Nicotine absorption from electronic cigarette use: Comparison between first and new-generation devices

Abstract

A wide range of electronic cigarette (EC) devices, from small cigarette-like (first-generation) to new-generation high-capacity batteries with electronic circuits that provide high energy to a refillable atomizer, are available for smokers to substitute smoking. Nicotine delivery to the bloodstream is important in determining the addictiveness of ECs, but also their efficacy as smoking substitutes. In this study, plasma nicotine levels were measured in experienced users using a first- vs. new-generation EC device for 1 hour with an 18 mg/ml nicotine-containing liquid. Plasma nicotine levels were higher by 35-72% when using the new- compared to the first-generation device. Compared to smoking one tobacco cigarette, the EC devices and liquid used in this study delivered one-third to one-fourth the amount of nicotine after 5 minutes of use. New-generation EC devices were more efficient in nicotine delivery, but still delivered nicotine much slower compared to tobacco cigarettes. The use of 18 mg/ml nicotine-concentration liquid probably compromises ECs' effectiveness as smoking substitutes; this study supports the need for higher levels of nicotine-containing liquids (approximately 50 mg/ml) in order to deliver nicotine more effectively and approach the nicotine-delivery profile of tobacco cigarettes.

Full text

Nicotine absorption from electronic
cigarette use: comparison between first
and new-generation devices
Konstantinos E. Farsalinos
1
, Alketa Spyrou
1
, Kalliroi Tsimopoulou
1
, Christos Stefopoulos
1
,
Giorgio Romagna
2
& Vassilis Voudris
1
1
Onassis Cardiac Surgery Center, Sygrou 356, Kallithea 17674, Greece,
2
Abich s.r.l., Biological and Chemical Toxicology
Research Laboratory, Via 42 Martiri, 213/B-28924 Verbania (VB), Italy.
A wide range of electronic cigarette (EC) devices, from small cigarette-like (first-generation) to
new-generation high-capacity batteries with electronic circuits that provide high energy to a refillable
atomizer, are available for smokers to substitute smoking. Nicotine delivery to the bloodstream is important
in determining the addictiveness of ECs, but also their efficacy as smoking substitutes. In this study, plasma
nicotine levels were measured in experienced users using a first- vs. new-generation EC device for 1 hour
with an 18 mg/ml nicotine-containing liquid. Plasma nicotine levels were higher by 35–72% when using the
new- compared to the first-generation device. Compared to smoking one tobacco cigarette, the EC devices
and liquid used in this study delivered one-third to one-fourth the amount of nicotine after 5 minutes of use.
New-generation EC devices were more efficient in nicotine delivery, but still delivered nicotine much slower
compared to tobacco cigarettes. The use of 18 mg/ml nicotine-concentration liquid probably compromises
ECs’ effectiveness as smoking substitutes; this study supports the need for higher levels of
nicotine-containing liquids (approximately 50 mg/ml) in order to deliver nicotine more effectively and
approach the nicotine-delivery profile of tobacco cigarettes.
Electronic cigarettes (ECs) have been introduced to the market in recent years as alternatives to smoking.
They are considered part of tobacco harm reduction, a strategy of reducing adverse health effects by
providing low-risk nicotine products to substitute smoking
1
. They deal with both the psycho-behavioral
(through motor simulation and sensory stimulation) and the chemical (through delivery of nicotine) aspects
of smoking addiction
2
. ECs mainly consist of a lithium battery and a part called atomizer, where the liquid is
stored and evaporated by applying electrical current to a resistance and wick setup. There is a substantial
variability of devices; small devices, looking similar to tobacco cigarettes (commonly referred as first-genera-
tion), consist of a low-capacity batteries and polyfil-filled atomizers, while new-generation devices consist of
larger-capacity batteries, larger atomizers and electronic circuits providing the ability to set the power delivery
to the atomizer.
The growing popularity of ECs
3,4
has raised significant controversy in public health authorities. Organizations
such as the World Health Organization and Food and Drug Administration have expressed concerns about the
safety of e-cigarettes and the effects of nicotine intake. Recently, European Union has developed a new regulation
which implements an upper limit of 20 mg/ml nicotine concentration in liquids that are used with ECs
5
. The
decision was based on a study from our group, in which nicotine consumption and delivery to the user was
evaluated
6,7
. However, the route, speed and amount of nicotine absorption (and subsequent nicotine levels in
plasma) are important determinants of the efficacy of ECs to serve as smoking substitutes and of any concerns
about nicotine overdose or intoxication. Data on nicotine absorption are scarce. Initially, EC use (commonly
called vaping) was found to deliver minimal amounts of nicotine to the user as measured by plasma nicotine
levels
8,9
. However, there has been a fast evolution of new, more efficient devices, and devices used at the time of
those experiments are currently outdated and off the market. Surveys have shown that new-generation devices are
more popular in dedicated EC users and a significant proportion of these users report complete smoking
cessation
10,11
. However, no study has evaluated nicotine absorption from such devices. Therefore, the purpose
of this study was to compare the nicotine absorption from a first- vs. a new-generation device in experienced
vapers.
OPEN
SUBJECT AREAS:
RISK FACTORS
PUBLIC HEALTH
Received
3 January 2014
Accepted
5 February 2014
Published
26 February 2014
Correspondence and
requests for materials
should be addressed to
K.E.F. (kfarsalinos@
gmail.com)
SCIENTIFIC REPORTS | 4 : 4133 | DOI: 10.1038/srep04133 1

Results
Characteristics of the participants.Healthy experienced EC users
(n 523, all former smokers) were recruited for this study. They used
a first-generation (V2 standard Cig with cartomizer) and a new-
generation device (EVIC set at 9 watts with EVOD atomizer) on
two separate days in a randomized cross-over design. They were
requested to abstain from EC use, caffeine and alcohol intake for at
least 8 hours before each experimental setting. The characteristics of
the study population are shown in Table 1. Participants were former
heavy smokers. They were using the EC for 19 months, while 20 of
them reported that they had quit smoking within less than 1 month
initiation of EC use. Twelve of them reported at least one unsuccess-
ful attempt to quit smoking before trying ECs. Participants had lower
dependence to EC use compared to smoking according to their re-
sponses to the Fagerstro¨m Test for Cigarette Dependence (FTCD)
12
and the Cigarette Dependence Scale (CDS)
13
.
EC liquid used.For both experimental settings, the same liquid
(Flavourart MaxBlend) was used. The nicotine concentration as
mentioned in the label was 18 mg/ml. The liquid was analyzed for
the presence of impurities, with results displayed in Table 2. Nicotine
concentration was very close to the declared value, while impurities
and contaminants were present in trace quantities.
Nicotine absorption.Venous blood samples were drawn at baseline,
after abstinence from EC use for at least 8 hours. Additional blood
samples were drawn at 5 minutes (taking 10 puffs) and every 15
minutes during 1 hour of ad lib EC use (Figure 1). Plasma levels of
nicotine from the first-and the new-generation device are displayed
in Figure 2. Significant differences were observed between time
points (F 5113.0 P ,0.001). Additionally, significant differences
were observed between sessions (F 518.1, P ,0.001). At baseline,
no differences were observed between the two sessions (P 50.355).
However, subsequent plasma nicotine levels were significantly
higher when using the new-generation device (P 50.003 at 5
minutes, P #0.001 for all other time points). At 5 minutes (10
puffs), mean plasma nicotine levels rose from 2.80 ng/ml (SEM:
0.42) to 4.87 ng/ml (SEM: 0.45) with the first-generation device,
while levels went from 2.46 ng/ml (SEM: 0.33) to 6.59 ng/ml
(SEM: 0.62) with the new-generation device. Maximal levels were
obtained at the end of the ad lib use period, with levels reaching to
15.75 ng/ml (SEM: 1.2) and 23.47 ng/ml (SEM: 1.94) respectively.
The mean percent differences between sessions at each time point are
displayed in Figure 3. Nicotine plasma levels were approximately
70% higher using the new- compared to the first-generation device
at 20 minutes, with the difference subsequently decreasing but still
remaining at almost 50% at the end of EC use period.
Reduction in craving and perceived satisfaction.The Cigarette
Withdrawal Scale (CWS), a questionnaire commonly used to assess
smoking craving
14,15
, was used to assess the effects of EC use on
craving to vape. There was a significant difference between timings
(F 548.1, P ,0.001) and a significant timing by session interaction
(F 59.2, P 50.040). At baseline and at 5 minutes there was no
statistically significant difference in the score between the two
sessions, while at 65 minutes the score was significantly lower after
using the new- compared with the first-generation device (P 50.004).
Significant differences between timings (F 5258.7, P ,0.001) and
between sessions (F 539.6, P ,0.001) as well as significant timing
by session interaction (F 540.6, P ,0.001) were observed for a
simple craving rating (score from 0 to 100). At baseline, craving was
similar in new- and first-generation sessions [72.3 (1.9) and 71.1
(2.1) respectively, P 50.382]. At 5 minutes, craving was significantly
reduced in both sessions and was significantly lower in new- com-
pared to first-generation session [47.9 (1.9) and 60.2 (2.11) respect-
ively, P ,0.001 compared to baseline and between sessions]. The
score was much lower at 65 minutes for both groups, with similar
differences between new- and first-generation session [25.3 (2.5) and
32.0 (2.7) respectively, P ,0.001 compared to previous timings and
between sessions].
The results for the direct effects of EC use and effects of nicotine,
derived from 100-mm visual analogue scale questions answered at
the end of the 65-minute period, are displayed in Table 3. For the
effects experienced from using the ECs, ‘‘satisfying’’ and ‘‘throat hit’’
was significantly higher for the new-generation device, while ‘‘feels
like a tobacco cigarette’’ and ‘‘looks like a tobacco cigarette’’ were
higher for the first-generation device. From assessing the effects of
nicotine, only ‘‘burning throat’’ was significantly higher for new-gen-
eration device; however, this is not necessarily a negative experience
since it may be a response to the throat hit sensation which is favor-
able for smokers to feel. In general, negative effects had a low score.
Carbon monoxide levels.Exhaled carbon monoxide levels (ppm)
were measured at baseline and 10 minutes after the 65-minute period
of using the EC devices. There was no significant difference between
timings and between devices, and no significant timing by session
Table 1
|
Characteristics of the study population
Characteristic EC users (n 523)
Males, n (%) 17 (74)
Age, years 40.0 (1.9)
Smoking duration, years 21.5 (1.9)
Smoking consumption, cigarettes per day 33.6 (2.5)
EC use duration, months 18.9 (2.3)
Smoking cessation duration, months 18.2 (2.3)
FTCDsmoking 6.96 (0.40)
FTCDsmoking-modified
1
4.70 (0.30)
CDSsmoking 53.26 (1.13)
CDSsmoking-modified
1
49.00 (1.02)
FTCD-EC 6.09 (0.32)
2
FTCD-EC-modified
1
3.91 (0.27)
2
CDS-EC 45.13 (1.51)
2
CDS-EC-modified
1
41.27 (1.46)
2
Data are presented as mean (SEM) and number (percentage).
Abbreviations. FTCD, Fagerstro
¨m Test for Cigarette Dependence; CDS, Cigarette Dependence
Scale; EC, electronic cigarette.
1
Score by subtracting the question about cigarette and EC consumption.
2
P,0.05 compared to the respective scores for smoking (paired-samples t-test).
Table 2
|
Analysis of the electronic cigarette liquid used in the study
Analysis Quantity
Nicotine 17.7 mg/ml
Propylene glycol 389 mg/ml
Glycerol 751 mg/ml
Diethylene glycol ND
Aldehydes (total) 18.17 mg/ml
Acetaldehyde 8.51 mg/ml
Crotonaldehyde 6.33 mg/ml
Formaldehyde 3.33 mg/ml
Diacetyl ND
Tobacco-Specific Nitrosamines (total) 2.08 ng/ml
NNN ND
NNK 2.08 ng/ml
Heavy metals (total) 35 ng/ml
Arsenic 35 ng/ml
Chromium ND
Lead ND
Nickel ND
pH 8.55
Water 4.3%
Abbreviations. ND, not detected; NNN, N’-nitrosonornicotine; NNK, 4-(methylnitrosamino)-1-(3-
pyridyl)-1-butanone.
www.nature.com/scientificreports
SCIENTIFIC REPORTS | 4 : 4133 | DOI: 10.1038/srep04133 2

Figure 1
|
Protocol and materials used in this study.
Figure 2
|
Plasma nicotine levels at baseline and at 5, 20, 35, 50 and 65 minutes after using the first- and the new-generation device. Error bars represent
1 SEM. There was a statistically significant difference between devices at all timing points except from baseline.
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SCIENTIFIC REPORTS | 4 : 4133 | DOI: 10.1038/srep04133 3

interaction (F #1.0, P 5NS for all). Carbon monoxide levels went
from 6.04 (0.43) before to 5.96 (0.32) ppm after using the first-
generation device. For the second-generation device, the respective
values were 6.39 (0.49) and 6.04 (0.46).
Comparison with nicotine absorption from a tobacco cigarette.To
compare nicotine absorption between tobacco cigarette and EC devices,
we used the results from a study by Vansickel et al
8
.Inthatstudy,
minimal nicotine absorption from the ECs was observed, while
smoking one tobacco cigarette in 5 minutes led to an increase in
plasma nicotine levels from 2.10 ng/ml to 18.80 ng/ml. Projection of
the findings by Vansickel et al to our data is displayed in Figure 4. After
5 minutes of EC use, plasma nicotine levels were substantially lower
compared to smoking one tobacco cigarette (almost 3-fold lower
compared to new- and 4-fold lower compared to first-generation
device). Plasma nicotine levels were equal between tobacco cigarette
use at 5 minutes and new generation EC device at 35 minutes
(18.52 ng/ml); however, tobaccocigaretteshowed73%and19%
higher levels of nicotine compared to 35 and 65 minutes ad lib use of
the first-generation device (10.88 ng/ml and 15.75 ng/ml respectively).
Discussion
This is the first study that has compared the effect of using first- vs.
new-generation EC devices on nicotine absorption. An 18 mg/ml
nicotine-containing liquid was used, which is a popular ‘‘strength’’
consumed by experienced vapers and is close to the maximum level
set by the European Commission regulatory proposal. Experienced
vapers were recruited, who use the EC devices more intensively
compared to novice users
7
. The results of the study showed that
new-generation devices with high wattage output to the atomizer
resulted in higher plasma nicotine levels compared to first-genera-
tion devices. However, both devices delivered to the bloodstream far
lower nicotine compared to a tobacco cigarette.
ECs are the only nicotine delivery devices that resemble the
motion and behavioral patterns of cigarette smoking. Although the
psycho-behavioral part of smoking is an important part of the overall
addiction to smoking
16
, nicotine delivery still plays a major role.
Smoking characteristically delivers significant amounts of nicotine
to the blood stream at a fast rate
17
. This is probably the main reason
for making it the most reinforcing and dependence-producing form
of nicotine administration
17,18
, although recent data suggest that
other substances in tobacco cigarette may reinforce the addictive
properties of nicotine
19
. Studies have shown that the vast majority
of EC users continue to use nicotine-containing liquids despite hav-
ing quit smoking for several months
2,10,11
. Therefore, it seems that
nicotine is important in ECs’ success as smoking substitutes. In this
study a liquid with 18 mg/ml nicotine concentration was chosen,
Figure 3
|
Percent difference in plasma nicotine levels between first- and new-generation devices at each time point. At 20 minutes, use of the
new-generation device resulted in 71.6% higher plasma nicotine levels compared to the first-generation device. The difference was reduced in subsequent
timing points but was still 49.0% at 65 minutes.
Table 3
|
Assessment of electronic cigarette direct effects and nicotine effects after using the electronic cigarette devices
Questions First-generation device New-generation device P
1
Effects of electronic cigarette use
Satisfying 62.8 (2.8) 74.7 (2.8) 0.003
Throat hit 61.6 (3.9) 75.1 (3.8) ,0.001
Calm 72.5 (2.7) 75.5 (2.3) NS
Concentrate 76.1 (2.2) 76.0 (2.5) NS
Feel sick 10.6 (1.1) 11.9 (1.4) NS
Tastes good 68.0 (3.3) 71.7 (3.7) NS
Tastes like tobacco cigarette 51.5 (4.7) 52.1 (4.6) NS
Feels like tobacco cigarette 69.8 (4.0) 56.9 (3.7) 0.004
Effects of nicotine
Nausea 10.5 (2.1) 10.1 (1.8) NS
Clammy skin 8.7 (1.8) 9.9 (1.8) NS
Dizziness 16.9 (1.8) 18.1 (2.4) NS
Lightheadedness 26.6 (2.3) 29.2 (3.3) NS
Burning throat 27.4 (1.9) 40.7 (2.8) ,0.001
Tingling sensations 6.5 (1.3) 7.1 (1.2) NS
Heart racing 5.3 (1.1) 6.4 (1.3) NS
Data are presented as mean (SEM).
1
Paired-samples t-test.
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SCIENTIFIC REPORTS | 4 : 4133 | DOI: 10.1038/srep04133 4

based on previous findings from our group showing that this is
approximately the level of nicotine concentration needed for experi-
enced vapers to consume 1 mg of nicotine in 5 minutes (which is
similar to the level of nicotine in the smoke of one cigarette when
smoked according to ISO 3308)
7
. Despite that, the main findings
herein showed that such a liquid is insufficient to deliver nicotine
to the blood stream as rapidly as smoking. In fact, it took about 35
minutes of vaping with the new-generation device at high wattage in
order to obtain plasma levels similar to smoking one cigarette in 5
minutes. The first-generation device was even less efficient in nic-
otine delivery; even 65 minutes of ad lib vaping was insufficient to
deliver to the bloodstream nicotine at levels similar to smoking. This
was reflected in participants’ answers to questionnaires, showing that
satisfaction and craving reduction was higher after using the new-
compared with the first-generation device. Moreover, better nicotine
delivery may be the reason why new-generation devices are more
popular in dedicated users, most of which have quit smoking by
using ECs
10,11
. Considering that it is reasonable to expect EC users
to self-titrate nicotine intake in a way similar to smoking
20
, this study
indicates that there is an inherent inability of the EC to deliver
nicotine to the blood stream at levels similar to tobacco cigarettes
within the same time-period of use, although a previous study from
our group showed that an 18 mg/ml liquid would theoreticaly be
adequate for that in terms of liquid consumption
7
. Possible reasons
for these findings may be that nicotine delivered to the EC aerosol is
not absorbed from the lungs but from the oral mucosa. Therefore,
nicotine absorption would be expected to occur at a similar rate to
nicotine-replacement therapies (NRTs). Moreover, a significant part
of nicotine deposited to the oral mucosa is expected to be swallowed,
with subsequent first-pass metabolism to the liver which reduces bio-
availability
21
. Another possibility is that the vehicle of nicotine deliv-
ery (liquid droplets of propylene glycol and glycerol) may negatively
interact with nicotine absorption from the lungs compared to the
particulate matter, which is the delivery-vehicle of nicotine in smok-
ing. More studies are needed to define the reason for this lower rate of
absorption from ECs. The new-generation device was more effective
in this study because the higher amount of energy delivered to the
atomizer results in higher amount of liquid aerosolized per puff,
while first-generation devices deliver far lower energy and do not
have an internal current stabilizer which maintains constant energy
delivery until the battery is discharged. Due to this, it is reasonable to
expect that new-generation devices may be more effective as smoking
substitutes compared to first-generation devices. Two randomised
studies evaluating the efficacy of EC use in smoking cessation have
used first-generation devices
22,23
. New-generation devices seem more
promising because they deliver nicotine more effectively, and this
should be evaluated in future studies. In any case, findings from this
study indicate that ECs may also have less addictive properties and
lower abuse liability, similar to what has been observed with NRTs
24
,
due to the slow rate of nicotine absorption. This has been specifically
observed in a study by Vansickel et al
25
. Herein, participants reported
lower dependence to ECs compared to smoking, however the ret-
rospective nature of the answers for smoking could have biased the
results.
The European Commission has recently released a proposal that
the highest permissible levels of nicotine concentration in liquids
used for ECs will be 20 mg/ml
5
. The decision was based on the level
of liquid consumption from 5 minutes of use
6,7
, but did not take into
consideration that consumption is different from absorption; the
main factors associated with the effects of nicotine are the levels in
the bloodstream and the speed of absorption. Results of this study
show that such nicotine concentration would be insufficient to
deliver nicotine at levels similar to tobacco cigarettes unless ECs
are used continuously for a long time. Moreover, the incidence of
nicotine overdose or intoxication from EC use can be virtually
excluded. Adopting the 20 mg/ml as the highest level of nicotine
content in EC liquids might significantly reduce the efficacy of ECs
to substitute smoking and will especially affect first-generation
devices which are more popular, more attractive to first-time users
(smokers) due to their resemblance to cigarettes and easier to use
compared to new-generation devices. Based on the results of this
study, showing very low levels of nicotine absorption from using
ECs in a similar way to smoking one tobacco cigarette, it seems that
nicotine levels in EC liquids should be close to 50 mg/ml in order to
approximate nicotine delivery from smoking. This could also result
in reduced daily EC use and liquid consumption, since the amount of
nicotine needed by each user could be obtained by reducing the time
and intensity of EC use. Clinical studies should be performed
Figure 4
|
Comparison between tobacco cigarette and electronic cigarette devices in plasma nicotine levels. Data for tobacco cigarette was derived from
Vansickel et al
7
. Nicotine levels after smoking a tobacco cigarette in 5 minutes (18.8 ng/ml) are 185% and 286% higher compared to using the first and
new-generation electronic cigarette device respectively. Additionally, plasma nicotine levels after smoking one tobacco cigarette are almost equal to the
values after using the new-generation device for 35 minutes (18.52 ng/ml), while they are 73% higher compared to the values after using the first-
generation device for 35 minutes (10.88 ng/ml).
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SCIENTIFIC REPORTS | 4 : 4133 | DOI: 10.1038/srep04133 5

assessing the efficacy and speed of nicotine delivery by using higher
nicotine-containing liquids. There is a possibility that using higher
nicotine-containing liquids may elevate the addictive potential of
ECs; however, considering that there is currently minimal adoption
of EC use by non-smokers adults and youngsters
11
, it is reasonable to
expect that the current proposal will reduce the effectiveness of ECs
in substituting smoking while no beneficial effect to other population
groups will be observed. Obviously, careful monitoring of use by
these population groups is warranted; however, considering the cur-
rent situation, a strict regulation banning the sales of ECs to minors
would be more appropriate rather than adopting upper limits in
nicotine content that would potentially reduce the efficacy of ECs
to substitute smoking.
In conclusion, new-generation EC devices delivering higher
energy to the atomizer seem to be more effective than first-genera-
tion devices in nicotine delivery to the user and in reducing cravings
for nicotine. However, both types of devices were significantly less
effective in nicotine delivery compared to tobacco cigarettes when an
18 mg/ml nicotine containing liquid is used. It is reasonable to
assume that nicotine levels in EC liquids should be considerably
higher in order to improve their effectiveness in nicotine delivery,
which is expected to make them more successful as smoking
substitutes.
Methods
Study participants.Healthy experienced EC users (vapers) where recruited for this
study. To participate to the study they had to be: (1) former daily smokers of at
least 5 years; (2) daily EC users for at least 1 month; (3) between the ages of 18
and 60; (4) clinically healthy, with no history of cardiovascular and lung disease or
hematological problems; (5) able to remain abstinent from EC use for at least
8 hours; and (6) willing to provide blood samples. Exclusion criteria were: (1)
pregnant or lactating females; (2) history of fainting or feeling faint associated
with providing blood samples; and (3) being unwilling to provide written
informed consent to participate to the study. The protocol was approved by the
ethics committee of our institution and written informed consent was signed by all
subjects before participating to the study.
Materials and clinical procedure.Two types of EC devices with the same liquid
were used by the participants on two separate days, in a randomized cross-over
design (Figure 1). The first-generation device was a typical cigarette-like EC
(V2cigs, Miami, Florida, USA). The lithium battery has a capacity of 250 mAh
and was fully charged before use. Empty cartomizers were bought by the same
company and were filled according to company’s instructions with approximately
1 ml of an 18 mg/ml nicotine containing liquid (Max Blend, Flavourart SRL,
Oleggio, Italy). Users were provided with more fully-charged batteries if
discharged and new cartomizers if emptied during the 65 minute period. The new-
generation device consisted of a large lithium battery part (capacity of 2600 mAh)
with an internal electronic circuit which includes a current stabilizer and allows
the user to manually adjust the energy applied to the atomizer (EVIC, Joyetech,
ShenZhen, China). A new-generation atomizer (EVOD, KangerTech, ShenZhen,
China) was used and was filled with approximately 2 ml of liquid. The energy
delivery to the atomizer was set to 9 watts.
Participants visited the laboratory after abstaining from EC use, caffeine,
alcohol and food intake for at least 8 hours. Carbon monoxide in exhaled breath
was measured by a calibrated Bedfont Micro Smokerlyzer. Subsequently, a venous
catheter was introduced in an antecubital vein and 8 ml of venous blood was
collected in lithium-heparinized vacutainers. Participants were asked to take 10
puffs in 5 minutes, simulating tobacco cigarette use
26
. After this period, they were
asked to use the ECs ad lib for 60 more minutes (total duration of use: 65
minutes). Ten minutes after the end of the 65 minute period, carbon monoxide
levels were measured again.
Blood samples and nicotine measurements.Blood samples were taken after the 5
minute period and every 15 minutes during the additional 60 minute period. The
samples were stored in ice and were centrifuged within 1 hour. Plasma was separated
and stored at 270uC until analyzed. Measurements of nicotine levels were performed
in a specialized laboratory by Gas Chromatography with an NPD-80 Specific
Detector. The lowest limit of quantification (LOQ) for this method was 0.5 ng/ml. For
samples with nicotine levels below the LOQ, a value of LOQ/2 was assigned for
statistical analysis.
Questionnaires on smoking and EC dependence, craving assessment and EC use
effects.To define their past dependence to tobacco cigarettes, two tests were
performed; the Fagerstro¨ m Test for Cigarette Dependence (FTCD)
12
and the
Cigarette Dependence Scale (CDS)
13
. To evaluate their current EC dependence, the
previously mentioned tests were also applied for EC use. Since both questionnaires
include a question for cigarette consumption, the question was adjusted for EC use
based on the results of a survey of 19,441 EC users performed by our group
(unpublished data). The consumption was classified according to percentiles
(quartiles for FTCD and quintiles for CDS). The results of the two tests after excluding
the question on cigarette and EC consumption were also reported. To avoid any
interaction between the answers, the questionnaires for smoking and EC use were
administered on separate days to the participants.
To assess craving for nicotine before and after EC use, a shortened version of
the Cigarette Withdrawal Scale (CWS) was used
14,15
. It consists of rating the
extend of agreement with the following statements, adopted for EC use: (1) ‘‘The
only thing I can think about is using (vaping) an EC’’; (2) ‘‘I miss the EC terribly’’;
and (3) ‘‘I feel an irresistible need to vape’’. For each question, answers were
scored as: 0 5‘‘totally disagree’’, 1 5‘‘mostly disagree’’, 2 5‘‘more or less agree’’,
35‘‘mostly agree’’, 4 5‘‘totally agree’’. The sum of the scores from each question
was calculated and reported. Additionally, a simple craving rating was used, by
using a 100 mm visual analogue scale and asking: ‘‘How much do you crave an EC
right now?’’. Participants were asked to draw a cross through the horizontal line
and the score was calculated by measuring the distance between the cross and the
left anchor. Both CWS and simple craving rating were asked at baseline, after 5
minutes and after 65 minutes of use.
To assess the effects of nicotine and EC use, participants responded to 100 mm
visual analogue scale questions after the end of the 65 minute period of EC use.
Questions were adopted from Vansickel et al
8
. and from Hutsmuller and Stitzer
27
.
Each word or phrase was centered above the horizontal line that represented a scale
from 0 to 100 points; the left anchor was ‘‘Not at all’’ and the right anchor was
‘‘Extremely’’. The score was assessed in a similar way as described above for the simple
craving rating.
Statistical analysis.Categorical variables were expressed as number (percentage)
while continuous variables as mean (SEM). To compare CWS and simple nicotine
craving scale, repeated measures analysis of variance (ANOVA) was used, with
two within-subjects factors: timing (3 levels) and session (2 levels). To compare
exhaled carbon monoxide levels, repeated measures ANOVA was also used but
timing had 2 levels (baseline and post-65 minute); for nicotine levels, timing had 6
levels. To assess perceived effects of nicotine and EC use, paired student’s t-test
was used. A two-tailed P value of #0.05 was considered statistically significant.
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Author contributions
K.F. was responsible for the protocol design. K.F., A.S., K.T. and C.S. were responsible for
participants’ recruitment, blood samples collection and exhaled carbon monoxide
measurements. C.S., K.F. and G.R. were responsible for data collection and analyzing
answers to the questionnaires. K.F. and G.R. was responsible for statistical analysis and
interpretation of the data. K.F. and V.V. were responsible for manuscrip t preparation. All
authors reviewed and approved the manuscript before being submitted for publication.
Additional information
Funding: The study was funded by American E-Liquid Manufacturing Standards
Association (AEMSA). This is an officially non-profit association [501(c)(6) status by the
IRS] that was founded and is run by electronic cigarette consumers. AEMSA has provided
advocacy to public health authorities, including the Food and Drug Administration (FDA)
Center for Tobacco Products, about electronic cigarettes. The study was
investigator-initiated and investigator-driven. The funding body had no involvement in the
study design, data collection, analysis and interpretation, writing or approving the
manuscript and decision to submit the manuscript for publication. The study was presented
in part during a meeting with the FDA Center for Tobacco Products by Konstantinos
Farsalinos.
Competing financial interests: The authors declare no competing financial interests.
How to cite this article: Farsalinos, K.E. et al. Nicotine absorption from electronic cigarette
use: comparison between first and new-generation devices. Sci. Rep. 4, 4133; DOI:10.1038/
srep04133 (2014).
This work is licensed under a Creative Commons Attribution-
NonCommercial-NoDerivs 3.0 Unported license. To view a copy of this license,
visit http://creativecommons.org/licenses/by-nc-nd/3.0
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SCIENTIFIC REPORTS | 4 : 4133 | DOI: 10.1038/srep04133 7