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.