Abstract
Propylene glycol and glycerol are e-cigarette constituents that facilitate liquid vaporization and nicotine transport. As these small hydrophilic molecules quickly cross the lung epithelium, we hypothesized that short-term cessation of vaping in regular users would completely clear aerosol deposit from the lungs and reverse vaping-induced cardiorespiratory toxicity. We aimed to assess the acute effects of vaping and their reversibility on biological/clinical cardiorespiratory parameters [serum/urine pneumoproteins, hemodynamic parameters, lung-function test and diffusing capacities, transcutaneous gas tensions (primary outcome), and skin microcirculatory blood flow]. Regular e-cigarette users were enrolled in this randomized, investigator-blinded, three-period crossover study. The periods consisted of nicotine-vaping (nicotine-session), nicotine-free vaping (nicotine-free-session), and complete cessation of vaping (stop-session), all maintained for 5 days before the session began. Multiparametric metabolomic analyses were used to verify subjects’ protocol compliance. Biological/clinical cardiorespiratory parameters were assessed at the beginning of each session (baseline) and after acute vaping exposure. Compared with the nicotine- and nicotine-free-sessions, a specific metabolomic signature characterized the stop-session. Baseline serum club cell protein-16 was higher during the stop-session than the other sessions (P < 0.01), and heart rate was higher in the nicotine-session (P < 0.001). Compared with acute sham-vaping in the stop-session, acute nicotine-vaping (nicotine-session) and acute nicotine-free vaping (nicotine-free-session) slightly decreased skin oxygen tension (P < 0.05). In regular e-cigarette-users, short-term vaping cessation seemed to shift baseline urine metabolome and increased serum club cell protein-16 concentration, suggesting a decrease in lung inflammation. Additionally, acute vaping with and without nicotine decreased slightly transcutaneous oxygen tension, likely as a result of lung gas exchanges disturbances.
Highlights
Propylene glycol and glycerol, the main constituents of electronic-cigarette (e-cigarette) liquid (e-liquid), produce an aerosol when heated that carries flavoring and nicotine
High-wattage vaping, with and without nicotine, has been shown to induce transcutaneous hypoxia, constriction of the airways, and lung inflammation in healthy naïve vapers [10, 12]. The latter was marked by a rise in serum club cell secretory protein-16 (CC16) without a change in surfactant protein-D (10 –12)
Whereas the baseline level of serum nicotine and urine cotinine were in accordance with the study protocol for 72 (95%) study sessions, abnormally high levels of baseline serum nicotine (Ͼ2 ng/mL) [20] and urine cotinine (Ͼ600 ng/mL) [32] were found in 3 nicotine-free-sessions and in 1 stop-session
Summary
The main constituents of electronic-cigarette (e-cigarette) liquid (e-liquid), produce an aerosol when heated that carries flavoring and nicotine. High-wattage vaping, with and without nicotine, has been shown to induce transcutaneous hypoxia, constriction of the airways, and lung inflammation in healthy naïve vapers [10, 12] The latter was marked by a rise in serum club cell secretory protein-16 (CC16) without a change in surfactant protein-D (10 –12). When vaped in large amounts, this aerosol can transiently accumulate deep in the lungs [42] and interact with the epithelium [50] This hygroscopic and hyperosmolar deposit could theoretically disrupt the rheological properties of surfactant and mucus [21, 23, 31, 49, 50, 52], resulting in bronchiolar and alveolar collapse and impairments to lung gas exchange [40]. We explored whether e-cigarette cessation for 5 days could shift serum and urine http://www.ajplung.org
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