Background: Although well documented in tobacco smokers, there is little empirical evidence on self-titration (i.e. adjusting puffing patterns to obtain desired blood nicotine levels) in e-cigarette users. The primary aim was to explore the inter-relationships between e-cigarette puffing topography, nicotine concentrations and e-cigarette characteristics. Other aims were to identify the possible predictors of smoking cessation
in smokers attempting to quit using an e-cigarette.
Methods: Study 1 (N = 12 experienced e-cigarette users) employed a within-participants design and measured how puffing topography differs between high (24 mg/mL) and low (6 mg/mL) nicotine concentrations in 2 separate ad lib vaping sessions. Study 2 used a mixed-participants design in which e-cigarette naïve smokers (N = 70; 62.9% female) were randomly allocated to a cigalike (18mg/mL) or a tank containing either 18 or 6 mg/mL nicotine concentrations to obtain profiles of puffing topography characteristics associated with each of the aforementioned conditions and how these evolve over a 2-week period (in 3 separate 20-minute ad lib vaping sessions).
Puff duration, number and inter-puff intervals (IPI) were recorded along with exhaled carbon monoxide (CO), cigarette dependence, craving and withdrawal, and subjective effects at each session. Participants were given the e-cigarette to take home and asked to record cigarettes smoked per day (CPD) and subjective symptoms. In Study 3, Study 2 participants were followed up at 1, 3 and 6 months. Logistic regression analyses explored whether device type, nicotine concentrations, craving reduction, mean puff duration, cigarette dependence and motivation to quit could predict cessation.
Results: Study 1: Liquid consumption and puff number were higher and puff duration longer in the low nicotine concentrations condition (all ps < 0.01). There were no statistically significant differences between conditions in self-reported craving, withdrawal symptoms, satisfaction, hit or adverse effects. Nicotine plasma levels was significantly higher in the high nicotine concentration condition. Study 2: Puff duration significantly increased one week post e-cigarette initiation whilst puff numbers and IPI decreased. Cigalikes were associated with longer puff duration, shorter IPI and greater
number of puffs; the use of Tank 18 led to longer IPI and shorter puff duration but this was not statistically significant when compared to Tank 6. The Tank 18 and cigalikes were more efficient in reducing craving compared to the Tank 6 at baseline.
Participants rated both Tanks (18 and 6 mg/mL) as more satisfying at baseline and Time 1 compared with the cigalike. CPD, CO and nicotine dependence reduced significantly at week 1 then plateaued between week 1 and 2, but did not differ between conditions.
Study 3: Lower cigarette dependence, greater craving reduction with e-cigarette use reported at baseline and reports of tank use at follow up were significant predictors of cessation at 1, 3 and 6 months respectively. Nicotine concentrations, mean puff duration and motivation to quit at baseline were not significant predictors.
Conclusion: Consistent with the self-titration theory, e-cigarette users engaged in compensatory puffing with lower (6 mg/mL) nicotine concentration liquids, nearly doubling their consumption. Although self-titration was incomplete with significantly higher plasma nicotine levels in the high condition, compensatory puffing was sufficient to reduce craving and withdrawal discomfort. The rapid adjustment in puffing topography and the more erratic puffing regimen in the cigalike condition both lend support to the self-titration theory. Whilst higher nicotine concentrations are more effective in reducing craving, tank systems are preferable in achieving satisfaction. This suggests an important role for device type in providing satisfaction and equally important role for nicotine concentrations to reduce craving. Delineating the mechanisms by which device types play a role in providing satisfaction and its subtle difference with craving should be one area to concentrate for future research. Those with lower cigarette dependent scores were more likely to quit at 1 month, whilst those who reported greater craving reduction following e-cigarette use in the lab were more likely to have quit at 3 months; the predictive utility of measures of craving reduction at first use can be fostered to inform smoking cessation programmes. The odds of quitting at 6 months were higher for those using a tank device at the time of follow-up compared to those using a cigalike, which is in line with previous studies suggesting that tank systems are associated with greater likelihood of successful cessation. Key findings suggest that e-cigarettes have good potential in helping reduce tobacco smoking.