Almost two dozen people in the Midwest were hospitalized with severe breathing difficulties associated with vaping, and doctors are not sure why.
It is not clear exactly what patients – many of whom are young adults – inhaled or what kind of devices they used. Doctors also do not know where they bought devices or e-liquids.
Some patients said they used e-cigarette devices to inhale both nicotine and THC, the psychoactive ingredient in marijuana.
"We know that some features are common with these cases, but we were not able to understand exactly what aspect of the liming habit, product, solvent or oil causes injury," said Dr. Emily Chapman, medical director of the Minnesota Children's Health Care Center in Minneapolis.
Four cases were reported in Minnesota, 12 in Wisconsin and six in Illinois.
Chapman told NBC News that four teenagers admitted to Children & # 39; s Minnesota came with what doctors initially considered a serious respiratory infection such as pneumonia.
But instead of improving treatment, they got worse.
"They managed to have significant breathing difficulties and increased lung problems," said Chapman. "After all, they needed our intensive care unit, and in some cases breathing assistance."
Doctors in Illinois and Wisconsin faced a similar situation.
"All patients reported vaporization before hospitalization, but we don't know all the products they've used," said WGBA, NBC News affiliate in Green Bay, Wisconsin, Andrea Palm from the Wisconsin Department of Health Services.
You literally don't know what you are breathing into your body.
One such patient, 26-year-old Dylan Nelson from Burlington, Wisconsin, became ill after several hits from a new vape cassette. The next morning he went to the hospital and his symptoms gradually got worse during the day.
Before nightfall, his lungs filled with fluid and doctors had to put him in a coma. He has been released from the hospital since then and is slowly recovering.
His brother, Patrick DeGrave, said that Nelson bought his vape cartridge from the street, not from a reputable store.
"People will buy them from states where it is legal and bring them back to states such as Wisconsin, where it is illegal," said DeGrave.
"You don't know if you're buying something from the average man who picked him up at the clinic, or you're buying from someone who faked him and made his own mixture," he said.
"You literally don't know what you're breathing into your body."
It is unclear whether there has been any contamination of devices or e-fluids that has led to clusters of cases, including Nelson. The brand he bought, called Dank Vapes, ceased to exist a few years ago, but the packaging is still rising.
"Is it possible that these specific patients were smoking something in common? Definitely possible. It's also possible that once the clusters become visible to doctors, we'll start looking for something more, "said Dr. Christy Sadreameli, a children's pulmonologist at Johns Hopkins Hospital in Baltimore and a volunteer spokesperson for the American Lung Association.
Sadreameli also pointed out that e-cigarettes are harmful to the growing bodies of teenagers – regardless of the source.
Teenager's lungs are not fully developed, which could potentially make them more susceptible to chemicals found in e-cigarettes.
"The spray contains heavy metals and the finest toxic particles that penetrate deep into the lungs," said Sadreameli.
Because the Food and Drug Administration does not require e-cigarette manufacturers to put all of their ingredients on product labels, scientists have resorted to taking devices to the laboratory to determine the ingredients.
One recent study from Yale University identified chemicals called acetals in some Juul e-cigarette liquids. Scientists have found that these chemicals can be particularly irritating to the lungs and cause damage when inhaled.
"These incidents are a major concern and highlight why the FDA should review e-cigarettes and determine their health impact before they are released," the campaign for tobacco-free children wrote in a statement to the NBC.
The Wisconsin Department of Health Services has contacted Centers for Disease Control and Prevention to coordinate investigations with countries.