Physiological Effects of Electronic Cigarette:A Systematic Review and Meta-Analysis

Importance: 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 recently reported. Objective: To conduct a systematic review and meta-analysis of studies assessing the immediate physiological effects, i.e., cardiovascular, respiratory or blood-based responses, of acute e-cig usage in humans. Data Sources: PubMed, Web of Science, Cochrane and Scopus databases were searched for published articles until 20th May 2020. Study Selection: English or French peer-reviewed articles measuring at least one physiological parameter before and after using an e-cig. Data extraction and synthesis: 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-regression was 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 17102 articles screened, 37 articles were included for the qualitative synthesis, and 23 articles (800 patients) were included in the meta-analysis. Acute use of nicotine e-cig was associated with increased heart rate (SMD=0.51; 95%CI 0.34-0.68), systolic blood pressure (SMD=0.33; 95%CI 0.13 -0.52), diastolic blood pressure (SMD=0.50; 95%CI 0.26-0.73), and augmentation index AIx75 (SMD=0.580; 95%CI 0.220- 0.941), along with a decrease in FeNO (SMD=-0.327; 95%CI -0.599 – -0.055). E-cig exposure wasn't associated with significant changes in any spirometry measure. Conclusions and Relevance: Acute use of nicotine e-cigs was associated with significant cardiovascular and respiratory responses. Despite being considered safe, these devices have a physiological impact that needs to be further explored especially in term of its long-term consequences.