenting with a different approach to carbon monoxide poisoning. They engineered a molecule that’s based on a protein called neuroglobin, which is found in the retina. Scientists aren’t exactly sure what it does — but they do know it loves to bond with carbon monoxide. Rose and his colleagues tweaked a particular amino acid in the protein to strengthen neuroglobin’s bond with carbon monoxide.
In a 2016 study, the researchers infused the protein into mice with severe carbon monoxide poisoning. It latched on to carbon monoxide that had previously been bound with hemoglobin in seconds. The protein is one of several so-called “scavenger molecules” that scientists hope could one day be an antidote to carbon monoxide poisoning, rapidly hunting down the toxin and doing away with it before it can do damage. Rose founded a company, Globin Solutions, to continue work on the scavenger molecule.