Abstract
AimsTo compare the effects of (i) high versus low nicotine concentration e‐liquid, (ii) fixed versus adjustable power and (iii) the interaction between the two on: (a) vaping behaviour, (b) subjective effects, (c) nicotine intake and (d) exposure to acrolein and formaldehyde in e‐cigarette users vaping in their everyday setting.DesignCounterbalanced, repeated measures with four conditions: (i) low nicotine (6 mg/ml)/fixed power; (ii) low nicotine/adjustable power; (iii) high nicotine (18 mg/ml)/fixed power; and (iv) high nicotine/adjustable power.SettingLondon and the South East, England.ParticipantsTwenty experienced e‐cigarette users (recruited between September 2016 and February 2017) vaped ad libitum using an eVic Supreme™ with a ‘Nautilus Aspire’ tank over 4 weeks (1 week per condition).MeasurementsPuffing patterns [daily puff number (PN), puff duration (PD), interpuff interval (IPI)], ml of e‐liquid consumed, changes to power (where permitted) and subjective effects (urge to vape, nicotine withdrawal symptoms) were measured in each condition. Nicotine intake was measured via salivary cotinine. 3‐Hydroxypropylmercapturic acid (3‐HPMA), a metabolite of the toxicant acrolein, and formate, a metabolite of the carcinogen formaldehyde, were measured in urine.FindingsThere was a significant nicotine concentration × power interaction for PD (P < 0.01). PD was longer with low nicotine/fixed power compared with (i) high nicotine/fixed power (P < 0.001) and (ii) low nicotine/adjustable power (P < 0.01). PN and liquid consumed were higher in the low versus high nicotine condition (main effect of nicotine, P < 0.05). Urge to vape and withdrawal symptoms were lower, and nicotine intake was higher, in the high nicotine condition (main effects of nicotine: P < 0.01). While acrolein levels did not differ, there was a significant nicotine × power interaction for formaldehyde (P < 0.05).ConclusionsUse of a lower nicotine concentration e‐liquid may be associated with compensatory behaviour (e.g. higher number and duration of puffs) and increases in negative affect, urge to vape and formaldehyde exposure.
Highlights
Awareness and use of electronic cigarettes (e-cigarettes) has increased rapidly during recent years, with an estimated 23.1 million smokers in the European Union (EU) reporting ever trying an e-cigarette in 2012 [1] and 12.9 million people using e-cigarettes in the United States in 2014 [2]
Puff duration was significantly longer with 6 compared with 18 mg/ml nicotine e-liquid in the fixed power condition [6F versus 18F: t18 = 5.26, P = 0.000, mean difference = 0.85, 95% confidence interval (CI) = – 0.51 to 1.19) and longer with 6 fixed versus 6 adjustable power (t18 = 3.15, P = 0.006, mean difference = 0.66, 95% CI = 0.22–1.09)
Urge to vape and nicotine withdrawal symptoms were higher and positive effects were lower in the low nicotine condition, when the power was fixed
Summary
Awareness and use of electronic cigarettes (e-cigarettes) has increased rapidly during recent years, with an estimated 23.1 million smokers in the European Union (EU) reporting ever trying an e-cigarette in 2012 [1] and 12.9 million people using e-cigarettes in the United States in 2014 [2]. Nicotine delivery from e-cigarettes varies considerably, and depends upon a variety of factors: the nicotine E-cigarette users (vapers) tend to lower the nicotine concentration in their e-liquid [13,14]. This may be due to: the belief that it is healthier; to allow changes to the device/tank (e.g. subohming—using an atomizer coil with a resistance of < 1 Ohm with increased power); or to wean off e-cigarette/ nicotine use entirely. Vapers may self-titrate to a level of satisfaction which is optimal to their needs when adjusting to a lower nicotine concentration e-liquid
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