Immediate physiological effects of acute electronic cigarette use in humans: A systematic review and meta-analysis

Background: Electronic cigarettes (e-cigs) are widely used devices that were initially created to aid in smoking cessation. However, their acute physiological effects are unclear and there have been a number of E-cig and Vaping Acute Lung Injury (EVALI) events reported.

Research question: What are the immediate physiological effects (i.e. cardiovascular, respiratory or blood-based responses) of acute e-cig usage in humans?

Study design and methods: PubMed, Web of Science, Cochrane and Scopus databases were searched for English or French peer-reviewed articles published until May 20, 2021 and measuring at least one physiological parameter before and after using an e-cig. The study followed PRISMA guidelines and assessed article quality using the Downs and Black checklist. Independent extraction was conducted by two reviewers. Data were pooled using random-effect models. Sensitivity analysis and meta-regressions were performed to explore heterogeneity.

Main outcomes: Systolic and diastolic blood pressure, heart rate, augmentation index (AIx75), fraction of exhaled nitric oxide (FeNO), and spirometry were the most frequently assessed parameters and were therefore chosen for meta-analyses.

Results: Of 19823 articles screened, 45 articles were included for the qualitative synthesis, and 27 articles (919 patients) were included in meta-analyses. Acute use of nicotine e-cig was associated with increased heart rate(SMD = 0.71; 95%CI 0.46-0.95), systolic blood pressure (SMD = 0.38; 95%CI 0.18-0.57), diastolic blood pressure (SMD = 0.52; 95%CI 0.33-0.70), and augmentation index AIx75 (SMD = 0.580; 95%CI 0.220-0.941), along with decreased FeNO (SMD = -0.26; 95%CI -0.49 to -0.04). E-cig exposure wasn't associated with significant changes in any spirometry measure.

Interpretation: Acute use of nicotine e-cigs was associated with statistically significant cardiovascular and respiratory responses. These devices have a physiological impact that could be clinically relevant, especially in terms of cardiovascular morbidity. However, the direct consequences of long-term e-cig use needs to be further explored.