The ESTxENDS Trial- Substudy on the Effects of Using Electronic Nicotine Delivery Systems (ENDS/Vaporizer/E-cig) on Respiratory Symptoms

--\> This is a substudy of the main ESTxENDS trial (NCT03589989). Respiratory symptoms outcomes should be considered secondary outcomes of the main smoking cessation outcome formulated in NCT03589989. Cigarette smoking is the leading cause of preventable death in Switzerland. Cigarette smoking eventually kills one in two smokers, mostly through cancer, heart disease and respiratory failure. Recently, electronic nicotine delivery systems (ENDS; also called vaporizer or electronic cigarette) have become popular with smokers who want to stop smoking or reduce their exposure to inhaled chemicals since ENDS use appears to be safer than tobacco smoking. Studies suggest that ENDS use improves health outcomes, such as reducing respiratory symptoms, and presents only minimal respiratory risks, such as mild throat irritation and dry cough. In a prospective 6-month randomized, controlled trial evaluating smoking reduction/abstinence in 300 smokers not intending to quit experimenting two different nicotine strengths of a e-cigarette model compared to its non-nicotine choice, respiratory symptoms similarly improved in all three study groups. One study compared the short-term effects of cigarette smoking to ENDS use and found that cigarette smoking led to an acute reduction in lung function, which was not observed with ENDS. Findings on short-term airway resistance is conflicting. Short term increase in resistance in ENDS users might be caused by aerosolizing the liquid, and not by the same substances that harm lung function in cigarette smokers. Smokers who shifted from tobacco cigarettes to ENDS have offered anecdotes of dramatically improved lung function, but animal models suggest that ENDS liquids can increase markers of asthma. No large randomized trials have tested the effect of ENDS on respiratory symptoms. For the main ESTxENDS trial (NCT03589989), cigarette smokers motivated to quit smoking cigarettes will be included. Participants in the intervention group will rec