Study procedures

Apart from the study product (NRT or END), which was given to patients at the end of the baseline visit, the NRT and END groups underwent identical study procedures. The study consisted of 3 in-person visits (preoperative baseline, day of surgery, and 8-week follow-up) and two phone-calls (30-day postoperative and 6-month follow-up). At each in-person visit, exhaled carbon monoxide (CO) was measured using the piCOSmokerlyzer(Bedfont Scientific Ltd., Kent, England) and forced expiratory volume in the first second (FEV1) and forced vital capacity (FVC) were measured using the EZOne Spirometer (NDD Medical Technologies, Inc, Andover, MA, USA). A saliva sample was collected for cotinine analysis. At each visit and phone call, smoking status was assessed.

Participants in both groups were asked to refrain from the use of cigarettes and all study products at the end of 6-weeks and return unused products at the 8-week visit. Given the lack of long-term safety data for e-cigarettes, we felt it would be unethical to encourage their long-term use. We instructed the NRT group similarly to maintain comparable instructions between groups.

Recruitment/preoperative baseline visit

After written informed consent, baseline demographics, smoking habits, exhaled CO, FEV1, FVC and saliva sample were obtained. Participants were educated on the use of both products prior to receiving their allocated product, which was prepared by the study pharmacist and placed in a brown paper bag to mask the contents to the investigator. All participants received brief counseling by the research team, a brochure produced by the American Society of Anesthesiologists explaining the benefits of preoperative smoking cessation, and a referral to the California Smokers' Helpline. The referral was an online form completed by the research team, which would trigger a phone call to the participant by the California Smokers' Helpline.

Day of surgery

Participants were seen by study personnel pre-operatively on their day of surgery. Smoking status, exhaled CO, FEV1, FVC and saliva sample were obtained. Participants were asked about the occurrence of adverse events or side effects related to use of product. For those whose surgical date was cancelled, a make-up day of surgery visit was scheduled to be as close to the original surgical date as possible.

30-day postoperative phone call

Participants were contacted by phone 30-days post-operatively. If participants could not be reached 30-days post-operatively, subsequent attempts were made until contact was established, to a maximum of 10 attempts. Seven-day point prevalence smoking status was assessed by self-report. Adverse events, side effects, and surgical complications were also assessed.

8-week post randomization visit

Seven-day point prevalence smoking status was assessed and exhaled CO, FEV1, FVC and saliva sample were obtained. Participants were asked about the occurrence of adverse events or side effects related to use of product. After these measures, participants revealed product allocation to study personnel. Study personnel conducted a 30-45min long qualitative interview to assess product usage, and participants' attitudes toward both products, the results of which are reported separately. For those that refused an in-person visit, but agreed to telephone interview, exhaled CO, FEV1, FVC and saliva were not obtained. Patients were mailed a $100 check after completion of the 8-week follow-up visit (or telephone interview).

6-month follow-up phone call

Seven-day point prevalence smoking status and use of e-cigarettes was assessed.

1. I need the study design. Please explain in detail.

2. Based on the research questions and study design, I need to discuss the causation. I need to know whether authors justify the causal association, even if the proposed study design might be less than perfect. I need to explain the thought process. Please explain in detail.