Immediate physiological effects of acute Electronic Cigarette use in humans: a systematic review and Meta-Analysis

Abstract 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 20th May 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- -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.