Vaping affects blood vessels after one use — even with no nicotine, study finds

PHILADELPHIA - A new study from the University of Pennsylvania’s Perelman School of Medicine revealed that vaping affects blood vessels after a single use, even when the e-cigarette being used contains no nicotine.

As more people pick up vaping — especially teenagers and young adults — and medical professionals see more cases of vaping-induced illness, scientists and lawmakers are becoming increasingly concerned with the potential effects of e-cigarette inhalation.

“E-cigarettes are advertised as not harmful, and many e-cigarette users are convinced that they are just inhaling water vapor,” said Alessandra Caporale, lead author on the study and post-doctoral researcher in the Laboratory for Structural, Physiologic, and Functional Imaging at Penn. “But the solvents, flavorings and additives in the liquid base, after vaporization, expose users to multiple insults to the respiratory tract and blood vessels.”

Studies in the past have focused quite heavily on the health effects of using nicotine-filled e-cigarettes, but this new study aimed to determine if there were any negative effects arising from the inhalation of aerosol alone.

For this study, researchers measured the effects of inhaling nicotine-free e-cigarette aerosol by performing MRIs on non-smoker participants before and after inhalation to look for things like vascular reactivity and tone changes.

The study looked at 31 healthy, young adult never-smokers between the ages of 18 and 35. Participants were excluded if they had hypertension, asthma, respiratory tract infection within six weeks, cancer, HIV, were pregnant or breastfeeding.

While under supervision, participants were asked to take 16 three-second inhalations from a nicotine-free e-cigarette containing pharma-grade propylene glycol and glycerol with added tobacco flavoring.

After completing the requested vaping, a few participants reported dizziness and/or feeling lightheaded, but none of them experienced coughing and all completed the challenge.

Researchers then evaluated vascular reactivity by constricting the vessels of participants’ thigh with a cuff and then measuring how quickly blood flowed after the cuff was removed. Participants’ femoral artery and leg vein were scanned using an MRI procedure that recorded several parameters both before and after each vaping episode.

Researchers found that a single instance of vaping resulted in reduced blood flow and impaired endothelial function in the femoral artery, which delivers blood to the leg.

They observed an average reduction in the femoral artery’s dilation by about 34 percent, a 17.5 percent decrease in peak blood flow, a 20 percent decrease in venous oxygen and a 28.5 percent decrease in blood acceleration after cuff removal (the speed at which blood returns to its normal flow after being constricted).

“While e-cigarette liquid may be relatively harmless, the vaporization process can transform the molecules — primarily propylene glycol and glycerol — into toxic substances,” said the study’s principal investigator Felix W. Wehrli, Ph.D., a professor of Radiologic Science and Biophysics. “Beyond the harmful effects of nicotine, we’ve shown that vaping has a sudden, immediate effect on the body’s vascular function, and could potentially lead to long-term harmful consequences.”

One of those long-term consequences could be an increased risk of heart attack or stroke.

Endothelium refers to the cells that line the interior surface of blood vessels and lymphatic vessels which are responsible for maintaining proper blood circulation. If the endothelium becomes damaged, arteries will thicken over time, cutting off blood flow to the heart and brain which can result in heart attack or stroke.

Wehrli performed a separate study on the effects of acute e-cigarette use in nonsmokers in July which found that such use can result in vascular inflammation, and he says that these findings along with those of the more recent study suggest that e-cigarettes could potentially be far more hazardous than most people have been assuming.

During a congressional subcommittee hearing held on July 24 to examine the role of popular vaping company JUUL on the current youth nicotine addiction epidemic, Dr. Robert Jackler, an otolaryngologist and founder of Stanford Research Into the Impact of Tobacco Advertising, referred to current e-cigarette trends as an open-ended experiment.

"Nobody knows what it does to the human lung to breathe in and out aerosolized propylene glycol and glycerin over and over. It's an experiment, frankly," said Jackler. "We will find out, years from now, the results.“Wehrli warns that the safest course of action in the face of uncertain long-term health affects is to simply avoid e-cigarette use altogether.

“I would warn young people to not even get started using e-cigarettes. The common belief is that the nicotine is what is toxic, but we have found that dangers exist, independent of nicotine,” Wehrli said. “Clearly if there is an effect after a single use of an e-cigarette, then you can imagine what kind of permanent damage could be caused after vaping regularly over years.”