In the summer of 2019, clinicians began noticing and reporting scattered cases of acute lung injury associated with e-cigarette use. As of early October, 1,479 cases had been reported to the Centers for Disease Control and Prevention (CDC) from every state except Alaska. There had been 33 confirmed deaths in 24 states and no confirmation of what is causing the outbreak beyond a clear association with vaping products containing nicotine, THC, or both.
The CDC currently advises against vaping products containing THC. The wiser move is to avoid vaping altogether.
“The only way to ensure that you are not at risk is to refrain from all e-cigarette products,” said David N. Weissman, MD, FCCP, of the CDC.
Dr. Weissman opened a late-breaking update on the current state of the lung disease outbreak associated with vaping to a packed room on Sunday. E-cigarettes were introduced into the US market in 2007, he noted, but clinicians recognized the current nationwide outbreak only this past summer.
A retrospective survey suggests that scattered cases of similar acute lung disease were being reported as early as the spring of 2018, noted Jennifer Layden, MD, of the Illinois Department of Public Health.
“The theory is that a new substance has been added as a diluent or cutting agent to e-cigarettes that has caused this,” she said. “But we don’t know the cause.”
No one knows the cure, either, or the best treatment. The common thread in patients who recover is corticosteroid treatment, said Kevin Davidson, MD, of the University of Colorado.
“Anecdotally, prednisone seems to speed recovery,” he said. “We don’t have the long-term data, but early data suggest that recovery can be good.”
Common names for e-cigarettes include e-cigs, vapes, e-hookahs, vape pens, mods, tanks, and electronic nicotine delivery systems. All include a pod or reservoir containing a liquid to be vaporized and inhaled, and a heat source, usually powered by batteries. The liquid can contain varying proportions of propylene glycol and glycerol as solvents or carriers, nicotine, tetrahydrocannabinol (THC), flavorings, and assorted other ingredients.
The liquid is heated to a vapor, which condenses into a dense cloud of droplets, which is inhaled.
THC can be vaped as powdered dry herb, liquid, or concentrated oil, a thick, gummy resin called dabs. The resin is often mixed with solvents and cutting agents such as terpenoids, medium chain triglycerides oil, vitamin E acetate, and others.
Most patients are hospitalized, Dr. Layden said, often after presenting at the emergency department. The most common complaints include shortness of breath and GI upset. All patients have constitutional complaints such as fever and chill.
“Our youngest patient to date is 13; the oldest in their sixties,” Dr. Layden said. “This has been a very novel investigation for all of us. We weren’t even sure if this is an existing syndrome or one that is newly recognized.”
Four months into the outbreak, the answer appears to be an existing syndrome. Evidence to date suggests that it is an outbreak of lipoid pneumonia associated with vaping.
Macrophages from some patients are engorged with lipids, said Kevin Davidson, MD, of the University of Colorado, but not all. The problem, he said, is that most patient samples were formalin-fixed and paraffin embedded—a process that washes away any lipid content.
“If you send samples to the lab, do at least part as fresh or frozen,” he advised. “That will give a clearer picture of what is going on in those affected lungs.”
Lipoid pneumonia has been known for at least a century, he added, but not in the young patients that make up the vast majority in this outbreak. More typical is an older patient who ingests large amounts of mineral oil as a laxative and aspirates some of the liquid.
There has been little research on the effects of vape products on the lungs compared with combustible tobacco and no long-term work. What is known is that as little as four months of e-cig exposure changes pulmonary macrophage morphology in animal models.
Alveolar macrophages accumulate lipids independent of nicotine content in the e-cig vapor, said Farah Kheradmand, MD, of Baylor College of Medicine, implicating the liquid vaping vehicle. The lab did not test THC vapes. The e-cig liquid also impairs immune responses and enhances viral-associated inflammation, possibly by disrupting lung surfactant homeostasis.
“What we observe in a preclinical setting may have some clinical relevance,” Dr. Kheradmand said. “The lung damage we see in mice is very similar to the lipoid pneumonia seen in human patients.”