In a new study, researchers have found that MRI has potential as a non-invasive tool for evaluating the effects of vaping and tobacco smoking (Radiology 2022; https://doi.org/10.1148/radiol.211327). Vaping devices, or electronic nicotine delivery systems (ENDS), have been promoted as a tool to aid smoking cessation and, as this study's authors point out, randomized control trials suggest that ENDS can successfully do so. However, research has shown that some users may continue to vape past the point of quitting cigarettes, which could lead to negative health outcomes.
"ENDS is associated with a safer risk profile than conventional cigarettes," wrote investigators from Bern University Hospital in Switzerland. "However, vaping increases heart rate and blood pressure similarly to conventional tobacco smoking. Previous in-vitro studies showed that electronic cigarette or e-cigarette exposure induces inflammation and oxidative stress in pulmonary endothelium and stem cells."
Citing limited evidence regarding the short-term effects of ENDS and tobacco smoke on lung ventilation and perfusion, a team led by investigators from Bern University Hospital set out to examine the immediate effect of ENDS exposure and tobacco smoke on lung ventilation and perfusion by functional MRI and lung function tests.
Study Details
Researchers conducted a study including 44 adults, 10 of whom were healthy control patients who had never smoked, along with nine former tobacco smokers, 13 electronic nicotine device users, and 12 active tobacco smokers. Study participants underwent non-contrast-enhanced matrix pencil MRI and lung function tests before and immediately after the exposure to ENDS products or tobacco smoke.
The researchers acquired baseline measurements after 2 hours of substance abstinence, performing post-exposure measurements immediately after the exposure. MRI showed semiquantitative measured impairment of lung perfusion and fractional ventilation impairment as percentages of affected lung volume, according to the authors, who assessed lung clearance index (LCI) by nitrogen multiple-breath washout to capture ventilation inhomogeneity and spirometry to assess airflow limitation.
Absolute differences were calculated with paired Wilcoxon signed-rank test and differences between groups with unpaired Mann-Whitney test. Healthy control participants underwent two consecutive MRI measurements to assess MRI reproducibility.
Overall, MRI showed a decrease of perfusion after exposure and no systematic change among tobacco smokers. Meanwhile, perfusion increased in participants who used ENDS after exposure did change. Only tobacco smokers saw LCI elevate after smoking, and spirometry indexes did not change in any participants.
"MRI showed a decrease of lung perfusion after exposure to tobacco smoke," the researchers wrote, "and an increase of lung perfusion after use of electronic nicotine delivery systems."
In tobacco smokers, a regional decrease of lung perfusion at functional MRI was shown following a single smoking session compared with the baseline measurement. A local increase of lung perfusion was shown after exposure among study participants who used an electronic nicotine delivery system. In healthy control participants, the mean difference between both measurements for perfusion impairment was -0.1 percent, the authors noted.
"Our functional lung MRI technique is able to measure inhomogeneity of pulmonary ventilation and perfusion," noted Sylvia Nyilas, MD, PhD, from the Department of Diagnostic, Interventional and Pediatric Radiology at Bern University. "We hypothesized that smoking can affect the regional distribution of pulmonary perfusion, and we were able to observe an increased inhomogeneity in smokers after exposition to tobacco. Users of electronic nicotine delivery systems have shown increased regional perfusion."
In terms of assessing vaping and smoking's short-term effects, she believes MRI could offer certain advantages over other imaging modalities.
"Unlike standard pulmonary function tests, MRI is able to capture subtle regional changes in lung ventilation and perfusion impairment. Moreover, functional lung MRI, in contrast to the nuclear medicine imaging modalities, does not use ionizing radiation and is considered a non-invasive procedure," said Nyilas, noting that the functional lung MRI examinations for this study were performed "in free breathing and without application of intravenous contrast agents or inhalative tracers."
The use of MRI could also change how radiology and radiation oncology teams approach the assessment of vaping and smoking's detrimental effects.
"Before morphological changes occur, the ventilation and perfusion in the lung is likely to be affected, but may be missed by previous imaging or lung function techniques. The qualification of ventilation and perfusion allows estimating early changes of the latter," Nyilas noted.
This is particularly true with regard to the Euler-Liljestrand reflex, inducing vasoconstriction in unventilated peripheral lung compartments.
"The 'new era' of less severe disease, given by new treatment targets and better therapeutic options, demands sensitive physiological and structural outcomes to prevent irreversible airway changes. Personalized diagnostic tools enable personalized treatment, which plays an increasing role in [today's] clinical practice," Nyilas concluded. "Potentially reversible functional impairment can now be detected before irreversible morphological changes occur in the lungs. We want to draw attention [to] new functional imaging modalities to determine fractional perfusion impairment in the lung before structural changes occur."
Mark McGraw is a contributing writer.