The Influence of Electronic (ECIG) Heater Resistance on ECIG Acute Effects

The purpose of this study is to measure the individual and combined influence of electronic cigarette (ECIG) heating element resistance and liquid nicotine concentration on ECIG acute effects. Thirty-two experienced ECIG users will complete four independent laboratory sessions that will differ by heater resistance (0.5 ohm or 1.5 ohm) and liquid nicotine concentration (3 or 8 mg/ml). Other factors such as voltage, liquid solvent ratio, and liquid flavor will be held constant. Plasma nicotine concentration, subjective effects, and puffing behavior will be recorded for each condition.

Electronic cigarettes (ECIGs) are a popular and rapidly evolving class of products. ECIG users can manipulate several device features including liquid nicotine concentration (mg/ml) and heating element resistance (ohms). An emerging class of ECIG models includes "sub-Ohm" devices that employ low resistance heaters that are often used to achieve high device power. Some clinical laboratory data suggest that high power devices deliver nicotine to the user effectively, even when paired with a low liquid nicotine concentration. However, given that ECIG heater resistance and liquid nicotine concentration have not been manipulated in clinical laboratory studies, the influence of these factors on ECIG acute effects remain unclear. The purpose of this clinical laboratory study is to measure the influence of heater resistance and liquid nicotine concentration on ECIG acute effects. Participants will attend the lab for four experimental sessions where they use an ECIG. For each session, the participants will be randomly assigned (like the flip of a coin) to receive an ECIG with one of two different levels of heating coil resistance (which will determine overall device power) and one of two different liquid nicotine concentrations. The four sessions will begin at approximately the same time each day, will be separated by at least 48 hours, and will not occur more than two times per week. The primary hypotheses are that the low resistance heater paired with the 8 mg/ml liquid nicotine concentration, will result in greater nicotine delivery and subjective effect profiles, suggestive of higher abuse potential. Results from this study will further our understanding of the factors that influence the dependence potential of ECIGs and could inform future regulation of these devices.

Eligibility Criteria:
Inclusion Criteria:

* Willing to provide informed consent, attend the lab and abstain from nicotine/tobacco as required, and use designated products according to study protocol
* Experienced ECIG users (use ≥1 ml of ECIG solution daily, use ECIG solution with a nicotine concentration ≥3 mg/ml, and have used their ECIG for ≥3 months)
* Urine cotinine test result ≥ 3

Exclusion Criteria:

* History of organ-related diseases or current psychiatric condition
* Regular use of prescription medication other than vitamins or birth control
* Past month use of cocaine, opioids, benzodiazepines, or methamphetamine
* Using marijuana greater than 10 days in the past 30 and/or alcohol greater than 25 days in the past 30 days
* Pregnant or breastfeeding women
* Weight less than 110 pounds
* Daily use of \>5 cigarettes or use of other tobacco products (i.e., hookah, cigars) \>3 times a week