Risk assessment of inhaled diacetyl from electronic cigarette use among teens and adults

E-Cigarette or Vaping Product Use-Associated Lung Injury: A Comprehensive Review

E-cigarette or vaping product use-associated lung injury (EVALI) is a critical and potentially fatal form of lung injury that gained considerable public health concern in 2019. The use of e-cigarettes and vaping products is causally associated with EVALI, a condition characterized by a constellation of respiratory symptoms, such as coughing, shortness of breath, and chest pain. This comprehensive narrative literature review explores the complexities of EVALI, including its association with the structure and composition of e-cigarettes and its epidemiology, pathogenesis, clinical and radiological manifestations, management strategies, and public health implications. Moreover, it uncovers the long-term repercussions of EVALI and underscores the ongoing research endeavors designed to mitigate and comprehend the risks associated with using e-cigarettes.

Comparison of toxic pyrogenic compounds derived from conventional cigarettes and heated tobacco products

Heated tobacco products (HTPs) have gained popularity as alternatives to conventional cigarettes (CCs). Nevertheless, assessing their health hazards remains challenging owing to variations in individual smoking habits. Thus, this study aimed to identify toxic compounds from simulated smoking conditions and evaluate their toxicity in humans. Tobacco leaves (TL) and reconstituted tobacco leaves (RTL), sourced from the CCs and HTPs, were used as model feedstocks. Thermogravimetric analysis revealed that RTL contained higher nicotine and glycerol levels but lower carbohydrate content than TL. The smoking mechanisms of both tobacco samples were found to be governed by pyrolysis under different temperatures (TL: 200-800 °C and RTL: 350 °C). In TL pyrolysis, the toxic compound formations are influenced by the temperature. Nicotine was dominant at ≤ 400 °C, whereas temperatures ≥ 400 °C led to increased formation of toxic compounds, particularly carcinogens. In contrast, RTL pyrolysis at 350 °C generated fewer carcinogens because controlled heating inhibited thermolysis of the lignocellulosic components. To assess carcinogenicity, peak intensities of TL and RTL-derived carcinogens were normalized using nicotine as an addiction factor. Relative carcinogenicity of RTL was reduced by more than two folds compared with that of TL. This comparative assessment suggests that HTP smoking may reduce exposure to carcinogenic compounds compared to CC smoking, although additional clinical factors should be considered for more accurate assessment of the associated health risks.

Single-cell transcriptomics identifies a dampened neutrophil function and accentuated T-cell cytotoxicity in tobacco flavored e-cigarette exposed mouse lungs

E-cigarettes (e-cigs) are a public health concern for young adults due to their popularity and evidence for increased oxidative stress and immunotoxicity. Yet an extensive study defining the cell-specific immune changes upon exposure to flavored e-cigs remains elusive. To understand the immunological lung landscape upon acute nose-only exposure of C57BL/6J to flavored e-cig aerosols we performed single-cell RNA sequencing (scRNA seq). scRNA profiles of 71,725 cells were generated from control and treatment groups (n=2/sex/group). A distinct phenotype of Ly6G-neutrophils was identified in lungs exposed to tobacco flavored e-cig aerosol which demonstrated dampened IL-1 mediated and pattern recognition signaling as compared to air controls. Differential gene expression analyses identified dysregulation of T-cell mediated pro-inflammation ( Cct7 , Cct8 ) and stress-response signals ( Neurl3 , Stap1 , Cirbp and Htr2c) in the lungs of mice exposed to e-cig aerosols, with pronounced effects for tobacco flavor. Flow cytometry analyses and cytokine/chemokine assessments within the lungs corroborated the scRNA seq data, demonstrating a significant increase in T-cell percentages and levels of T-cell associated cytokine/chemokines in the lungs of tobacco-flavored aerosol exposed mice. Increased levels of Klra4 and Klra8 expression also suggest an enhanced natural killer (NK) cell activity in this mouse group. Overall, this is a pilot study identifying increase in the percentages of Ly6G-neutrophils that may be responsible for dampened innate immune responses and heightened T-cell cytotoxicity in lungs of tobacco-flavored e-cig aerosol exposed mice. In addition, we provide preliminary evidence for sex-specific changes in the transcriptional landscape of mouse lungs upon exposure to e-cig aerosol, an area that warrants further study.

E-cigarettes, synthetic nicotine, heated-tobacco and smokeless nicotine delivery products: the nicotine landscape beyond combustible cigarettes

Cigarette smoking remains an enormous public health problem causing millions of preventable deaths annually worldwide. Although safe and efficient smoking cessation pharmacotherapies such as nicotine replacement products and the medications varenicline and bupropion are available, long-term abstinence rates remain low and new approaches to help smokers successfully quit smoking are needed. In recent years, electronic nicotine delivery systems such as e-cigarettes and heated-tobacco products, and novel smokeless nicotine delivery products like nicotine pouches have gained widespread popularity. These products can deliver nicotine without combustion of tobacco and might thus present an alternative to the currently available smoking cessation methods if they prove able to help smokers quit smoking conventional cigarettes while decreasing their exposure to toxicants. In this narrative review, we provide a summary of the characteristics of these novel nicotine delivery products and the available data regarding their efficacy as smoking cessation tools and safety profile with a focus on the current situation in Switzerland.

Review of quantitative and functional lung imaging evidence of vaping-related lung injury

Introduction

The pulmonary effects of e-cigarette use (or vaping) became a healthcare concern in 2019, following the rapid increase of e-cigarette-related or vaping-associated lung injury (EVALI) in young people, which resulted in the critical care admission of thousands of teenagers and young adults. Pulmonary functional imaging is well-positioned to provide information about the acute and chronic effects of vaping. We generated a systematic review to retrieve relevant imaging studies that describe the acute and chronic imaging findings that underly vaping-related lung structure-function abnormalities.

Methods

A systematic review was undertaken on June 13th, 2023 using PubMed to search for published manuscripts using the following criteria: [("Vaping" OR "e-cigarette" OR "EVALI") AND ("MRI" OR "CT" OR "Imaging")]. We included only studies involving human participants, vaping/e-cigarette use, and MRI, CT and/or PET.

Results

The search identified 445 manuscripts, of which 110 (668 unique participants) specifically mentioned MRI, PET or CT imaging in cases or retrospective case series of patients who vaped. This included 105 manuscripts specific to CT (626 participants), three manuscripts which mainly used MRI (23 participants), and two manuscripts which described PET findings (20 participants). Most studies were conducted in North America (n = 90), with the remaining studies conducted in Europe (n = 15), Asia (n = 4) and South America (n = 1). The vast majority of publications described case studies (n = 93) and a few described larger retrospective or prospective studies (n = 17). In e-cigarette users and patients with EVALI, key CT findings included ground-glass opacities, consolidations and subpleural sparing, MRI revealed abnormal ventilation, perfusion and ventilation/perfusion matching, while PET showed evidence of pulmonary inflammation.

Discussion and conclusion

Pulmonary structural and functional imaging abnormalities were common in patients with EVALI and in e-cigarette users with or without respiratory symptoms, which suggests that functional MRI may be helpful in the investigation of the pulmonary health effects associated with e-cigarette use.

Clinical guidance for e-cigarette (vaping) cessation: Results from a modified Delphi panel approach

Individuals seek help to stop their use of e-cigarettes from their healthcare practitioners. However, there is a paucity of published work addressing e-cigarette cessation methods empirically, and what evidence that is available is weak. Therefore, we developed an expert informed clinical resource to guide practitioners helping their clients quit using e-cigarettes. We conducted a modified Delphi process between September and December 2021 to reach consensus on clinical recommendations for e-cigarette cessation. Expert and Peer Panel members (n = 28) voted and provided feedback on the recommendations through three rounds of structured surveys, a discussion board, and one intermediate survey. The penultimate knowledge products underwent usability testing and were finalized based on user feedback. The Expert Panel maintained a 100% response rate for rounds 1 and 2 and 96% for round 3; the Peer Panel achieved a 100% response rate for all three rounds of the modified Delphi process. Consensus was reach on 24 recommendations and 2 statements spanning eight domains: severity and dependence; general approaches; treatment approaches; dual use; pharmacotherapy strategies; behavioural therapy strategies; harm reduction; and relapse prevention. Two additional 'no agreement' statements that did not reach consensus are included in the guidance resource. The recommendations were also contextualized for the following groups: adults; youth; people who are pregnant, breastfeeding and/or chestfeeding; and people with mental illness and/or substance use issues. The recommendations listed in the resource provide general clinical guidance on e-cigarette cessation to assist healthcare practitioners in the treatment planning process.

Chemical Profiles and Toxicity of Electronic Cigarettes: An Umbrella Review and Methodological Considerations

BACKGROUND

Electronic cigarettes (ECs) are often marketed as a safer alternative to combustible tobacco products. The global EC market has rapidly expanded since their introduction, creating an urgent need for research describing the toxicity and chemical composition of ECs. We conducted an umbrella review to summarize the evidence from existing systematic reviews (SRs).

METHODS

The search for SRs was conducted across four electronic databases through 25 January 2022. Methodological quality was assessed using the AMSTAR-2 quality appraisal tool.

RESULTS

Twenty-five SRs were included in our umbrella review. Chemical profiles widely varied across studies included in the reviews, which was mainly attributed to the lack of standardized protocols investigating the constituents, and differences in EC devices and e-liquids tested. Metals were more abundant in some EC aerosols than cigarettes, while carbonyls were typically found at lower levels. There was consistent evidence of in vitro toxicity from EC aerosol and e-liquid exposure. AMSTAR-2 revealed important limitations across reviews.

CONCLUSIONS

While most reviews concluded that ECs were likely less harmful than cigarettes, there was hesitancy to draw clear conclusions due to variable analytical procedures and inconsistent findings among the included studies. Future SRs with improved methodology and reporting are needed to adequately inform tobacco regulatory actions.

Impact of Electronic Cigarettes on the Upper Aerodigestive Tract: A Comprehensive Review for Otolaryngology Providers

Objective

The use and effects of electronic (e)-cigarettes (e-cigs) are particularly relevant for otolaryngology providers as tobacco plays a major role in benign and malignant diseases of the upper aerodigestive tract. This review aims to (1) summarize the recent policies regarding e-cigs and important patterns of use and (2) serve as a comprehensive resource for clinical providers on the known biologic and clinical effects of e-cigs on the upper aerodigestive tract.

Data Sources

PubMed/MEDLINE.

Review Methods

We conducted a narrative review on (1) general information on e-cig use and informative findings in the lower respiratory system and a comprehensive review on (2) the effects of e-cigs on cell and animal models and the clinical implications of these products on human health as is relevant to otolaryngology.

Conclusions

Although e-cigs are likely less harmful than conventional cigarettes, preliminary research on e-cigs suggest several deleterious effects including in the upper aerodigestive tract. Due to this, there has been increased interest in restricting e-cig usage, particularly among the adolescent population, and caution in recommending e-cigs to current smokers.

Implications for Practice

Chronic e-cig use is likely to have clinical implications. It is critical for otolaryngology providers to be aware of the rapidly changing regulations and use patterns regarding e-cigs and how e-cigs influence human health, particularly with regards to the upper aerodigestive tract, to accurately council patients regarding potential risks and benefits of use.

E-Cigarettes Reexamined: Product Toxicity

The introduction of e-cigarettes, or electronic nicotine delivery systems (ENDS), has been accompanied by controversy regarding their safety and effectiveness as a cessation aid and by an explosion in their use by youth. Their use does not involve the combustion of tobacco and the creation of harmful combustion products; they have been seen as a "harm reduction" tool that may be of assistance in promoting smoking cessation. Recognition that ENDS can deliver an array of chemicals and materials with known adverse consequences has spurred more careful examination of these products. Nicotine, nitrosamines, carbonyl compounds, heavy metals, free radicals, reactive oxygen species, particulate matter, and "emerging chemicals of concern" are among the constituents of the heated chemical aerosol that is inhaled when ENDS are used. They raise concerns for cardiovascular and respiratory health that merit the attention of clinicians and regulatory agencies. Frequently cited concerns include evidence of disordered respiratory function, altered hemodynamics, endothelial dysfunction, vascular reactivity, and enhanced thrombogenesis. The absence of evidence of the consequences of their long-term use is of additional concern. Their effectiveness as cessation aids and beneficial impact on health outcomes continue to be examined. It is important to ensure that their production and availability are thoughtfully regulated to optimise their safety and permit their use as harm reduction devices and potentially as smoking-cessation aids. It is equally vital to effectively prevent them from becoming ubiquitous consumer products with the potential to rapidly induce nicotine addiction among large numbers of youth. Clinicians should understand the nature of these products and the implications of their use.

Impact of vaping on respiratory health

Widespread uptake of vaping has signaled a sea change in the future of nicotine consumption. Vaping has grown in popularity over the past decade, in part propelled by innovations in vape pen design and nicotine flavoring. Teens and young adults have seen the biggest uptake in use of vape pens, which have superseded conventional cigarettes as the preferred modality of nicotine consumption. Relatively little is known, however, about the potential effects of chronic vaping on the respiratory system. Further, the role of vaping as a tool of smoking cessation and tobacco harm reduction remains controversial. The 2019 E-cigarette or Vaping Use-Associated Lung Injury (EVALI) outbreak highlighted the potential harms of vaping, and the consequences of long term use remain unknown. Here, we review the growing body of literature investigating the impacts of vaping on respiratory health. We review the clinical manifestations of vaping related lung injury, including the EVALI outbreak, as well as the effects of chronic vaping on respiratory health and covid-19 outcomes. We conclude that vaping is not without risk, and that further investigation is required to establish clear public policy guidance and regulation.

An Evaluation of Evidence Underpinning Management Recommendations in Tobacco Use Disorder Clinical Practice Guidelines

INTRODUCTION

Clinical practice guidelines(CPGs) are important tools for medical decision-making. Given the high prevalence and financial burden associated with tobacco use disorder(TUD), it is critical that recommendations within CPGs are based on robust evidence. Systematic reviews(SRs) are considered the highest level of evidence, thus, we evaluated the quality of SRs underpinning CPG recommendations for TUD.

METHODS

We used PubMed to search for CPGs relating to TUD published between January 1, 2010 and May 21, 2021. SRs were extracted from CPG references and evaluated using Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA) and A MeaSurement Tool to Assess Systematic Reviews(AMSTAR-2) tools. We then compared SRs conducted by the Cochrane Collaboration with non-Cochrane SRs using a Mann-Whitney U test and determined associations between PRISMA and AMSTAR-2 extracted characteristics using multiple regression.

RESULTS

Our search generated 10 CPGs with 98 SRs extracted. Mean PRISMA completion was 74.7%(SD = 16.7) and mean AMSTAR-2 completion was 53.8%(SD = 22.0) across all guidelines. Cochrane SRs were more complete than non-Cochrane studies in the PRISMA and AMSTAR-2 assessments. The regression model showed a statistically significant association between PRISMA completion and AMSTAR-2 rating, with those classified as "low" or "moderate" quality having higher PRISMA completion than those with "critically low" ratings.

CONCLUSION

We found substandard adherence to PRISMA and AMSTAR-2 checklists across SRs cited in TUD CPGs. A lack of recent SRs in CPGs could lead to outdated recommendations. Therefore, frequent guideline updates with recently published evidence may ensure more accurate clinical recommendations and improve patient care.

IMPLICATIONS

Systematic reviews used to underpin clinical practice guideline recommendations influence treatment decisions and, ultimately, patient outcomes. We found that many systematic reviews underpinning tobacco use disorder guideline recommendations were out of date and unsatisfactory in reporting and quality. Thus, including newer systematic reviews containing more recently conducted trials and better reporting could alter recommendations and improve the rate of successful tobacco cessation attempts.