Introduction:
The aim of the study was to confirm or reject the hypothesis that variation in throat-hit depends on the nicotine concentration and the voltage applied to the resistance. A secondary aim was to assess the influence of throat-hit on the willingness of subjects to switch from tobacco to e-cigarette use.

Methods:
In this experimental blind test participants were 35 students (aged 22.0±7.7), current smokers, who tested five e-liquids with a nicotine concentration between 0 to 18mg/mL, at 3.5 or 4.5 volts (at 1.8Ω) powered by EGO type e-cigarettes . After describing their smoking habits (heaviness smoking index (HSI), and signing consent, participants smoked 1 puff every 5 minutes, inhaling for 3 seconds, for each of the 10 conditions and rated their subjective experience.

Results:
Analysis of the 350 puffs from the 35 smokers,indicated a learning process of 5 puffs. Within this population a nicotine concentration of 12.6mg/mL combined to 3.5volts and 10.9mg/mL combined to 4.5volts was associated with OTH. Our results indicated a link between tobacco dependence and nicotine concentration of the e-liquid that provided an optimal throat-hit (OTH), with an +1.6mg/mL increase in nicotine content needed for the OTH for each one point increase in HSI. A link between the desire to switch from tobacco to e-cigarettes and the score of throat-hit was identified (r2=0.94). This desire is <1/10 when throat-hit is unpleasant (score 0-3) and exceeds 7/10 when throat-hit is optimal (score 7-10).

Conclusions:
The present data justify the need to further develop e-cigarettes so that an optimal OTH is identified quickly. Further research is needed to confirm the above results in other populations and to assess the specific influence of flavour on throat hit.